Entering autos: discussion split from Glasgow crash thread

[John Eacott]

Mea culpa, I failed to acknowledge your apology earlier: thank you for recognising that I had neither said nor inferred that of which you accused me.

John Eacott - let's get at least one thing crystal clear. The Newfoundland S92 comments I made are based on the intimation that the P1 was continuing flight under the misunderstanding that his MGB had a run- dry capability.

This discussion was, and has been in the public forum since that event.

Someone, somewhere released that erroneous information.

If this is incorrect challenge it.

I can only assume that you are disregarding the Canadian TSB Accident Report? I have emphasised the pertinent part which refutes your assertion about the P1s understanding of the S92 and my subsequent concern over your inflammatory comment about (I assume) Nick Lappos.

1.18.6 Social Media

The internet has greatly increased opportunities for individuals to interact and exchange information and viewpoints. Internet forums, a form of social media,139 have become a widely popular source of information exchange. On one such internet forum, the S-92A generated an enormous amount of discussion. Starting in March 2000, before the S-92A went into commercial use, website visitors engaged in discussions about the introduction of the S-92A. Many of the individuals who posted on this website chose to remain anonymous. However, others such as one of Sikorsky's senior managers for the S-92A program, who was a regular contributor to the online discussion, chose to identify themselves. Over the course of several years, the subject of the S-92A's compliance with Part 29 was discussed at length among members of this internet forum. From these online discussions, it was evident that those involved understood that the S-92A did not have a run dry capability.

It was determined during the TSB investigation that at least one senior manager, and several other pilots at Cougar Helicopters periodically reviewed the material posted on the above mentioned internet forum.

[HeliComparator]

I can only assume that you are disregarding the Canadian TSB Accident Report? I have emphasised the pertinent part which refutes your assertion about the P1s understanding of the S92 and my subsequent concern over your inflammatory comment about (I assume) Nick Lappos.

Although a good report in general, that particular conclusion I found strange. The subject was thrashed at great length on this forum, with me as a significant participant IIRC (by which I mean "so I remember it well"), for a long time. Even when finally the truth was established it was a constant battle to dissuade pop-up posters from repeating the old and false mantras for several years. The manufacturer's representatives in my view took no steps to encourage the truth to be promulgated, in fact it seemed rather the opposite.

So to say that because the issue was finally, after several years of confusion, put to bed on this forum, therefore there can have been no confusion elsewhere, is a leap of faith too far. Last time I looked PPruNE is not mandatory reading for all pilots!

Anyway, way off topic again, and all done to death before.

[Nubian]

DB,

In response to 500guy's accidents stats, you looks like you imply that the 5 serious and 2 dead linesman is an outrageous amount. This is over 35 years in one specific part of utility operation. Now, how many offshore deaths is it in the same period may I ask? And how many is in twin's? And how many did the pilot just c..k up? 35 years would amount to at least a 3 digit number
Obviously, 500's post only took the stats from one specific type of aerial work, and utility work as an overall may not be the same. However, the majority of the accidents happens in bad weather, flying into various obstacles in perfectly running machines..(a very different story) and NOT from engine failures in the h/v curve.

TC,

Not knowing the difference of hundreds of real engine failures in singles and practise EOL's (engine stopped or not) is quite shocking, coming from a self-proclaimed helicopter-god like you.
well tried fact of life that hovering inside the H/V curve ends in tears.....as it did with your previous post statistics.
You can try to sum up the amount of hours hovered in the h/v curve in that line of business over a period of 35 years, and then 2 persons have lost their life and 5 have sustained ''serious injuries'' like a broken wrist..... :rolleyes:

Same can be said about the conception that the h/v curve is part of the Limitations section. As the FM goes, it's only the limitations which is defined by law, the others are guides. ie. you can read out from the performance section your theoretical AUW OGE, but if you're able to lift off with more due to wind etc. that is what you work with in real life.

500,

I'd like to see you install markerballs while staying out of the HV curve
Yeah, would be a bit more challenging with a 500ft line:E BTW, it seems evident that TC don't have a concept of what aerial work is.

DB and TC,

If you think we are whazzing about in the h/v curve for the fun of it, it shows us that you don't have respect for the work we do. We all limit the time we are operating in there, and for every flight not requiring me to enter the h/v curve, I will avoid it. As said several time before, it is NOT a limitation.

Your argument would be like saying that operations down-wind is illegal as well... Not recommended, but legal either way.

[Thomas coupling]

Peter: good morning to you in sunny California.

If I might re-iterate a couple of points to further clarify some misunderstandings:

You said:
Note that I say "Cyclic back and collective (lever) down simultaneously, or in that order." It is simply wrong in my opinion to prioritize the collective ahead of the cyclic, especially if one's left hand is not on the collective. This would mean not moving the cyclic until the left hand could find the collective and lower it. This would be a huge mistake.

There is no harm at all in starting the cyclic back immediately to stop, not slow, the reduction of rotor rpm, which is all that lowering the lever does.
.

I have an admission to make. In all my years of flying (30+), I have probably spent 90% in the presence of military pilots. Both inside the mil and outside the mil (ex mil pilots). Occasionally I have flown with civilian (what we call "self improver") pilots and given the opportunity, changed their way of thinking about the controls in general.
We (and the convertees) were taught to keep our hands on the controls as much as possible and never be too far away from the collective. But I do understand the impracticalities of keeping your hand on the collective always.

Now: the main issue: "aft" cyclic (to use your terms) first. Because there are several permutations where aft cyclic would never be a good idea (in any climb / in the hover / travelling downwind at low speed / close to the ground at low speed / in a dive, etc etc) one can NEVER ever make the statement: aft cyclic first and then collective. But one can ALWAYS say: collective first and then cyclic. Because of this - I stand fast with this ethos.
Finally - I am very surprised at the lack of knowledge you advertise about your fraternity over there. Shocked even, when it comes to American Instructors being unaware of dropping the Nr out of the green. Obviously a systemic failure of the training world and I now fully understand why you and others have an uphill mission! Good luck with it........

Gordy:
H/V curve...I do understand and that is why I covered my 6 by quoting BOTH the operational AND the limitations sections for the H/V curve because it depends on the operation you are conducting (private Vs public for one) and where the OEM parks the notice.

Re the necessity to hover inside the H/c this has already been discussed with 50 / 170' and myself to everyone's satisfaction, I might add. Rest assured.

Feel free to support Peter's views - are you American trained? :rolleyes:

Double Bogey: you really do yourself no favours and certainly don't know when to give it a break - do you. How big is that chip on your shoulder. Let's move on - please, for the sake of the credibility of this forum....:ugh:

[Thomas coupling]

Nubian: are you on drugs or something??? Where is all this vitreol from. Calm down sunny.

What on earth are you on about re: hundreds of real engine failures Vs practice EOL's???? What? Non comprende.

H/V curve: For your information, communication between 500guy and 170' and myself resulted in a very amicable understanding of both our issues - read the f***g posts before transmitting.
My observation was that ALL those people injured/killed and all those cabs damaged will almost certainly NOT have happened OUTSIDE the damn H/v curve. It is BECAUSE you work inside the curve that these 2 dead people and 5 serious has happened - DUH!

Of course I dont have any concept of aerial work, I have never done it !!!

Please dont tarnish your industry with posts like this. Most professional helicopter pilots are top of their game, they also normally display elements of reasoning and competence outside their fundamental trade.....I simply can't believe you fall into this category after such a crass outburst....Calm down

[chopjock]

If you wish to improve your chances and extend the critical rpm to a lower figure, enquire to the manufacturer if you can increase the lower pitch travel to zero degrees or even a negative setting.
I have frequently practised auto rotation techniques with drones, allowing the pitch to stay on with a power cut in a high hover, watched as the main rotor blades stall in flight, nearly stop, then bottom the lever to a negative pitch setting and observed as the RRPM recovered. (with negative pitch, the angle of attack is less).
The only down side of this set up is often bottom lever is then too much (down)for normal approaches, so you have to be mindful of controlling the amount of down lever movement, as you do with cyclic.
Could be a safety enhancement to help recover rpm when normally it would not be recoverable.

[Thomas coupling]

ChopJock: You are not a well man...not well at all. Go and sit in a dark room preferably where there is no internet and for atleast a dozen years or so. :ugh: :ugh::(

[DOUBLE BOGEY]

Nubian - I read your post and it is compelling reading. At first glance 500 Guys posted stats look horrendous but as you say, caompared to other sectors they seem remarkable benign. Thanks for pointing this out.

Please do not think I do not respect the work 500guy does. It is the hand skilled kind of flying we, in our fully automated heavy helicopters have long since stopped dreaming about.

It is bizzarre though when you re-read 500guys post...it sort of says "Hey look how safe we are....we have only killed a few people and maimed a few more". Of course in hindsight, in the light of your explanation, it makes more sense.

DB

[SASless]

DB and HC,

Time to be honest here folks.

You two were the 225 side of the 92/225 argument here at Rotor Heads.

Nick Lappos was on the other side.

As documented by the TSB and quoted by John Eacott.....he posted here under his own name. You two did not...have not....and I assume will not.

You two safely hide your connection to the 225 program while Nick did just the opposite.

You attacked him and continue to attack him, HC much less so than DB, in defiance of the ROE's here particularly in DB's case, and reject the findings of a very detailed investigation and a very frank honest evaluation of all the evidence, testimony, and forensic examination of the factors that led up to that crash.

Bluntly, you two are pushing a MYTH and refuse to accept the findings of the TSB.

That needs to stop.

DB....you need to withdraw that comment that Eacott quoted.....and offer an apology to Nick and the rest of us. Plainly, many of us see it this way or you would not have gotten those PM's you mentioned.

I guess you cannot figure out that a PM is usually a polite way of telling you that you are wrong and giving you a chance to make things right before being called out in public by someone.

I find the quoted comment utterly offensive and a direct violation of the ROE here. Be the Gentleman and do the right thing.....remove it...and apologize.


3.0 Conclusions

3.1 Findings as to Causes and Contributing Factors

Galling on a titanium attachment stud holding the filter bowl assembly to the main gearbox (MGB) prevented the correct preload from being applied during installation. This condition was exacerbated by the number of oil filter replacements and the re-use of the original nuts.

Titanium alloy oil filter bowl mounting studs had been used successfully in previous Sikorsky helicopter designs; in the S-92A, however, the number of unexpected oil filter changes resulted in excessive galling.

Reduced preload led to an increase of the cyclic load experienced by one of the titanium MGB oil filter bowl assembly attachment studs during operation of CHI91, and to fatigue cracking of the stud, which then developed in a second stud due to increased loading resulting from the initial stud failure. The two studs broke in cruise flight resulting in a sudden loss of oil in the MGB.

Following the Australian occurrence, Sikorsky and the Federal Aviation Administration (FAA) relied on new maintenance procedures to mitigate the risk of failure of damaged mounting studs on the MGB filter bowl assembly and did not require their immediate replacement.

Cougar Helicopters did not effectively implement the mandatory maintenance procedures in Aircraft Maintenance Manual (AMM) Revision 13 and, therefore, damaged studs on the filter bowl assembly were not detected or replaced.

Ten minutes after the red MGB OIL PRES warning, the loss of lubricant caused a catastrophic failure of the tail take-off pinion, which resulted in the loss of drive to the tail rotor shafts.

The S-92A rotorcraft flight manual (RFM) MGB oil system failure procedure was ambiguous and lacked clearly defined symptoms of either a massive loss of MGB oil or a single MGB oil pump failure. This ambiguity contributed to the flight crew's misdiagnosis that a faulty oil pump or sensor was the source of the problem.

The pilots misdiagnosed the emergency due to a lack of understanding of the MGB oil system and an over-reliance on prevalent expectations that a loss of oil would result in an increase in oil temperature. This led the pilots to incorrectly rely on MGB oil temperature as a secondary indication of an impending MGB failure.

By the time that the crew of CHI91 had established that MGB oil pressure of less than 5 psi warranted a "land immediately" condition, the captain had dismissed ditching in the absence of other compelling indications such as unusual noises or vibrations.

The captain's decision to carry out pilot flying (PF) duties, as well as several pilot not flying (PNF) duties, resulted in excessive workload levels that delayed checklist completion and prevented the captain from recognizing critical cues available to him.

The pilots had been taught during initial and recurrent S-92A simulator training that a gearbox failure would be gradual and always preceded by noise and vibration. This likely contributed to the captain's decision to continue towards CYYT.

Rather than continuing with the descent and ditching as per the RFM, the helicopter was levelled off at 800 feet asl, using a higher power setting and airspeed than required. This likely accelerated the loss of drive to the tail rotor and significantly reduced the probability of a successful, controlled ditching.

The lack of recent, modern, crew resource management (CRM) training likely contributed to the communication and decision-making breakdowns which led to the selection of an unsafe flight profile.

The throttles were shut off prior to lowering the collective, in response to the loss of tail rotor thrust. This caused significant main rotor rpm droop.

The pilots experienced difficulties controlling the helicopter following the engine shut-down, placing the helicopter in a downwind autorotative descent with main rotor rpm and airspeed well below prescribed RFM limits. This led to an excessive rate of descent from which the pilots could not recover prior to impact.

The severity of the impact likely rendered some passengers unconscious. The other occupants seated in the helicopter likely remained conscious for a short period of time, but became incapacitated due to the impact and cold water shock, and lost their breath hold ability before they could escape the rapidly sinking helicopter.

[DOUBLE BOGEY]

"The pilots had been taught during initial and recurrent S-92A simulator training that a gearbox failure would be gradual and always preceded by noise and vibration. This likely contributed to the captain's decision to continue towards CYYT."


The pilots experienced difficulties controlling the helicopter following the engine shut-down, placing the helicopter in a downwind autorotative descent with main rotor rpm and airspeed well below prescribed RFM limits. This led to an excessive rate of descent from which the pilots could not recover prior to impact.

SAS - I have already made it clear that I did not mean to imply that Nick or JD were responsible for the above.................................

My point is that "the above" is the kind of inappropriate information that can directly lead to crews making mistakes. Stressing that in the case of S92 the investigators have only noted this was likely to have contributed. This is not about the S92. The old girl would have served the crew well no doubt had the crew been inclined to follow the procedures, but as your post suggest, even these were ambigous in this case.

SAS - CALLING FOR ME TO APOLOGISE

I will not apologise for implying that misleading pilots into the belief that the RPM can readily decay beyond the RFM limits is acceptable especially since this post was lodged in direct contradiction to the sound advice offered by Peter. I note that in doing so (see above) the horrible subject of decayed Nr and low airspeed seems to have eventually caused the loss of the crew and PAX in the S92. I wonder if that poor crew had had the benefit in hindsight of Peter's post whether they may have been able to fare better. Who knows.

I will apologise to all, including Nick and JD if any of you inferred from my posts that the misinformation stated above that you SAS posted kindly for us, had anything to do with them.

SAS the detail you have posted above serves only to remind us of the folly of listening too, being subjected to and following inappropriate advice and guidance especially when it is beyond the limits cleary stated in the flight manual. The limits in the flight manual are provided by the likes of Nick and JD, at significant personal risk to them, to keep us all safe. My respect for them and the work they do is implicit in my continued stated belief that we should follow the flight manual. That is my tribute to them!!

For John Eacott, thank you for recognising that I am capable of an apology when I am wrong. It does not happen often (being wrong) and hurts a bit so it took a bit of time to get back to you.

To SP - I hope now you can see the relevance of my posts and that my intent was not to link the TPs to the incident. It was the pirnciple of inappropriate information beyond the limits of the RFM.

To TC - now I know how it feels to be you!

DB

[SASless]

DB,

Let me refresh your memory.


John Dixon and John Eacott - the very fact is has taken you both a few posting to explain the numbers.......and then qualify that by saying you need to be close to the ground at low NR is testament to the utterly misleading and dangerous content of your posts.

Nick Lappos preaches "follow the RFM limitations"

No helicopter I am aware off has a power off limitation in the 60% range.

You cannot have it both ways.

Honestly I cannot believe the stupidity of such posts that seem determined to disprove what has clearly been proven on so many occasions with extensive loss of life. Quite possibly again at Glasgow.

I have a high regard for test pilots but the crap spouted on this last few pages makes me seriously wonder f that regard is misplaced.

Maybe Peter is right when he says "Cyclic Back" is a secret. You lot seem oblivious to its merits.

FYI - LOW RPM AT HEIGHT IS A STONE COLD KILLER. All helicopter pilots know this and every one should be taught how to avoid and recover from this situation.

Talking numbers beyond that published in the RFM and clearly printed on the NR gauge demonstrates that you know the price of everything and the value of nothing. This chest beating arse was responsible for the demise of the S92 in Newfoundland! Rubbish beyond the content of the RFM spouted by people who should know better.

DB

Do enlighten us as to who you think the "Chest Beating Arse" is that is responsible for the demise of the S92 in Newfoundland?

After you do....upon what evidence do you base that plainly held belief?

That is the comment I am holding you to account for....and shall continue to do so until you accept the impropriety of that.

[DOUBLE BOGEY]

SAS - I have said all I am prepared to say on this public forum and adjusted my position to remain within the scope of the NTSB report, which in hindsight is where it should have always been and for that I thank you.

I will say nothing more on this subject. To do so would be inappropriate and will not serve the prime purpose of my original post which, seeing as you seem to be constantly missing the point, is as follows:

Inappropriate information transmitted from credible sources can be dangerously misleading.

If you do not agree with this statement then I cannot help you any further.

DB

[SASless]

DB......who is the "Chest Beating Arse"you refer to.....that is the objectionable part of your post that demands explanation.

You continue to refuse to even acknowledge you said it.

Be a Man....not a Weasel.....explain yourself or admit you were wrong for saying such a thing. As you have said several times to others...."You can't have it both ways!"

[Lonewolf_50]

I love that phrase! True or not, it represents the content of many of the posts in this thread, helicopters are apparently flying on the edge of the performance envelope quite frequently. If that is the case, then relatively small changes in density altitude, humidity and temperature could have quite large effects on the performance of helicopters and particularly so with relatively low powered, low rotor inertia helicopters.
Helicopter flying isn't for the faint of heart. :p It's great, though. Give it a try.

Pete: Note that I say "Cyclic back and collective (lever) down simultaneously, or in that order." It is simply wrong in my opinion to prioritize the collective ahead of the cyclic, especially if one's left hand is not on the collective. This would mean not moving the cyclic until the left hand could find the collective and lower it. This would be a huge mistake I understand your point. As I pointed out earlier, and you seem to agree, the control inputs by either hand are not necessarily serial, they can be done together. The way you assert that one would NOT use the cyclic if one is not at the moment holding the collective strikes me as contradictory to that point.

Control Nr: that is the prime directive.

I may get slammed for saying this, but perhaps you gents in the civil sector could review what it means when the pilot says "I have the controls" or when there is only one pilot, just who has the controls, and what that means.
Like TC, I was military trained. You remove your hands from the controls, if ever, very briefly to do things like switch radios, write on kneeboard, copy clearances, etc. Then, your hands are on the controls if you are the pilot flying.
Please explain why this is not what you teach. Or did I misunderstand you? If so, apologies up front.
I realize that there are a lot of automation and autopilot features, but resting your hand on the controls while the aircraft is flying with automated assistance is not a taxing thing. I've done it plenty on those hours long drone-a-thons as radar or ESM picket, airborne, one each.
TC:
We (and the convertees) were taught to keep our hands on the controls as much as possible and never be too far away from the collective. But I do understand the impracticalities of keeping your hand on the collective always.
Agreed, but it's back on after a brief excursion.
I'll ask any of the experienced pilots and instructors here: how many fractions of a second does it take to get a left hand not on the collective back onto it to manipulate it?

Pete's point about 'not waiting' to control Nr with cyclic if necessary is a good one, if one is caught out ...

GF:
The multi-engine pilot response to a power failure is therefore slightly delayed (in principal) to that of a single engine pilot.
Really? When you get a power loss, do you always know it's only one engine when you are in a twin? Control Nr.
This delay is compensated for to some extent by the relatively low risk of double engine failures in twins.
No, it isn't, since the word you used there "compensated" has nothing to do with flying and engine failures. It may have to do with risk calculations and insurance actuarials.
With twins there are additional considerations, principally the second engine, and specifically determining which one has failed. The multi-engine pilot response to a power failure is therefore slightly delayed (in principal) to that of a single engine pilot.
Not quite. Single or twin, the correct response is: Control Nr, fly the aircraft.
This delay is compensated for to some extent by the relatively low risk of double engine failures in twins.
I'd say your reasoning has nothing to do with flying, and makes twin engine helicopter pilots out to be idiots.
I can't buy your line of reasoning.

Do you fly helicopters, GF? :confused:

[awblain]

Gouli & Lonewolf,

Having lightweight rotors - which is effectively all low-inertia means, give or take some ability to pull some mass inwards through clever composite structures - isn't necessarily a bad thing.

It does reduce the amount of energy stored in the rotor, potentially allowing it to winddown more quickly.

On the other hand, it saves fuel by having of order 100kg less to carry around, allows a quicker acceleration of the rotor with changes in power/airflow at low pitch should it get slow, makes debris a little less dangerous in the event of it coming into contact with something, and provides less gyroscopic restriction on the motion of the aircraft. By reducing the rotor mass, all of the bearings and shafts can also be made lighter, making the whole system more efficient. When there's not a huge overabundance of power available, as you say every 50kg counts.

[Lonewolf_50]

Gouli & Lonewolf,
Having lightweight rotors - which is effectively all low-inertia means, give or take some ability to pull some mass inwards through clever composite structures - isn't necessarily a bad thing.
Thanks for your post. I am modestly familiar with the weight bogey chased by aircraft design engineers, and chased^2 by helicopter design engineers! :8

@ chopjock:
About your RC drones (http://www.pprune.org/rotorheads/529796-entering-autos-discussion-split-glasgow-crash-thread-15.html#post8211530)...

Please look up the term "scaling" as it relates to design.

Also for your consideration: on all of the helicopters I flew, we had in the maintenance manual seasonal adjustments for autorotative Nr as a factor in control rigging. Each maintenance check flight I ever flew had at least one autorotation within a test profile, which was matched against GW, conditions of the day, and compared to the performance marks in the manual. A slight lengthening or shortening of control linkages were sometimes called for to get it right.

If you start messing about with control linkages to get negative pitch, you can run into some unintended consequences.

This was over 20 years ago, but I cannot forget an example in an SH-2.
I learned that a misrigging could create ground resonance due to "flat pitch" (no, not quite flat) trying to slightly pull the helicopter into the ground. We noticed it due to the wheel struts being compressed and the bird beginning to shake a bit. Shut down, worked with maintenance, and a few control rigging adjustments were made to remedy that error.

Your idea on pitch changes and rigging is likely to have undesireable outcomes.

[DOUBLE BOGEY]

SAS, my definitions in the context they were used:

CHEST BEATING

Making technical statements just to prove ones own knowledge - I am guilty of this too.

ARSE

The pointless nature of the content. Not the man saying it!
(as in........a load of arse!) - My wife reckons I spout a lot of this.


I really hope you did not think I was calling JD an Arse!! If my grammar led you to think that then of course I will apologise immediatley to you and JD.

I hope we have cleared that up!!

[Lonewolf_50]

DB: your missus probably also told you "when one has dug one's self into a hole, it is usually best to stop digging at some point." :}:cool::ok::hmm:

[DOUBLE BOGEY]

Lonewolf - I have dug no hole. I stand by what I have said. When people make statements about capabilities beyond that published in the flight manual is, and always will be "ARSE".

Surely even you lot can form sufficient metal dexterity to form the link between:

This:


This chest beating arse was responsible for the demise of the S92 in Newfoundland! Rubbish beyond the content of the RFM spouted by people who should know better.


and this:



"The pilots had been taught during initial and recurrent S-92A simulator training that a gearbox failure would be gradual and always preceded by noise and vibration. This likely contributed to the captain's decision to continue towards CYYT."


and this:


The pilots experienced difficulties controlling the helicopter following the engine shut-down, placing the helicopter in a downwind autorotative descent with main rotor rpm and airspeed well below prescribed RFM limits. This led to an excessive rate of descent from which the pilots could not recover prior to impact.


and the merits of Peter Gillies posts.

If advocating that we follow the limits in the Flight Manual and stop making claims beyond those limits.....is digging a hole then I will gladly dig.

There is none so blind as those that cannot see!

[Lonewolf_50]

... advocating that we follow the limits in the Flight Manual and stop making claims beyond those limits.....is digging a hole then I will gladly dig.
Since I didn't see anyone advocating not following the Flight Manual ... I see just fine, thanks. :ok:

Example:
If you bop on over to the V-22 discussion thread, and the back and forth about VRS, someone posted a link to the test flying done by test pilots, at altitude, who discovered a few things about how the bird reacts to VRS. That isn't something that goes into the flight manual "hey, go do this!" but it is useful information to understand the limits of a given airframe and a further admonition to do as the Flight Manual says, which is avoid to VRS. There is no harm in posting that.

Likewise, what John commented on regarding about where the engineers estimated the point of no return being for a helicopter he did some test flights on, I see that as further caution to make damned sure one doesn't even approach that region of Nr, but instead keep the Nr in the green.

With the various points made on how dire it is to reach that point of no return, I suppose the Flight Manual could include a memory item:
If Nr is now stalled, recite out loud as follows:
Our Father, who art in heaven, hallowed be thy name ...

But the point is not to get there.
Control Nr. Fly the aircraft.

[Thomas coupling]

DB: You're losing ground buddy. I had an element of support for you even before this debacle with SAS and JE - even when you were slagging me off left right and centre. But now it's fading fast.
For some reason you won't admit the error of your ways either in what you have said or how you practice your trade (denying the first rule of flying: keep the rotor in the green by lowering the lever first).
Are you so proud a man that you can't take the hit? Are you afraid of what people might think of you if you are wrong? Accepting you are wrong is what makes the man - no? [And before you start, I have openly admitted my misgivings on several other threads as much as I hated it. It comes with the territory :{].
C'mon, give it a try....we'll still like you afterwards - ish :E You might even feel enlightened..................

