Zero speed auto > Hover (without gaining airspeed)

[rudestuff]

My Roommate (who's recently got his CFI and therefore knows everything about flying there is to know) Was telling me his theory of how you could be in a zero airspeed auto, then recover to a hover just by pulling enough power fast enough.

He thinks that it is possible to 'power' his way out of it. I told him it seems to me he doesn't really understand the concept of SWP if he thinks that. I'm sure more experienced people than me can help convince him...

As I understand it, in autorotation the blade roots are stalled - any additon of power neccesitates up-collective (to prevent overspeed) which increases the stall/tip vortices etc and at zero A/S would send you straight into SWP.

[Matthew Parsons]

SWP...This could be entertaining.

Can you bring in power at the bottom of a zero airspeed autorotation to arrive at a hover?

Best answer: it depends. Depends on Nr droop, engine governing characteristics, rate of descent, and power available. (might have missed something)

Settling with power implies you don't have sufficient power to maintain level. If that is true then you will not be able to arrest your descent. If you have plenty of excess power and the Nr doesn't droop too much you might be able to get away with this.

Vortex ring state would be my biggest concern. You have zero forward airspeed, rate of descent, and then you bring in power, giving the three conditions that are required. Whether you get into VRS depends on characteristics of the helicopter, your rate of descent, and the power that you apply. This would be a very bad thing to encounter.

I do not recommend trying this.

Matthew.

[cl12pv2s]

Matthew,

Without wanting to start a debate on this, I think rudestuff was actually refering to SWP due to Vortex Ring State.

Rudestuff, you are saying,

Imagine you drop vertically in autorotation, aiming to pull collective really aggressively to reduce your rate of descent to a survivable rate...

I guess it could be possible to do given the right equipment and pilot...

I don't think that VRS would develop fast enough in this short timespan to be of consequence

...the deceleration required to reduce the decent rate to a survivable one is quite a lot. This would sup a great deal of Nr, so could only realistly be done with a high-inertia rotor system or with absolutely split second timing and a sharp yank on the collective.

Well, in practice the timing would need to be so perfect that it's not a method to count on as a means of surviving an engine failure...As Nick posts below, an experienced pilot with 'split' second accuracy in timing and the right helicopter could pull this one off

So no, I'm not going to try that any time soon!

cl12pv2s

[malabo]

Been there done that, only to landing, not hover. B206, H300 etc. You'd better have the throttle off, otherwise you'll overtorque at the bottom. Takes a fine eye to gauge the exact millisecond for that one sharp collective pull at the bottom. Clever instructor trick if you do it all the time. Wasted as a training technique to the unwashed that do a full on auto every 10 years or so.

[NickLappos]

The idea that it is "impossible" to go vertically upward from a vertically downward autorotation because you will somehow slip into unrecoverable vortex ring state is simply not true. The myths of vortex ring state are legend, and hardly worth repeating, so let me state the opposite:

The real rules of Vortex Ring State:

1) If you have lots of excess power, you can lift collective and fly vertically out of VRS. VRS is not a Black Hole, it is a place where the rotor has greatly increased power required, because it is wasting so much power recirculating air. If you have enough excess power (about twice the power needed to HOGE) you can simply apply collective and smoothly go from descent to climb, a vertical climb.

2) In a zero knot auto, you can recover with engine power and climb vertically, without gobs of excess power (but certainly with more than HOGE power) just do not dwell at VRS state descent rates (about 1500 to 2000 fpm for most helos, 1000 or so for light pistons) but rather climb smartly trhu the descent into a climb.

3) If you have enough rotor inertia, you can land from a zero knot autorotation without rolling up the engine throttles, simply lift collective and time it right. You will NOT experience VRS as you stop the descent, not even a burble. The flow for VRS has to establish, it does not automatically present itself when you get a momentary combination of ROD and speed. I have done these by the dozens in Bells, and VRS is not a consideration.

