Vie sans frontieres

Why do manufacturers design a hoist facility on their helicopters and market them as SAR aircraft if they know that any normal winching height for SAR is within the avoid curve? Sounds a bit irresponsible putting a facility in place that might encourage users to spend extended periods of time loitering in an area considered unsafe. Should the guy hanging underneath the helicopter take out extra insurance?

Or b) can it not be accepted that for the best to be got out of a helicopter's capability then sometimes its crew have to take the manufacturer's advice with a little pinch of salt?

PeteGillies

Jim -

You are so right! Flame the engine out and then see how the landing works out!

Pete Gillies

henra

Was that really in a fully developped descent at a high rate?
A transient drop to 60% - 70% (e.g. due to pulling collective while still in Forward flight) while the RoD hasn't built yet is something very different from a constant drop at a high rate of descent. The AOA figures in both cases will be quite different and thus the reaction of the rotor System.

I would be very careful spreading values in the range of 60% as survivable.
For a fully developped descent I have serious doubts. It will depend to some extent on the type of helicopter as well (Disc loading, pitch angle range)

PeteGillies

Good afternoon to all PPRuNe Rotorhead readers and posters. I have more thoughts to add to this thread concerning the satisfactory entry to a real autorotation.


It is obvious that many pilots understand the real picture of what will happen if cyclic is not brought back almost instantly when a total-surprise engine or drive-line failure happens.


The problem is the definition of “instantly.” I put it this way: When something happens to your helicopter that you did not purposely initiate, do two things as quickly as you can. 1. Start the cyclic moving aft, and 2. Start the collective (or “lever” as I'm learning to say on this forum!) down towards the bottom. This must be a gut reaction, not a thought-out move on the pilot's part. DON'T take time to troubleshoot the situation before moving the flight controls.


One can take any procedure and find faults with it. Is Cyclic Back needed every time no matter what the mode of flight? Of course not. Hovering or making a low-power descent are two examples. But I'll put it this way: Whatever prompts you to quickly bottom the collective lever in an emergency, real or otherwise, must cause you to apply aft cyclic simultaneously when in forward flight, especially in a climb or cruise configuration.


Do you fly anything powered by the excellent PT-6 Twin-Pac? Take a flight in a sim and ask the operator to fail the one-and-only drive shaft by surprise during powered flight. Unless you apply aft cyclic “right now,” you will probably crash and burn. How do you prevent this? Cyclic Back!


A serious yaw? Big upset? Loud noise? Sounds you've never heard before in powered flight? Applying aft cyclic and lowering the lever will not cause you any problems. AFTER you've done this is the time to try and figure out what has happened. Have you lost the power plant? Do you still have yaw control? Check the panel. Is something wrong? Warning lights on? Horns blowing? SIC screaming? Or did you just dream this...


Dick Sanford, thank you for joining this thread and applying energy management to Cyclic Back. I am going to use your example of trading airframe velocity for rotor rpm. You are so right. For years we've been teaching the three sources of energy available to the pilot when energy from the engine is no longer available, trading energy back and forth as needed, but I've never included your simple explanation in what I've written and lectured about concerning Cyclic Back.


And Shawn Coyle, I thank you too for joining this thread. How often I dream that I could have the knowledge, skills and background that you and Dick have.


I extend my most sincere thanks to every poster who supports Cyclic Back or who is at least open to learning about it. To those readers who have the “My mind is made up; don't concern me with the facts...”, or “Secret? What secret? Everyone in the world of helicopters knows all about this, Pete, and you don't know what you are talking about...” Well, I hope you'll reconsider and come on board with this before you find yourself in a situation where you wish you'd brought the cyclic back more quickly.


Two more things: Probably more than half of my career has been spent flying well within the H/V curve. I've been lucky and never had a mechanical problem while doing this. But those of you who have practiced and demonstrated hover autos initiated from within the H/V curve, in turbine-powered helicopters, have not seen a situation involving REAL engine or drive-line failures.