[helifreddy]

Hello @ all.
I am a retired :) helicopter pilot who worked 35 years as IP in twin engine helicopters and have some EC 135 experience too.
What we trained in cruising flight, safe altitude, was:
In case of visual/audio warning of OEI or Low NR:
Lower collective immediately,aft cyclic to maintain RRPM and to reduce airspeed to Vy (60-65 KIAS).
During this manoeuver check RRPM and N2 Rpm of both engines (other indicators and WL too).
If OEI, pull collective to continue single engine,shut down proc.for failed engine.
If AEI, continue in the AR,follow autorotation procedure.

In regard to the low RRPM,I demonstrated max.range in AR with RRPM minimum (red line).If RRPM would be much lower,its true,it will not recover anymore. But I think it should be more than 5% below minimum.
For the crash in Glasgow I have no explanation at the moment.
I think we have to wait for the accident report.
Fly safe and best regards.

[Grenville Fortescue]

Lonewolf 50

Firstly multi-engine pilots are not "idiots" in my view and, while how you arrived at such a conclusion may be fascinating for some, it holds no interest for me. The comment itself was delusive and the connection, however made, does not reflect my own belief. Secondly, my career is well known among those with whom I have served and I feel no obligation, or interest, in qualifying this to you. My comments will stand or fall on their own merit.

My observation is based on the fact that in multi-engine operations (MEO) the process of response to an engine failure contrasts with that practiced in single engine operations. This contrast centres about the need to verify the engine failure in MEO and which process involves steps which (for the previously stated reasons) are unrequired in a single.

This consideration accounts for how it may be possible to encounter a delayed response to the control of Nr in a double engine failure scenario in a twin engine helicopter (something I have witnessed numerous simes in the sim). Bleating on about Nr control is irrelevant in this context because my previous comments presuppose this as a trained response. In other words, Nr control in response to a total loss of power, is axiomatic, or supposed to be, and which was (for me) not the issue. It is what tends to happen before Nr is controlled that I am highlighting.

If you cannot appreciate that in MEO there is a need to "verify" the malfunction (not at the expense of responding to Nr control, but which consideration in the specific scenario mentioned may in fact lead to just that) and that this same process of verification is more readily accomplished in singles, then clearly there is nothing more I can say to help you appreciate my observation.

[TorqueOfTheDevil]

Lowering the lever first will NEVER be a bad thing (unless you are in a low hover - the exception to prove the rule) because it will prevent further Nr Decay.


The other exception is LL cruise flight, where dumping the lever may put the aircraft so low that it's impossible to flare without striking the tail. Hence the UK mil teaching which is (I understand) to prioritise flaring on entry to a LL EOL.

[Nubian]

TC,

Just the kind of response I had expected from you.

My observation was that ALL those people injured/killed and all those cabs damaged will almost certainly NOT have happened OUTSIDE the damn H/v curve. It is BECAUSE you work inside the curve that these 2 dead people and 5 serious has happened - DUH!

Say no more.

:ugh: or in your own educated way, DUH!

Anyways, get well soon!

[DOUBLE BOGEY]

Dear Nick,

For some inexplicable reason PPRUNERS have formed the impression that I somehow blame you for the S92 crash. This is due in most part to my indvertant link to the detail in the NTSB report intimating that the crew training may have led them to beleive that they could continue beyond the safe haven of the RFM limitations and procedures.

If you have this impression from me it is not true and if I have somehow implied that I apologise completley.

Reading back through your posts You and I preach the same thing. Follow the bloody flight manual.

I may have made a mistake attacking John Dixons post about low NR but I really beleive when you guys speak...it matters and people listen.

I worry about posts that suggest there are alternative values to minimum NR and of course I am not naive enough to realise that there is a safety margin, thanks to the efforts of you guys. However there is a continued danger present when values are quoted beyond true capability.

DB

[Devil 49]

DAPT said:

"Robinson video vs UK military primary training
The explanation and graphic video is the best way to understand how a helicopter can drop like a stone with rotors not turning.

The only way for that to happen is delayed entry into autorotation it does not matter where you received your training."

There are other factors that could make the autorotation a hopeless maneuver- control rigging, for example. Once flew a fleet spare (twin) on an autorotative check that wouldn't maintain NR in the green as I pulled power back in an established AR profile. Don't know how low it would have fallen with with further power reduction.
How often do you check yours?

[rotorfossil]

Ref cyclic first or lever first. Bearing in mind that there are occasions when aft cyclic first is perfectly acceptable and others when it definitely isn't, such as in the climb, on the approach or at any time when the speed is low, it has always seemed to me that the best teaching is to lower the lever (damn quick) and INITIALY maintain the pitch attitude with the cyclic.When you have decided what you want to do next, like increase speed to increase range or reduce speed to lose it, THEN change the attitude appropriately.To try to teach different initial reactions when the priority really is to get the lever down is not likely to succeed. History seems to indicate (particularly in low inertia types such as the R22) that people who lower the lever, whatever else they do, generally live, but people who don't, die.I agree that in the special case of engine failure in a single at high speed and just above the avoid curve, both together seems to work.

[Lonewolf_50]

GF:
It's the way you wrote it. I didn't find your mixing systems level risk assessment with actual flying in response to a power loss (twin or single) to be a lucid way to frame your position.

I have flown both singe and dual engined helicopters. The advantage to having two engines is that sometimes, when you have a loss of power, you have a second engine to help you do something other than fly that auto down to the bottom. Fly it, which means control Nr first, and then see what your engines are giving you. If it's your good day, you can use the good engine to fly you home. If it's your bad day, you are flying as you should be and have a chance at a decent auto all the way down. (and on your really good day, you have some altitude and time for a possible restart, depending on why the engine stopped. The whole time you are figuring this out, you are controlling Nr, flying the bird. Helo pilots can multi task ... it's in the nature of helicopter flying).
It is what tends to happen before Nr is controlled that I am
highlighting.
Really? Are you telling me that you don't teach that control Nr comes first? (Say it ain't so).
Even with a partial power loss, or a compressor stall in one engine, or a roll back in one but not both engines, the First step is Control Nr
and the implied associated first step is fly the aircraft.

Time delay in acting is another topic.

Nothing further. Out.

[PeteGillies]

Thank you for your comments, Gouli. No, I do not advocate making any extreme yanking-type movements of the cyclic. But any delay at all in applying aft cyclic can be critical because this is the ONLY control movement that will lead to stopping and reversing the falling rotor rpm. The movement should be as instant as possible and done so there is no doubt that positive g's are being applied to the airframe.

When drive to the rotor system is lost, the rotor rpm begins to fall instantly and the reduction of lift causes the nose of the helicopter to fall, or pitch forward. This in turn acerbates the problem of air coming through the rotor from top to bottom. This along with the drag of the blades and gearbox, etc., is causing the rotor rpm to fall. Add to this the negative g's applied by lowering the lever which also increases the downward pitch of the airframe and rotor, and you can see where this is going.

Applying aft cyclic quickly is the ONLY way to reverse this chain of events.

THIS is the critical situation that Cyclic Back addresses.

Two posters have said that aft cyclic should not be applied during a climb. A vertical climb, no, but in every other type of climb, YES! Why? Because indicated airspeed is of NO VALUE AT ALL at the moment power is lost. The ONLY airspeed that matters at that moment is the airspeed over the wings, which, of course, means the rotor blades. Cyclic Back done in time will catch the rotor rpm before it drops to the critical point. NOW you have a flying machine and can then dial in whatever airspeed you'd like, but be careful when nosing over because the rotor rpm you've just saved will disappear in a heartbeat if you push over aggressively. Keep an eye on the rotor tach as you lower the nose to gain speed.

In the case of the two law-enforcement accidents I investigated, the pilots said they lowered the lever the moment the engine failed and then immediately applied forward cyclic to gain airspeed. Both of these accidents happened when the helicopters were on a routine climb at about 400 ft. agl and somewhere between 60 and 80 knots. The rotor blades were barely turning when the ships hit the ground. Damage to the blades was "downward" bending, not damage associated with the blades turning and hitting something hard. Both ships burned. Both crews survived but barely. One blade from one accident showed NO DAMAGE AT ALL per the NTSB report. And both ships crashed badly on the left side, the pilot's side.

The application of aft cyclic in time would have given both pilots a controllable helicopter all the way to touchdown. But instead they were just along for the ride. This was not pilot error! They had never heard about Cyclic Back. Both were high time and one was former military.

Pete Gillies

[TorqueOfTheDevil]

this is the ONLY control movement that will lead to stopping and reversing the falling rotor rpm


Pete,

With respect, that's not considered to be correct in UK (mil) teaching - which I believe still includes a demonstration of Nr decay caused by rolling the (only) throttle to idle in the cruise, and doing nothing with the controls. The recovery from the ensuing rapid Nr decay was always to lower the lever to prevent further decay, then flare to restore the Nr. Perhaps someone currently active at Shawbury can confirm?

TOTD

[Lonewolf_50]

Pete: a few points from you explanation:


The movement should be as instant as possible and done so there is no doubt that positive g's are being applied to the airframe.

The ONLY airspeed that matters at that moment is the airspeed over the wings, which, of course, means the rotor blades.
... catch the rotor rpm before it drops to the critical point. NOW you have a flying machine and can then dial in whatever airspeed you'd like, but be careful when nosing over because the rotor rpm you've just saved will disappear in a heartbeat if you push over aggressively. Keep an eye on the rotor tach as you lower the nose to gain speed.
Depending on the situation you are in, a little turn while you are lowering the nose if you are adjusting airspeed can load the head a bit and keep the inertia from bleeding off ... but as that's situation dependent, in terms of where you are trying to land, a "hard and fast rule" on that might do as much harm as good.

I am beginning to appreciate a deeper side to your crusade: if your Nr is in the green and your airspeed ends up a bit low, you have some seconds where you can try to make an adjustment, whereas if you end up pushing down for airspeed, particularly in a low inertia head, the Nr decay from unloading the head may leave you where you are not able to make an adjustment since those wings aren't flying anymore.

As with a few more % Nr near the bottom ... in which direction would you rather be in error? In that light, your PoV and your emphasis on keeping the head loaded, with the cyclic, is a bit clearer.

Also: Thanks for your further explanation of the mishaps you investigated. :ok:

[Grenville Fortescue]

Lonewolf

I think there is an issue of context.

In my earlier post I was surmising as to those possibilities which exist which could have accounted for why an experienced pilot might delay in his response to controlling Nr. It was (and is) within this context that I am highlighting what I originally described as a mindset among multi-engine pilots which (for the right reasons) will seek clarification of an engine failure for the very purpose you stated "to help you do something other than fly that auto down to the bottom."

Nr control is what is required, most especially in the case of a double engine failure, but I am suggesting that on a "bad day" as you put it, it may be possible for a pilot to unintentionally delay their response to Nr control (for the reasons given), particularly if they have the hope/expectation that one engine remains operative and particularly if they do not want to sacrifice height.

[Lonewolf_50]

Thank you, sir, for the clarification. :ok: If I read something into your initial points, the fault is mine.

Cheers.

[FH1100 Pilot]

It's funny. Pete Gillies obviously "gets it" while some of you clearly don't.

Please let us all understand that Pete did not mean that we should emply "Cyclic Back" when the ship is in a hover. Puh-leeze. He obviously meant that it should be used during forward flight, which is what we're talking about here, right? I mean, no one was suggesting (and witnesses agree) that the Glasgow a/c was not in an OGE hover when that something bad happened.

And Pete is right.

TC says:...one can NEVER ever make the statement: aft cyclic first and then collective. But one can ALWAYS say: collective first and then cyclic. Because of this - I stand fast with this ethos.

Wrong. Just plain wrong, at least as far as forward flight is concerned, "Aft cyclic first" works. "Collective first" can be deadly.

Say you were cruising along at 500' agl in your Astar or 206 or 500...or even your S-76. This is a not-uncommon scenario. Most helicopters cruise with the tip-path plane at a low-to-negative angle of attack vs. the relative wind. Now the engine quits unexpectedly. If you dump the collective first, before making an attitude adjustment the nose will drop and the helicopter will begin a descent. Now you start coming back with the cyclic; will you arrest the descent? Probably not. You've severely handicapped yourself.

In the same scenario, if you quickly bring the nose up first (even before doing anything with the collective), you're getting the relative wind under the disk (which you need) and at the same time loading the rotor to increase RPM. A happy result is that the helicopter might not even begin descending as it decelerates to best-auto speed. "HC" understands this. "H-500" understands this. They get it.

This is what Pete Gillies is trying to communicate to you. It is surprising-bordering-on-shocking that so many of you seem to not only not understand it, but some even disagree!

It would be nice if all helicopter pilots always had their hands on both controls so that the response to a complete power failure would be an immediate, coordinated reduction in collective pitch with a corresponding raising of the a/c pitch attitude. But that's not reality. We rest our cyclic hand on our knee. But you cannot "rest your hand" on the collective without eventually pushing it down unless there's sufficient friction applied to keep it from moving. Keeping your hand on the collective all the time is a fatiguing way to fly when there's no one else in the cockpit to take the controls and give you a break once in a while. So we rest our collective hand on our (left) knee too.

"Collective first" is fine if you're already back at best-auto speed, with the disk level. (But even so, "cyclic first" won't be harmful as long as you don't hold that attitude until all your speed goes away.) But in cruise, with the main rotor tilted forward...I dunno...you've got to get the angle of atack of the disk up.

I'm firmly with Pete: In forward flight, "cyclic-back-first" is never wrong. And I'm proud that he's got the guts to go against the conventional wisdom of the (self-appointed) so-called experts on this board.

[HeliComparator]

GF and Lonewolf - I think there may be a disconnect here due to the cultural differences in how twins are operated. In the USA, as far as I am aware there is little concept of performance. If you go OEI you may or may not fall to earth, so you might as well just be in a single. Here in the UK we operate PC1 or 2, at least when we have passengers, and so the expectation when having an engine failure is that the flight will be continued. I am obviously on GF's side here, the multi pilot will not and should not react to an engine failure by dumping the collective, but as GF says that does create a probable longer reaction time to a simultaneous double engine failure. You would for example be considered a complete plonker if you went OEI coming off a rig in the N Sea, dumped the collective to enter auto and ended up in the water, when you could easily have flown away OEI. The correct response to an engine failure just on rotation from offshore (highly unlikely as that is) is to not move the collective for the couple of seconds it takes for the tail to clear the deck edge. Any significant lowering of the collective at that point is likely to wipe the tail of and result in fatalities.

You can argue until the cows come home about whether this is the right or wrong way to operate, but for the time being that is how it is over here.

[Grenville Fortescue]

Lonewolf

HeliComparator understands very well my perspective and which I partly summarised in my original post when writing:

However, on those rare occasions when a double engine failure occurs, it is possible to see how a multi-engine pilot may not instantly take the required action in the same way as a single engine pilot would, and for the right reasons, because the multi-engine pilot must assess the nature of the power failure, even if it is to determine that both engines have failed. In a single, any sort of interruption to powered flight is not only obvious but it is equally obvious that there is no recourse (ie. only one possible action to be taken). This is not the "normal" mindset of a multi-engine pilot who will be trained to recover from a power failure with partially powered flight from the remaining engine.

[HeliComparator]

Just a thought... Regarding emergency auto entry from cruising flight, we seem to be stuck somewhere between dumping collective then thinking about the cyclic afterwards, dumping the collective and maintaining the attitude, simultaneously dumping the collective and moving the cyclic back, and leading with the aft cyclic prior to moving the collective. One of the problems with "maintaining the attitude" is that, with a large and rapid movement of the collective comes a significant attitude upset (more so in some types than others) and to apply the correct amount of cyclic to maintain the attitude is not that easy especially bearing in mind the rapidity of the effect of dumping the collective vs the relatively slow response in pitch attitude to cyclic being fought by a SAS, muddied by probable yaw and its own effect on pitch attitude.

Therefore my suggestion is that the pitch attitude is not the thing to go for. It is hard to judge accurately under dynamic conditions (think IMC), you have to be looking in the right place when really you want to be looking at the Nr gauge, and ultimately it is not an important parameter. What is important is the restoration of Nr and there is one primary parameter that affects this (other than collective pitch) and that is g loading.

G loading is also very easy to assess - the body is pretty good at it. So what we need to do is to aim for at least 1 g, maybe a little more, in the first moments after a double engine failure is recognised.

Therefore my recommendation in the event of a need for emergency auto entry, is to lower the collective whilst moving the cyclic back to maintain at least 1g. If 1g or more is maintained, there will be little or no height lost in the first moments which satisfies those flying fast near the ground. Since the responsiveness of the cyclic depends on current g, leading with the collective will instantly reduce g and make it harder to regain it with cyclic. Therefore it is necessary to lead with cyclic, so as to maintain 1g or more throughout the early stages of entry.

I'm sure this is what we actually do, but I'm not sure anyone has vocalised it yet?

To reiterate, all this from cruising flight. As you can tell, I remain in full agreement with PG!

[SASless]

In the USA, as far as I am aware there is little concept of performance.

Company SOP's differ between the GOM and the North Sea do they?

Same company....same aircraft.....some kind of task....but different Standards?

Sometimes i wonder how we ever manage to survive in the USA....considering just how little we seem to know about helicopter flying as thought by some here.

HC....there is a huge difference between "Knowing" and "Doing"....and some Operators might ignore the EASA concepts of PC1 and all that....or as in the old days....Cat A.

But oddly, times do change even in the good ol' USA.

[Grenville Fortescue]

What is the unchecked longitudinal effect, in terms of pitch, on an airframe in level flight which suffers a double engine failure?

[PeteGillies]

Thank you, gentlemen. In reviewing the many posts I see several that claim lowering or bottoming the lever will stop the rotor rpm from decreasing. This is not true! This action does nothing more than reduce the rate at which the rotor rpm is falling. Period! It will continue to fall unless aft cyclic is applied in time to keep the rpm above the critical point.

Yes, with the rotor somewhere in the green, a turn during the descent will increase the rotor rpm, and this can be very handy when maneuvering to make a spot and will help keep the rotor rpm happy.

With the rotor rpm in the green, the helicopter can do any maneuver it can do with the engine(s) running except a sustained climb (from my initial post). As for picking a spot to land, I emphasize picking one that's too close. The pilot can handle too close, too high and too fast. Those are wonderful things to have. The opposites are not (too far away, etc.). And descending vertically works beautifully, especially if one has lots of altitude to get rid of. The high rate of descent is not a problem at all and the helicopter responds to all pedal and cyclic movements needed to keep the landing spot in full view of the pilot. A smooth forward movement of the cyclic quickly returns the descent to normal for the autorotation. I definitely prefer vertical descents to S turns or 360s. Keep the spot in view during the descent if at all possible. Ah, don't get me started on the mode of flight the helicopter prefers if given a choice... Think I'm kidding? Just ask your helicopter. It will answer that if you could fly all the time with the engine(s) not running, it would be wonderful!

My comments are directly aimed at the utility pilot doing field operations, not flying around the aerodrome or the practice area in a relatively sanitary training environment.

As for responding to falling rotor rpm in a twin, I think it is a huge mistake to do any troubleshooting before bringing the cyclic back and lowering the lever. Move the controls first, and THEN do the troubleshooting. The drive shaft failure in Twin-Pac powered machines is an example. Even if it is the failure of one engine, applying aft cyclic and lowering the lever a bit can help the remaining engine pick up the load.

It's time again for me to express my appreciation for the support of my efforts to make Cyclic Back a part of all training and publications everywhere.

Pete Gillies

[PeteGillies]

To FH1100 pilot...THANK YOU, THANK YOU, THANK YOU! You put it perfectly!!

Pete :-)

[SASless]

In reviewing the many posts I see several that claim lowering or bottoming the lever will stop the rotor rpm from decreasing.

This is not true!

This action does nothing more than reduce the rate at which the rotor rpm is falling.

It will continue to fall unless aft cyclic is applied in time to keep the rpm above the critical point.

Pete,

Every time I am about to agree with you....making some allowance for wording.....you throw me another curve ball.

Are you saying a fully bottomed Collective, in fully established Autorotation (in a properly rigged helicopter), will not result in a safe Rotor RPM......and that the only way to achieve a safe Rotor RPM is by use of a decelerative maneuver using Cyclic?

You say the RPM will fall until it reaches the "Critical Point".....are you saying the "Critical Point" is where the Rotor can no longer be driven by air moving upward through the Rotor System and thus the Rotor will continue to decrease in RPM till it no longer facilitates an autorotative landing?

Answer a few other questions please.

Every Aircraft Type Maintenance Manual has a procedure for calculating and checking for Autorotational RPM.

As part of routine maintenance and checking for air worthiness....that Check is done using the approved procedure.

The Target RPM always falls within the authorized Power Off RPM Limits set forth by the Manufacturer of the Helicopter.

That Target RPM is not the "Critical" RPM that has been discussed here in the definition of the RPM at which loss of rotational drive in autorotation is lost.

As I read your post quoted above.....I interpret it to say a properly rigged Helicopter will never stabilize Main Rotor RPM in a steady state Autorotation.

Am I not understanding what you are trying to say?

[HeliComparator]

SAS - Putting my merry quips in red into your post:

Company SOP's differ between the GOM and the North Sea do they?
Of course, you don't think we would want to fly crazy like you do over there?
Same company....same aircraft.....some kind of task....but different Standards?
Yup, and your point is?.... But of course in reality, not the same aircraft in general - you are happy to fly folk around over the ocean in singles!
Sometimes i wonder how we ever manage to survive in the USA....considering just how little we seem to know about helicopter flying as thought by some here.

Fortunately there are a lot of you to start with.

HC....there is a huge difference between "Knowing" and "Doing"....and some Operators might ignore the EASA concepts of PC1 and all that....or as in the old days....Cat A.

But oddly, times do change even in the good ol' USA.

Yes I think they are actually, but only in the last few years. Certainly when the "globalisation" of Bristow was going on, maybe 10 years ago max, S76 was being operated GoM without any concept of OEI performance. Not sure if LW has caught up with that concept - seems not from his postings.

[HeliComparator]

...and again...


Are you saying a fully bottomed Collective, in fully established Autorotation (in a properly rigged helicopter), will not result in a safe Rotor RPM......and that the only way to achieve a safe Rotor RPM is by use of a decelerative maneuver using Cyclic?

...

Every Aircraft Type Maintenance Manual has a procedure for calculating and checking for Autorotational RPM.
Stabilised at 1 g

As part of routine maintenance and checking for air worthiness....that Check is done using the approved procedure.
Stabilised at 1g

The Target RPM always falls within the authorized Power Off RPM Limits set forth by the Manufacturer of the Helicopter.
When stabilised at 1g

As I read your post quoted above.....I interpret it to say a properly rigged Helicopter will never stabilize Main Rotor RPM in a steady state Autorotation.
It will, but entry into autorotation is not a steady state. It may be that by the time steady state is reached, rrpm has fallen too far and the steady state becomes one of a brick.

Am I not understanding what you are trying to say?
Obviously not!

[Lonewolf_50]

HC:
Well, if I had said "DUMP COLLECTIVE" we'd be having a different conversation. I did say "control Nr" which may mean lower the collective a little or a lot or to the bottom, whatever it takes (your eyes going to Nr in parallel, not in serial) and likely your cyclic probably giving slightly aft pressure, as you don't want to dump the nose ... anyhoo, let's not argue with what someone didn't say, alright?

Pete:
Move the controls first, and THEN do the troubleshooting We are in violent agreement.
HC:
The core point on keeping the head loaded, versus unloading it, seems to be the core point of agrement, about which the disagreement seems to go round and round. If one delays lowering the collective (be it a little or a lot) and thus keeping pitch on the blades, the decay of Nr seems a foregone conclusion.

Pete:
Collective full down, with an Nr above the stalled Nr, I would expect to see Nr stabilize at the rigged Nr when descending at the usual autorotational airspeed (a range of values for any helicopter).

And as HC repeats what I raised earlier, we seem to actually be in violent agreement: you don't move the controls independently of one another, you tend to work them together ... and keep the lead loaded so it will perform as you more or less expect it to in re its autorotatoinal properties.

What Pete's short summary on those mishaps points to is people unloading the head in a hurry and perhaps not realizing that they are unloading the head ... and thus changing the nature of the airflow and AoA through the rotor system.

I note in your latest, Pete, that you have refined your point to a particular regime of flying where there is not a lot of stored energy in terms of arispeed to trade for Nr. With your crusade aimed at a particular flight regime, and given what else you have shared, it makes it clearer what informs your concerns in the first place.

Bombing along at max range airspeed (and with a lot of knots to trade for Nr) is a different case, though perhaps the Mosby crash serves as ample warning that one cannot be complacent. :eek:
HC
maybe 10 years ago max, S76 was being operated GoM without
any concept of OEI performance. Not sure if LW has caught up with that concept - seems not from his postings.
You lot were a couple of decades late to the show, seems to me. :p

As I don't fly, nor ever flew the S76, why was that crap tossed at me?
In the twin engine helicopters I flew, we had separate performance charts for SE operations. SEAS was a critical T/O (reaching and passing) and Approach (going below) call out in the cockpit. Gee, I wonder why we did that, flying off of small deck ships. Care to share your pet theories? (Where is a sarcasm smiley when you need one?) We also had to practice, over and over, single engine landings to a spot at constant descent angle. Gee, I wonder why we did that? :rolleyes:
Started for me in about 1982.

[SASless]

HC....we live in a 1G world don't we.....anything over that is not a normal situation.....or is gravity more intense where you live?

Perhaps your control touch left you thinking a 1G+ feeling in your hind end was normal?

Care to offer a serious answer to the questions?

[HeliComparator]

HC:
As I don't fly, nor ever flew the S76, why was that crap tossed at me, HC? In the twin engine helicopters I flew, we had separate performance charts for SE operations. SEAS was a critical T/O (reaching and passing) and Approach (going below) call out in the cockpit. Gee, I wonder why we did that, flying off of small deck ships. Care to share your pet theories? (Where is a sarcasm smiley when you need one?)
Started for me in about 1982.

