tail rotor failure at hover
 

wat i think as a point of discussion is tail rotor failure is the gravest of all the emergencies.pl fwd some valuble inputs to how to recover successfully recover from a TR Failure at hover. regards

er...land?

immediately !!!

G

before the rate of rotation gets too high!

But don't get confused with Loss of Tail Rotor Effectiveness. Shame to dump a perfectly serviceable aircraft on the ground. Of course better to be on your side with a serviceable tail rotor than still flying with a broken one - but knowledge of your aircraft should help work out what's happened.

If in a Gazelle or other Fenestron aircraft you need to understand how a Fenestron puts out its power so you can fly it appropriately and not getting into what is incorrectly called Fenestron stall. I know the Guimbal service letter on the topic is excellent if you can get your hands on it.

You might want to cut the power first, it slows down the spinning sensation.

First-what is a "tail rotor failure"?

Pitch link failure?
Tail rotor drive shaft failure?
High Power failure?
Low Power failure?

It makes a HUGE difference.....

But if you´re talking about a full tail rotor (thrust) failure:
Autorotate-IMMEDIATELY.

There is NO "fly away" possible...

Had one in the Zagross mountains in 1970 just coming into the hover in a AB204. Tail drive shaft coupling went. Lever down but still spun 270 degrees and bounced twice from what I can remember:ok: The aircraft remained upright and we all climbed out unhurt

Read the manual and train one more time...

I'm sure not everyone would agree with that statement.

I had six T/R failures in the RotorWay 162POS, uh, I mean 162F. Most of them were recoverable by getting the tailrotor to stop stalling (yes it can) and nursing it back.
The most exciting was one in which I didn't take it away from the student until it had already wandered halfway off the asphalt and was halfway over the desert - a drop of about six inches.
If I'd chopped it then we'd have hit while turning on that uneven surface and rolled.
So I had to keep it in the air, while keeping the cyclic pointed East, until I had black blur on both sides. Then I chopped it and sat it down. No worries.
They told me later that the guys in the sales office were diving under their desks as I came spinning toward their floor-to-ceiling window.
Fun! ;)

Nursing????
 

Hey Aerobot....a Tail-Rotor failure; recoverable by stopping stalling? WTF & I always thought a TR failure meant loss of thrust due to the TR drive-shaft or some other failure which could be recovered by closing the throttle & holding off ground contact with collective, hopefully till the spinning stopped. Hmmmmm :\

Happy Happy :ok:

AKA loss of tail rotor effectiveness. :rolleyes:

@ Two´s in

you don´t have time to cut power if the tail rotor quits working - just slam the collective down, if you wan´t to live another day.....

Not sure that's a good idea. Unless you have throttle levers and can not get to them or are flying someone else's machine and don't care about damaging it.

In HIGE: land immediately.

In HOGE: how about pointing the cyclic towards a fixed point of the horizon, which means - with the cabin spinning - moving the cyclic in a counter rotating cyclic fashion, so that it points "away from tree/building/offshore-rig" towards the "desired direction". :8

W/o touchng the pitch the rotormast should inclinde towards "desired direction",
the a/c will pick up speed in that direction, and weather vane effect will stop rotation.
continue run on landing according to AFM. :hmm:

Never done that of course, never heard of someone trying it either := ,
but RC-helo pilots do a butt load of maneouvers with the cabin deliberately spinning,
hence they're rused to "rotating the cyclic". search for "prio",
Paul's Helicopter Pages see Piroloop Paul's Helicopter Pages

Then again they don't sit inside a spinning cabin...

It is important to mention to never let the turning rate build up so high that the pilot would lose situational awareness and/or dificulty to reach the controls of the helicopter. The pilot must act quickly and promptly to avoid this scenario, so one must know how the aircraft would respond to different emergencies such as tail rotor failure, stuck controls (with positive and negative pitch) and LTE.

In most helicopters....does the thrust produced by a full application of right pedal(American direction of rotation) equal or exceed the amount of torque (turning force) of the Main Rotor System in a hovering aircraft?

Question being....if a full right pedal application equals or exceeds the Turning Moment of the Main Rotor system....one could test various techniques to control the spinning of the aircraft.

I guess if one were brave enough....one could apply full right pedal at a Hover and attempt to fly away and establish some sort of controlled flight with the nose of the aircraft yawed from the direction of flight.