Several posters have made this point. Try this: Hover at 250 feet agl and have your SIC flame out the engine while you are looking out the window. Now let's see what happens! Even chopping the throttle to idle is a lie. No matter how rapidly you or your SIC “chops” the throttle, the fuel control is in charge of how rapidly the engine heads towards flight idle. The best example is the very popular Allison/Rolls-Royce C20 series found in so many makes and models of helicopters. Wonderful engines. I've trusted them for years and never been disappointed.


Do a hover auto in a JetRanger or 500. Watch the dual tach. Notice something? The needles never split! The fuel control dials down N1 rpm at a rate that will not cause the engine to flame out or compressor-stall. YOU don't control this; the fuel control does.


Each make and model of turbine engine has its own rate of deceleration to idle when the throttle is chopped. The C28/C30 engines used in the 530FFs and LongRangers L-1 through L-4 drop much more quickly to idle, and a needle split usually occurs, but the idling engine power is over 40 horsepower to make the pitch pull look so easy... Same for AS350Bs/Squirrels.


And when you pull pitch...er,the lever...just before ground contact, you are benefiting from the 35 horsepower the C20 series will give you at that time! Do you doubt that? Check your Rolls-Royce technical publications. Look under “Horsepower available at idle.” See the number 35?


How about in the wonderful Huey? Same thing. Could you use over 80 horsepower to make you look so good when pulling pitch at the bottom? Sure you could. And the result makes you look like a super pilot...with a bit of credit given to the “high inertia” rotor system. And for you “Hook” drivers, each of your engines will put out about 300 horsepower at idle. See where I'm going with this?


No, if you want to see just how little time and rotor energy are available to you when the drive shaft fails or the engine(s) flame out, list me on your insurance and then find someone who will flame the engine(s) out OGE when your eyes and mind are elsewhere. This is the real world.


Every “contact” maneuver, whether a practice EOL (see? I'm catching on, guys!) at the end of a normal or hover auto benefits from the idling horsepower from the turbine. This is the same power that makes the rotor blades move at idle! It's always there, making the pilot and the rotor system look good when doing these training maneuvers.


By the way, several posters mentioned situations where the pilot does not have his left hand on the collective. This is true and getting truer as our cockpits demand more and more heads-down attention from the pilot. Lots of things to do with your left hand; frequencies to change, waypoints to insert, switches to switch, and on and on. It's beginning to look like a Space Shuttle cockpit. Except when on autopilot, most of us keep one hand or the other on or very near the cyclic. The collective requires very little attention unless power changes are being made. It is, after all, simply the thrust control, right? In a turboprop airplane it would be called the Beta control (prop pitch control). So it is very common to not have one's left hand on the collective at all times. Here we go; Cyclic Back, and THEN find and lower the lever...er, collective.


A few days ago I was thinking I'd made a big mistake in wanting to share Cyclic Back with my fellow professional pilots on PPRuNe. The snarky remarks were beginning to grind on me. But those of you who echo my thoughts or who have at least been willing to consider them have given me the confidence and support to stick with it. For this I thank all of you.


Pete Gillies

John Eacott

Henra,

John D was very careful in explaining that the decay was calculated by the SA guys in response to an accident investigation: not done in 'real flight', and also that the number 'was in the 60% range' which could be 69%!

For you to allude to a drop to 60%Nr can be considered is a bad move on a helicopter forum, since it can morph into an assumption by some and then, before you know it, we're into the 30 minute S92 run-dry scenario where it becomes a firm belief.

I hope that you can see the sense in modifying your post to remove your reference before it becomes assumed to be valid.

henra

Hmm, I'm a bit confused. My Point was exactly that I think assuming 60% might be recoverable is very dangerous grounds. I would consider everything below 75 - 80% sustained as potentially irrecoverable.


When doing the Maths 1g at 60% corresponds to 2,78g at 100%. Even taking into consideration drag effects of the cabin /airframe itself in a rapid descent this means a very significant AoA of the rotor system. Doubtful if you can achieve autorotation at such angles.

Savoia

I'm not sure if taking "the manufacturer's advice with a little pinch of salt" is the best approach.

Helicopter operations (like many other modes of transport) have been subject to continuous development. Since the end of the Korean War in the early 50's (where the helicopter first 'proved' itself) helicopter development (both military and civilian) has been pursued in earnest.