It was tossed at you because you don't seem to "get" the fundamental difference in mindset between a single engine pilot and a multi engined pilot on this side of the pond. S76 was just an example of twins that I know to have been flown in GoM without adequate performance to land offshore or return home on one engine - if one engine failed, a controlled ditching was considered quite acceptable (and I don't just mean during To/LDG exposure period).

Wading through a lot of waffle and bickering on this thread, I do think this point may be critically relevant to the original topic (135 accident, in case we have forgotten!)

[HeliComparator]

HC....we live in a 1G world don't we.....anything over that is not a normal situation.....or is gravity more intense where you live?

Perhaps your control touch left you thinking a 1G+ feeling in your hind end was normal?

Care to offer a serious answer to the questions?

Do you really not "get" that when you rapidly lower the collective in response to a complete loss of engine drive, without moving the cyclic, the g will fall to near zero or even below if you are in the cruise, and thus the Nr will continue to decay despite collective on the floor. Scary if so. I do hope you are just being obtuse!

[hillberg]

Pete is 100% on the money, Aft cyclic in forward flight will delay RPM decay even with a delaied lowering of collective! Army/NASA tests on Rotor RPM on the low side with the Bell OH 5 found powered flight to 70% & no recovery without power posable. parachute required.
Bash & trash all you want that's pride messing with you.
(Still remember that 500 with the log stickin out the pilots floor.)

[henry_crun]

.......Powered Rotor..............Unpowered Rotor
....http://mike-wsm.org.uk/zpp001helirot.jpg.......http://mike-wsm.org.uk/zpp002autorot.jpg

Pull on cyclic - get nose up - get wind going UP through rotor


credit for images: jefflewis.net

[Lonewolf_50]

HC, the obvious answer was found by both EHI and Sikorsky with the Merlin and the Sea Stallion: deal with dual engine failure risks by adding a third engine. :E Simples. :} :ok:

hillberg: henra made that point ages ago, in the original thread. That is what got some of this discussion about stalled rotor blades kicked off. ;) Thanks for your NASA/Army test info. :ok: Reaffirmation of "keep Nr in the green" if there needed to be any.

[Pittsextra]

Do you really not "get" that when you rapidly lower the collective in response to a complete loss of engine drive, without moving the cyclic, the g will fall to near zero or even below if you are in the cruise

Not sure if I'm reading that correctly but you are saying that a rapid lowing of the collective in the cruise whilst holding the cyclic stick stable generates a sustained zero/negative G? (reading below zero G as negative).

[nomorehelosforme]

Maybe once a year we should chill out rather than rant? Especially at this time of year?

[HeliComparator]

Not sure if I'm reading that correctly but you are saying that a rapid lowing of the collective in the cruise whilst holding the cyclic stick stable generates a sustained zero/negative G? (reading below zero G as negative).

Yes, with caveats. It varies by type due to the exact head geometry. It varies a lot according to speed, so at 100 kts not much effect, at 150 kts yes g will go negative. "Sustained"? - well not indefinitely, of course, but probably for long enough to allow Nr to decay to unrecoverable. Eventually g will settle at 1 when the heli reaches terminal velocity with the rotors stopped (height permitting)

[Pittsextra]

OK thanks HC - yes "sustained" to mean beyond mere spikes off the back of harsh control movements if you like; but as you say its sustained enough for the Nr to decay more quickly than the re-establishment of +ve G?

[awblain]

It's picky and pedantic, but I assume here the "negative g" being bandied around means g<1. If it's g<0 then that's one hell of a rotor. Unless you can accelerate upwards at 9.8m/s/s under power, it seems unlikely that you can beat a cannonball to the ground just by playing with the settings of the blades without power.

I also think there's also an issue with the idea of "wind going up through the rotor". Unless the flow slows substantially during that trip, leading to a lot of drag, that change in wind direction would help to push the aircraft to the ground.

The inrushing wind is deflected down in powered flight, pushing the aircraft up.
The same holds for autorotation, but the power for the deflection then comes from gravity rather than burning kerosene.

[HeliComparator]

Let's see, rotor blades detach, initial g around zero until vertical speed builds up towards terminal. So to get zero g requires no power at all.

Or to out it another way, with rotors suddenly producing no lift at all, g will initially be zero, no effort required.

In my personal experience rapid lowering of the lever at fast cruise can take the g a little below zero - things float up from their resting place in the cockpit - though certainly not as much as -1g. Not hard to see how, with the blades at flat pitch and airflow coming down from above due to the tilt-forward of the disc and attitude pitching down causing a negative angle of attack. What's not to understand?

Edited to say that if you have only flown helicopters that cruise around 100 kts or so, you probably don't notice it much, but at 150kts+ you certainly do.

[AnFI]

I'm pretty sure he means negative as in g<zero - like free fall plus some additional negative thrust from relative wind from above the disk (at high airspeed with nose down attitude)

same problem happens when peeps talk about negative pressure ... meaning negative relative pressure. 1/2g is not -1/2g

Cyclic would need to come aft as lever is lowered just to maintain the same attitude - but it's obviously better to bias it towards nose up - so cyclic needs to come back - it's often useful to increase aircraft pitch attitude even at low lower speeds...

[SASless]

Edited to say that if you have only flown helicopters that cruise around 100 kts or so, you probably don't notice it much, but at 150kts+ you certainly do.

I assume you limit your comment to Single Rotor helicopters of course.

[HeliComparator]

I assume you limit your comment to Single Rotor helicopters of course.
Yes, I've no experience of twin rotor and no idea what if any pitch attitude change you get with a rapid lowering of the collective. I guess it will depend on the front to back collective control mixing?

[Thomas coupling]

DB: Good call and well done for coming out :ouch: Don't you feel better now?
The CIA will now go away and stop bullying you.
Peter (and his cronies nubian and fn1100). Here is a a little quiz for you:

1. During your departure whilst flying through 150' and 50kts, the donk stops. Do you (a) dump the collective first or (b) select aft cyclic first to contain Nr?

2. In the hover the donk stops. Do you (a) dump the collective first or (b) select aft cyclic to contain Nr?

3. You are doing aerial work and operating inside the H/V curve. The donk stops, do you (a) dump the collective first or (b) select aft cyclic first to minimse Nr decay?

4. You are a police helicopter orbiting @ 30kts over the city at 500'. As you pass through the downwind heading, one of the donks stops (or if in the USA: the only donk stops). Do you (a) lower the collective or (b) select aft cyclic to conserve Nr?

5. During a helipad departure (backwards) as you are passing up and backwards through 30 feet, the donk stops. Do you (a) select collective down or (b) select aft cyclic to conserve Nr.

Now if the aft cyclic brigade chooses (a) in any of the above, it blows your argument out of the water.
Do me a big big favour would you?
Qualify your statement to read thus:
IF in the cruise or at significant forward speed, should the Nr decay for any reason whatsoever, the pilot can select down collective and/or aft cyclic as part of the immediate leading actions.

That way Peter it leaves absolutely no ambiguity whatsoever to your american pilots as to what to do during a decaying Nr scenario. The ab initio's and naive ones amongst your fraternity cannot afford to be misled at their embryonic stage of flying training. It seems that UK pilots and the FAA are already up to speed with this recovery process.

And finally, to clear up one more ambiguity; provided the Nr remains in the green, it will never decay any further of its own volition. Thus if one was to select down collective ONLY during entry to an EOL and that selection arrested the decaying Nr such that it remained inside the green (or above min Nr)...IT WOULD NOT CONTINUE TO DECAY. And that is because you would be in autorotation.

For the hard of hearing: One doesnt have to 'flare' by selecting aft cyclic to "get air up under the disc" (:oh::oh:). Lowering the collective automaticlly induces air below, to go through the disc...is that too difficult for some newbies to understand.

Did anyone understand Hilberg's post:confused:

[PeteGillies]

Hello TOTD...You said

"With respect, that's not considered to be correct in UK (mil) teaching - which I believe still includes a demonstration of Nr decay caused by rolling the (only) throttle to idle in the cruise, and doing nothing with the controls. The recovery from the ensuing rapid Nr decay was always to lower the lever to prevent further decay, then flare to restore the Nr. Perhaps someone currently active at Shawbury can confirm?"

Lowering the lever does NOT by itself prevent further decay. Never. Repeating myself again, nothing but applying aft cyclic IN TIME will prevent further decay. The procedure above should be reversed: Flare first if not simultaneously with lowering the lever!

Thank you, TOTD. Pete Gillies

[HeliComparator]

... Lowering the collective automaticlly induces air below, to go through the disc...is that too difficult for some newbies to understand.

Difficult to understand because it's wrong. At least in the case of fast cruise, as I have been at length to explain in my last few posts, to which you seem oblivious.

I liken it to your point about moving the cyclic back being inappropriate under some circumstances - you are right of course, and no-one is disagreeing. But to say that collective down will always induce an autorotative flow is equally fallacious.

[Thomas coupling]

Peter I beg you to stop spreading false statements on this web site...please!

I believe you are an Instructor - yes? I was one for many mnay years too. Several posts back someone asked how many EOL's I had actually done in a single engined helo. I estimated conservatively that it was around 2500 EOL's and they ranged from 50'/120kts to 12000'/0kts to downwind @800'. Now many of those entry into EOL manouevres required me to either lower the collective first AND flare simultaneously or just flare first and then adjust with collective.
BUT please believe this Peter for I am alive and kicking (much to the consternation of many on here :yuk:) to prove it, but all I ever ever did on several hundred+ EOL's was simply lower the collective and NOTHING ELSE. In the UK (and because I currently teach 5 other countries' pilots) several other countries, the standard response to MOST entries is LOWER THE COLLECTIVE TO RETAIN Nr. It is most definitely not, no never ever will be: ALWAYS SELECT AFT CYCLIC FIRST.

Please qualify your claims before you confuse new pilots on this site:ugh::ugh:

[awblain]

HC, I agree: detach the rotors, and you will briefly free fall: there will be weightlessness, which then rapidly (~5s later) returns to normal conditions at the terminal velocity (c.f. AF447).

However, you're not blowing the blades off to experience this, you're pitching them down.

If your clipboard drifts up off a flat surface in the absence of any lateral acceleration to make it bounce off a projecting lip, I agree: that's (briefly) real negative g, with g~-0.0X, where X~1-5. Things "drift" at 0.0Xg; they "fly around" at -0.Xg, and at -Xg they hurt you.

I find this a very interesting discussion - there seems possibly to be a transatlantic polarization developing about old Isaac's ideas, and how air interacts with whirling blades, and that's definitely not based in physical reality. If it's not all just a mix of semantics, cultural difference, sloppy description and misunderstandings, then getting to the bottom of these differences will surely lead to greater awareness of the energetic perils of rotary wing flight, and make everyone's life safer.

[PeteGillies]

Hello SASless...

Hey, I'll be glad to answer your questions, but since a rock knows more than I do about writing to this forum, please help me. Tell me how to highlight your sentences or paragraphs and then to write an answer or comment immediately after them. Think I'm kidding? I'm not. Thanks, SASless - - Pete

[HeliComparator]

Hello SASless...

Hey, I'll be glad to answer your questions, but since a rock knows more than I do about writing to this forum, please help me. Tell me how to highlight your sentences or paragraphs and then to write an answer or comment immediately after them. Think I'm kidding? I'm not. Thanks, SASless - - Pete

Pete, if you click "reply" alongside the previous post in question, you get a blank form to make a new post. But then look in the address bar of your browser and you will see some gobbledygook at the end of which is "noquote=1". Change the 1 to a 0 and press enter to reload the page. Now the post in question is quoted and you can insert your text. Best to change the colour of your text so that your additions are obvious.

[HeliComparator]

HC, I agree: detach the rotors, and you will briefly free fall: there will be weightlessness, which then rapidly (~5s later) returns to normal conditions at the terminal velocity (c.f. AF447).

However, you're not blowing the blades off to experience this, you're pitching them down.

If your clipboard drifts up off a flat surface in the absence of any lateral acceleration to make it bounce off a projecting lip, I agree: that's (briefly) real negative g, with g~-0.0X, where X~1-5. Things "drift" at 0.0Xg; they "fly around" at -0.Xg, and at -Xg they hurt you.

I find this a very interesting discussion - there seems possibly to be a transatlantic polarization developing about old Isaac's ideas, and how air interacts with whirling blades, and that's definitely not based in physical reality. If it's not all just a mix of semantics, cultural difference, sloppy description and misunderstandings, then getting to the bottom of these differences will surely lead to greater awareness of the energetic perils of rotary wing flight, and make everyone's life safer.

Yes as I said, not much below zero. But even at zero g, that means no autorotative effect and the Nr will continue to decay with collective right down, though of course much less quickly than if it was left up. I suspect the difference is less about which side of the Atlantic you live, and more about range of experience. TC's resolve to not grasp my point can I think only arise because of his very formulaic military flying and presumably he has never tried entering auto at 150+ kts. As he himself said, he does it at 120 and there is a bigger difference in the result than the speed difference might suggest.

[SASless]

Typical British method.....complicated.

I highlight the post contents....click copy....go to my post....hit paste....edit as i wish.....highlight the text....hit the Quote thingy on the tool bar....done.

More steps probably....but far easier for a Dinosaur like me to figure out.

[SASless]

That way doesn't include the original author's name or a backlink to the original post. The "typical British method" is indeed typically British, i.e. better than the Colonial one ;) :}

OK....let's see how this works then!

I take it back....much simpler.....I can go to sleep now....I learned something!:D

[John Eacott]

Pete, if you click "reply" alongside the previous post in question, you get a blank form to make a new post. But then look in the address bar of your browser and you will see some gobbledygook at the end of which is "noquote=1". Change the 1 to a 0 and press enter to reload the page. Now the post in question is quoted and you can insert your text. Best to change the colour of your text so that your additions are obvious.

To make it even simpler, just backspace and delete the 1. No need to change it to a 0.

[SASless]

You Aussie Bikies are always creating trouble!:E

[RotorIP]

PG's statement is utter nonsense and may contribute to an accident.

After recently trialling a large helicopter in auto entry the only thing that will save you is lowering collective. NR decay is critical and aft cyclic did little until collective was lowered. The aft cyclic comment is usually due to cruising above max speed for engines off. A comment about 0 g , that's because the helo is accelerating down and will build NR - feeling 0 g in cockpit means zip unless in a teetering rotor system - then you have bigger problems.

If you have questions talk to training staff or an instructor about your specific type. There are way too many variances between types to generalize. What works in one will cause a severe problem in another.

[hillberg]

In cruise flight,The power stops,add aft cyclic & lower collective as needed,:p A +G is good for the rotor system, Aft cyclic loads the system ,It helps get air flow up though the disk, No flow no autorotation, a delay just drags your RPM down & it takes time to get it back. Pete is spot on.:ok: ARMY/NASA tests are public record down loadable,
Heck you can trade speed for altitude and still do a good auto (& with a well timed flare on the bottom end no collective's needed.:eek:)

[SASless]

Read it and weep.....the 65% Critical Nr Number shows up in an actual flight test.

The caution that the report results should not be applied to other aircraft or conditions reminds us of what has been said.

IAS parameters were limited to 25-80 Knots....and airspeeds outside that range resulted in excessive vibrations.


http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19690019854_1969019854.pdf

[RotorIP]

The test mentioned was for looking at extended range performance in a light teetering rotor system - not really for this discussion. No argument aft cyclic will increase NR if you have airspeed and if you have lowered collective.
Don't confuse positive G with aerodynamics, all positive G means in an auto is you are slowing by flaring either in pitch or during a descending turn. There is no level flight in an auto. The flare is increasing NR by increasing the angle of attack of the relative airflow to the rotor system.
An Auto by definition means the helo is descending and the relative air flow to the rotor system is from below, angle dependent on airspeed, no requirement for aft cyclic other than to control nose tuck. Just tested it at a variety of airspeeds in a large helicopter.
If you induce aft cyclic at low IAS you just made the situation much worse as you have bled off Airspeed and as indicated by the study where they mention recovering entry auto rpm by lowering collective. Now your in the worse of both worlds, no airspeed and low Nr.
Don't confuse technique to get a smooth entry during routine practise with what will happen when your caught by surprise and NR is already 90%.
To answer PG , NR will recover by doing nothing more than lowering collective aft cyclic is not required to regain NR, it does control nose tuck, done it numerous times, even waiting for the 2 sec count and doing nothing else. In fact it is better in a helo with stabilization not to touch anything except the collective, stabilizes in the auto much quicker., yes you need to re reference the IAS.
please discuss with training staff, this is a complicated discussion and varies by type there is no one answer that fits all and cannot be properly discussed in this forum

[RotorIP]

Yeah you can do a good auto flying a high inertia system with weighted tips, haven't flown that type of system in a long time, my experience with modern systems are that they are low inertia, better get the collective down because with low inertia NR disappears fast and it won't climb far.

[G0ULI]

SASless
A brilliant find of a document published in 1969. There are numerous caveats in the document about the test conditions and that the results should not be applied to any other type of helicopter. I particularly note that all tests were carried out with forward airspeed and that the collective was lowered and rotor speed increased in the final stages of the descent to complete the landing.

The purpose of the test appears to have been an attempt to so whether the published manufacturers figures for autorotational glide could be improved upon. The answer was a tentative 'yes'.

The forward speed of the helicopter would have provided some lift and the apparent wind direction through the rotor disc would have been angled, so rotor speeds lower than those normally associated with the onset of rotor stall in a vertical descent could be attained without the helicopter falling from the sky. The vibration and buffeting effects described in the text clearly indicate that the tests were carried out right at the edge of what could be achieved.

Attempts to stretch a glide in any aircraft, fixed or rotary wing, rarely end well. It is however a wonderful tribute to the bravery of the pilot(s) who carried out these tests and proof that there is a bit of latitude in the manufacturers published figures if you have the skills to stretch the limits and the nature of the circumstances absolutely demand you take the risk.

Absolutely fascinating!

[SASless]

There is a lot of information in that report that bears discussion as it relates to some issues raised in this thread. The test aircraft was the forerunner to the OH-58A.....and Bell 206. The basic concept seemed to be validating Glide Distance can be improved by using a raised collective setting rather than a full down collective setting.

G Loadings was shown in one graph....which had some interesting results.

Some of the comments about effect of controls, the actual bottom limit of NR they used in the test, amount of delay it takes for Torque to drop to Zero following an engine failure, time and height it takes to regain safe Nr to carry out a an EOL, and some other points.

The Test flying was done for a specific purpose but that does not mean the data created cannot be considered for what does tell us.

The fact the aircraft was flown power off at 65% Nr is note worthy as that is 30% below the Handbook Minimum Nr.....well beyond the 5% figure the PG has given as a Critical Point.

As we have been told that a mere 5% below the Normal Power Off Minimum Nr puts us into very dangerous territory. That would not be borne out based upon the test results. The test certainly confirms such a low Rotor RPM does not afford the capability to perform a safe EOL landing.....but that the aircraft flew well at moderate airspeeds with a very low Nr.

The difference in Nr caused by the movement of the cyclic in either the forward left quadrant or the aft right quadrant gives rise to questions of why that is for us that are aerodynamically challenged.

The Report certainly provides some insight into how the Rotor System reacts in very low Nr autorotative flight regimes. Page 4 and 5....just before the Conclusions Section that is on page 5 hold some very interesting comments. The slow decrease of engine Torque was noted as was the rate of increase in RPM during recovery from the Test RPM of 65% to the Normal RPM limit of 95% along with the associated increase in ROD.

There was also a comment about the results not being representative of any other type and model of aircraft or in conditions other than those noted in the Report.

The one thing it certainly does is remind us there are many ways to fly the same helicopter.....some that are within the Normal Limitations of the aircraft contained within the RFM as approved by the Certifying Authority and other non-approved and non-certified methods.

In keeping with the Nanny State Mentality of some here......the caveat that was not done in Big Bold Bright Type was "Do Not Attempt This At Home Kids!.....as it ain't kosher!".

[RotorIP]

Agreed there are ways then there are ways.......but not everyone is at the same level in terms of understanding, ability and applicability to type. This is a public forum where very inexperienced pilots may read something and take it as fact, I have never read anywhere on 15 different helicopter types of a 5% NR decay being critical. Have you? Yet a supposedly knowledgable person posted it.....
The initial point of this thread is largely pointless as we are talking fractions of a second, get the collective down and worry about the rest.....but it can be very misleading to a junior pilot who delays reacting because he read..... And yes I have seen that, not just autos, and the aftermath because somebody said......

[Prawn2king4]

I, like many experienced UK pilots on this forum, have been following this thread with interest and have refrained from entering the discussion. In the past I’ve had a reluctance to display my experience as it’s no different from many others. But to support the following statement, I am an ex military QHI and civilian TRE/IRE, have been instructing/testing in the military and civilian world for over 30 years (including N.Sea and police aviation) and have therefore engaged in countless auto rotations – as many others here have. I comment here because inexperienced pilots on single engine types who have been following this thread may hesitate a little to assess parameters before reacting to an engine failure.

I agree with Rotor IP and TC. Lower the lever – immediately. Simple. Think about everything else after that action; most times, instinct will drive cyclic inputs, but it won’t help at all if the NR is irrecoverable.

[[email protected]]

HC - just out of interest, since your theory is based on 150 kt double engine failures, how many of those have you had, how many double engine failures have you initiated at 150 kts by pulling back both engines - ie what is your concept of ops based on?

Simulator time perhaps? Calling practice double engine failure in the cruise with both engines running normally?

You are very hardover about this entry to auto technique so where has it grown from?

[HeliComparator]

Crab as you know I (used to) fly EC225 in oil and gas support. In that role perhaps 95% of the flight time is at MCP doing 145-150 in the cruise, and up to 165 on descent. So taking into account climb time, perhaps 90% at 145+. Obviously the cause of a double engine failure in the cruise is hard to envisage, but since we spend the vast majority of time in the cruise and double engine failure is something we are required to train for, it seems sensible to take the cruise case - and for example I guess the PHI 76 was probably doing 145 when it hit the bird.

Before we had the simulator we used to do this in the aircraft. But we were wimps and simulated auto entry purely by lowering the lever - engine control switches were not retarded due to the risk is using real OEI power. So the "failure" was pilot flying initiated - pretty benign you might think.

Nearly everyone got it right, flaring the aircraft as the lever was lowered to maintain 1g+. But a few (mainly fairly junior IIRC) pilots just lowered the lever rapidly and all hell broke loose with things floating up at sub-zero g including the pilots, then they would react to that and pull the cyclic back a bit, the disc would bite and the Nr would wind up at a phenomenal rate. I recall on my TRE check having a trainee do this and I just caught the Nr with a massive pull as it reached the max transient power off Nr. Scary!

Regarding the bit about Nr continuing to decay at zero g, obviously the nature of our auto entry means I have never seen this, but I think the aerodynamics of it make the consequence clear.

So in summary, from fast cruise rapid entry into autorotation can either be a benign affair if leading with the cyclic, or absolute mayhem if the collective is lowered without any cyclic input.

Thinking back to my days on the AS332L where we did retard the throttles to practice autos, with the entry from say 120kts the effect was less critical, but still noticeable. Entry without aft cyclic was messy rather than mayhem.

[Pittsextra]

Got to be totally honest the theory and mathematics are beyond me but perhaps someone can pick the good points out of this? I think page 44 onwards talks autos....


http://www.scribd.com/doc/81931718/Helicopter-Test-and-Evaluation-Aiaa-Education-Series

[Thomas coupling]

Is there any more to be said really? Peter - you have to go away and think hard about conveying your message properly (I don't think you have got it wrong - simply having problems getting it across to us Brits perhaps?).
All those who genuinely believe his mantra need to have a long hard think about what you have been practicing all these years?
[A big thank you to Rotor IP and Prawn2 for backing this up].

Finally and most importantly:

To ALL ab initio's, newbie's wannabee's, observers:

UNDER ALL CIRCUMSTANCES (no exception whatsoever) - LOWER THE COLLECTIVE FIRST IN THE EVENT OF A TOTAL ENGINE(S) FAILURE.

On certain occasions: lower the collective AND simultaneously select appropriate cyclic movement to co-ordinate entry into autorotation.

These 2 statements well serve you well and never do you any harm as you learn to fly any helicopter.

[chopjock]

UNDER ALL CIRCUMSTANCES (no exception whatsoever) - LOWER THE COLLECTIVE FIRST IN THE EVENT OF A TOTAL ENGINE(S) FAILURE.

Not me if in a fast cruise, especially when low level. I will be leading with aft cyclic in this case.

[DOUBLE BOGEY]

Peter, I have been a strong supporter of your CYCLIC-AFT policy for all normal operations (excluding hovers and extreme low level where specific techniques need to be taught and practised that are paradoxical).

However, your statement that lowering the collective will not stop the Nr decaying must surely not be true if the Nr, at the point the lever hits the floorplate, is at least in the green and probably in the "Safe" margin proved during certification (thanks TPs).

There is always a little hiatus until the ROD develops and the airflow reverses through the disc. This differs according to type but does not last long if the lever is lowered fully with NR in the green range.

I think the flare (cyclic aft) removes the hiatus by more rapidly reversing the airflow through the disc and therefore will help any situation where the NR is too low and certainly nuetralises decay faster than waiting for the hiatus to end. For this reason I support the cyclic aft policy for normal cruise flight BUT surely, the lever must be fully lowered as fast as possible.

If your statement was true I beleive there would be no condition of stable Nr in autorotation.

DB

[Thomas coupling]

Chop: I think your aim in life is to be a tw*t for a s long and as often as possible. That is why I put the second paragraph in - just for prats like you, but even you couldn't get that far with the reading of it before posting could you.

Please stick to RC drones and find a drone web site to plague but you really are making a complete and utter d*ck of yourself lately (even more than usual).