In flight, we know if one reduces the MR RPM to the bottom of the Green Arc (Power On Limit) the resulting yaw is minimized or removed.

You CFS Rotor Scholars might answer the question about the amount of Torque applied to the Rotor System when RPM is reduced....does the Torque decrease with the decrease in RPM even though more pitch is applied to the Rotor? In my younger days I would offer my own calculations but I am well beyond that in my old age. CRS (Can't Remember Squat) has firmly set in and prevents me from throwing out the answer.

Any thoughts on this?(The flying parts...not my CRS!)


Brother John Dixon or Professor Lappos would be great sources of thinking on this!

is a very good publication to read.

Unfortunately, since the CAA website was changed, I cant find the download link.

Edit: now found it!

http://publicapps.caa.co.uk/modalapp...detail&id=1127

SASless, I tend to think that there are too many variables to give a "one size fits all" answer to your question.

During my time as a simulator instructor we were tasked by Boscombe Down to experiment with tail rotor malfunctions in order to provide further guidance on tail rotor failures for RAF Puma pilots.

Until that time the only tail rotor "failure" covered in the FRC checklist was drive shaft failiure. We flew many different scenarios in the sim which enabled us to provide guidance on other types of failures. We were careful not to give actual drills to follow by rote because correct diagnosis of the actual type of malfunction was critical and we were "flying" a simulator, not the real aircraft and the response of the sim may not have been exactly as per the real airframe.

The FRCs said that in the event of a tail rotor driveshaft failure the pilot should "find a speed and power combination which will enable the aircraft to be flown to a suitable area for an engine off landing" - total rubbish! It isn't safely possible to do that in a Puma; the only suitable speed power combination with no driveshaft is nil power and best auto speed.

I do know that we probably saved one aircraft after it suffered a tail rotor pitch control failure, rather than a drive shaft failure. Using the guidance we provided and later taught, the aircraft was successfully ditched in the North Sea. The crew escaped unscathed and the aircraft was recovered, despite floats not being fitted. The pilot told us that had he not received the training we provided he would have just pulled both throttles, which would probably have caused total loss of aircraft control in the circumstances.

Check tail rotor blade pitch min. angle of attack acc. AFM
If it's 0° or even negative, I'd say full right pedal would result in zero "counter thrust",
e.g. same "counter torque" as if tail rotor fell off.

Flying bull,

If you are in the low hover, you should not just dump the lever. Chop the throttle and cushion with remaining lever.

If you are in the high hover, then yes, dump lever AND chop throttle. Then endeavour to get forward airspeed. Unless you are very quick here, then it's curtains; irrecoverable unless you are quick.

Im with Flying Bull.


If you're sitting in a type with twist throttles on the collective, and you can react and cut all engines within 0,5s: then do it in the same time as you dump the collective.
Otherwise, dump collective as Flying bull said, or crash.


Never experienced this live, but a lot in Full Flight Sims, different types. All Sims teach the same = if you dont react quick, the rotation speed will be very high very soon.

AAKEE,

Next time you are in the sim, try both techniques, with a reasonable delay for pilot reaction.:)

As a front seat passenger in a US Army Huey (I was a Chinook Pilot) on a free ride to Saigon for a bit of R and R....I had the occasion to participate in one of these events.

At first, I thought the guy flying was making a right hand pedal turn to look for a parking place....as the rotation was quite mild as the Tail Rotor wound down. The first full revolution as we passed what I considered our entry point heading was not too bad but was gaining in rate. As we went by the second time...the rate was very significant and noticeably increasing at a faster rate than the on the first trip around the mast. I had now tweaked to it being a for real problem and not the doing of the Dunderhead who was driving.

As I was a passenger and not part of the crew I was deferring to his Duty Status but began to suggest a course of action....by clearly stating over the Intercom..."Chop the Throttle!".

He did not...and we started around yet another time and on the third time past the starting point....things were becoming a blur...and my suggestion to chop the Throttle was now an emphatic plea!

As we went around on the fourth rotation...my Aviator Ray Bans were leaving my face propelled by my bulging eyeballs...and I elected to take matters into my own hands and chopped the throttle myself.

We were still rotating but at a much reduced and slowing rate...things were coming into focus again...and eyeballs were returning to what seemed a normal position.