With each new 'generation' there has been a constant and relative increase in performance and reliability resulting in today's models which allow professional SAR organisations (for example) to conduct winch operations in the knowledge that, if flown within the manufacturer's prescribed parameters and in accordance with proven operating procedures, there is every reason to be confident that in the event of, say, a loss of a power from one engine, it remains possible to fly away.

Most (if not all) of the early helicopters (including the early twins) were woefully under-powered and (as with initial single-engine helicopter operations) pilots and operators had to do their best to mitigate as much of the risk as they could but .. this was played-out alongside the need to continue proving the helicopter as a viable vehicle in an increasing arena of activity.

That 'struggle' continues to this day in different parts of the world .. and for different reasons (primarily financial) where operators in regions where helicopter use is relatively new or where a new uses are being pioneered .. and where an operator is under pressure (often self-imposed as part of commercial endeavour) to prove the viability of helicopter use. That's where (for example) you could get a single-engine helicopter being sold to a country with a limited budget and the aircraft is fitted with a winch.

Safety (in broad strokes) is expensive and often it takes an operator and or client a little time develop adequate recognition of the value of 'helicoptering' before they will commit the resources necessary to raise the standard of their operation to the best that the market has to offer (I speak mainly of clients/operators with considerable budget limitations .. such as some of the developing nations .. but not only the developing nations!).

These are just two considerations .. but there are several more.

What I can say is that the RFM limitations are there for a reason and I believe those reasons to be valid and for the benefit of all.

John Eacott

henra, you missed quoting the first line in which I tried to point out that JD did not say 60% as a specific number.

That was my issue, and something that I felt needs nipping in the bud.

SASless

I taught in the 212/412 Sim.....and used that very event in training many Pilots.

I do not endorse your comment about the the "Crashing and Burning" due to the absence of Aft Cyclic during that situation.....in fact I would suggest that just is not the case at all. It might be part of the resolution of a problem but it alone is not the most important part of the response.

Reaction Time is the key.

Followed by use of the most critical response and then doing secondary control movements.

What is far more key to the outcome is the amount of delay in reacting to the failure and thus being able to minimize the decrease in Main Rotor RPM.

I think you put way too much emphasis upon "Aft Cyclic" as again....where and when the failure occurs is far more important and directly affects the amount of time that can elapse without a Pilot response to the failure before the situation becomes unrecoverable.

It is far easier to make up a small loss than a huge loss....that is plain commonsense. Any Helicopter Pilot who has an automatic response to lower the Collective when "Bad" things happen suddenly in a helicopter will probably live to see Retirement as compared to one who sits there wondering what the hell just happened before reacting. Anything you do to keep the Rotor RPM in the Green Normal Range is the right thing to do until you figure out the exact situation you are dealing with.

Rotor RPM is the very foundation of Life in Helicopter flying.....always has been....always shall be.

As you note....low power setting with a moderate IAS....and time is not as critical as compared to a very high Power Setting and a very high airspeed.....or no forward airspeed. In the latter....response time is very critical to defend against a large decrease in Rotor RPM. If moving the cyclic will assist in minimizing a loss of Rotor RPM then it should be done to the extent possible without causing other problems.

I will accept moving the Cyclic Aft will not necessarily hurt you in most situations....depending upon the amount of cyclic movement you make. Too much and you risk chopping off the Tail Boom on a 212.


Your other comment about the lack of Needle Split on some aircraft.......just how do you check for proper function of the Free Wheeling Unit? If you cannot split the Needles then that would be an indication of a malfunctioning Free Wheeling Unit.

If you have done much Maintenance Flying then you know that check is a normal test flight procedure....usually done on the ground prior to take off.

I am thinking you have some good ideas, and genuinely good intentions....but you are using much too broad a brush in some of your statements, in my opinion.

FH1100 Pilot

SASless:You don't, at least not in a Bell 206, FH1100, H-500 or just about anything else powered by the RR250 series.

You do this before start, by turning the main rotor backward. (Haven't we been through this like a million times?)