Happy Christmas CJ. :}:yuk::bored:

[[email protected]]

HC - yes, I have had students slam the lever at the floor to enter auto and it does make the nose drop and generate less that 1g - as I said earlier, a co-ordinated entry is nearly always the best solution, as you advocate.

However, I cannot agree with Peter's aft cyclic assertion - flare effect is temporary, min pitch is a far more permanent solution where Nr is concerned.

In certain circumstances, flare effect can be used to gain height from a high speed entry to auto - the Gazelle would climb 2 - 300' from 120kts and you could hold the lever above min pitch during that zoom climb.

However, people were often lulled into a false sense of security by it as it was usually initiated verbally - when the same exercise was flown and initiated by hacking the throttle, the amount of climb was reduced and the lever had to be lowered further to prevent decay - and that was without the 1 -2 second reaction time that would occur in the real case.

So I come back to - lower the lever first, and always (except low hover) and do with the cyclic what you want or need to in order to recover the lost Nr.

No big secret - it's been taught that way for years:ok:

[Dick Sanford]

Dear TC. On the understanding that the single engine helicopter pilot should always have their hand on the collective lever, there are going to be times when they do not for various good reasons. Should the pilot suffer an engine failure during one of these situations, then if their first action was to lower the lever they would most probably end up being a passenger until they hit the ground. It will take a period of time for the pilot to recognise and react and a further period of time to move their hand back onto the collective lever and lower it. However they will always have their hand on the cyclic, therefore able to trade airspeed for RRPM in a much shorter time scale, it has to make sense to use airspeed energy should you have it. The understanding is that this energy transfer is transient, the pilot is going to have to put that lever down, it just allows for a bit more time to do so. I would go so far as to say; ' it should be a criminal offence for a helicopter pilot not to try and use all available energy to prevent Low RPM rotor stall' DS.

[Grenville Fortescue]

Can anyone confirm what happens to "attitude" in the longitudinal axis when suffering a double engine failure while in the cruise?

[whinetyler]

Good Grief! I have just come back after a trip away from the electric net and though I'd logged into just helicopters by mistake! Gents, there are an awful lot of quite respectable contributors to this site who appear to me, to be caught up in an never ending competition to be the 'most correct'. It's almost Christmas, why don't you all take a few days off, read what you have all actually written and come back after you have had a nice lie down!:rolleyes:

[[email protected]]

Dick, I understand where you are coming from in your last post but consider an R22 at 80 kts with the pilot using his left hand to play with the GPS for example: the engine fails and he, having read your post, immediately flares the aircraft without lowering the lever (considering it a secondary action as he has some forward speed to trade for Nr) - the speed washes off quickly, he then gets round to lowering the lever and his next action will be to push the stick forward to prevent further speed decay - this reduces +g below 1 and the combination of forward cyclic, low Nr and reduced g causes mast bumping and MR blade strike to the fuselage - game over!

Yes, use both hands if necessary to retain/recover Nr but don't promote cyclic flare over lowering the lever - it is only valid in certain circumstances and in many others can be disastrous.

Anyone actually brave enough to try a throttle chop in the 90 kt cruise in a Robbie and delay lowering the lever because you can flare a bit? Thought not:ok:

[GipsyMagpie]

Grenville

After an total power failure assuming no pilot action and forward flight the rotor speed will decrease. This will have greatest effect on the advancing blade (think standard lift formula). This will result in the front of the disc flapping down (flap forward - effect 90 degs onwards). The aircraft will therefore pitch nose down. In the hover there is no difference in lift across the disc so the dominant effect would probably be a reduction in downwash on the horizontal stabiliser so again nose pitch down. This may also contribute in fwd flight. :8

A lot of other stuff happening will mask this however like the yaw.

And I humbly suggest this is probably wrong. (But seem to remember this occurring on a demo I saw once upon a time.)

And for interest my opinion is that a one size fits all is stupid for entering autorotation. Entry should be tailored to the circumstances. There are some basics to get you started (fly the aircraft, maintain NR, make a plan and follow it, get the gear down if appropriate, say something funny for the CVR) but slavishly following advice in the face of different circumstances could get you killed. AVIATE!

[[email protected]]

GM - or the retreating side would stall and cause pitch up and roll towards the retreating side.:ok:

[Grenville Fortescue]

After an total power failure assuming no pilot action and forward flight the rotor speed will decrease. This will have greatest effect on the advancing blade (think standard lift formula). This will result in the front of the disc flapping down (flap forward - effect 90 degs onwards). The aircraft will therefore pitch nose down. In the hover there is no difference in lift across the disc so the dominant effect would probably be a reduction in downwash on the horizontal stabiliser so again nose pitch down. This may also contribute in fwd flight. :8

A lot of other stuff happening will mask this however like the yaw.

And I humbly suggest this is probably wrong. (But seem to remember this occurring on a demo I saw once upon a time.)

GipsyMagpie much obliged.

Therefore I suggest that if one is in the cruise flying manually the instinctive response will be to "level" the aircraft (ie. apply aft cyclic), followed by a reduction in collective.

What I am interested to know is what are the current procedures for a two crew response to a double engine failure.

Flying the early twins single pilot you had to decide fairly quickly which engine had failed in a loss of power scenario, in a two crew environment responsibilities can be shared between flying the aircraft and confirming instrument readings.

[GipsyMagpie]

Ooo, good one. But I think I am still right

[GipsyMagpie]

Again pilot should be flying the aircraft. Co pilot does the drills. The input on engine failure is irrelavent. You just need to do what is required to keep the aircraft attitude where you want it. Look out or in IMC at the instruments and FLY. You cannot fly by rote.

[Grenville Fortescue]

But are we now saying that at Vmax the aircraft is going to assume a nose high attitude?

[TorqueOfTheDevil]

UNDER ALL CIRCUMSTANCES (no exception whatsoever) - LOWER THE COLLECTIVE FIRST IN THE EVENT OF A TOTAL ENGINE(S) FAILURE.


TC,

While I agree with much of what you write, are you really advocating lowering the lever when in a low hover or hover-taxi (ie 5' or so for a single)? I always understood the correct actions to be to maintain lever position until it was time to cushion (at which point the lever goes up not down!). This has certainly been practised many times over many years with successful results. Is this not a significant exception to your rule?

TOTD

[GipsyMagpie]

Lower the collective (a little check?).

[Grenville Fortescue]

Lower the collective (a little check?).

Do you speak of powered flight?

[SASless]

Crab as you know I (used to) fly EC225 in oil and gas support. In that role perhaps 95% of the flight time is at MCP doing 145-150 in the cruise, and up to 165 on descent. So taking into account climb time, perhaps 90% at 145+. Obviously the cause of a double engine failure in the cruise is hard to envisage, but since we spend the vast majority of time in the cruise and double engine failure is something we are required to train for, it seems sensible to take the cruise case - and for example I guess the PHI 76 was probably doing 145 when it hit the bird.

Exactly how many Dual Engine failures have ever occurred on the North Sea?

Before we had the simulator we used to do this in the aircraft. But we were wimps and simulated auto entry purely by lowering the lever - engine control switches were not retarded due to the risk is using real OEI power. So the "failure" was pilot flying initiated - pretty benign you might think.

it was also not representative of an actual simultaneous Dual Engine Failure.

Nearly everyone got it right, flaring the aircraft as the lever was lowered to maintain 1g+. But a few (mainly fairly junior IIRC) pilots just lowered the lever rapidly and all hell broke loose with things floating up at sub-zero g including the pilots, then they would react to that and pull the cyclic back a bit, the disc would bite and the Nr would wind up at a phenomenal rate. I recall on my TRE check having a trainee do this and I just caught the Nr with a massive pull as it reached the max transient power off Nr. Scary!

Had you had a real Dual Engine Failure....with a complete loss of power input to the MGB....with a resulting decay in Rotor RPM....would not that increase in RPM be what you needed to offset the Loss of RPM that the loss of input would have caused?

Regarding the bit about Nr continuing to decay at zero g, obviously the nature of our auto entry means I have never seen this, but I think the aerodynamics of it make the consequence clear.

How long can you maintain a Zero G condition? Seconds or Minutes?

So in summary, from fast cruise rapid entry into autorotation can either be a benign affair if leading with the cyclic, or absolute mayhem if the collective is lowered without any cyclic input.

Thinking back to my days on the AS332L where we did retard the throttles to practice autos, with the entry from say 120kts the effect was less critical, but still noticeable. Entry without aft cyclic was messy rather than mayhem.

Perhaps "messy" actually describes a situation where transient effects were causing variations in the Rotor RPM which would only be "normal" considering the loss of drive from the Engines, the shift from the Rotors being driven by the engines to an autorotative descent, shifting airspeeds and aircraft attitudes, and change in Tail Rotor Torque demand?

[Dick Sanford]

Crab. You do not need to bleed off a great deal of airspeed at 80kts to gain a lot of RRPM (energy). You can see the effect quite well in an R22' if you switch the gov off, reduce the RPM to 95% at 80kts and just apply aft cyclic. The RPM increases quickly and by a good amount, however it is transient and will decay again. Not scary and useful to see. No need for large cyclic inputs, no low 'g' no need to be dramatic. DS

[[email protected]]

Dick, I agree - in a benign, pre-briefed and planned scenario and with a steady Nr. From a no-notice engine failure with rapidly decaying Nr I suspect things would go more as I suggested, especially without an experienced pilot at the helm.

[Dick Sanford]

Crab. I have had an engine failure in an R22. As it happens I was at 80 kts. The application of aft cyclic worked a treat, entry into auto un dramatic, did not need to increase IAS for my 65 kt auto IAS. No low 'g' I'm still here ( sort of). DS

[Thomas coupling]

Gipsey: You have already confused the abbo's and newbies with your incorrect disc response description (Grenville for one). Crab got to you before I did :D
Which now means someone like me/crab/RotorIP/SAS/ eta l have to come back on here wasting our time re-iterating what has been siad time and time and time again.

Once more mon amie (and because there is either misunderstanding or confusion with all these suggestions on entering auto):

ALWAYS ALWAYS ALWAYS LOWER COLLECTIVE FIRST - you will never ever go wrong. It is a "slavish" statement. It is a "rote" technique but it is.....wait for it...... TRUE Trust me when I say that in every single alternative view thrown at this thread, be it whatever reason or excuse, there is always an alternative to positioning the cyclic during entry to an auto, there is also time to positioning the cyclic too.
There is NO alternative to selcting down collective and so very little time.
Which brings me onto Dick Sanford. [Hello Dick, we have met professionally - you came and did a safety audit for me on my police air wing many years ago???].
Dick - I'm not 100% certain of this, but I believe you were not military? It is burned into the mind of every single mil pilot in the UK (especially) to be milli seconds away from the collective at any one time. Mil pilots have no truc with anyone who use their hands to wander around the cockpit. (a) there are NO circumstances to leave the collective unattended for more than a couple of seconds and only then to even contemplate taking your hands off the lever is seen as a cardinal sin.
Same goes for cyclic but to a lesser degree. Complex systems in complex cockpits invariably find themselves being manned by two pilots. Less complicated cockpits with one pilot (like the SPIFR EC135) are designed to minimise dextrous demands in the office - I might suggest.

[HeliComparator]

Getting messy, too many colours!
I in green now
Originally Posted by HeliComparator http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/buttons/viewpost.gif (http://www.pprune.org/rotorheads/529796-entering-autos-discussion-split-glasgow-crash-thread-post8213375.html#post8213375)
Crab as you know I (used to) fly EC225 in oil and gas support. In that role perhaps 95% of the flight time is at MCP doing 145-150 in the cruise, and up to 165 on descent. So taking into account climb time, perhaps 90% at 145+. Obviously the cause of a double engine failure in the cruise is hard to envisage, but since we spend the vast majority of time in the cruise and double engine failure is something we are required to train for, it seems sensible to take the cruise case - and for example I guess the PHI 76 was probably doing 145 when it hit the bird.

Exactly how many Dual Engine failures have ever occurred on the North Sea? One that I can think of, another one where the failures were not simultaneous. If you are trying to say that it's rare and improbable then I quite agree, but nevertheless this is the circumstance we are considering.

Before we had the simulator we used to do this in the aircraft. But we were wimps and simulated auto entry purely by lowering the lever - engine control switches were not retarded due to the risk is using real OEI power. So the "failure" was pilot flying initiated - pretty benign you might think.

it was also not representative of an actual simultaneous Dual Engine Failure. Correct, with an actual simultaneous dual engine failure the Nr would likely be pretty low before the collective was lowered due to pilot reaction time.

Nearly everyone got it right, flaring the aircraft as the lever was lowered to maintain 1g+. But a few (mainly fairly junior IIRC) pilots just lowered the lever rapidly and all hell broke loose with things floating up at sub-zero g including the pilots, then they would react to that and pull the cyclic back a bit, the disc would bite and the Nr would wind up at a phenomenal rate. I recall on my TRE check having a trainee do this and I just caught the Nr with a massive pull as it reached the max transient power off Nr. Scary!

Had you had a real Dual Engine Failure....with a complete loss of power input to the MGB....with a resulting decay in Rotor RPM....would not that increase in RPM be what you needed to offset the Loss of RPM that the loss of input would have caused? Of course when the g came on, the increase in rpm is exactly what is needed. But the problem is that the effect is delayed by have low g for the first few moments of the recovery into auto. The pilot's inevitable delay in entering auto is bad enough and will quite probably result in the Nr getting perilously low. Add to that a pilot reaction that does not initially get an autorotative flow going, ie one that allows further Nr reduction after the recovery is initiated, and it could lead to the Nr becoming unrecoverably low. Let's also remember that the issue is blade stall, so if there is a period of zero g, lowering Nr, then aft cyclic is applied (with a bit of reaction time) to correct zero g, initially a poor response to the cyclic due to low g, then as the g starts to come on the cyclic really "bites" and well over 1g is produced. Whilst this would normally be a "good thing" as you say, to restore the Nr, in fact low Nr + high disc loading = increased propensity to stall, so those actions might make the unrecoverable Nr somewhat higher than it might otherwise be. Even if the blades don't stall, whilst you might get the Nr back you will get more than you bargained for as the Nr shoots way over the max transient Nr. If you are used to flying metal bladed helicopters, you will be amazed at how fast the Nr can rise on a plastic bladed helicopter under g loading.


Set against all that is leading with the cyclic to maintain 1g, and it all goes swimmingly well!

Regarding the bit about Nr continuing to decay at zero g, obviously the nature of our auto entry means I have never seen this, but I think the aerodynamics of it make the consequence clear.

How long can you maintain a Zero G condition? Seconds or Minutes?


I suppose if you really tried and didn't care about recovery, you could put the heli into a ballistic dive and hold zero g for as long as the heli could stand the speed increase. You would end up in a vertical dive but I suppose would run out of fwd cyclic fairly quickly if nothing else gave way.


But practically speaking I am only talking about a few seconds. Any Nr loss greater than that arising from pilot reaction time is to be avoided, maintaining 1g+ (for which you have to lead with the cyclic) minimises that. Just lowering the collective makes it a whole lot worse.


So in summary, from fast cruise rapid entry into autorotation can either be a benign affair if leading with the cyclic, or absolute mayhem if the collective is lowered without any cyclic input.

Thinking back to my days on the AS332L where we did retard the throttles to practice autos, with the entry from say 120kts the effect was less critical, but still noticeable. Entry without aft cyclic was messy rather than mayhem.
Perhaps "messy" actually describes a situation where transient effects were causing variations in the Rotor RPM which would only be "normal" considering the loss of drive from the Engines, the shift from the Rotors being driven by the engines to an autorotative descent, shifting airspeeds and aircraft attitudes, and change in Tail Rotor Torque demand?

[Thomas coupling]

TOTD: well spotted and congrats on spotting that (unless you have been speaking to Crab earlier who commented the same elsewhere).
This is indeed an area which requires careful deliberation (on the ground before it goes per shaped for real) regarding a response from the pilot.
I think it was mentioned by a previous poster that each a/c is different when it comes to its characteristics during an engine failure.
I could write a book on donks stopping because of this but I have got to go and watch paint drying shortly so I won't...but in brief:
"generally" if the donk stops @ 5 ' taxiing or in the hover, you will probably hit the deck before you know what the f*ck has happened. Any higher and an element of check down on the collective is fed into the equation to reduce the amount of decaying Nr such that the final raising of lever to absorb the landing is less exciting to bystanders. From 30-40 feet and higher, almost all helos will require a slight check down on collective to slug the decaying Nr before the big armpit up movement of collective. In all situations, you will be pleased to note that no aft cyclic was used in the making of any of these simulations :p

[Lonewolf_50]

A few thoughts:
a. You are a helicopter pilot. You fly with both hands and with your feet. Maybe that is Rule 0.

b. The collective and cyclic work together, even if the engine just quit. Know the cases for engine failure, there isn't just one. There are multiple.

c. Slamming the collective down isn't a technique any instructor I ever had would ever endorse, and certainly not me when I taught for a few years.

d. Keeping pitch on all four blades by not reducing collective will result in Nr decay if the drive from the engines goes away. To assert otherwise, particularly in a low inertia head, strikes me as curious. With pitch on the blades, you have lift and drag both. If you have drag, and no power driving the blades, they will slow down ... which is what we all want to avoid, reduce to as small a reduction as can be. Keep it in the green, or as close to as possible. The case of near the H-V operations that has been raised seems to be where Pete's recommendation has the most merit ... but the Nr preservation/maintenance is transitory, as that energy is used up. So long as it keeps your Nr in/near the green as you work your way back to Mother Earth, good. The pitch on the blades still needs (in most cases) to be reduced to reduce the drag that drags down Nr, until you flare and pull.

e. If above the "sweet spot" airspeed for autorotation, trading for Nr seems instinctive, but maybe it isn't. (Mosby? ) Autorotative descent has a range of airspeed sweet spots for a given helicopter .... as Dick tells us, 65 kts for R22. In the Seahawk we used to practice at 80 knots, but I found the RoD at 75 kts to be a bit less, DA dependent. We used to cruise at 120-130 frequently in teh Seahawk, but the desired airspeed range for autorotation was 80-100 knots. If you lost it in cruise, you'd need to lower the collective and flare for two reasons: that pitch on the blades at that speed would probably decay your Nr, and you need to transition to a better autorotational airspeed anyway ... win win. Controls work together.

f. Did we mention that you fly with two hands? Did we mention that both hands work together? Did we mention you don't manipulate the controls in isolation from one another? Is Rule 0 being lost with all of the fancy automation now available, even in helicopters? (Say it ain't so, Joe)

i. It seems that ops near the edge of H-V is where Pete's crusade is aimed (But maybe not, given the Mosby accident). The margin of error is narrow. Lack of airspeed (stored energy if you will) should the engines quit makes coordinated reduction of collective and loading of the head (cyclic is all that is left to do that) with such energy as is available the immediate concern. One does not have a hundreds of feet to sort out a sweet spot airspeed. Rotor energy maintenance needs to be almost reflexive, particularly for a low inertia head. The "cyclic back" benefit looks to be transient. You've still got plenty of work to do in order to get down and walk away form the landing.

What is agreed in all the pages of argument?
Unloading the head and pushing the nose over accelerates Nr decay when drive is lost.

Does anyone teach that? :confused:

Oh, also agreed by all parties: don't stall the main rotor blades.

Declare victory, off to the pub, I am buying the first round.

[Dick Sanford]

TC. Hope all is well fine fellow. Yes and no, I am ex military but not as pilot. It may be a simple case of training platform. Mil' pilots tend to have been taught on medium to high inertia platforms and then go on to fly the same. The basic platform for so many pilots now is quite different, i.e. the R22, which as you know has a very low inertia rotor system. The low inertia system as we all know has a negative in as much as the energy stored in the rotor is small, therefore the rotor decay is rapid. However one of the great benefits is that by applying a small amount of aft cyclic the rotor response is very quick, instantaneous. There is absolutely no disagreement with lowering the collective as a must, it is just that the aft cyclic technique can extend the time the pilot has to lower the collective. We all agree; primary task post engine failure is to maintain RRPM above stall. We all agree, one size does not fit all. We all agree we have a number of areas of stored energy we can use to prevent Low RPM rotor stall and we should use what we have to survive. The platform you fly will go some way to determine your actions, however, there is one action that is common to all and that is " lower the collective lever". DS

[SASless]

As I look back over a few years of doing this.....I could sum it up this way:

Get the Collective down

Get the Rotor in the Green

Pick your Landing Spot

Adjust Airspeed and maneuver as required

Arrive at the Surface with the Maximum RPM possible

Use up all the RPM in Landing


We can argue about everything else....but simple concepts work too.

If you are a Helicopter Pilot....you should know how to accomplish those simple goals by manipulating the controls.

There are too many variables to be able to issue an Edict that requires exactly one response or method of moving the flight controls that will work in every single possibility.

Doing more than one of the steps I listed at one time works too and most Pilots are capable of doing that.

If you are not....perhaps you might want to consider alternative employment.

[DOUBLE BOGEY]

OK it seems we all know how to get into autorotation!!!!!

At the risk of starting another war (some of which was my fault), can I ask what the current Flight School teaching is for a standard EOL.

I have always been taught, and therefore taught:

Variable Flare, Check with Collective, Level, Cushion.

However I have had a lot of candidates leaving out the "Check" bit. Is this the new teaching or does anyone know where this has come from??

DB

[SASless]

Sounds about right to me.

One question would be about the use of a "Check" every time.

The "Check" pull, with the aircraft in a nose high attitude, works to slow both ROD and Forward Speed.

If your forward speed and ROD is acceptable....omitting that "Check" is not necessarily wrong or improper is it?

That would allow maximum Nr for the Cushion Pull.

Recall my training early on was to aim for a maximum One to Two Skid length ground travel.....which usually necessitates a fairly aggressive deceleration (flare) at the bottom....and provides a good increase in Nr during that flare. By the end of my initial Army training....less than One Skid Length ground travel was the target.

I would consider the "Check" an option depending upon the ROD and Ground Speed as it works to reduce both at the cost of some Nr. Probably it would be useful more often to "Check" than not however.

We have to remember.....there is such a thing as a "Zero Pitch Pull" Autorotation and in a perfect World....that would be the Norm!

[Thomas coupling]

SAS: Bang on big guy :ok:

DB: You are calm and collected for once :ok: Can you just move away from SAS a little more please - there thats better.

Now: bottom of the auto....

I do believe the check bit was peculiar to Gaz drivers in the mil on this side of the pond and is darned difficult to eliminate from my way of doing things today, but I understand it is not necessary in most helos nowadays.

Some even dont use the collective at all for the recovery ;)

[Lonewolf_50]

DB, doesn't that depend on the model a bit? While we are talking incremental and fine bits of collective movement in the flare to pull transition, in your "check" there is a consideration, perhaps esoteric, about some of your Nr in the flare building due to a bit of coning from load and thus the old ice skater arms in arms out illustration. Since part of the flare is breaking the rate of descent, in some models a modest and brief bit of collective (which I think is what you mean by "check") keeps the Nr from running through the roof, but it has to be taken out. it's the old correction, counter correction ... and it all depends on the day, how your auto went before you got to the flare, are you heavy or not, are you into the wind or not, do you have only a spot or do you have a lot of room ... lots of factors.

My experiences is with high inertia heads, I don't have a point of reference compared to Dick's explanations on those fine points of how well it all works out at the end. (Dick, I appreciate your point on how in a low inertia head the cyclic can rapidly build Nr, which fits Pete's point ... )
If you are going to err, the consensus seems to be to err a bit on more Nr (hence a smaller or no "check") as you'll still bleed it off in a hurry when you at last pull ... if you need to and aren't in a perfect world of the no pull auto.

(Talked to an old Navy friend last week. He used to practice running autos to the deck in CH-46's (decades ago) which, when the GW was pretty low, they could do with virtually no collective at the bottom).

[SASless]

Lone,

In the Chinook as well as the 46...."No Pitch Pull" Autorotations were not hard to to do or rare....provided there was room and proper surface contours to accept some ground run....well in excess of the one/two skid length done in the Hueys and other Army Single Rotor Helicopters. It did require a high nose up pitch attitude....but then the normal hover attitude was 5-7 degrees nose high to begin with. Touchdowns were limited to something like 23-27 Degrees (if my memory serves me right) before the Aft Rotors made contact with the surface.

As the Rotor RPM went away....and the Nose still well up....the sensation of sitting in a runaway elevator was quite strong when the Nose fell to the surface.

The Cyclic position at the stabilized at two inches aft of center....confirmed by the Cyclic Position Indicator.....which was the same position used to achieve the normal hovering attitude or during ground taxi on just the aft landing gear (known as two wheel taxi). In the Chinook.....Pitch Attitude in some ground maneuvers was controlled by the Thrust Lever (Collective) while the Cyclic was left stationary in the two inch aft position and centered laterally.

When you see those photos of the roof top or ridge landings where the Wokka is perched on just two aft gear and the Nose hanging in space....that is what is going on.

[[email protected]]

Lonewolf 50 - agree 100% with your last but one post, spot on the money:ok::ok:

The check works with a reasonably high inertia rotor (why is was taught on the Gazelle) where it serves to reduce forward speed and RoD without leaving you with too little Nr to safely cushion once you have levelled the skids.

In an R22 however, the whole 'flare - check - level - cushion' happens much quicker and closer to the ground such that, unlike on the Gazelle, the check doesn't get time to have much effect and is pretty much rolled into the level and the cushion.

On the Lynx, the check was specifically excluded from the teaching - apparently due to the disc loading and needing to preserve the Nr for the landing. We don't teach a check on the Sea King because snatch engaging freewheels on practice autos doesn't do them much good.

Dick - you are an experienced pilot who is more than capable of dealing with an engine failure in the cruise in a Robbie - there are very, very many pilots bimbling along out there who aren't which is why I am so opposed to Peter's aft cyclic preaching.