[rotorrookie]

My Roommate (who's recently got his CFI and therefore knows everything about flying there is to know)
and he really thought this was possible ?????
was he sleeping in principles of flight classes????

and he's CFI now.... omg

[MightyGem]

(who's recently got his CFI and therefore knows everything about flying there is to know)
Hmmm...I don't think there's anyone who knows all there is about flying. Or will somebody prove me wrong...:rolleyes:

[212man]

rotorookie, you obviously didn't read the post above yours!

[WSPS]

Hi there,

any of you chaps out there tried it with an R22 or R44?

We do quite a lot of no-flare auto's where you come in at 40-50 KIAS, bring your rotor-rpm up to maximum and do a full touch-down. This works quite well even in a light piston.

But trying a no-speed in an R22 would seem very hairy at best to me.

So anyone out there who gave it a try?

Keep the rotor in the green :ok:

[oldpinger]

I'm pretty sure it is impossible to get into vortex ring in any kind of auto (except a botched power recovery) as you need an induced flow through the disk to get into vortex ring, therefore in auto, no induced flow and not possible. A low speed auto only gives you two of the requirements for VRS, ie low speed and a rate of descent. I imagine if you are pulling power to overshoot from an auto and still descending with low speed on, could be exciting, but from experience, some helos are difficult to get into vortex ring even if you try.
Back in the days of gazelles and 705sqn we used to do zero speed autos by plummetting down at about 40kts indicated, with the engine at idle, wait until the requisite moment and cushion like a b#stard running along the ground at about 30kts. VERY sporting and I'm sure the instructors didn't get paid enough.
Never hit VRS in that case anyway.


Oops, :O just read Mr Lappos' reply above, all covered...

[cl12pv2s]

we used to do zero speed autos by plummetting down at about 40kts indicated

Hold on...are we talking two different things here?

I read the original question to mean, vertical descent with 0 indicated airspeed. That to me is a 'zero speed auto'.

Oldpinger, you are describing what I would call a 'constant attitude / no flare' auto.

Nick, which were you refering to?

cl12pv2s

[Aesir]

I have done these by the dozens in Bells,

This is the key here! Don´t try this in any other product ;)

[BlenderPilot]

I attended Bell 206 training at a large GOM operator, (my company paid for me to go there, I didn't work for them) and when I got there I was shown the helicopter that I was going to begin training in, a 206 with fixed floats, I inquired as to why we were going to do autos in a float equipped helicopter since I never flew over water?

They said that from they have been told by my boss I spent a lot of time flying low and slow and that they were going to teach me vertical autos from the within the "dead man's curve".

So off we went, hover at say 250 feet, chop the throttle, vertical descent and as the world came up to us fastest than I have ever seen before, a sharp collective pull stopped the descent, lots of water splashing everywhere, chin bubbles partially submerged for a second or two (reason for a float equipped helicopter) and I even got to see a Crawfish sliding down the windshield once!, helicopter and passengers in one piece.

And there you go, almost vertical autorotation with no flare, just a collective pull to stop the descent, on a side note, the collective pull had to be extremely well timed, sharp without being abrupt, and I remember the collective almost touching the roof! I would never try this in skid helicopter since the chances of messing it up seem astronomical to me.

[170']

More in context with zero speed auto's than SWP...

I had a chance to go thru CHC's mountain flying course in Penticton...

This was a long time ago (JR was the CFI,maybe still is, anyone know?)...During the course we were taught 100' hovering auto's in the Short leg 206's used for training...

Pretty spooky stuff at first, but by the time you get to do it yourself, you were pretty happy that the IP's there are (were?) helo God's, and would keep you out of trouble.

These weren't power recoveries, but to the ground...

It was the first and last time I ever got to practise the manouevre and wouldn't want to try it solo as a training exercise. But life gave me an opportunity for real, with a busted short shaft in a UH1H .

Basically just went 210 feet straight down, did a partial pitch pull(and lever down again) around 80-100' and then waited 'til I couldn't stand it any more and pulled it all in....wrecked the machine due hostile terrain. Can't really say how it would've worked out on flat clear ground. but I think SWP or VRS is the last of your worries in this type of scenario, no time for anything to develop....more a case of lucking out with the timing...