JohnDixson

Henra, that number, in the 60% range was a calculated value. To my personal knowledge, transient power off flight test experience goes down to around 80%. Talking about the in flight data. Power off Nr may well go a bit lower during the landing phase ( although, one better have the machine close to the ground and the rate of descent within limits by the time Nr has drooped to the low 90% range because, well as you all who do these landings know, your ability to produce more than one G, and thus decelerate vertically, is about gone by then).

So, I completely agree with your, may I say, " experienced reluctance " to use that range as usable. I did not mean to covey that idea.

Two's in

When the Lynx first came in with BERP blades, every auto was major excursion into some corner of the Nr envelope. Eventually the accelerative Nr nature became more familiar and you soon learned to control Nr with judicious use of the collective. The point being there was no magic collective setting, you worked fast and furious at keeping everything in the governed range on the way down. It's should be the same for every helicopter, you enter autos in the prescribed manner and keep the Nr in the governed range through use of the collective, plus of course whatever you might want to be doing with the cyclic to get your speed/field/flare sorted out at the bottom.

I am perplexed by this "here's what you do with the controls" approach to an auto. There is no fixed solution, just the one that saves your life on the day. But as SASLess has mentioned, without Nr you have no vote or input in the subsequent events, so you really should get that sorted out at the start - assuming you aren't prevented from doing so by some other malfunction.

G0ULI

The Robinson Flight Safety video certainly scared me as a fixed wing pilot. 1.1 Seconds for the rotor rpm to decay to a critical level does not seem allow a lot of reaction time if there are other distractions in the cockpit. I appreciate that this is a worst case scenario, but it certainly made me think. The other point made was that autorotation is a pretty quick process when trading height for maintaining rotor rpm. Descent at 1,500 ft per minute doesn't give a whole lot of time to pick a landing spot. Okay, two engines make it more unlikely, but there appears to be virtually zero margin for error. Makes one appreciate just how skilled helicopter pilots are considering the accident rates per flying hours.

Bertie Thruster

Flaring the cyclic 'aft' might not be effective if whatever problem you are responding to is turning the airframe backwards.

DOUBLE BOGEY

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

Grenville Fortescue

Double Bogey

I don't see where John Dixon or John Eacott are advocating the use of 60% Nr. My understanding is that John Dixon was relaying research findings.

You've just said it's a "stone cold killer" but then you say everyone should be taught to recover from it! Are you also trying to have it "both ways"?

What exactly do you mean by that statement?

Who are you referring to and in what context?

All in all, a somewhat confusing post.

DOUBLE BOGEY

Grenville - if you do not understand my post just do yourself a favour and follow Peter Gillies advice.

DB

Thomas coupling

OMG! What a page of posts.
A lot of "big hitters" all turning up at the same time. I have to say this in itself is a reason why I find Pprune fascinating and very enjoyable at times. It's a shame it has to be spoilt by erroneous and undeserving out of control comments from DB at the end of it all and I apologise on his behalf.

Peter Guliies - you started all of this If I may, I would like to commend you for your contribution. You are obviously a passionate end user and (from others) recognised 'expert' in your field. Comments from people such as your good self are always welcomed, I would suggest.
Might I shine light on where,perhaps it has caused enormous consternation from others (me included)?
It is you way with words, it is the way in which you convey your message that has raised a few eyebrows amongst the old and bold amongst us.
Words and statements such as "best kept secrets" and "AFT cyclic" first.....are bound to wind some of us up for all the reasons posted here.
It really boils down to semantics, I would suggest. Perhaps if it could be kept benign, the best way forward for ALL of us to agree, would be to state the following:
In the event of a total power failure or malfunction requiring an entry into autorotation the pilot is required to maintain Nr (ideally in the green) by judicious lowering of the collective whilst maintaining attitude.

My reasons for this wording being that ALL helicopter pilots irrespective of their background, are taught from infancy to maintain Nr (it is their life blood). The EASIEST way to retain Nr in ALL circumstances is to lower the collective. Yes I totally agree with you that selecting aft cyclic will also assist, but it is NOT guaranteed is it: Example (as mentioned by you): in a climb (at say 70kts), if the donk stops, one would instinctively lower the lever but one would not wish to select aft cyclic becuase of the unwanted speed reduction. Again in the hover - aft cyclic is not requried. So I think that because there are situations where AFT cyclic is not necessarily essential/mandatory then it should take second place to "lowering the collective" during that instantaneous window of decision making. I hope you understand where I am coming from. You are not wrong in what you say, it is how you have conveyed the mantra.
I have to say that SASless's post in responding to your entry are exactly my thoughts, so too are Two's In. Also excellent posts from the great JD - thanks for your post and good to hear from you.