[Hughes500]

Well this is how I teach an EOL, do about 20 a week to the ground while teaching students. This is for a 300
Overhead airfield at 1000ft 65 kts
Close throttle shut. Ac will yaw about 30 degrees to left before student sticks in right boot. At the same time lever must go down and quick as rrpm is now down from 460 ish to about 410 ish ( min is 390 ) rear application of cylic will prevent the huge nose down attitude ( applied as lever goes down) This will bring ac back to a 50 ish kt attitude and rrpm back to 460/470 ( limit 504, best auto speed 48kts)
Once established in auto and if time Mayday call ( remember the guy on the end of the radio can do one of three things depending upon your actions, send a taxi, ambulance or hearse !!!so fly the fing thing !)
At about 30 to 40 ft ( can see blades of grass) flare hard, this will reduce horizontal and forward speed to near zero.
Now a check of about 3 inches of up lever. This is will stop the rotor over speeding and will further put the brakes on
Hold check until about 10 to 20 ft. Level ac with cylic
Then cushion ac on to ground by lifting lever
If doing with a 500 then
If in cruise speed 130 kts lower lever by about 50 to 60% at the same time rear cylic . As you load the disc rrpm is kept up but for about 10 secs you will have a rate of descent from close to zero to 500 fpm as speed comes back to 60 kts ( best auto speed )
The rest is the same for a 300 except start the flare earlier / higher

Done this for 15 years teaching and thousands of EOL's works very well and is easy for student to practise rather than a variable flare.
But it might not be the best for all types ( eg 206 is easier ):ok:

[AnFI]

in the FAST CRUISE

on engine failure - lowering the lever would require aft cyclic movement to maintain attitude (due to the asymetric proportionate pitch change, since the advancing side pitch is MUCH lower already than the retreating side, and the collective pitch reduction would be proportionally greater on that advancing side, leading to a change of plan of rotation in the in the forward pitching direction)

Not moving the cyclic aft as the lever is lowered would become the equivalent of pushing the stick forward - since it would be further forward than the reference position which would result in no attitude change.

Pushing the stick forward results in lower g (which could be quite violent - and disasterous)
Lowering the lever also results in lower g.

Lowering the lever without simultaneous aft cyclic is the equivalent of 'bunting' forward at the same time as unloading due to lever lowering - potentially DISASTEROUS.

So (TC) aft cyclic should be hand-in-hand with lever lowering in the fast cruise - and it is potentially dangerous to suggest otherwise. Rapid lever lowering with no simultaneous aft cyclic could be a major problem. (agreed not as bad as not lowering the lever at all)

Also there is approximately as much Kinetic Energy in the 10kts from 120kts to 110kts as ther is in the first 50kts - good use of Energy is the second part of what autorotation is all about. You start with Energy distributed in Height, Speed and RRPM - you consume it at a rate that depends largley on your speed (and pitch) and the trick is to apportion the energy as appropriate for the circumstances - at the bottom the pilot decides whether he wants to apportion his remaining cushioning energy for a gentle vertical closure rate or spend some degree of it to reduce the horizontal componet of his Kinetic energy.

{Since Energy is the resource and Power required is the (time) Rate of Consumption of Energy , THEN: Energy becomes Time. In some cases time to establish steady autorotation , in other cases Time to cushion.}

TC I note that you have more than average Autorotations but if you had about 15 times that you would probably find that you still have some room to develop - THEN perhaps you should write your book on the subject.... You are very firm about your opinions - to the point of unjustifiable rudness IMHO

[AnFI]

if time Mayday call ( remember the guy on the end of the radio can do one of three things depending upon your actions, send a taxi, ambulance or hearse !!!so fly the fing thing !) Quote H500

:D

[SASless]

Hughes.....does your 300 have the spoiler on the top rear of the rear bulkhead?

The TH-55A that I learned to fly on in the Army oft times did not and those without them really liked to tuck their noses upon entering autorotation. With the fairing....that tucking tendency was no where nearly so noticeable.

[DOUBLE BOGEY]

Thanks all. As I started on the Gazelle that's obviously where my "Check" has come from. It works well in the OEM SIM but obviously we can't throw euro 26m of real helicopter at the ground so I am not sure how this translates.

I only have Few OPCs on the B206 20 years ago so cannot really remember if we "Checked" or not.

TC and SAS - I have laid off the red meat for a while and feeling much calmer now thank you. I think SAS hates me now though:{:{:uhoh:

[AnFI]

if time Mayday call ( remember the guy on the end of the radio can do one of three things depending upon your actions, send a taxi, ambulance or hearse !!!so fly the fing thing !) Quote H500

:D

[SASless]

Sorry to disappoint you DB.....don't hate you now.....or before.

I much rather have you stuck in here.....as you have a lot to offer in our discussions.

[Lonewolf_50]

Hughes550, much obliged for the example.

crab: it seems that Pete's teaching point is as much about "don't forget to keep the head loaded with cyclic when reducing collective" as it is about the aft cyclic itself. I may be misreading or misunderstaning his emphasis, however.

[[email protected]]

Lonewolf 50 - yes, if only he had said exactly that instead of talking about 'best-kept secrets' and special techniques that fly in the face of conventional wisdom - we wouldn't have had a 20 plus page thread with insults and handbag swinging!

[SASless]

Now that we have the 1969 NASA Report on the OH-5 Autorotation Test Flights.....I am waiting for Pete to get back with us once he has had time to read through that document.

There does seem to be data in that report that presents a contradiction to some of the things he said. It would be nice to hear his comparison of his thoughts versus the Report.

A few others have made comments that do not necessarily coincide with the Report's data.

[Thomas coupling]

The report from nasa tries to open but then stalls. Anyone got another link please?

ta

[RVDT]

Looks like the ladies have put the handbags away!

As to the why's and wherefores -

I have a soft spot for Ray Prouty always making sense of these matters and managing to put it into terms for the average Joe to understand.

His articles have been around for years and have thankfully been resurrected into modern digital format from multiple sources. Even available or the "i" fraternity as well I think thanks to Shawn Coyle.

Read Ray's sensible articles and you may find that there is a little bit more to it than the hissy fit demonstrated previously on this thread!

I have met him a couple of times and he is a true gentleman.

He is even a "go to" guy for Pete Gillies.

[G0ULI]

When reading the report it is also necessary to remember that the Vietnam War was in full swing at the time and that obviously influenced the mindset at the time. An extra couple of hundred yards flight in a battle damaged helicopter might make the difference between escape and capture by the enemy, or quite literally, life and death. Given the choices facing a pilot in that situation, they may well have considered the risk worth taking at that time. This experiment was clearly undertaken due to stories that some pilots had managed to stretch the autorotation range under combat conditions, but I suspect that there were many more who didn't and paid the ultimate price. A very interesting historical document, but not the basis for ignoring the figures in your helicopter manual.

[SASless]

GOULI,

Having spent a bit of time there....if you think there are variables in autorotations.....the variables in determining one's fate flying helicopters in combat are far more varied and much less susceptible to codification than the matter of helicopter aerodynamics.

Might I ask you how you arrived at the opinion the NASA Testing was predicated upon such a notion?

That it was done on an Aircraft that did not make it into the inventory and not on the Huey would suggest otherwise.

The OH-58A was late in the War and in much fewer numbers than the Huey....as the OH-6A was the primary light helicopter in service.

Each aircraft in use had the standard Autorotation Airspeeds identified and established procedures for doing such kinds of descents and landings.

Lord knows we did enough of them in practice and for real over the years.

If you are interested....this web site is an interesting place to take a wander through.....it is not a complete data base but does have a wealth of information about US Army Helicopter Losses over the years.


http://www.armyaircrews.com/index.html

[G0ULI]

SASless
Apart from the Vietnam War, this was also the height of the Cold War. NASA and the US military would naturally investigate anything that might allow an aircraft to perform that little bit better. The helicopter used was probably just what NASA had in its inventory for use at that time as being representative of a general purpose helicopter. As the report implies, it was the first time anyone had explored helicopter performance right at the edge of it falling out of the sky. During and after any war there are numerous tales of pilots achieving the impossible. It was probably only in 1969 that the expertise and equipment became available to actually quantify whether these stories contained an element of truth. Nobody would believe a plane with one wing would fly, but an Israeli pilot landed an F15 in 1983 with a wing missing after the plane was involved in a collision with another aircraft. There is always something new to learn and reality doesn't aways match the theory. As you rightly point out, it is just my considered opinion that this was what prompted the experiment at the time, but 45 years on I suspect all current helicopter pilots are benefiting to some extent from those experiments.

[SASless]

For those folks that have trouble getting to sleep at night....and as a reminder to most of us the difference between working pilots and Test Pilots....I recommend this Research Paper for some light late evening reading. It was done in 1985.


http://www.ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19860020337_1986020337.pdf

The statement that jumped out at me was the comment about Autorotation being an Energy Management Technique.

The aircraft used in this study was a Jet Ranger with a High Energy Blade System....weights in the Spar Cavity at the end of the blades for those of us that have trouble tying our shoes.

[GipsyMagpie]

Gipsey: You have already confused the abbo's and newbies with your incorrect disc response description (Grenville for one). Crab got to you before I did
Which now means someone like me/crab/RotorIP/SAS/ eta l have to come back on here wasting our time re-iterating what has been siad time and time and time again.
So glad I am wasting your time. I love a challenge so time to engage the brain in a quest to supress smart arses like you. I have thought on the subject some more and realised I was wrong but so are you. The pitch up on engine failure in forward flight is not solely due to the retreating blade stalling (Although I suppose at high speed this could also occur). It probably has to do with the following factors:

1. The reduction in rotor thrust on engine failure

2. The relationship between the thrust line and the fuselage aerdynamics such as the amount of tail down force in forward flight

3. Flapback

So:

I think we can all agree that thrust reduces on engine failure.

So in forward flight you need a download on the tailplane to balance out the moments generated. If you change that balance by a loss of thrust (and for hubs with a hinge offset, the hub moment too) you still have the tail download so you pitch up.

Finally there is flapback. This depends on the advance ratio - as you go faster forwards the advance ratio increases (forward speed over rotor speed - giving differential lift between the advancing and retreating blades which gives maximum rate of flap up on the advancing side and vice versa - net effect is flapback). So if rotor speed suddenly slows then advance ratio increases and you get flapback.

There are probably exceptions of course. :) I believe the aircraft standards specify that there must be no more than a specified maximum change in pitch, roll and yaw. I seem to remember the spec saying a change which assists the pilot reaching optimal autorotative parameters is preferable.

[topendtorque]

Gypsy, go back to your caravan in Romania, that's frog's manure. I've been silent but I'll come back sometime soon with what I do, it's saved me and others heaps of times.

Gouli, mate, there ain't a plot behind every tree.

cheers tet

[SASless]

Suck Backs...and Blow Backs in the game of Uckers i fully understand....but most of what is said here might as well be Swahili to me.

DB,

The latest NASA Paper I linked.....says the US Army did not teach the "Check" method.....which I faintly recall being the case.

We sometimes started the Collective Pull with the Nose of the aircraft still a bit above level after the Flare and held that till the Heels of the Skids almost touched then getting the skids level as full touchdown was made using the rest of the Collective Pitch. The Pitch Pull was one steady movement from the first application of Collective till the end of the maneuver.

[Hughes500]

Sasless

All the 300 have the spoiler, never flown one without, it's bad dough with one on !
Have fun

[GipsyMagpie]

Gypsy, go back to your caravan in Romania, that's frog's manure. I've been silent but I'll come back sometime soon with what I do, it's saved me and others heaps of times.

I rather think you have missed the point. What I have explained is why a helicopter will pitch nose up when the engine fails (all by itself with no help from you) NOT what a pilot should do. What you do is really of interest to me but trust me when I say I have explored and survived every corner of the avoid curve. Recovering rotor speed with lever is critical but there is much more to it. Ever tried from the hover at the top of the avoid curve? Trying to balance the need to maintain rotor speed against the need to gain forward speed in the height available. Marvellous fun. The one from the knee is also eye popping (low speed and low height).

And anyway, so glad your racial prejudice is alive and well.

[Tailspin Turtle]

SASless: The aircraft used in this study was a Jet Ranger with a High Energy Blade System....weights in the Spar Cavity at the end of the blades for those of us that have trouble tying our shoes.

I was at Bell at the time. (The paper says OH-58A but I remember it being a Jet Ranger.) The object was to provide increased safety in nap-of-the-earth flight within the low altitude/high speed avoid area. If I remember correctly, it eliminated both avoid areas. One demonstration was rolling the throttle off at flight idle on the ground, lifting off and making a 360-degree pedal turn, and landing back. (There was a light on the cowling to indicate that the throttle had been closed.)

Of course, the rotor would still be turning the next morning...

[Lonewolf_50]

The pitch up on engine failure in forward flight is not solely due to the retreating blade stalling (Although I suppose at high speed this could also occur).
Uh, at the moment of engine failure, if you aren't already in retreating blade stall it is unlikely that losing an engine will cause it. But that depends. If you are at max conserve airspeed, probably won't hapen. If at max range, maybe. In a twin going at max, I suppose that losing one and trying to fly at the same speed (instead of slowing down to max S.E. air speed as one should) might get one into such a flight regime, since my back of the napkin sketch shows a decrease in Nr which influences AoA which gets you nearer to where the retreating blade might stall in higher speed flight. I will suggest that such combined factors influence why the test pilots lay out the charts to identify why you don't go faster than X in a twin with one engine off line. (HC earlier made a point about the underpowered S-76 and it not so great single engine performance, maybe there you'd be more likely to see it ... )

The rest of your post: I am not sure what flight regime the helicopter is in before engine loss.
1. The reduction in rotor thrust on engine failure
2. The relationship between the thrust line and the fuselage aerdynamics
such as the amount of tail down force in forward flight
3. Flapback
I think we can all agree that thrust reduces on engine failure.

Huzzah, we can indeed.
So in forward flight you need a download on the tailplane to balance out the moments generated. If you change that balance by a loss of thrust (and for hubs with a hinge offset, the hub moment too) you still have the tail download so you pitch up.
Which model of aircraft are you referring to? Some have horizontal stabs that change their pitch a bit to accomodate the airspeed one is flying. Others do not.

In closing, I'd like maple syrup with that order of flapbacks, sir, two strips of bacon, grits, and a cup of black coffee. :}:cool::8 Cheers.

[SASless]

Turtle,

The Photo shows a Jet Ranger and the Report says OH-58A.:oh:

Just typical Bell attention to detail!:ouch:

As I am not one for interpreting Hieroglyphics in the Original Greek....can we trust the findings of the Test Data in light of the slight error we have detected in which aircraft was used?

Why is it Jet Ranger Blades turn....turn....turn...and turn....while you are busting for a Pee and there are people standing around gawking at the pretty helicopter?:{

How many pair of Army issued half leather flying gloves ever got wrapped around the T/R drive shaft of a 58A?:rolleyes:

[topendtorque]

I will spend a couple of seconds replying before I get out, do a bit as I am fearful of what newbies might read into your deliberations. They should refer to the basics until they become operational where they should then be taught survival in whatever mode they operate in and don't clutter themselves with your, ahhhh, procrastinations.

It was explained to me in the beginning that the helicopter would slowly pitch downward with only the collective bottomed after engine either stops or is rolled off quickly, and it is easily demonstrated. Try it, lock the cyclic and see what happens. What it might or might not do momentarily is of no consequence.

Mate I live in the avoid curve, have done for forty years and I do the avoid curve stuff as a straight line to any height down to fifteen knots in the 47 and 25 knots in the R22, I have survived and had pupils survive sudden stoppage at 60 and 70 feet (one of which in my case a free-wheel failure, the accompanying noise is terrifying) without a scratch in the '47 and regularly do the hover stuff at down to 250 feet in either, I have had heaps of failures and practices at any speed any higher height, never ever have I experienced nose pitch up of its own violation that has been a worry. I did tho, bend the skids of an R22 when it failed at fifty feet and just starting to translate above trees at max gross and had to do a 90degree turn port to get into the only avbl space on a stinking hot day with moisture dripping everywhere. However I found later that machine was rigged wrongly (auto RPM too high) as the beacon went off in my headset, prior to the low RRPM warning horn, so I had unwittingly signed myself to heartache by doing the automatic full down quick time.ROD too high.

If you are an instructor or are influencing anyone with your theories please talk to your counsellor, I do think you need some medication.

I should add that we also practice controls locked or jammed in various scenarios and the resultant swings that one can get by locking the cyclic and playing with throttle, and pedals, should not confuse this discussion.

[John Eacott]

The statement that jumped out at me was the comment about Autorotation being an Energy Management Technique.

Do pay attention SASless: 368 posts ago (http://www.pprune.org/8203535-post55.html) :p

[henry_crun]

http://www.daveswarbirds.com/usplanes/photos/kellett_YO-60.gif

credit: daveswarbirds.com


As a side issue, it does seem that autorotative flight training is limited by descent time. Would it not be beneficial to keep a few small autogyros and use them to gain longer experience of flight with unpowered rotor? I suppose the surviving autogyros are now in museums, but could not some designs be put back into production for training and sport purposes?

Did I just want to break up the discussion with a nice piccie? Er, yes m'lud, guilty as charged.

[SASless]

Eacott....better start wearing a Hat while outside.....the Sun is working on your bald spot!

Some where back in the few pages of this thread.....I endorsed that notion.


Now that Henry brought it up....I too thought about Auto Gyro's and the fact they are always in autorotation. Plus, they have no Collective.

My first and only crash in a Rotor Winged device was one of them things that was loosely chained to a platform built on the bed of a Pick Up Truck.

We got the Rotors to spinning by Hand.....the Truck Driver took off down the runway and we flew the Bensen Auto Gyro over the platform staying about six inches to a foot off the platform.

Mind you we were like 15 years old or so....and in our course of instruction no one reminded us of the dangers of pulling too hard on the chains by applying aft cyclic and "climbing".

As the Chains were far stouter than the Rotor Blades....at some point two of us learned the hard way about that sad situation when the Rotor Blades went 600 different directions all at once except for the remains of the one blade which purely beat the Hell out the two of us that were flying the machine. Not only did it whip hell out of us....it did it really quickly when the blade made about three rotations down across where we were sat.

I should have learned from that beyond what i did.....never again had anything whatsoever to do with Auto Gyro's....and refused even to do Biennial Flight Reviews for Auto Gyro Pilots as I did not want any mention of an Auto Gyro in my log book when they went out and killed themselves.

My next experience with Rotor Craft was an Air Force H-21 at Langley AFB one Summer while a Civil Air Patrol Cadet. We got a ride in the thing and made it all of about three minutes when it dumped a Jug and made a Forced Landing.

Autorotations have been a part of my flying career from the start it would seem.

I digress but it does make one wonder why auto gyro's (well designed and professionally built) died out.



http://www.youtube.com/watch?v=KN4q1BNDjtk

[newfieboy]

I have followed this thread and read every post as a 13500hr utility pilot. Be interesting to know just how many posters have had actual engine failures, single or twin. Myself have had three all below 1000ft in single turbines. Dumped the pole on everyone didn't have to think about cyclic inputs. It just happened instinctively to keep nose up and RPM. Most of my time on the end of a 100ft line, if you guys can't decide the right action, too late. Me I have a cunning plan every turn in the curve....tis to stay alive whatever it takes. Worked up to now.

[SASless]

Just shy of 13,000 hours....one engine failure in a Hughes 500D....landed with no damage to the Helicopter. One in-flight shut down on a single engine on a 212.

One engine failure in the cruise, one engine shot out flying low level with a forced landing due to being too heavy, and one event where one engine had terminal compressor stalls followed seconds later by the other engine doing the same....while dropping a sling load on a mountain top....autorotated down the side of the mountain and regained the use of one engine, in the Chinook.

Only the dual engine problem was a very near thing.....and it was a dilly.

As Newfie says....have a plan in mind if time is short as you do not have time to cook something up sometimes. The Dive off the Mountain had been planned months before in a discussion over several Beers as we flew to that site often....and there was no place to land there. Granted, the discussion was about a single engine failure.....not both at the same time!

[newfieboy]

Right on SAS, now we getting somewhere....hats/beret off. Lets start another thread tilted Been there, Seen it, Got the tee shirt thread......only can post real life adventures...

[GipsyMagpie]

I am exactly talking about what happens with controls locked. That's what the whole post was about. Its theoretical. If you haven't as you've stated done something about it you are dead! And yes the nose does drop when the pilot drops the collective. Its like the demo on flapback and inflow roll you get when first doing basic transitions - nice for a demo but the pilot (hopefully) instantly compensates and it becomes something the instructors scribble about on a board.

And turns out my explanation is remarkably close to the one in FTM 107 - Google it. Chapter 10 is the one you want.

As for not passing it on to students, it all depends on the student. Sure, not a basic guy, but its a worthy discussion point on a black weather day. I am in no way advocating any technique based on the fact the nose might pitch up a tiny amount on engine failure. The yaw will be the dominant factor.

Great to hear the war stories. All my experience is from practice engine failures to determine the avoid curve and maximum pilot intervention delay time so hearing real stuff is great. Had plenty of single fails though - perhaps you should go to a nice reliable twin or triple.

Cheers GM

[cattletruck]

I recall our fixed wing brethren have a description for how one shoves the stick, from memory I think they refer to it as flying through either feel or flying through displacement. With all beginners it's displacement then as they build experience they (or most of them at least) learn the feel, and the flying bit becomes second nature.

A rotary wing example of this was when I was learning the hovering autos in the low inertia rotor r22. Instructor chops the throttle and up goes the lever - control displacement pure and simple. I have no recollection of where the cyclic was shoved as I just wanted the skids to land flat. Then I moved to the high inertia rotor B206. Instructor chops throttle and up goes the lever and up went the JetBanger http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/eek.gif. But I was onto it quickly and beat my instructor in pushing the collective back down then pulling it back up again in a more sympathetic way relative to our rate of decent. I think my instructor was suitably impressed, I even had the nose yaw pinned on its heading without much thinking about it.

Not a terribly exciting story I know but one that does show the development mode of learning to fly under supervision. Autorotation is a stable mode of flight that one should be able to transition into automatically and easily after a loss of engine power, so that when one looks up and sees that one is about to park the machine in a big dead tree looming up ahead one may have brought themselves that extra few seconds of flying around it. We may learn this maneuver through displacement technique first, but after we get the hang of it and explore the envelope under supervision, we should find that moving into the stable flight mode of autorotation becomes second nature.

Having said all that, I know some fixed wingers, albeit low timers, that never mastered flying by feel and probably never will. Yes they are capable of flying to an acceptable standard, but they tend to work harder at it than most to achieve a rather ordinary outcome.

[Gordy]

Newfie.....

You brought me out before the 14 pages were up....

How ya been? You gonna make it home for Christmas this year? Hope so... Hopefully I head home on Friday.....Happy holidays and all that crap, & Say hi to your lovely wife. Have just found out tis cheaper to fly to Cyprus than the UK, not that I really wanted to visit the UK but oh well ---ya in?

Oh and to keep it relevant...... I too have my "cunning plan"... (although to be honest, mine is all about IIMC---never really had to think about the plan for engine failure....it just came natural like), anyways, best advice to any student.....you better have one.... Whether it is down or aft first---who cares, just have a plan.

[FH1100 Pilot]

Gordy says:I too have my "cunning plan"... (although to be honest, mine is all about IIMC---never really had to think about the plan for engine failure....it just came natural like)

Well I guess for the 2011 "Mosby" pilot (the texting EMS guy), his plan didn't come "natural like." Either he didn't have a plan at all or he messed up the plan he did have. And since he was a 2500 hour, military-trained pilot...it makes you wonder, doesn't it?

If you're cool with bottoming the lever first and starting an immediate descent upon engine failure, hey that's fine by me. Because maybe in your limited way of thinking the descent is inevitable anyway, so why not start now?

But me, I'd rather get the nose up first and hold altitude (if I can) while searching for a place to put it down. Getting the nose up buys precious seconds, especially when I'm bopping along at well above best-auto speed.

Engine failures don't always happen in the training environment at 80 knots with good forced-landing areas in reach.

I know that all of the helicopters I've flown will benefit from "cyclic-back" first in cruise. Now don't be stupid. Don't be dense. Don't assume that I mean you can bring the cyclic back and...la-la-la...do nothing else. OF COURSE the collective needs to go down now! Of course. Nobody is disputing that. But the instinctive priority should be on getting the nose up while you get your hand back on the collective and start pushing it down. While you're doing these things (without looking at the controls) you can be looking for a place to set down. In my last job my flights were frequently 1.5 to 2.0 hours long in stabilized cruise. No way am I going to sit there with my hand on the collective the whole time. No thank you, my left hand will be on my knee, just inches and microseconds from the control.

The "Mosby" pilot was down to around 300' agl at 116 kts GS when his engine quit. And then, according to the NTSB, five seconds later the helicopter hit the ground at a...a 40° nose-down attitude at a high rate of descent with a low rotor rpm.
A 40 degree angle. Huh? How could that happen? I'm sure his "plan" was to bottom the pitch, which, is probably exactly what he did...first. I mean, do we think he was incompetent? Do we assume that he did nothing? That he froze on the controls? Not me. I believe he at least bottomed the collective as we all would. After all, he was worried that it would quit...expected it to quit. And still F'ed it up. Why? Let's let the NTSB fill in some blanks.
The simulator flight tests conducted after this accident showed that when a loss of engine power occurs in the Eurocopter AS350 B2 at cruise airspeeds, the pilot must simultaneously apply aft cyclic and down collective in order to maintain rotor rpm and execute a successful autorotation. However, the pilot’s autorotation training was done at airspeeds below cruise where less aft cyclic is needed to enter an autorotation. Further, FAA guidance on performing autorotations stresses lowering the collective as the initial step in entering an autorotation, does not emphasize the importance of other flight control inputs, and provides minimal information on the critical entry phase of autorotation.