I suppose I could have helped with the Collective Pull but then he was signed for the aircraft and was at the controls and one would think he would just instinctively do what was necessary at this point. I was wrong...he did not...and the Skids nicely cushioned our Landing and at the same time made it much easier to get out of the Cockpit as there was no need to climb down but rather to step up just a short bit.

I thanked him for the Ride....and lied when I said I would look forward to a return flight with him in a few Days.

Long story....but should help to describe how quickly things happen when the Tail Rotor decides to take a Holiday.

Getting the power off is the key. Get that right and the rest is pretty much an after thought. Don't and you are in for the ride of you Life that even Disneyworld cannot beat.

Hi Marly Lite,

as AAKEE says, if you don´t dump the collective immediately, you get a very high rate of rotation, which increases the risk of being killed.

You have to condition yourself to accept a hard landing in case of hoverfailures in favour of surviving.
The tendency of pilots is to try to control the bird - which leads to desaster.

I actually know a pilot, who got a big reinforced plastic bag into his fenestron - and he said, his simulatortraining - putting the bird instantly down - saved his day.
Christoph 13 nach Zwischenfall nicht mehr flugfähig (2x ergänzt) | rth.info - Faszination Luftrettung | Rettungshubschrauber online

Surf the internet and see, what happens, if pilots try to cope with tail rotor problems...



should have accepted the fate of being in the water - but you can see, how fast the spinng starts...

and that french army puma could still be flying, when the pilot would have accepted a hard landing - instead....



So I won´t spend any time in trying to kill an engine - before being on the ground.
Rather have some bend skids/wheels and walk away - as you know, every landing, you can walk away from is a good landing...
every landing, you still can use the aircraft - is a very good landing :E

In (almost) any machine with overhead speed selects or a fuel control away from the collective grip you must dump the collective as soon as you identify the problem. There is no time to faff around letting go of the collective to wind back the engine(s).

That covers most types, and those with a collective twist-grip throttle would still find you dithering around whilst the rotation builds up. Lower the lever and accept the machine will still be building up a head of rotational steam on the way down.

Been there, done that, in a BK117 where I stuffed the tail into a tree at night in a high (20-30ft) hover. Collapsed the skids but only turned about 120 degrees in all: if I'd hesitated before dumping the lever it may have been far, far worse.

I agree with FB and JE.

The most appropriate immediate actions really have to be type specific (which is why I replied to SAS's post by saying that were were too many variables to give a "one size fits all" answer).

The favourite saying of some is "lucky left, rotten right" when it comes to TR failures / malfunctions. That only works if you fly "American Rotation" rotor bladed aircraft.

It's more accurate to say that the "lucky" side is the retreating blade side.

ST and JE,

I'll happily agree with you for single pilot operation with awkward speed selects in the roof etc. And sure, twin pilot requires a switched on P2!

Certainly for twist grip I maintain that you are better off chopping the throttle. SASLESS's example explains why. Unfortunately in his case the driver forgot the 'cushion' part!

FB

FB, IF you close the throttle, the rate rotation stops accelerating, and starts to slow. Only now, you still have the ability to cushion.

As someone who actually has had a complete loss-of-thrust t/r failure at an IGE hover in a Bell 206 I can speak to this issue from a practical standpoint not theoretical. Once the anti-torque is gone, the yaw rate builds up blindingly fast.

First, get rid of the torque if you can. In my case I chopped the throttle. After that it's just a hovering auto. If the throttle/FCL is not on the collective, then yes, dump the lever and fast. Recognize it early and get the landing gear on the ground before the rate of rotation gets too high. Do not wait.

Sorry to say this-but this is where a lot of "false advise" comes from, as the simulator only simulates whatever someone programmed into it (usually based on facts and data fed from live aircraft, but-in case of emergency procedures-mainly from "pilot tells" stories)..


To simulate the effects of a tail rotor failure, someone would have to hook up computers to a helicopter in flight EXPERIENCING a tail rotor failure.....
Even then, this data can only be used for this specific model (although general procedures might result out of it).

For many years, pilots were told that one is able to "fly away even with a separated tail rotor", as long as one has enough airspeed.....this is slowly changing now due to studies carried out like the one in the UK....

We were fully aware of that. We were in very close liaison with the person who wrote the software we were dealing with and he was able to keep us very well informed.

Did you not read the rest of my post? Especially this paragraph:

No, i read the whole thing....sorry, i should have made that more clear...