Finally Peter - I have done hundreds of real engine failures in singles most of which were not at FI, but actually stopped - fuel and all. So HP drag didnt come into it I'm afraid.

And I agree - a real engine failure inside the dead mans curve may result in damage to airframe and/or those onboard. The curve has been designed for the use of Joe average responding at an average response time. The words FATAL are not used when describing operations inside the H/V diagram and never have been in my experience.

SASless

DB,




The failure of the Captain to comply with the Emergency Checklist and the Co-Pilot's desire to do so.....by Ditching in a timely manner was the cause of the outcome that resulted from that refusal to ditch.

The descent that followed the first indications of a problem took Eleven Minutes, a conversation with Base Ops took place, and the descent was stopped and a return to level cruise flight was undertaken.

During that process, the Co-Pilot on two occasions reminded the Captain of the Checklist Entry that CLEARLY called for a Ditching.

So despite the Checklist and a Co-Pilot being in favor of ditching.....into very cold and very rough water.....the Captain elected to continue flying.

The existing Sea State, OAT and Wind, and the lack of a Ready Crewed SAR aircraft.....and perhaps a mistaken notion about the 30 minute Fly Dry capability....and whatever guidance the Management Rep provided the Captain....all played a role in the fatal crash that should have been a Controlled Ditching.

SA had run a MGB for an extended time to meet the FAA's Certification requirement.....which we all know now was not representative of an actual "Dry" gearbox. So you need to lay some blame on the FAA as well.

You and HC need to tell the whole story when you bang the Drum about the 92 Crash off Newfoundland. We know the two of you are very much proponents of the 225 which is a direct competitor to the 92. You should be wary of coming across to others as being incapable of having a professional, business like discussion about all things helicopter.

Neither Dixon or Lappos made any comment or suggestion that would lead any Pilot to thinking operating outside the published HV Charts or Main Rotor RPM Normal Operations limits was safe, authorized, or recommended. Just the opposite in fact.

To say otherwise as you have done is not being accurate.

Dixon and Lappos are Professional, experienced, and very capable Test Pilots who know of what they speak. They grant you the courtesy of respecting you in discussing your posts......you should do so in return.

Inquiry finds 16 separate problems in 2009 Nfld. helicopter crash - The Globe and Mail

DOUBLE BOGEY

SAS - I consider myself mildy admonished......HOWEVER....

The S92 is a fine ship and there is no intimation in my post that the AC let them down. A poorly timed set of maintenance requirements within the airworthiness constraints contrived to cause their problem. But as you clearly allude to, the mistaken belief that the crew may have had more time to react due to a false assumption may have been the reason for the final catastrophe.

It is to this which I refer when seemingly qualified people dismiss Peter Gillies doctrine to recover NR by challenging the values of NR using alternatives that are not in the RFM. Proffesional they may be but these are dangerous statements made in direct contradiction to the very sound advice from Peter that, unless we are morons, is completely irrefutable. Surely SAS you must agree that the most efficient and sensible way to recover decayed NR is to flare. If you do not have the speed to flare you are in deep do do.

TC please do not apologise on my behalf. Your ridiculous presumption that the cyclic should not be moved in case you need to do a range auto sets you apart from your peers as not really knowing of what you speak. However, being a fair man I will offer you a chance to withdraw that statement and agree that the number one priority is to safely establish into autorotation....followed by assessing your options.

Regardless of the totally distracting irrelevant information posted by some on this forum I have and will continue to follow Peter Gillies doctrine. If the pilots instinct is to trade speed for NR, ASAP, he will always end up in a better position than any possible alternative.

DB

Edited: to say on reflection I did not want to be rude to the two Johns although reading my post this seems apparent. I would just like them to step in line with Nick's posting that the RFM, is our only reference and in doing so hope that the Test Pilots (maybe them) got it correct the first time.