Oh snap! Talk about the NTSB "dissing" the FAA! Wow. Because that's what's important here: The ENTRY into autorotation. Did you notice how the NTSB put "aft cyclic" first in their description of the entry into an auto for the AS350? Even the NTSB concedes that bottoming the pitch isn't the solution; it must be accompanied by a simultaneous aft cyclic input. How much and how fast you make that input will depend on how low you are and whether you have a forced-landing area all picked out. So there you have it, straight from the horse's (NTSB's) mouth: Collective-first is wrong.

In our hero brains we all assume that we'll respond expertly and correctly to every emergency God can throw at us. "Mosby" proved otherwise. Because - from cruise speed, anyway - the urge to bottom the collective first is the wrong one. Yes, it's what we've all been taught since our first days of dual in that helicopter that auto'd at the same speed it cruised at, or in the training scenario where the engine was pulled at 80 knots in the traffic pattern. But in reality...out in the real world, in aircraft that cruise along at a speed much higher than best-auto, the instinctive reaction should be to get the nose/tip path plane up first, and then get the pitch going down. That's my plan.

Will other plans work? Sure, obviously, if you have the time and altitude to get into a stabilized auto before you start running out of options. But if you don't...?

[DOUBLE BOGEY]

FH1100 - Brilliant posting!!

DB

[Devil 49]

1, on the ground after rolling back to ground idle
1, a Twinstar in flight

Add 1 power train failure in a H 269B

[Devil 49]

The Mosby accident FH1100 mentions is startling, especially the final 5 seconds- quoting from the NTSB report

http://www.ntsb.gov/doclib/reports/2013/AAR1302.pdf:

"The pilot’s awareness of the helicopter’s low fuel status and the near zero indication on the fuel gauge as the flight continued should have given the pilot ample warning of the impending engine failure and provided him with the opportunity to prepare to execute an autorotation. However, it was evident from the helicopter’s impact in a 40° nose-down attitude, on a heading nearly opposite to the direction of travel, at a high rate of descent, and with a low rotor rpm that the pilot did not successfully execute an autorotation following the loss of engine power."

[Lonewolf_50]

I don't think those words mean what you think they mean. So there you have it, straight from the horse's (NTSB's) mouth: Collective-first is wrong.
That's funny, I read the same report and did not find them saying that.
Let's peak at what they actually wrote, and what you excerpted from the report:
the pilot must simultaneously apply aft cyclic and down collective in order to maintain rotor rpm and execute a successful autorotation.
However, the pilot’s autorotation training was done at airspeeds below cruise where less aft cyclic is needed to enter an autorotation. They identify the case as "at cruise speed." They identify his training as not covering the loss of power at cruise speed. That's a systemic error, or "supervisory error" as we used to call it in the Navy when we investigated mishaps. To a certain extent, you can argue that by that lack in his training he was set up ... if you want to so argue. But shouldn't a professional pilot know about how that works and should work? I'll argue that a professional pilot should, and I hope you'll agree with me.

The key takeaway is that he was a 116 knots, which I gather is higher than "best" autorotation speed.
When he lost the engines he did not transition to best auto speed as he lowered the collective, which you do have to do. Funny, the NTSB concurs with me, on the simultaneity of how that happens. As before, helicopter pilots fly with both hand, and helicopter pilots multi task. If you don't or can't, fly something else.

As to your analysis, it is misleading to taking these control inputs in isolation. That isn't how helicopter flying is done. The controls work together.

Other than that little carping, I think you made some good points in your post. I completely agree with you that he either had no plan, or the plan he had was badly executed.

[Hughes500]

I have to say that I am gob smacked that so many professional pilots seemed to have been trained so badly and or their opc's are done without an auto from a cruise speed :uhoh: Or am I missing something ? it is bleeding obvious that you have to apply aft cylic ( from a fast cruise)as the lever goes down otherwise you are in a very uncomfortable nose down attitude. Which will then require a massive amount of collective as you load the disc to recover attitude with cylic.
Again have I missed something here ?

[FH1100 Pilot]

But Lonewolf, look at the way the NTSB wrote it. Yes, they said "simultaneously," but then they put "aft cyclic" first before saying "down collective." I, for one, find the wording of that phrase curious. It's like they know that during the autorotation entry, the aft cyclic input is as important, if not more so, than lowering the collective. But who knows.

And Hughes, you're not missing something. We've heard over and over in this thread from people who claim that the first response to an engine failure is "LOWER COLLECTIVE!!" with a kind of "oh yeah" addition of "maintain attitude" as if the latter part isn't as important as the prior. And that's fine...up at altitude where there's plenty of time to sort things out. But we don't always have the luxury of time. The "Mosby" pilot didn't.

I think there are three reasonable scenarios for the "Mosby" crash.

1. When the engine quit, the pilot uttered either one or two or three four-letter words as he rapidly dumped the collective, just as he was trained to do and just as Thomas Coupling suggests. This probably bunted him over into a 40 - 50 degree nose-down attitude. In the remaining three of the five seconds left in the flight, I'd bet that he had the cyclic back in his gut, but it was largely ineffective and only got the nose back up to 40 degrees before impact.

2. When the engine quit, maybe the pilot did actually panic and freeze, and did nothing with the controls for the remaining five seconds which probably seemed very short to him. Hey, I've seen it happen! Pilots freeze up! And it would explain why the ship impacted the ground on a reverse heading to the initial. If he did nothing to any of the controls, tail rotor thrust would've yawed the thing around as it plummeted to the ground at a 40-45 degree angle.

3. When the engine quit, he knew he was boned and that it was all going to come out...the lack of preflight, the poor planning, the texting with his girlfriend...the girlfriend herself (and wouldn't his wife be surprised to hear about that!). So maybe he just said, "Goodbye, cruel world!" and rode 'er in with a feeling of intense resignation and despair.

I don't know. I *do* know that if he merely dumped the collective first, as so many here seem to suggest, then he sealed his own fate.

[Lonewolf_50]

But Lonewolf, look at the way the NTSB wrote it. Yes, they said "simultaneously," but then they put "aft cyclic" first before saying
"down collective." I, for one, find the wording of that phrase curious. It's
like they know that during the autorotation entry, the aft cyclic input
is as important, if not more so, than lowering the collective. But who knows.
And again, auto entry from cruise airspeed. There is more than one case of the need to enter an auto, as you know.
And Hughes, you're not missing something. We've heard over and over in this thread from people who claim that the first response to an engine failure is "LOWER COLLECTIVE!!" with a kind of "oh yeah" addition of "maintain attitude" as if the latter part isn't as important as the prior.
No, that's not right. Control Nr, fly the aircraft, and the controls work together.
But we don't always have the luxury of time.
True. In the Mosby case, trading airspeed for rotor energy was available but not taken as a method to get into the best auto situation his circumstances presented.
1. When the engine quit, the pilot uttered either one or two or three four-letter words as he rapidly dumped the collective, just as he was trained to do and just as Thomas Coupling suggests. This probably bunted him over into a 40 - 50 degree nose-down attitude.
If you let the nose fall like that, you aren't flying the aircraft, it is flying you.
2. When the engine quit, maybe the pilot did actually panic and freeze, and did nothing with the controls for the remaining five seconds which probably seemed very short to him. Hey, I've seen it happen!
Possible. This goes well with the idea that he didn't have a plan, as noted a few posts back.
3. When the engine quit, he knew he was boned and that it was all going to come out...the lack of preflight, the poor planning, the texting with his girlfriend...the girlfriend herself (and wouldn't his wife be surprised to hear about that!). So maybe he just said, "Goodbye, cruel world!" and rode 'er in with a feeling of intense resignation and despair. Probably not.
I don't know. I *do* know that if he merely dumped the collective first, as so many here seem to suggest, then he sealed his own fate.

And if anyone here has suggested that one applies the controls in isolation from one another, they need to be reminded that such is not how helicopters fly nor should be flown.

The energy management concept certainly seems the better framework for teaching about this facet of helicopter flying.

Cheers.

[SASless]

The pilot must simultaneously apply aft cyclic and down collective in order to maintain rotor rpm and execute a successful autorotation.
However, the pilot’s autorotation training was done at airspeeds below cruise where less aft cyclic is needed to enter an autorotation.

You Bill Clinton Wannabees and drop outs from English Grammar courses in Junior High School need to quit trying to parse words.

Since you are all very challenged re sentence construction and the elements of Grammar that means you are quite wrong and need to pay attention.

Simultaneously......is defined to mean "At the same time".....the usage of the phrase "Aft Cyclic AND Down Collective" is not order specific. Either way it could be written with the words Collective or Cyclic in either sequence means nothing other than the one set of words has to be written before the other.....and that is all the hell it means.

The use of the word "less" connotes Aft Cyclic was required.....but not as much as in a high speed cruise situation.

Jesus Guys.....quit twisting what was written to try to buttress your argument.

This is getting silly.


DB.....as you know some folks at EC due to your 225 experience and background in the past.....how about asking them to replicate the Mosby Crash Scenario for you....and report back what they find out?

I would really like to know if only lowering the Collective while in a level Cruise at 116 Knots in a 350 during an entry into Autorotation and not moving the Cyclic will result in a 40 degree or more Dive.....it cannot be that complicated to find out!

Likewise.....how does one accomplish a 180 degree turn at the same time and ...and lose Rotor RPM....as it is going to be a steep turn from 300 feet in a screaming ass dive where one would assume there would be some G Loading on the Head that would tend to build RPM.....something you all insist G Loading shall do?

Any 350 Drivers willing to try......Devil 49....you fly those EC things.....what you think?

[FH1100 Pilot]

Lonewolf:The energy management concept certainly seems the better framework for teaching about this facet of helicopter flying.

Boy, you hit the nail right on the head here. Instead of robotically lowering the collective at the point of engine failure, it's far more important to be concerned with energy management.

In cruise flight, a helicopter rotor has an enormous amount of energy stored in it. It would be a crime to let it go to waste. Sure, lowering the collective is of paramount importance, but that's not the FIRST thing you should consider doing - because that act will waste precious energy and time. In the first place, it will start a descent. Hey, you might not want to descend right away! Using that stored energy in the rotor to maintain level flight - even for just a few seconds - seems pretty dang important to me.

And you can't just "maintain attitude" either. Most helicopter cruise at a slightly nose-down cabin attitude, and a more pronounced "nose-down" attitude of the disk. So at the point of engine failure the disk *has* to be brought up to level, at least!...OR you're going to descend immediately. With the forward tilt of the mast in modern helicopters, that means the pilot would have to select a positive cabin attitude of around 5 degrees (more in an S-76) just to keep the disk level. But you want to do more than that. You want to get the airflow reversed from "down through the disk" to "upward through the disk." This will...eventually...happen automatically as the helicopter descends and the autorotation stabilizes, but you'll be using up precious altitude to do it...altitude you may not have if you're like many, many helicopter pilots I know who routinely cruise at 1,000' agl or less.

If you are cruising along at 500' agl with the wind behind you when the engine quits in your AS350 and you immediately bottom the pitch first, I guarantee that you'll probably not be able to get it sorted out and get the ship turned around into the wind in time for a landing. You'll probably just land straight ahead. If you do it right, you might not land at a 40 degree nose-down attitude. But if you insist that lowering the collective first is the proper way to enter an auto (especially in an AS350) you just might.

[DOUBLE BOGEY]

I do not want to be dick but......surely most competent, well co-ordinated pilots would "Simultaneously" move both controls and the pedals for that matter. Is that not the fundamental principle we all learnt right at the beginning. You cannot move one control without having to move the two others!!

That's why we can pat our belly and rub our head (or some such) at the same time.

I do think however, that slamming the lever down at high speed will initiate, and lead to, a strong nose tuck for some types. Maybe this is what happened in the Moseby accident. Paradoxically, knowing he was short of fuel, he my have slammed the lever to the floor and just failed to prevent the nose tuck and the subsequent loss of control it leads to.

SAS - sorry just saw the end f your post. I have about 3k on 355s (of course two engines) but the fuselage is essentially the same shape. The nose definitely drops if the lever is lowered aggressively and I think this is similar to most types but most of us make a "joined up" control movement instinctively and the tendency is overcome without us seeing it through to its full manifestation.

Same as Flapback and inflow roll during take off run. How many of us, not doing basic instruction, actually recognise this anymore. It's become a subconscious set of contro movements in response to attitude.

DB

[FH1100 Pilot]

SASless:Simultaneously......is defined to mean "At the same time".....the usage of the phrase "Aft Cyclic AND Down Collective" is not order specific. Either way it could be written with the words Collective or Cyclic in either sequence means nothing other than the one set of words has to be written before the other.....and that is all the hell it means.

I think that's very presumptuous of you. The NTSB reports are not thrown together as haphazardly as some people post on PPRUNE. They're carefully thought-out and worded. The fact is, they didn't put the "lower collective" item first. So nobody, least of all the great and wonderful, all-knowing SASless can infer or imagine or fantasize what they meant by writing it the other way 'round. (See, Bob? That's why nobody likes you! You have absolutely no respect for any of the egotistical, self-important blowhards on forums like these.)

In any event, it's true that a coordinated, simultaneous lowering of the collective and making an aft cyclic input would not hurt. But neither would making the aft cyclic input first. And in fact there are some obvious benefits to doing so, as I've stated. Had the "Mosby" pilot listened to the preachings of good Brother Gillies, he and his crew might not be dead now. I know, I know...pure speculation. But let the record show that, *if* he put the pitch down at all, the aircraft ended up lawn-darting at 40 degrees nose down. OUCH!

For the record, the "Mosby" Astar was not in level cruise when his engine quit; he was in a shallow descent. He stayed pretty much at 600' agl during the 30 minute flight, but as he neared the airport, being obviously over-anxious and stressed-out he began a premature descent and was only at 250-300' agl while still more than a mile from the field boundary when it quit on him. So...what...maybe another degree or two nose-down?

The other thing is that the NTSB did a lot of research about AS350 autorotational qualities in the sim. We all know that as good as sims are, they do not and cannot replicated every flight regime with complete accuracy. There may be aspects of the very weird dynamics of an engine failure at high speed cruise-descent that the sim "misses" or just synthesizes differently from the real aircraft.

[topendtorque]

I been thinking to myself, "self I must read this thread thru and contribute something, seeing as how that low level is where I have lived for the last forty years and check and training of survival in the small survivable areas of it is second nature to me, and many have come back and thanked me for getting them out of the poo at times".
I would like to keep it simple. At the end of it all I encourage people to think why it is not a good idea to be in an impossible to do a safe auto area, say hovering at 80 feet. They simply must come away from these exercises thinking how they will change their mustering or LL techniques when between 20 and 250 feet to always involve a safe airspeed.

1. As Nick Lappos says discussions and training in these aspects encourage us the think. The Robinson safety course is an excellent example in stimulating thinking in their explanation of energy management during autorotation; I assume other factory courses to be the same.

Thought process one, all helicopters are designed and tested for certification to sustain the inactivity of a brainless pilot for at least a second without further control adjustment once the power source becomes silent, one doesn't need to be violent. So entry is to position the A/C in a good auto flight or termination mode and you will drop quite a-ways doing that if starting from a low or zero airspeed.

Thought process two, my ab-initio instructor (ex Brit army) encouraged me to think along these lines. "There may be any number of reasons why you have to quickly enter autorotation. Upon noticing that things are not right you are to firstly, rationalise the problem - solve with your solution - then ACT. Because you're a blasted country bumpkin I'll give a full quarter of a second to start acting, any more and I'll thump you, which he would." A later debrief would explore my thought processes and actions.

2. Of the very many emergencies I have experienced all bar one were at LL and thanks to my ex Brit army mate I always had a spot in sight, it’s amazing what you will fit into at times.

Thought process three, always but always pick spots and plan your approaches to them as you are tooling along.

3. During my early check and training experience, in fact when I was getting checked out to conduct C&T having by then done a bit of it by one CASA man (or whatever the fed agency was called then) Holga Von (something long name, ex Oz army), he says to me. "You seem to be teaching autos at cruise speed 8 feet, 50 feet or 500 feet, or hovering autos at 300 feet, why not is it that you do not teach them at 40 knots and 250 feet where you seem to operate mostly all day?"

Thought process four, Jawohl! We quickly found some error inducement in pilots doing autos at 250 feet had they been conditioned to do them at 50 feet say and at high cruise settings. That error was to fairly quickly bring the cyclic back thus leaving one with no airspeed at a most uncomfortable height. (Not enough thought process)

There seem to me to be four parts of an auto; 1, entry, 2, decent during auto (range chasing if needed) 3, the termination area - say one knot of airspeed must equal one foot of height 50 /50 is nice where one begins to flare, then 4, the touchdown. It matters not how far one will fly in descent if at all, the main game is to arrive at a nice 'termination area', and the rest should follow. A good entry will easily facilitate this and it is where this discussion started so that brings me to what I do now which is to check out several regimes of our LL practices.

a) Fast cruise at super low level where one will bring a whole lot of pain if the cyclic is brought back too early and slams the T/R into something solid beneath, one first must give the collective a quick flick up, then down again as a small cyclic zoom climb is performed as part of a quick stop technique to arrive comfortably in the 'termination area'
b) More than 50 knots at say 50 feet where one simply enters a quick stop routine, collective going down smoothly as the cyclic aft is being applied to arrive at the same height and now established in the 'termination area'. Less than 50 knots down to say 25 knots, leave the A/S where it is until you intercept a 'termination area' further down, but that collective must be got down smartly.
c) At 50 to 250 feet and between thirty and seventy knots, under no circumstances do I want to see a quick check back on cyclic, cos it may hurt you when I thump you and me if it turns real and you have run us right out of airspeed in that nasty height area.
d) Normal cruising at a higher height as between 40 knots and above, checking back on cyclic is not necessary as it may condition you to a bad mistake in tighter circumstances, refer point 1 para 2.
e) Very slow A/S or hover at LL. This procedure is checked at 300 feet after demonstration and follow thru, and at lower heights it is demonstrated only with power recovery and always positioned to reach a target spot. Here I use the point process. Point everything you got brother at your spot, collective, cyclic and right pedal. The RRPM will not decay too much and can be easily got back in hand after about 80 to 120 feet which is where the A/S will again be approaching 60 knots. Do not check back on cyclic until the aircraft is pointed downwards, then I will calmly say, “60 knots attitude please - not 600”, it is then quite a large check back. First couple of demos as hands off I ask them to strongly monitor both the RRPM and A/S. it only takes a second to get down that first bit with the cyclic forward and the RRPM will be still be in the green.

I often use the analogy of the F/W being a bit high on finals; one can simply quickly dive off the extra altitude without increase of speed to arrive a nicer height, so too do we dive off height with the point process to arrive at a safe 'termination area' with enough inertia still in our M/R. You may even be lucky enough to have picked up a small extra airspeed which can be flared off to help arrest ROD. In all slow entries either maintain or increase your A/S if possible. I.E. Do not check back on cyclic at entry.

In all instances I talk a lot about ROD being at the very minimum you can achieve at ground level as high ROD is what will kill you.
It is incredibly important that the auto RRPM must be set up as the Manufacturer describes in the manual. If it is too high ground the A/C as it is too easy to slam the collective down and increase the ROD too much, and I have the back to prove it.
There are four items that need to be completed and checked when an entry to auto is required; 1. collective down RRPM in the green, 1. Set the A/C attitude for max range A/S or the desired A/S under the circumstances, 1. Safe to reach a spot or already turning into wind. 1. Get a mayday out.
Note the generic priority, one doesn’t need to psyche oneself to think about a mayday, just hold the blessed xmit button down while you are briefing others or whatever. Any person listening to a radio is an attentive person, they will do something to help.
Autos from higher heights can induce errors in a pilot's range assessment if auto flight is continued after joining needles. The glide path then changes, so when joining needles at say 300 feet fly away and look away.

Please fly a little higher and a little faster if possible and no passengers while doing Air-work.
None of the above is a recipe for survival or designed as a pissing contest from a predicted height A/S combination say, as every A/C and day is different. It is amazing how easy it is on a very cool, windy day and, lightly loaded compared with a muggy, hot day with a heavy A/C.
MERRY XMAS tet.

[PeteGillies]

Hello again to the PPrune crew. This is Pete Gillies, away for a couple of days doing my day job.


As before, I extend special thanks to FH1100 Pilot for his great support in getting this simple message across to the many readers and contributors to this thread. And yes, Ray Prouty is at the top of my list of helicopter aerodynamics gurus. In fact it was at one of his lectures years ago that I picked up the first clue of what turned out to be my quest to make Cyclic Back an integral part of getting into a survivable autorotation.

I just reread my original post, the one that began this thread, and I see that I definitely made a mistake when I said that if the rotor rpm drops more than about 5% below low green or the lower red line (same thing), the flight is over. I should have said it may be over. In posts following that initial one I agreed that the absolutely critical rotor rpm may be well below that figure, but "low red" is determined after many, many flight tests that cover a particular make and model and just about every conceivable variation in D/A, airspeed, flight weight, center of gravity and things I haven't mentioned and probably have never heard of. The sales department wants the rotor rpm operating range to be from zero to infinity, but the engineering department seems to have difficulty reaching those limits.

So to those of you who have been bashing me about this "over" statement, please ease up a bit. I apologize for my initial choice of words. Let the un-powered rotor rpm drop below 5% below low red line and the flight MAY be over. Good luck to you if you want to explore that region without an engine to back you up.


It's been a long day for me here at our "left coast," but I promise to contribute again tomorrow. Guys, it's so simple: Here is is again: Power fails. Cyclic back and lever down, simultaneously or in that order. Pick a place to land. Make that spot.

Works every time but the cyclic back part is not needed from a hover.

We're already writing new software for power failures when on autopilot. And guess what? Cyclic back and lever down simultaneously! Duh. Lever down and then cyclic back? No way in hell...

This Cyclic Back thing is the Swiss Army knife of what to do when you are caught completely by surprise by a power failure while in forward flight. Can't remember anything else? Do this and you'll have a flyable helicopter all the way to the ground or water.

And for you non-mil pilots... Take a look at how many times and for how long your left hand is off of the lever during a typical flight. God gave us left legs so we could steady the lever conveniently while our left hand was, ah...well, you know...ah...hmm...have to be politically correct here...so YOU insert here (_______________) what sort of things you do with your left hand while flying SPIFR, for instance. As I said in a previous post, the lever (collective for all you Yanks) :-) is nothing more than a thrust control, a beta control. Set it and forget it for many types of missions. And it's a great place to rest your left hand, too.

Hey, I'll stop now and save something for tomorrow. My sincere thanks to all of you who support Cyclic Back in any way, shape or form. I'm buying the beer for all of you!

Pete

[henry_crun]

Cheers, Pete!

Mine's a......

http://img1.etsystatic.com/009/0/5374187/il_570xN.455643841_r1iu.jpg

henry_crun

[John Eacott]

henry, Pete was offering to buy the beers.

Not lolly water :p



I'll have either a

http://media.au.timeout.com/contentFiles/image/generic/craft-beers/little-creatures.jpg

or a

http://www.thebasketcase.com.au/wp-content/uploads/2013/09/gift-baskets-one-boutique-beer.jpg

Then I'll shout one for you, even though I'm more an energy management proponent :cool:

[Ornis]

It's been interesting, reading the thread. I don't think I could learn to fly a helicopter now, but I understand the broad theory. I know fixed wing pilots have trouble switching to gyrocopters. After climbing to avoid an obstacle they naturally push the stick forward to gain airspeed. That unloads the rotor and it's off for a quick post mortem.

Therefore, speaking with all the authority of an old coward, it seems two things about helicopters are important: if the engine fails you don't have any time to think, so you'd better have a repertoire of reflexes.

If you're hovering to do a job, you're probably waiting for something to go wrong. If you're cruising along thinking about beer, you twitch the stick back and buy a bit of time to think.

Note. There are many factory-built gyrocopters available now. Some are enclosed side-by-side. Germany and Italy make superb machines.

[SASless]

https://scontent-a-atl.xx.fbcdn.net/hphotos-ash3/t1/1476365_578511098901512_936041720_n.jpg

[awblain]

There's lots of energy in a rotor, but not too much.

The kinetic energy of a rotor in a small helicopter is in MJ.
Generally (in J) ~ 0.005 x rotor mass (in kg) x disk area (in m-squared) x rpm-squared; for Glasgow, 200kg, 75m^2 and 200rpm gives ~3MJ.

However, it's powered by a MW or so, so if you turn off the engines from a high power setting and do nothing else, the energy stored is only matched to a few seconds of power.

Other relevant quantities are the energy from forward speed
(in J) ~ 2 x total-mass (in kg) x speed-squared (in kts); for Glasgow, 2500kg and 100kts gives ~5MJ.

And potential energy from height
(in J) ~ 3 x total-mass (in kg) x height (in feet); for Glasgow, 2500kg and 700ft gives ~5MJ.

Each of these energies is comparable, and so all need to be taken into account.
When cruising along, there's a good fraction of a MW going into beating the air too.

While I'm sure you should "Keep Calm", sometimes you'll need to "Act Quickly" as well.

[FH1100 Pilot]

Well sure, Awblain, we all understand that the energy stored in the unpowered rotor is not limitless. But here's the thing: If you're zooming along at 115 to 120 knots in your 407 or 350 or 119 or whatever, you're well above the speed for a stabilized autorotation. So you need to decelerate to that speed.

There are those who squawk like parrots, "RAWK, MAINTAIN RPM, MAINTAIN RPM! RAWK!!" But they're missing the point. Sure, RPM is important, I get that, I'm not an idiot and neither is Pete Gillies. But that's not all there is to it, right? There is a whole other half to the equation of entering an autorotation.

The "Maintain RPM" squawkers apparently would prefer to decelerate from cruise to best-auto speed while descending for a power-off landing. I, on the other hand, would prefer to do that decelerating in a level (or nearly so) cruise. If I can use the stored energy to buy a couple of those "...few seconds" that you talk about, then all the better! If only the "Mosby" pilot had had those "few seconds" more than the five seconds he ended up with.

I think it's truly laughable - and by that I mean the sheer arrogance of some of the pilots on this board who apparently all think they're better than me. And maybe they are, I don't know. Maybe everybody here is a better pilot than both me and the "Mosby" pilot.