I was intending to issue a warning to all pilots thinking that-because they handled things well in a simulator, they now know everything about what's happening in the real aircraft......and that´s not the case...

HueyRacer, that was the advice we gave. It was meant as guidance and food for thought. It was never meant to be a complete answer but it later proved far better than that previously taught, or rather, what had been previously glossed over, by the UK military and civilian training organisations alike. At least, three Puma pilots who subsequently suffered tail rotor malfunctions for real said so.

The CAA paper which I provided a link to in my earlier post shows that the conclusions of the later trials team were very similar to what we had found some years previously and passed on to Puma pilots during their sim. training with us. The TRCF incident I referred to is incident #27 in that document. Pages 151/152 gave further information on the training we provided.

Not had one go in the hover,but about 50-60 knots in formation climb;whole tail-rotor and gearbox departed,about 90 deg yaw,and the stick on the back stop,as the C of G was now over the nose as well.Entered auto,then chopped the engine and eol`d into a clearing.Aircraft was lifted out by Belvedere,bits of t/r were found,caused by a fatigue crack in the t/r blade spindle.New g/box and t/r replaced,aircraft flew again a couple of weeks later.

Few pics in `Rotorheads around...cockpit views(not video),p15...

A couple of days later an American Flight Safety magazine turned up with an article about`How to handle a tail-rotor failure`.....

Folks used to look at me cross-eyed when I announced my preference for an aircraft that had its CG at the rear limit. I asked them what it would feel like to have a very forward most CG location and experience what you did.

The venerable old Huey had some teething pains early on when the D and H models were coming into service.

It started with entire Tailbones leaving the attach point on the Fuselage....moved back to the 42 Degree Gearbox attach points....then to the 90 Degree Gearbox attach points....and in time after more than a few Tail Rotors got shucked.....the Bell Engineers got it all sorted out.

Fort Rucker had two Tail Boom separations in a single day....it was that bad.

FH1100 Pilot says:
Well, I've never had LTE or a TR failure, so take this with a grain of salt, but:

When I was first instructing, we had another CFI who had an LTE on top of a mountain and crashed the R22 he was flying. A few weeks later I flew with him and he demonstrated a very fast rotation (still probably not as fast as if you have a TR failure but still pretty damn fast). He pointed out that if you don't try to look at individual items out the windshield, but instead treat the trees/houses/whatever as a blur representing the horizon, you can at least maintain a level attitude for a short time.

I find that most people who have never seen this demonstrated tend to drop a wing or the nose and start doing a pirouette, the danger being that not only are you spinning, you are now starting to translate so you are even more likely to tip the machine over upon landing.

Oh, and someone mentioned LTE vs TR failure. My feeling is that if torque is spinning me, I don't have time to diagnose the cause. I'm gonna get rid of the torque and put it down and we can figure that stuff out later. Not sure why LTE would be any less serious than a mechanical failure. (Yeah, maybe you could have prevented it, but once it happens seems like it's just as deadly). Not sure whether you'll get the same rotation rates out of LTE vs TR fail. Hoping not to find out!

We practice this stuff, but I have no illusions that a real life TR failure will be as benign as when we practice.

I have to say, though, that I have a strong preference for machines with throttle(s) on the collective because of this.

P C
Well for one thing, LTE is temporary. Lowering the lever and nose should lead to recovery (if you have enough height that is).

I'm intrigued at your rationale to justify such a teaching? There is no way that I'd have held the hover and gently lowered the collective following my loss of tail rotor in a high hover, at night, in my BK117. I'd have been in a world of hurt: instant dumping of the collective and a spread set of crosstubes gave a minimal rotation on the deck.

If I'd made contact with a higher rate of rotation then a roll over would have been almost guaranteed.

Apologies for the thread drift.

Throttles in the roof - during one sim session in a 76 level D we were taught, if single pilot (we always were), a tail drive failure in the hover could be handled, if power available, by climbing vertically to height (1,000 suggested), nosing over to gain airspeed, accept side slip, and fly to suitable, spot for auto. It worked in the sim, but in real life? Always had my doubts having seen a fully loaded Huey lose drive in the hover. First question is sim modelling accuracy. John Dixon might give his considered opinion.

Helicopter flying is not inherently dangerous, it's only as dangerous as you want to make it. Three decades with an offshore operator and they never had an accident, nor injured anyone.