I think the average pilot(me) is pretty lucky to land undamaged from a vertical auto above the normal hover auto height,plus or minus a few feet...simply because we don't get a chance to practice!

In regards to flying out of SWP/VRS (hard to find a difference while it's happening) with Power, I have to agree with Nick Lappos...Done it many times with 214B's which leads me to agree with Aesir on Bell products...

Merry Christmas to all...

[KikoLobo]

Where did you do this?

Its a nice idea... The floats i mean :)


I did some OGE Hovering autos at bell school, we where about 200-250 feet and the 206B, gladly stopped the descent rate with an abrupt collective pull at the right time (at the bottom :) )...

The only thing to notice, is that it was me, the pilot and 40 minutes worth of fuel on board on a very low altitude place (alliance airport, in Dallas), the only thing that was not on our favor was low winds (almost zero wind) and hot day. Not humid though. But very low on weight... Certainly teached me what i should try to avoid flying in.... :)

QUESTION (NO DEBATE PLEASE!): SWP or VRT, requires POWER... So how can one enter one in an auto rotation??? (Not possible). Also some concerns grew that you could enter one on the recovery process, well if you pull collective at the last moment, arrest descend and the open the throttle, you can't get in there, cause ur descent rate its going to be slower than 300fpm, or you are dead.

A word though... I would never attempt to recover from this, i would go to land, and attempt it with a good instructor that knows what he is doing... If on a robbie, try it with a factory instructor or someone with vast experience, if on a bell try it with a good bell instructor.

170\'

How did the UH1H bahaves on autos, compared to a 206B?

That was a job well done man!
Congrats. Do you have any pics?

What cause the shaft brakage?

[happyhamster]

Blender - was that the recommeded procedure for landing a 206 with floats onto the water ?

[diethelm]

I thought in autorotation that the rotor system was, in "Autorotative State"?

[170']

KikoLobo

It was intergranular cracking due to corrosion on the inner surface according to the Feds, Which I think is fairly unusual.

Normally the unmodified S/S fails with too many high cycle counts on 35 year old grease...This was way back when and we were using pretty old machines and original shafts and exmil grease..The K-flex solved the problem...

The UH1H is a sweetheart in an auto, but I prefer the 206 if we're playing Auto's as it's more manouverable close to the ground if you really want to make that spot... and I'll try to dig up the photos after the break, not very good as they were taken by our POI with a Fed camera...supplied by the lowest bidder ;-)

Feliz Navidad

[Matthew Parsons]

Just to clear a few things up because unlike any other topic, this one has expanded from the orginal question.


1. Landing a zero speed auto without an engine is possible. Many of us have done it, but it is a technique requiring timing, the right machine, the right conditions (DA, weight mostly).

2. Power recovery from a zero speed auto is a very different thing from #1. With power recovery you can get into other problems.

3. If you had enough power you can avoid spending too much time at a possible VRS condition. If you had enough power you can fly out of VRS (I've never tried it, but theory seems valid). However...everyone who has complained about not having enough power in your helicopter, raise your hand. Thought so.

Unless you can be convinced that you have enough power to try this before entering, there is no way you should even consider it. If it's not in your flight manual don't do it. If you have better options, use them.

[BlenderPilot]

These pictures were taken on precisely the day of my vertical autotraining.

This was some of the best training I have ever recieved, out of the box, real world oriented, to say the least.

Compared to factory training I have found that going to real operators for training is very useful, for example last year I went for training in Oregon with an operator, now that was an eye opening experience! Real world, not routine, the other guys at my company have recently been to Canadian H for AS350 training and say it has been the best training ever had, better than factory. Same in my case for Bell training, the training recieved from real operators has been better than factory training, MUCH CHEAPER TOO.

IMHO Factory is good for ground training, but in my experience flight training has always been better with operators, their instructors are usually not political about training, they will keep you safe and everything else comes second, could it have to do anything with lawsuits?