I don't think I'm better than anyone. In fact, I know that overall I'm a pretty "average" helicopter pilot despite having a logbook with just as many hours as some of the more pompous credential-wavers on this forum. I read accident reports and go, "Dang, that could've been me!" I'm 58. I don't have lightning-sharp reflexes and powers of perception (if I ever did). I know that in any given emergency it might very well take me "...a few seconds" (but hopefully no more than two or three) to figure out what's going on and react properly to it.

We talk about a "normal pilot reaction time" of one second...one second? One-thousand-one. There, that was one second. Did you process the engine failure and react to it in time? Probably not. But you know what? Even two seconds is not a whole lot of time either.

I usually fly at a higher altitude than many of my friends...pilots who tell me that they, "...just prefer to fly low," who seem inordinately concerned (bordering on paranoid?) about some catastrophic failure that will require them to be on the ground right-goddam-now!

So when I fly I like to give myself time. You can squawk about rotor rpm all you want, but you're not looking at the complete picture.

[awblain]

I'm not suggesting you're wrong to say "the rotor has lots of energy", but I think it is helpful to quantify how much energy it has, and to bring these issues of trading and juggling energy to the fore.

That the energies in rotor speed, forward speed and typical height are comparable emphasizes the importance of managing that energy. I get the impression from the extended discussion that there are incorrect assumptions being made that the rotor energy is either dominant or negligible.

This is much more relevant than for fixed-wing flying where there is a much-simpler single height-speed conversion that always applies. The trade in helicopter energy is both three way and potentially rapid - the total energy is quite low by the standards of a fixed-wing aircraft of the same price.

[check]

There seem to be a number of posters here who read, then analyze, and somehow come up with hidden meanings from within the text. What a load of tosh! A prime example, the word "simultaneously", dictionary meaning: Happening,existing or done at the same time. What is so difficult about that that some people have to then go and say because the word cyclic comes before collective then there must be a subliminal message. The meaning is the same whether cyclic or collective is written first.

SAS go to the top of the class.

[DOUBLE BOGEY]

I am just wondering if we should really move the pedals first before we move the cyclic and collective.......

So:

1. Pedals to correct yaw
2. Mayday
3. Collective
4. Cyclic

Will that work?

DB

[SASless]

Moving all three Controls at the same time works too, DB.

Trimming the Aircraft reduces Yaw, Drag, and helps center the Cyclic, as well as point the aircraft nose in the direction it is traveling which would help the Crew see what is actually in front of them and perhaps make the other control movements more efficient and useful .....don't you think?

Why this constant focus upon moving a single control unilaterally.....are some of you unable to mentally figure out how to do that....or only able for some physical reason to move one extremity at a time?

Doesn't the wonderful 225 AFCS/Autopilot do all this when Captain George is put in charge of things?

If the Autopilot can....and does.....why do Humans have such problems with doing it?

[Ornis]

Your wife is going shopping. You give her a list of things to buy at the same time. So what do you put at the top of the list?

The instruction "Do A, B, C, ... simultaneously" contains two elements. The first is the action and the second is the timing. Logically they are independent and it does not imply all actions are equally important, just that they're to be done at the same time.

Unless otherwise stated, the first in a list assumes greater importance. It's the way we think. Ask people in an election whose names start with "A". They get far more random votes. Why? Because they're first.

The fact is, the advice "Move A and B simultaneously" is not exactly the same as "Move B and A simultaneously". The outcome may be the same but the emphasis is not.

[DOUBLE BOGEY]

SAS - I expected a Bite but not from you......I was joking Bud.

Ornis - my wife tells me to "Shut up and tell me the answer" is that simultaneous as well.

DB

[Ornis]

"Shut up and tell me the answer"

It means to stop nattering and think because you can't do two things at once, that is, simultaneously?

[SASless]

Small flaw in your logic sport.....as we have an Alphabet that is based upon order....when you use the Letters A...B....C....D....you inject order into the sequence.

Nice try......but still wrong.

Grammar Rules set forth the concept that the use of the conjunction "and" is used to connect two equal sentence segments.

"Equal" connotes "the same"....."as one".....and not in a"ranked" order.

As the way we communicate is by language.....we have to use the established rules (Grammar) that sets forth the construction and meaning of what we speak.

You want to discuss "Probability" or "Statistics".....that will be done using proper Engilsh Grammar as the foundation of the arguments.....don't you agree.

The only we can have commonality of definition is to have settled rules on language otherwise we have anarchy which would prevent effective communication.

[Ornis]

SASless. All you are saying is: "First is first."

[SASless]

For no other reason than First is First and only by sheer physical location in the Sentence.....and if worded just the opposite.....again First would still be First purely by its position in the sentence......thus each equally could be in front of the other and its being there has absolutely no significance re importance or rank.

If there was a way to have both "First" simultaneously then there would be no chance for some to continue with their word twisting.....but that is not possible due to English Grammar.

In this case.....the Law is the Law and there is exactly one interpretation.

Exactly - Definition and More from the Free Merriam-Webster Dictionary (http://www.merriam-webster.com/dictionary/exactly)

[Ornis]

SASless. It's not about about grammar or syntax it's about concepts.

A + B = C, where B = 8 and C = 10
What value has A? Ans, A = 2

So, the ranking is C, B, A

[HeliComparator]

Doesn't the wonderful 225 AFCS/Autopilot do all this when Captain George is put in charge of things?


I know its not a serious question, but the answer is "more or less, but not quite!" The AP will of course maintain attitude and heading, and it always wants to have at least 96% Nr, therefore it will lower the collective (regardless of a collective upper mode engaged or not) until 96% is restored. I say "almost" because the max trim rate is not that fast and it will probably take too many seconds to lower the lever enough. Also, once it has lowered the collective, there is no mechanism as far as I know, to raise the collective again once the Nr is restored and inevitably overshoots into overspeed.

Anyway, someone mentioned the yaw pedals and it is interesting to contemplate what should be done with them. Many helicopters have collective /yaw coupling so that the pedals are pretty much in the same position at cruise power as they are at flat pitch (EC225 excepted) so why the need to move the pedals when the engines fail? Well it's just to cover the period when the lever is still up - so the collective /yaw coupling is applying a fair bit of pitch to the tail rotor - but the engine torque has disappeared. So a dab of pedal is required simultaneous with starting to lower the collective, to kill the yaw. After that, on many helicopters the pedals go back to the neutral position, just a little bit in the anti-power direction. The initial yaw - occurring during the pilot reaction time - will typically cause the nose to dip (I am talking about in cruise flight, where me and my colleagues spend most of their time) so another good reason to apply some aft cyclic as an autonomous action, rather than in response to a perceived attitude change - the latter taking longer to process of course.


If the Autopilot can....and does.....why do Humans have such problems with doing it?

Because the 225 autopilot is your GOD and you should bow down and worship it. Obviously.

[Grenville Fortescue]

The initial yaw - occurring during the pilot reaction time - will typically cause the nose to dip (I am talking about in cruise flight, where me and my colleagues spend most of their time) so another good reason to apply some aft cyclic as an autonomous action, rather than in response to a perceived attitude change - the latter taking longer to process of course.



This being similar to the point I made previously although I feel "spontaneous" may be a better adjective to describe the reaction which can occur when flying hands on but, agreed, if the failure occurs with AP engaged then yes, it must be a conscious (and I suppose you could say autonomous) decision - but not for very long before other things need to start happening.

[PeteGillies]

A fellow poster clued me in on a very significant AAIB accident report that has a lot to say about pilot reaction time to a double engine failure. I am impressed by the thoroughness of the typical AAIB investigation. Check out Report 4/83 on the AAIB website. A Westland Wessex 60, G-ASWT, 13 Aug 81. It's a long read but well worth it. Check out paragraph 1.16.2 regarding pilot reaction time, and paragraph 2.3.2 regarding rotor speed decay. And throughout this detailed investigation there was no mention whatsoever of applying any aft cyclic at all following the failure of the two engines.

So how quickly did pilots react to the double engine failures: The minimum reaction time was 1.5 seconds. The maximum was 7 seconds. The mean was 3 seconds. THREE SECONDS before the flight controls were moved.

Pete

Pete

[Lonewolf_50]

Pete, before you go on about leading with the cyclic, I suggest you ponder on how a lot of models of helicopters
have control mixing that make compensatory movements in other control channels when one moves a single channel. Each helicopter model will have its own unique mix and balance based on its overall design.

The difference between the lateral coupler in an SH-2 and the far more complicated control mixing in the SH-60 mixing unit is an example I am familiar with. I am not up to speed enough on FBW suites to understand how that control mixing is done.

With some aircraft, you may have a control mixing combination that, when you lower the collective is already compensating with a pitch command independent of cyclic input, and that coupling may be up, may be down. You really have to know which aircraft you are flying, which once again makes me leary of your one size fits all approach.

Interesting thing about reaction times. As true in FW as RW, but maybe more dire in RW due to our peculiarities.

Factors will include: training, recency of experience, quality of experience, do you really know your aircraft, and of course and the "startle factor."
I think we agree that we have a crap load more variables in autorotational entry than the current energy state of the aircraft and the rotor system. Nice of you to cherry pick a crash, how many non crashes did you investigate? ;)

Don't get me wrong, Pete. I appreciate your efforts.
My skepticism regards the oversimplification you are pounding away at.

Control Nr.
How do you do that?
Depends on your flight condition and energy state.

Your complaint of oversimplification in re the collective (as though people only fly with one hand ... do they? **** me, that's scary!) can be applied to your oversimplification in re the cyclic.

I like the emphasis on simultaneous.
Why?
It's how I was trained.
It's how helicopters are (generally) flown.

FH110:
The "Maintain RPM" squawkers apparently would prefer to decelerate from cruise to best-auto speed while descending for a power-off landing
Please don't make **** up. What you did there is called a strawman, which weakens your attempts at argument.
But one of your points I'd like to heartily concur with:
When you aren't otherwise constrained, fly at an altitude and airspeed that gives you TIME to deal with that problem ... cannot agree more!
Well said. :ok:

[FH1100 Pilot]

It's not a strawman, Lone. If you bottom the pitch FIRST, then you WILL start a descent at whatever speed the helicopter was going at the point of engine failure. Guaranteed. Anyone want argue that?

Thought not.

Okay, once the descent is started, THEN the pilot who bottomed the pitch must now decelerate back to best-auto...unless the plan is to come screaming down at cruise speed which, doesn't sound like a good idea to me.


So, Lonewolf, tell me again how my statement is wrong?

[MightyGem]

Topendtorque, as no-one else seems to have noticed it; excellent post! :ok:

[Lonewolf_50]

FH1100:

The statement of yours that I identified is A STRAWMAN (look it up, you obviously don't understand the term) in that you dishonestly characterize a number of other poster's position with your own made up line of crap.

Your dishonest characterization, that they advocate moving the collective in isolation of other flight controls is YOUR STRAWMAN.

The amount of dishonesty in this thread, applied by any number of folks in the conversation, most likely comes from people passionate talking about a topic, with the shortcoming of being in broadcast mode only.

I don't think this is intentionally dishonest, in a malicious sense, but it is dishonest nonetheless to mischaracterize another's position.

I return to a fundamental concept of flying helicopters: you fly with both hands, and your feet.

Have a great weekend, all, and a Merry Christmas.
Santa Don't Hover :p

[helmet fire]

Agree, great post TET. This thread is otherwise a chore to read.

I am with the half who will not get a free beer from Peter. I believe the aft cyclic fixation is not appropriate and introduces a robotic response that is sometimes more dangerous than helpful. Re read TET's post for one example.

I do agree that it is appropriate in some circumstances, but the point is not ALL circumstances which is what is being offered up as the mantra. I do not understand the fixation on arguing with everyone about why it works and then only using examples where it is appropriate. FH1100's last post continues that methodology.

If you really need a simplification for a complex flight system that really does fit every scenario, in every emergency then try this:

NR is life. Maintain NR. Nothing else is more important.
The next most important is potential energy. Potential energy is airspeed and altitude (yes blade inertia too and some other factors, but keep it simple)

And to exploit this NR then potential energy system, sometimes aft cyclic will help. Sometimes it will not. Are we really not smart enough to train and learn which actions are appropriate in which circumstances?

Potential energy gives you ...well... Potential! And TET said it best, fly at height and speed wherever possible. I do. And those who want to always pull back on the cyclic first and earn a free beer from Peter had better REALLY make sure they do too.

[FH1100 Pilot]

Lonewolf:The statement of yours that I identified is A STRAWMAN (look it up, you obviously don't understand the term) in that you dishonestly characterize a number of other poster's position with your own made up line of crap.

No I don't, Lone, and I'll thank you to stop putting words in my mouth. There are posters here who advocate lowering the collective FIRST after an engine failure. I'm not making this up and I'm not dishonestly characterizing their positions. Because I'm sure they genuinely believe it based on conventional wisdom.

Yet the NTSB clearly, unequivocally, in no uncertain terms tells us the importance of the order of tasks that need to be accomplished after an engine failure

Simutaneously:
1) Aft cyclic input;
2) Lower collective.

How much clearer do you guys need it to be? Must I spell it out for you? Hmm, it's already spelled out so that probably wouldn't even help. Do I need to read it to you more slowly perhaps?

Guys like TC say over and over that the FIRST response to an engine failure is to lower the collective. What guys like Pete Gillies and I are saying is that this is often a very, very WRONG thing to do, especially if you're in cruise at 500' agl or less. Ask the "Mosby" pilot if he'd like to reconsider that "collective-first" policy. Oh wait, you can't.

[Ornis]

Seems to me Pete Gillies is trying to advise those pilots who are likely to kill themselves if they have a real engine failure because they won't act quickly enough. It's obviously most important for students - students need a method, not more "knowledge". Mantra?

The accident reports show it's not only beginners who cock it up, so maybe "knowing" what to do is simply not enough for everybody.

(Note: Airspeed (motion) is kinetic energy not potential energy, as stated above.)

[helmet fire]

Most of the time I agree, but Airspeed is also potential energy in a helicopter as it can be converted into NR.

FH1100, sticking to your guns. So, EFATO: cyclic back or collective down? Low speed bucketing, collective down or cyclic back?

Yes, am aware of the many times me cyclic back would work....but "very very often" and "always" are subjectively applied to support your otherwise good idea in certain circumstances.

I will stick to my guns too..... It is not an appropriate mantra to be robotically training helicopter pilots to do. It is a great skill to teach them to maintain and exploit potential energy after recovering NR.

Yes, I know I will not get a free beer from Peter - such is the price of my convictions.:}

[Ornis]

Well, if "cyclic back" works 90%(?) of the time then wouldn't it be a good place to start? Just on the basis of statistics fewer lives would be lost, surely. (Those advocating this are talking about helicopters travelling from A to B.)

There are no perfect simple answers to anything and if you have no time to think a quick imperfect response is better than nothing. Talking generally.

[SASless]

it is appropriate in some circumstances, but the point is not ALL circumstance

Correctly said....but when dealing with those who are trying to type out a Cook Book.....with exactly one Recipe....that is what causes the problem.

Perhaps if we started a bit closer to the top.....say....."Maintain Nr within the Power Off Rotor RPM limits!".....all this arguing can be avoided.

As by doing that ....then we discuss how to accomplish that in all the varied situations that can occur....some of which can require quite different techniques.

I guess first we have to determine what it is we wish to do....what is it we are trying to accomplish....or avoid.

Is that too complicated?

To define the problem in very simple, clear, definite, unambiguous words?

The crux of the argument really is that for every situation one can give that application of Aft Cyclic would be the best move......I can offer up another where moving the Collective first is the best move.

With that in mind.....how do you "One Rule Fits All Cases" Thinkers respond to that?

Mind you I know one situation where my starting point does not apply!

[helmet fire]

So what is the percentage estimate where it becomes a bad idea?

A to B pilots may be the target market, but that was not specified in the brochure offered up, and still it does not address all their needs either.

And sometimes doing nothing is a much better idea than rushing into a solution with a patently incorrect reaction. The word is "sometimes". The problem with application of simple solutions to complex issues is that exceptions are inevitable......

.......hence the 1.5 billion posts on this topic which is really an attempt to apply a simple rule in the face of many exceptions. Even though it works in "very very very" many events and not in "very very" many others.

[Devil 49]

"I would really like to know if only lowering the Collective while in a level Cruise at 116 Knots in a 350 during an entry into Autorotation and not moving the Cyclic will result in a 40 degree or more Dive.....it cannot be that complicated to find out!

Likewise.....how does one accomplish a 180 degree turn at the same time and ...and lose Rotor RPM....as it is going to be a steep turn from 300 feet in a screaming ass dive where one would assume there would be some G Loading on the Head that would tend to build RPM.....something you all insist G Loading shall do?

Any 350 Drivers willing to try......Devil 49....you fly those EC things.....what you think?"

I really don't know what would happen in that scenario. My experience is that the aircraft will yaw quickly right (vertical fin camber) and the nose will drop. A retreating blade stall as the NR decays would tighten up the action, I would think.

AMC does not do power chops at cruise, at least not in the AS350B2, due to the lack of a flight idle stop. The accident pilot may never have had anything but the 90 knot traffic pattern altitude training autorotative descents to a power recovery, a very benign, non-representative exercise.
We very rarely fly without medical crew so I can't take it out and throw it around the sky, either.

I would have to consider that this pilot was relatively low-time in the airframe. the hard right yaw and pitch down would be outside his experience base, it might delay recognition of an engine flaming out and the appropriate response. I would have though that a gun pilot would know about fast and low, and would have immediately pulled cyclic back, gaining the few extra seconds to avoid all the Kansas he was seeing in the windscreen the last five seconds of the flight...

[SASless]

Devil,

The 135 based just south of me which supports a large hospital just north of me.....keeps whizzing by in cruise not much more than 500 feet.....and a Bell 407....might get up to 500 feet.

As they pass right over the house particularly the 135....I cannot help but worry just a bit about that in light of the Mosby and Glasgow crashes.

Do EMS Operators specify a "normal" minimum enroute altitude for Day/Night VFR Local Area flight?

I have checked my Home Owners Insurance and it would appear I am covered for damage to my roof by falling objects so I am not too worried should something happen while I am in the LZ Bar located in my basement.

So it is only idle curiosity and not with an intent to file a complaint that I ask. it is more to satisfy a question that arises when I see this happen.....as that altitude does not afford a great deal of cushion should something ugly happen....and perhaps Pilots set themselves up for extra problems by staying low rather than getting on up a bit.


This is the latest EMS Aircraft in the area....pretty thing!


http://i1127.photobucket.com/albums/l629/wakeforestbaptist/AirCare%2025th%20Anniversary/ED051511-089.jpg

[[email protected]]

Yes, I would be interested to see the results of all the R22 instructors in the world teaching their students to flare in the event of an engine failure rather than lower the lever....wonder if that would get sanctioned by the Robinson safety course?????

Wonder if anyone would be brave enough to do a throttle chop in a 22 having taught the student 'aft cyclic is the gift of life'and 'lowering the lever is a minor and secondary consideration'.

[tyl3r]

@crab - At the risk of muddying the waters, I attended the ‘Robinson Safety Course’ with Dick Sanford in 2008 and he explicitly stated (to an all-male and ostensibly heterosexual audience) that if you found yourself in an R22 in the cruise with your left hand enjoying the contents of your passenger’s blouse when everything goes quiet, then there was sufficient energy to manage with the cyclic (coning et al) to allow you to finish off what you were doing, remove hand and re-fasten buttons before finally lowering the lever. He said there was around 6 seconds of time. Everyone present asked him repeatedly to clarify this and he did so and was quite insistent that the famous 1.1 seconds could be extended massively in the event that the collective is not or could not be lowered immediately.

I have to say that this flies in the face of so much training to the contrary, and in the absence of any video evidence to prove it, then when the donkey quits I'm aiming to get the lever down quickly irrespective of what the cyclic might be doing.

[SASless]

OH MY! The Cat is smack dab in the middle of the Pigeons with that one!:uhoh:


One other source about the Safety Course that quotes Robinson about Entry to Autorotation and Energy Management....and quotes the 1.1 second number.

Robinson helicopter safety course (http://www.ukhelicopterpilot.com/robinson-safety-course)


As it is a UK Source, we know it of course is impeccably correct.

[Tailspin Turtle]

For what it's worth, when I informally checked out in the AH-1G Cobra circa 1970 (long story, begins with a missive that started out "Your friends and neighbors...), it was made clear to me that if the engine quit while we were in cruise flight (which was pretty fast but to my surprise not as fast as a lightly loaded Chinook), I was not to immediately lower the collective but simply to keep the thing straight and level for a short while without moving the collective (exactly how long, I don't remember), wake up the pilot in the back seat, and then lower the collective. This suited my helicopter flying aptitude since I pretty much knew how to work the cyclic and pedals as a 1,000-hr fixed-wing pilot and flight instructor, whereas my response to a unexpected helicopter-engine failure from a collective standpoint was usually "Whut?" followed by a dawning realization that the sound of the rotor was changing. (That reaction time also stood me in good stead for engine failures in a hover.)

[henry_crun]

9kxu543VwlA

Faster than a Speeding Motorbike

But - watch that rotor - the disc is always at positive aoa.

May I suggest that the flight phases are:

HELICOPTER FLIGHT
In forward flight disc at negative aoa

CATACLYSM
something breaks or stops

TRANSITION
from helicopter mode to autogyro mode.

AUTOGYRO FLIGHT
In forward flight disc at positive aoa.

The key here is knowing in advance what control inputs will effect the transition. In forward flight the disc aoa has to be quickly flicked from -ve to +ve and other normal control adjustments made. It is misleading to call this a flare. It isn't, it is just a quick flick to change attitude. It you sail or fly a wind-powered machine you will understand.

Yes, OK, I'm not even a novice, have never been anywhere near a real live helicopter, my interest is purely theoretical, so please feel free to tell me to "go away".

Thank you for your kindness and tolerance.

Best and most humble regards,
henry_crun

[13snoopy]

[email protected]
said...

Wonder if anyone would be brave enough to do a throttle chop in a 22 having taught the student 'aft cyclic is the gift of life'and 'lowering the lever is a minor and secondary consideration'.


Crab,

Where did the OP say that the lowering of the collective was a minor and secondary consideration?? Or better yet, where did he even insinuate that??
It's silly to twist and distort a man's words.

[topendtorque]

twice Crab i have been frightened in auto C&T. they bear the semblance of being too complacent with a semi experienced person, but then the crash comics are full of those stories with where two experienced, thought the other was driving.

1. a1500 hr careful, but self opiniated and quite strong pilot in a '47 3B1. i was further being complacent as we would all agree an easy auto machine. bear in mind i did this bloke LL/muster training, me, on the first auto of the check ride, "ok lets do a straight ahead, you fly I will follow, enter smoothly from 500' 60 kts". at 150' ol mate brings the collective up strongly to about half way, the throttle has been checked by me after a safe entry was done, in loud voice as, "throttle in over ride check."

2. an 1800 all on R22 pilot, new to me but supposedly mentored and trained by a couple of hotshots, was asking me at least twice during ride,"could you show me some autos?". this - i have learnt is a danger sign. i thinks to myself, self i better work out what this blokes knows first. hmmm. this young fella is mentally and physically fast. surely he has been taught the basic rules, yep ok let's see, catch him unawares, chop the throttle at 70 kts cruise power. yep nothing, i waited and waited, then roll throttle back on snapping the collective down and flaring, 82% good boy. next exercise, cup of coffee, long talkies, another hour of basics and simple autos, I simply must be sure he will react correctly before i let him go.

apologies for grammar punctuation, etc, iPads and me, we don't get along all that well.
tet.

[awblain]

Autogyros aren't the same as autorotating helicopters, unless there's no thrust from their engine. While flying an autogyro might build respect for managing energy, perhaps like glider flying would for a fixed-wing pilot, what's done with a big propellor behind your back, and usually with no collective pitch control, isn't directly equivalent to balancing height and speeds to bring an unpowered helicopter (or autogyro) safely to Earth.

[Hughes500]

IMHO I think SASless has bought some sense to this discussion by saying lets call it energy management.
Every scenario is different as are each machine, that is why we are pilots the " loneliness of command" we have to decide what to do and really it should be instinctive. Perhaps that is the problem , training. EOL's are always done by lots of schools I see from 70 kts over head the field straight into wind. Is this due to " most " instructors using the instructing role as a stepping stone to a better paid job. I have always found it quite perverse that the most inexperienced teach the new guys ???????:ugh:
Doing an EOL from a hover at 500 ft compared to 120 kts is way different technique in energy management
Example in a 500 D in hover you have to dump the lever, which instantly causes a massive nose down attitude and will prevent a catastrophic loss of rrpm. This is actually helpful as it will bring airspeed up very rapidly ( yes I know it unloads the disc and increases rod) but that nose down attitude will mean very quick acceleration followed by a large rear cylic which will start to level the ship and bring back your rrpm. Tried doing it the other way round, all I can say is holy ****.
Now do it at 120 kts, close throttle slight right pedal, hold lever up and pull cylic back, ac actually climbed just but lost rrpm very very quickly as we got back to 60 kts. Better technique to lower lever about half way at the SAME time applying aft cylic ( rod 500 ft for about 8 secs). watch the rrpm and control airspeed and rrpm with collective. As airspeed decays to 80 kts ( best range speed ) gradually lower lever this will increase rrpm and gradually drop nose until you get to 60 kts ( best auto speed) by this time lever should be bottomed to gain as much rrpm as possible and to allow a stable auto and set you up for the EOL which again seems to have fallen off the must do things for instructors ( There is a difference in the mind to yes lets bring the engine in at the level stage, to put it down every time so the brain knows it can do it !!!)

Perhaps I will get my tin helmet on and dig a foxhole quick ..... incoming

[Thomas coupling]

FN1100:
the NTSB clearly, unequivocally, in no uncertain terms tells us the importance of the order of tasks that need to be accomplished after an engine failure

Simutaneously:
1) Aft cyclic input;
2) Lower collective.

How much clearer do you guys need it to be? Must I spell it out for you?.

Are you telling us that your assumption of this statement based on its order of presentation (1 then 2) is that this is how you enter auto ("in the cruise")?
Mustn't forget "in the cruise" because ALL of FN's arguments are predicated on "in the cruise"....ain't that right FN?

[[email protected]]

Hughes 500 - you are absolutely right and most of us fully understand the energy management concept which is why there is no 'one size fits all' solution to entering auto because there are so many different combinations of entry parameters.

Consider PG's (and others) assertion that cyclic flare is the best form of energy management - why waste 100hp/sec (Dick Sandford's figures from the Robinson Safety Course) just keeping the Nr up by flaring when you could stop the Nr decaying by lowering the lever fully AND still have that extra energy available to you.

If you have lots of speed then fine, use flare to minimise the height loss (or even gain some if you are quick and have a responsive aircraft) but for goodness sake lower the lever (maybe not fully in the high speed cruise) - why would you use your precious energy up overcoming rotor drag (from having pitch applied) when you don't need to.

Try the aft cyclic first technique in a max power climb at 60 kts and you will probably die because in this case and many, many others, the lever down MUST be a priority.

Remember - engine fails.......pause, 1 second, two seconds for real world reaction times - where is your Nr now in the fast cruise at 14 degrees of pitch???? decaying very, very rapidly! Lower the lever AND flare might just save your bacon - flaring without lowering the lever might slow down the rate of Nr decay but it won't stop it, not at such high collective pitch angles.

None of the anti-aft cyclic heretics such as myself have ever said lower the lever without moving the cyclic, we have all said use both controls but lead with lever always.

[muffin]

In the past couple of years a new clause has crept into my insurance policy that specifically bans deliberate autos (except in emergencies) unless an instructor is on board. So consequently I am unable to practice them. Very interesting thread nevertheless.

[nigelh]

Not surprising really !!! I have always had a deal with my insurance that I never do full touchdown autos in my helicopters . We have covered this before but if you can keep rrpm in the green , flare and then level off at say 5-6ft , at a slow forward speed , then what happens next is pretty un important . As an owner I would be very happy for full down autos to have to be separately covered by insurance companies as that would save countless utterly pointless write offs which then push my premium up !!!!!

[chopjock]

In the past couple of years a new clause has crept into my insurance policy that specifically bans deliberate autos (except in emergencies) unless an instructor is on board.

IIRC that only applied to turbines or was it pistons? But not both.

[Ornis]

Energy (or work) is power times time: kilowatt-hours for electricity or horsepower-seconds in Robbie-speak, hp-s (not hp/s).

After engine(s) failure, the energy in the rotor will keep the aircraft flying for a second or so. Then it's gone and the rotor will stop, forever. It's how one adds energy to the rotor immediately that is the crux. In the cruise one can easily get some from the kinetic energy - motion - using the cyclic. In the hover one can't, one can get it only from descending - potential energy - and then only while the rotary wing is flying. Otherwise the aircraft is falling, not flying. Which introduces the other important factor - the angle of attack. Once the AoA has passed the stall angle the rotor stops, forever. So, lowering the collective lowers the AoA which helps keep the wing flying and slows the rate the energy is used by decreasing the lift and drag. Lowering the collective does not primarily add energy to the rotor.

Clearly entering autorotation in a genuine emergency is not as easy as falling off a log, or this thread wouldn't have started. More importantly, a helicopter wouldn't have punched through the solid roof of a pub, it would have landed. Somewhere else, probably.

[henra]

Remember - engine fails.......pause, 1 second, two seconds for real world reaction times - where is your Nr now in the fast cruise at 14 degrees of pitch???? decaying very, very rapidly!


I think this is an important aspect in this discussion.
While theoretically cyclic back will be an effective means of keeping and restoring RRPM this will only work in a certain AoA range. With the collective in your arm pits you will likely see a significant decay in numbers even while in cruise flight.
That said the same will happen if you leave the cyclic fully forward and just drop collective. You will unload the disc and not get the necessary upward flow through the disc. At least not until a very high RoD builds up at which point the NR may already have dropped below PONR.
In Autogyros this is a frequent cause of fatal accidents:
Push the cyclic forward a bit too agreesively, watch the rotor NR decay in 1 or 2 seconds beyond PONR and drop with a stopped rotor from altitude, even with your engine in the back still pushing.
So both actions have to happen. Relax cyclic, lower collective.
You can discuss to which extent you do what but failing to do one of the two will likely end in tears.

[Hughes500]

Nigel
Sorry cant go with you on the power recovery. Think of it as in the mind. If you regularly do them to the ground then the brain does not have that added problem to consider if the donkey goes on holiday !
Examined someone the other day who did a perfect power recovery but a bit high. Then asked him to do it to the ground which he had never done, all I can say is if I wasn't on the controls the insurance company would have had a big bill and I quite like being over 6 ft tall not under !!!!!!!

Muffin

Are you sure your insurance says instructor as opposed to competent person ? Personally I would have that removed or changed to EOL's which I could understand. I think you will find it is a terminology problem
Just remember keep it in the green

[awblain]

Horsepower-seconds is indeed a unit of energy.

The kinetic energy of the rotor depends on the moment of inertia of the rotor, and the rotational speed squared. Note that it doesn't depend on the blade pitch, although the deceleration rate does.

The rotor typically stores ~2-5s of FULL engine power, so you typically have rather longer than 1s stored up, but you're right - there's not enough: you need to transition quickly to converting potential energy or kinetic energy from forward speed in order to maintain that reserve of energy.

To stop the rotor dead would require some specific choices. If it slows markedly, the the lift will be inadequate, the aircraft will drop, and this would certainly increase the airspeed from a hover, which could provide suitable airflow to get it going again, depending on its configuration.

[chopjock]

Muffin,
In the past couple of years a new clause has crept into my insurance policy that specifically bans deliberate autos (except in emergencies) unless an instructor is on board.

I just checked with my insurance company. Believe it or not, that only applies if you have a piston engined machine. Perfectly insured to practice with out an instructor if you do it in a turbine. :confused:
Work that one out.

[Attila]

When I did my Bell 214B conversion in Oman, the QHI warned me about rotor decay in the event of engine failure, 33 inch chord blades, remember!!

At 120 knots in the cruise he told me to be ready to lower the collective and to watch the rotor RPM as he counted down to the "engine failure" and chopped the throttle. As I lowered the lever very quickly I watched the RRPM decay instantly to 85%.

Some time later whilst carrying out a topping check at Seeb International I had an engine surge whilst climbing at a great rate of knots and before I knew it, I had closed the throttle, lowered the lever, rolled on some bank and applied aft cyclic to load the head and put out a mayday call. The rpm were still in the green but the engine wasn't very happy as part of the bleed band had gone through the compressor, so I had to shut it down for an engine off landing back onto the main runway. I then discovered, at 5000 ft in the descent, that the auto rpm were outside limits, a little too low for the AUW, which did make an interesting approach, i.e. a little faster than normal with a slightly exaggerrated flare to recover them, followed by a run-on landing without any damage to the aircraft.

Incidentally, there was a rate of climb limit in the Flight Manual, not to exceed 2000 ft/min below 2000 ft agl and during the above, I was well over 7000 ft climbing at 4000 ft/min. Interesting day...........

[Lonewolf_50]

Huges500 (in cruise) Better technique to lower lever about half way at the SAME time applying aft cylic ( rod 500 ft for about 8 secs). watch the rrpm and control airspeed and rrpm with collective. As airspeed decays to 80 kts ( best range speed ) gradually lower lever this will increase rrpm and gradually drop nose until you get to 60 kts ( best auto speed) by this time lever should be bottomed to gain as much rrpm as possible and to allow a stable auto and set you up for the EOL which again seems to have fallen off the must do things for instructors
I note that this example is someone talking about using both hands to solve the problem. :ok: The false dichotomy of "either or" being dispensed with would improve this conversation (should it continue) immensely.

[AnFI]

AWblain: Nice to see someone being accurate about the energy picture, there are a few incorrect posts and referenced posts above in which HP/Sec is used:rolleyes:.

Horsepower seconds is Hp x Sec OR HP.Sec NOT Hp/sec

Hp is Power, ie energy per time - so Hp times time is an amount of energy.

EXAMPLE: 20000Hp.sec means you can consume energy at the rate of 200Hp for 100seconds.


It's a abstract but useful unit for energy since most people have a feel for how many horse power they need to acheive a mode of flight. If you know the Hp you need and you know how many Hp.sec there are in your HEIGHT, SPEED and RRPM then you know how many Seconds of that Hp delivery each of those 'stores of energy' can provide.

Interesting Factoid:
For every 330lbs you weigh the VSI is calibrated in units equivalent to Horsepower - so if you weigh 3300lbs then 1 unit on the VSI is 10Hp
(assumes VSI calibrated in sensible units ie 100fpm)

[Tailspin Turtle]

Attila: Incidentally, there was a rate of climb limit in the Flight Manual, not to exceed 2000 ft/min below 2000 ft agl

I don't know whether this is an example of it, but the avoid region is only applicable for unaccelerated level flight. If you're in autorotation or even a low-power rate of descent, the avoid region is very much smaller. In a high-power low-speed climb, the avoid region (if the manufacturer had to depict it), would be somewhat bigger than the one in the handbook. As Attila notes, the 214B was capable of very high rates of climb since it had a Chinook engine in what was basically a Huey.

[paco]

"but the avoid region is only applicable for unaccelerated level flight"

Beg to differ - the top half above the knee is for that regime, below the knee is for the climb, where your hand is assumed to be on the collective.

cheers & happy xmas

Phil

[Tailspin Turtle]

Phil: "but the avoid region is only applicable for unaccelerated level flight"

Beg to differ - the top half above the knee is for that regime, below the knee is for the climb, where your hand is assumed to be on the collective.

Thanks for the amplification. The test pilot is allowed to respond much quicker on the collective at the knee of the curve and below. However, as far as I know, the test condition is still with power (collective pitch) for level flight, not climb. Since the delay required is almost instantaneous (0.3 second?), having the collective pitch higher (which means the blade drag is higher) than the test condition for establishment of the avoid area results in a quicker decay in rotor rpm for a climbing helicopter, meaning the knee is not, strictly speaking, valid, nor is the rest of the avoid area.

The difference in avoid area for level flight versus climb may be a small and even negligible for most helicopters but for one like the 214B, a single-engine helicopter with enough power, rotor, and tail rotor to hover out of ground effect at something like 11,000 feet, my understanding is that it did make a difference.

[RotorIP]

Beg to differ the test pilot can't do anything for 2 secs. Average reaction time for a pilot . The HV curve is very restrictive and no it's not for unaccelerated flight, empire test pilots jump in here. The HV curve as has been described to me by test pilots is to ensure you can land OEI or no engine in a single without damaging anything doesn't matter if your accelling or decelling or flying at one speed. Think steady state is worst case. Yes incredibly long when your sitting there and yes NR bleeds fast, is there a test pilot out there that can clarify this?
Seriously discussion about hp per second? What are you talking about?? It's useless info....oh yeah the engine quit so if I pull out the calculator ...really??
Autos are simply lower collective don't bottom it as NR will climb incredibly fast at altitude, if you need to check aft to build NR but only if you need to.
I go back to talk to training staff.....

[RotorIP]

Sorry don't know what type of rotor your referring to, ancient metal weighted tip Blades maybe, composite blades bleed NR very fast, went from 100% to 90 % in about a second and that was waiting for it and knowing the throttle chop was coming.
It's exactly this misinformation that will cause havoc in the industry. A 214 and a 225 are completely different animals you can't generalize.
Reading thru this thread nobody seems to know what the starting parameters were of the helo in Glasgow? Ie what was the actual airspeed and altitude when the engine quit? Was it recoverable ? Nobody seems to know they are just speculating and offering advice on technique. it really doesn't matter why the engine quit. Likelihood of two engines quitting at the same time almost 0. That's what we should be discussing, before it starts most crashes involving multi engines occurred because they were operating in a performance area requiring two engines. Modern Helos have much better performance OEI and can be operated in a manner that does not require two engines.

[AnFI]

RotorIP: "Seriously discussion about hp per second?" NO !! - It's HP.Secs !! - its arbitrary and doesn't require a calculator - It helps people 'get a feel' for how much energy is where and how valuable it is - once you've done the exercise you don't need to calculate anything - you'll have a 'feel' for it.

Understanding ENERGY is fundamental to flight - that particular unit is irrelevant of course! - but the fact that you (obviously) don't understand it is alarming! ( Power x Time = Energy )

(and waiting 2 secs in the high speed cruise is questionable - given a pilot is intervening on the cyclic at what 1-3Hz perhaps? (Second opinion?))

"Autos are simply lower collective don't bottom it as NR will climb incredibly fast at altitude, if you need to check aft to build NR but only if you need to.
I go back to talk to training staff..... " Good idea!

[RotorIP]

No I understand energy and teach it but your reply is exactly my point. Nobody teaches HP.secs. Seriously I don't know of an instructor or ground school anywhere that taught something like that because it has no relevance to actually flying. Maybe at the test pilot school for calculations but that's it, too many variables.
Waiting 2 secs before reacting is a certification criteria. Look it up.

[AnFI]

No I understand energy No you don't and teach it probably but your reply is exactly my point. Nobody teaches HP.secs yes they do. Seriously I don't know of an instructor or ground school anywhere that taught something like that because it has no relevance to actually flying really? . Maybe at the test pilot school for calculations but that's it, too many variables. IT THE FUNDAMENTALS - it's VERY easy the ENERGY is in Fuel, Ht, A/S, RRPM, you feed it one of those at the rate the helicopter requires it - don't run out of RRPM till the drop won't kill you.
Waiting 2 secs before reacting is a certification criteria. Look it up. part 27 or 29? Happy to beleive you on that - thought it was 1 sec but dependant on phase of flight - sounds reasonable but I am sure the intervention at 2 seconds is not lever down without (simultaneous) aft cyclic (for high speed cruise ;) )


"has no relevance to actually flying"
Pilots do need to understand the Fundamentals of Energy:
Where it is
What it's worth
How fast you need it
How you can access/exchange it
- it's not rocket science, shirley?


HP.Sec is just a vehicle for doing that - some people use the unit the BANANA - you may have heard of those?
(Talking BANANAS: You may say u need 4 Bananas to fly at 60kts, 8 to hover, 9 at 140kts. 100ft is 1 Banana, 30kts is worth 1Banana 60kts is worth 3 bananas, 120kts is worth 7 bananas.) I don't like bananas!

but the Hp.Sec is pretty simple and easy and gives a clear representative understanding of the principles - without getting out a calculator.

[AnFI]

... and the VSI is practically in Hp anyway

[RotorIP]

Hmmm no never heard either HP or bananas referred to on the VSI ...even in soviet helicopters...because it's irrelevant depending on what the aircraft is doing. A zoom climb requires less HP even though you are bleeding energy.

My point is you have to frame the discussion in a way a pilot can relate to. HP.sec is meaningless to the average pilot and even the experienced pilot because it is not something we use when flying - for anything, there is no frame of reference . I have been taught by 3 different militaries and several civilian companies and have never heard anyone refer to a power demand in terms of hp.sec. Might be technically correct but it's practically useless as it has no relation to anything I am doing in a cockpit that I can reference. Sorry nobody works in HP anymore outside of the US, it doesn't mean anything outside of a design department.
If your talking generalities in energy management hmmm appropriate for basic flight training but assumed for a commercial pilot.
If your referring to a specific energy demand and its effects then yes there is a different discussion helo pilots use to correlate effects of a power demand to various issues encountered in Helos but it is specific to a type and varies by rotor design. But it ain't in terms your using.

[AnFI]

I think you are right - not so widespread but simple and useable nonetheless - you know how many Horspower you use to fly at different speeds - right? You know how long you can fly for using only the energy from airspeed from 100kts to 90kts? It doesn't take too long to work out the figures and you might like it.

The unit of VSI is in 100fpm
A HorsePower is 330lbs raised at 100fpm
So every 330lbs you weigh is 1Hp for 1unit on the VSI

If you weigh 3300lbs then its 10Hp per unit of the VSI ... not essential but interesting.

'Soviet units' km, m, m/s don't work so well for flying.

[JimEli]

Waiting 2 secs before reacting is a certification criteria. Look it up.

RotorIP, Do you have a different reference? No time stated in FAR Parts 27/29. However, AC27-1 states:
“The knee of the curve separates the takeoff portion from the cruise portion and is defined as the highest speed point on the low speed portion of the HV envelope. Altitudes above this point are considered cruise, or “fly-in,” points, and these test points require a minimum time delay of 1 second between throttle chop and control actuation (reference § 27.143(d)). Altitudes below the knee represent takeoff profile points. For test points in the takeoff portion, takeoff power (or a lower power selected by the applicant as an operating procedure) and normal pilot reaction time for corrective control actuation will be used.”

[[email protected]]

I believe the 2 second delay is that specified for military certification whilst the 1 second is the norm for civil certification. Possibly why we don't see low inertia rotor systems on modern military helps.

[SASless]

.....or quick thinking pilots evidently:E!

[Lonewolf_50]

Crab, that sounds right. SASless: speak for yourself, soldier. :E

The point raised about low inertia heads (which are popular in design for a variety of reasons) and energy management of a low inertia head get me to three core points:

1. If you are flying somewhere at "best cruise" or "max conserve" airspeed, it would seem that one needs to ensure one's transit airspeed is some knots above best auto speed because anyone will have a slight delay in reaction, and need some energy in the bank to not get behind the problem. With a low inertia rotor head, delay can be fatal. Know your aircraft.

2. FH1100 had a point a few pages back that I agree with: when flying somewhere, where possible plan to give yourself as much altitude to cruise at as you can. That is a form of energy that gives you choices that low altitude flying won't.

3. Your Nr is your life, until you get back to Mother Earth, so you have to control Nr, know how to control Nr (see energy management), fly with two hands, and stay ahead of your aircraft. That last point gets a severe test when a surprise loss of power compresses your time, energy, and decision timeline.

A few extra knots, or a few hundred extra feet may save your chili.

[[email protected]]

It's 5 seconds for Army pilots apparently:E

[paco]

Yeah, we need time for a brew :)

Phil

[[email protected]]

AnFI, I don't seem to be able to find the hp gauge in the cockpit so is my VSI calibrated in hp, brake hp or shaft hp?

Of course you know that hp is derived from torque at various rpm so you will need to know the exact rpm of the engine at any moment to calculate the hp - that's a lot of extra stuff to think about when you are flying but I know how brilliant you are;)

For those not stuck in the Dark ages - one hp equals 0.76 Kw (that is a kilowatt an FI, the watt being the SI term for power):E Or shall we just use the torque gauge that the nice man who made the helicopter gave us? (yes I know not every helicopter has a Tq meter but which RFM has limits based on hp????)

RotorIP - don't worry, he has got lots of stuff like this that he believes everyone should teach:ok:

[SASless]

Too much knowledge can be a dangerous thing.

We increased the thru-put of a Saw Mill by reducing the number of choices the Head Sawyer had after the Log Optimizer did its scan of the Log. Thru-put went up....production went up...Grade went up....and most importantly....profitability and Crew Bonus went up!


I would suggest the same concept works in helicopter flying.....narrowing the options to those that are necessary and appropriate is the wiser path.

[awblain]

I thought I was referring to the ~200kg rotor of the Glasgow crash aircraft, assuming it operates at ~200rpm. Its rotational energy should then have corresponded to ~3s of full power.

However, in post #995 (http://www.pprune.org/rotorheads/528850-police-helicopter-crashes-onto-glasgow-pub-50.html#post8197441), I'd overestimated the energy in the rotor (at 2MJ).

Trying again: Four 5-m-long 50-kg blades, give a moment of inertia of 4 x 1/3 x 25 x 50 (~1500) kg.m-squared). At 200rpm (~20 radians/s), the energy - 0.5 x 1500 x 400 J ~ 0.3MJ. With up to a MW of power available, that's indeed a very brief reserve. The airflow complicates things, and makes it different from a spinning object without air, but the energy stored in the rotors is substantially less than I'd assumed.

[Hughes500]

I know I am a simpleton on these matters but so f--king what the Hp of the rotor is ! All you have to know is the bit that turns it whether it be a piston, turbine or a donkey stops what you need to do !:ugh::ugh:
I can certainly vouch when Mr Lycoming threw his toys out the pram at 30 kts and 80 ft I didn't give a flying f--k for the hp on the rotor in fact I had never heard it spoken about so what does that tell you ? By the way I didn't hurt myself and only put a smile on a 300's rear cross beam ( Thank you Mr Hughes )

[[email protected]]

awblain - you might want to do your sums again as the RRPM won't be 200 - I'm not 135 qualified but I suspect it is in the high 300s at normal RRPM.

Whatever your maths tells you, there will be a very rapid decay in Nr if both engines fail in the high hover and the ONLY option is a rapid lowering of the collective lever - this will allow continued flight but only in a downward direction to the scene of the accident.

[awblain]

Agree. If the rrpm is twice as high as I stated, then there's about 4 times the energy, but it's still only a matter of seconds before that would be spent if the power stops and nothing else changes.

A safe return to earth certainly needs the engines' contribution to be replaced by gravity or exchanged with forward speed in short order.

[Devil 49]

Look up autogyro "buntovers", not direcly applicable, although they are in an established autorotaional state. Quote from here:

Popular Rotorcraft Association :: Gyroplane Stability (http://www.pra.org/default.aspx?p=gyroplanestability&i=22)

"Power Push-Over is just one form of what is also called a "bunt-over". These typically refer to the gyro pitching rapidly forward to inverted. This typically results from an unbalanced propeller thrustline that tends to rapidly rotate the gyro forward once the rotor looses significant lift and drag (thrust).

A "bunt-over" is typically considered to occur from any or all of several factors:
Pilot rapid forward cyclic stick motion causes reduced rotor lift and drag, allowing the rotor to slow, perhaps too much!
A strong wind down-gust disturbance which also "unloads" the rotor - reduces rotor lift and drag.
Upon severe and/or extended loss of lift, the rotor slows below its ability to autorotate and support the gyro's weight.
An unbalanced propeller thrustline offset pitches the airframe rapidly nose-down upon loss of rotor lift and drag.

The unstable airframe, pitching rapidly nose-down results in moving the rotor thrustline forward, relative to the CG, causing further nose-down pitching in reaction to reducing or negative rotor thrust."

[Reely340]

Maybe a stupid questions, may be already answered (pls. link to it) but why do manufacturers not add a springloaded "minus section" to the bottom end of pitch level travel?

As currently "pitch fully down" is ~ 0° blade angle, we can stall blades due too low an RRPM, and lacking any negative angle we - even theoretically - cannot recover from that situation w/o engine power.

I'd like to suggest to provide us with - from the "current bottom" of pitch lever travel - an additional 1" travel, for which one has to overcome a strong spring, where no friction would hold the lever, which turns blade angle to say -20° with respect rotorplane.



from 0 up to full pitch blades would be at 0° till 5-8ish°, as we are all used to.



from 0 down to the new "hard stop" we'd get 0° to -20°


That way one could (at FL100) let the RRPM deliberately reach today "unrecoverably low values", when switch engine to idle.

THEN one could bring the (stalled) blades to -20°, even while falling w/o laminar flow over any section of the blades they'd windmill, thereby increasing RRPM, till the combination for say ~5000ft/min "freefall" and the increasingly regained RRPM create an angle of attack that produces laminar flow again. At that point one should bring the pitch lever back into normal range and could commence a std. autorotational landing.

That helicopter would be autorotational fool proved, lacking "unrecoverable rotor speed".

I'm pretty sure there is some good reason why we don't get the negative blade angles the RC-Helis do. (They have rigid heads with +/- 15° balde angle linear on the RC stick, normal flying happens on upper half of pitch stick travel, upside down fly is down using the lower hlaf of pitch stick travel)

Maybe stuffing 20° blade angle in a rel. small section of pitch lever tavel is mechanically tricky, but certainly not impossible, methinks.

comments anyone?

[sycamore]

Reely, you mean as fitted to the Wasp and Naval Lynx..? Keeps the a/c nailed to a ship`s deck...

[Lonewolf_50]

reely, one reason may be the potential for ground resonance. (Model dependent). The other is that control rigging adjustments, particularly seasonal adjustments for autorotational NR, might run crosswise with a sort of "negative pitch" default blade pitch on the head that you are proposing.

I'd need to do a bit more asking around, but I also think that a negative pitch provision like that might unload the head and lead to some undesirable blade performance ... a bit of guess there, some of our aerodymanically bright folks can probably expand on that.

As to the ground resonance:

Some decades ago, we were doing a post maintenance check flight. Bird had a fully articulated head, and wheels not skids. Helo was on the ground, flat pitch (collective on the bottom). My boss and I were observing the operation, and his eyes got big. He motioned frantically and gave the cut signal. Engines shut down. He told me: "Oleo struts compressed, shoud not be compressed at flat pitch. We have a flight control rigging problem." He made reference to a bird that had gotten into ground resonance due to a crap rigging of this sort some years prior.

He was right. Rigging problem. It had to be corrected before we were going to try and put that bird into the air.

Not sure how viable your suggestion is.

@ sycamore: do Wasp or Lynx run into ground resonance in that mode very often? :confused:

[sycamore]

LW50, it`s over 40 yrs since I last flew both..officially,and never to a deck,but I`m sure someone will correct me,and add knowledge.
It also brings into asking the question about auto-revs setting after blade changes/tracking,and how often is that checked,as blade condition can deteriorate..
The other occasions that we used to adjust the basic/minimum pitch setting was doing icing(real)trials..no heated blades, and the possibility of having ice on the blades in the event of either engines failing(due ice damage/surge,etc),or a transmission failure,which did happen(oil filter came adrift), going to the ultra low pitch would hopefully keep one safe( and a lot of spiral descent for good measure)..We also wore parachutes...