That's me in both pictures.

http://homepage.mac.com/helipilot/PPRuNe/PHIAutoTRNG2.jpg

[KikoLobo]

Blender.

Where was that trainning you took?

[170']

Blender

How did the 206 handle in general with fixed floats?

Yeah! I know it's a thread hijack, but it's not a hill to die for?

did you do any autos to the hard in it?

170

[Thomas coupling]

Some 'americanisms' need sorting out first before one can answer the Q. Correct me if I'm wrong:

Auto Vs EOL:
When a yank states "auto" he means that the engine(s) is/are OFF. Brits call this an EOL (engine off landing) to differentiate from a brit auto which means power available throughout the manoeuvre (Brit spelling!).

VRS Vs SWP
When a yank says VRS (vortex ring state), they sometimes mean SWP (settling with power). The two of course are completely different phenomena. The former is a state where the pilot has NO control over the machine. The latter is where the a/c remains within its flight envelope and the pilot simply has too little collective margin left to compensate for the ROD at the bottom of a descent.

VRS Vs IVRS
Perhaps not an americanism, perse (french not american!) but sometimes when pilots talk about VRS, they mean the incipient stage where there is still the ability by a pilot to input a control demand and expect a response. As Nick stated earlier - "powering out of VRS"...actually it should read IVRS.
VRS - fully developed is where the pilot and crew (against their wishes) become passengers and aerodynamic forces will decide if control is returned to the pilot (by falling out of the VRS state of their own accord) or not.

Assuming the above:

A yank auto (EOL) cannot experience VRS, because the induced airflow decays as it is being injected (Decaying Nr).

A zero speed auto (EOL) ending in a massive collective input to position it in the hover cannot result in SWP, because there is no 'power'.
An auto with the engine running - ending in a massive collective input to the hover requires well above average skill, judgement and practice. But provided the ROD is inside the a/c's margin for collective recovery (Nr and AUM), then SWP shouldn't develop.

An engine running auto to a full stop in the hover from zero speed wouldnt incur VRS because the immediate onset of VRS is not possible, it wouldnt have time to precipitate.

Observations invited..............................

[NickLappos]

I hate to establish an argument (yea right!) but when you land an autorotation, you go into Powered flight! The concept is that the "power" comes from the rotor inertia, and is applied to make the rotor behave as if the engines were connected. There is no aerodynamic difference between a touchdonw auto in the final landing sequence and a hover touchdown.

If you took a snapshot of the helo at the touchdown phase, you would find the rotor pumping air downward, in mass sufficient enough to develop thrust that is more than the weight of the helicopter (because the rotor is slowing down the vertical speed, and thus accelerating the helo upward). A G meter will read slightly above 1 g when the landing is being accomplished.

[Matthew Parsons]

Thomas Coupling, I know where you're going when you talk about the "time required to precipitate" but I'm not convinced.

How long is this time to precipitate and how long will you be in the VRS likely conditions? Until those questions are answered I don't think you can make your statement.

In the worst case your ROD in the auto is the highest that puts you in danger of VRS and when you apply full power you can only slow to the minimum ROD that puts you in danger of VRS. Okay, that's a bit of a stretch but pretend you tried to power out of a zero speed hover at 8000' DA, max AUM. In this odd case, how can you say there isn't time? If it's possible in this case, isn't it possible in many others? What if the pilot doesn't use enough power to vertically accelerate out of the condition?

It might make for some interesting research flying if nobody has studied this before.

As far as terminology, very little is standard. It seems that most are using auto or autorotation to indicate when autorotative forces are turning the rotor rather than an engine. Whether this is because the engine is shut down or if the clutch is not engaged is not acknowledged. The EOLs are sometimes called "full autos" or "autos to touchdown" but again, not standardized.

[NickLappos]

Matthew,

Please don't confuse ROD in autorotation with ROD in powered flight. In autorotation it is IMPOSSIBLE to get VRS, because there is no rotor downwash. The flow is going UP through the rotor, and is powering the rotation by what is called the "windmill brake state" where the rotor is a pinwheel. Any vortex pattern from the rotor is swept up and away from recirculation. There is no downwash to get captured and recirculated through the rotor, thus no VRS.

When Thomas talks about "not enough time" he is referring to the very brief event at the end of a touchdown autorotation where the rotor is recovered from autorotation to a powered operating state (by your application of collective pitch), with or without engine power applied just prior to touchdown.

I think you are right about the terminology, Autorotation is what the rotor does, engines on, engines off or engines missing (autogyros!)

I don't agree with thomas about the distinction between IVRS and VRS. The loss of control and lack of response to power demands that we experience in underpowered and low control helicopters is not because VRS removes ALL control and climb. It is because VRS removes more than those helicopters have. The data is clear and available to support this. To support Thomas's point though, the distinction is theoretical if you are in a typical training helicopter.

[Matthew Parsons]

Nick,

I didn't mean to imply VRS in an autorotation. The idea here is to transition from autorotation to a powered hover (using engine power, obviously). Once the engine is providing power, the ROD will still be near to what the ROD during autorotation was, hence my reference to the autorotation ROD.

As far as what Thomas Coupling meant, he's the best judge, but he did say, "An engine running auto to a full stop in the hover...[VRS] wouldnt have time to precipitate." Doesn't sound like an auto to touchdown to me.

Mr Selfish,

You\'re right that its a compromise between minimizing ROD and maintaining Nr. If you\'re authorized to do zero speed autos you can determine what ROD and Nr will stabilize and how quickly it will happen. However, the Nr will decay quite quickly if you\'re hovering OGE and to reach a stabilized condition you first need an even lower collective to recover Nr, then increase to maintain.

I did these in a 206 starting at 10 feet - not difficult, increasing to 30 feet - things happening quickly, but minimal loss of Nr...more difficult, then to 50 feet - again things happening quickly, more loss of Nr...most difficult (of what I tried), and finally from about 75 feet...entry the same, time to stabilize, time to peek inside and see what\'s happening...less difficult than 50 and maybe 30 feet. Any higher and I\'d extrapolate that the stabilized condition just lasts longer or you\'d opt to achieve forward flight.

In a Gazelle, I did these from 2 feet up to almost 10 feet. It was not comfortable above 5 feet. Rotor decay didn\'t seem to end and the reduction in collective effectiveness was dramatic.

Technique then is to learn from type experts about what works for what you\'re flying. In general, you\'d have to recover Nr with the lowest collective comfortable, then raise to stabilize, and check at the \"right\" height. Very much a learned technique not a written one.

[BlenderPilot]

Mr Selfish
I do remember taking the collective all the way down, but I must say I am no expert at this, I just feel comfortable having seen what the helicopter can do if the need ever arises.

170'
I vaguely remember that the 206 with floats flew pretty close to a normal 206, can recall feeling any difference.

[170']

Thomas

Yanks!

What? are we back in '43 and stealing your womenfolk agin?

'Yanks' are not an homogenous mass, staring eastward, looking for collective ways to confuse your sense of what's proper and correct, and further distort the Queens English.

We have types like Lappos,yourself and several others who have put in the time and developed, what for me, seems like an uncanny level of knowledge...

Then we have your common or garden!yank/polack/frog/canuck/et al, such as myself, who just fly helicopters.No great aviation education other than what we learned in flight school, just been out flying for a living all my life.

No claim on being any kind of Guru, but nonetheless like to throw in our 'two bits' ...Just for the fun (as the French say!)

The Spanish milled dollars were easily cut apart into equal "bits" of 8 pieces. One "bit" would be equal to 1/8 of a dollar, and 2 bits would equal 2/8 (a quarter of a dollar). So, that's why the coins were called "pieces of eight", and "2 bits" was commonly used to refer to 25 cents.

When contributing my little piece to this august forum, I write as if I'm speaking to a guy in the hangar...I don't really think about the pedantics.As most guys (I think) just intrinsically understand the jargon. If the check airman says to me, "give me a 180 to the ground"...I don't ask, a 180 What?......I just kinda know what he means! and go ahead and do it best I can...

I appreciate that some people want to get to the marrow, but then again, some of us just throw out a few comments without needing to write something for peer review.

Your clarification of the nomenclature makes sense to me, although I don't know that you'll find too many people adhering to it, with this degree of accuracy.

I'm not arguing the need for accuracy, just that many of us 'cousins' are a little more relaxed about nomenclature, or maybe just a little more relaxed period...

Most 'Yanks' think of an auto, simply as an auto! with the codicil attached... to a power recovery or a full down...touchdown...take it to the ground etc...

VRS v SWP....In my working world (logging) the approaches might start out as upflow/upwind, and just as everyone gets in the groove, we get a windshift and you end up falling thru a little....Am I in VRS or SWP....I don't know? because as soon as I feel it happening, I fly out of it before I get bent too far outta shape..... I work with it, until the next cycle break, and try to get the guys/landing reset. It's just not that big a problem... But when I read that in VRS I'm just along for the ride, makes me wonder if I'm safe doing what I've done for a long time. maybe I just don't get it? but I get paid for heading downhill (normally) as fast as I can and somehow I always seem to stop at the bottom...Go figure?

I've heavily edited this from the original to remove the apparent vitriol, I got a couple of emails saying I'd gone overboard...

You see! ....I find the way you say 'Yanks' offends me...Don't know why exactly,some folks can say it fine. The way you say it just irritates the hell outta me!

I feel better now!

170

[[email protected]]

170 - that's what us limeys love so much about you yanks - your easy going nature, ability to take criticism and sense of humour.

[170']

He who walks sideways...

Think you need to re-read my post with a less jaundiced eye. No problem with you supporting your countryman, you and he can't help being British, any more than I can help being American. I guess it's clear neither of us would want to swap places...

Unfortunately, I resemble your remarks regarding SOH, criticism etc!

I used to possess some of the your stated qualities until hitting the UK shore...After many months of exposure to the few, I'm just not the man I used to be...Try dealing with the CAA as a foreigner...

Before I'm accused of widening the existing chasm between Yank and Brit, let me state clearly that my feeling about the British are by no means a blanket disapproval.

I've met a bazillion great people, along with the pompous, self serving few. The majority of us, Yank and Brit alike, laugh at pomposity wherever we find it, and from whatever nationality the source...Just sometimes the tone of voice or style of written word, makes the laughter stick in the craw!

....170

edited for grammar!

[Matthew Parsons]

I didn't realize this went so deep. I just thought the use of 'yank' was in reference to the collective action at the touchdown/full auto/EOL with a parallel to a frequently misused term for someone from the US. :)

[170']

Mathew

Probably not as deep as it looks, I just read one too many comments that I thought to be condescending and pompous.

I'm no better than anyone else, and often refer to someone using common argot. Gotta say though, that Limey and Yank are from Dad's generation not mine, and I'm early fifties!

Not such a big deal I suppose!... but when you hear constant criticism of the US system. It gets old real soon!

Especially when they spend 10 minutes telling you whats wrong with US licensing, and the reckless nature of US Operations. Followed be tales of what great vacations they have in FL and how they'd move across tomorrow if possible! This was a recent episode from a local, not referenced to TC

Anyway, back to fixing the brand new dining table and chairs that arrived this morning, just in time for dinner for 14 tonite.

Unfortunately I missed the small sign saying " Some assembly required" been at it 2 hours and so far got 4 of the chairs together...170

[Thomas coupling]

170' chill out big guy....do u c any other yanky doodle dandies getting their knickers in a twist old boy?

Wouldn't like to be cooped up in the space shuttle with you for more than a couple of hours.

Brits / yanks/ japs/ frogs......who cares.

[Darren999]

I have shown pilots vertical decent auto's in bell 47's. No problem, as people have said must have good judgement at the bottom. A slight wind always helps....

I always found it nice to know I could land it where I wanted it...

Darren

[Teefor Gage]

Thanks Darren999............ I was beginning to lose track of what this thread was really about until you brought it back on-line again.......