Tailrotor failure - is it always unrecoverable ?

[Fonsini]

Newbie question here, so please forgive my ignorance.

All the tailrotor failures I have seen training videos of, invariably seem to show a high sink rate often accompanied by a spiralling nose down attitude until impact.

Is there a best practice recommendation for cyclic and collective use in such a situation, or are you really just along for the ride at that point?

[n5296s]

I'm sure you'll get plenty of answers from the professionals here, but even as low-time heli pilot I know it's not unrecoverable - though when it happens IRL it may be a bit of a shock, like any emergency.

You can enter autorotation, supposing of course you have somewhere to go. Or in the R44 (yes, I know), and I guess most other types, you can fly in a peculiar feeling slip at about 70 knots until you can find somewhere safe to autorotate to.

This is when your instructor has spent half an hour prepping you for the exercise, then counts down before putting the pedals in a more-or-less neutral position. How it works when the TR suddenly parts company with the airframe, or the drive snaps, is another matter. By the time you've realised what's happening, instinctively tried to counter it with pedal, realised it's getting worse, had the "aha! TR failure" light bulb go on, and dropped the collective... you'll be going round quite fast, so your reactions may not be quite that good.

[army_av8r]

A loss of tail rotor thrust is all about the balance of torque and anti torque. In normal flight we have some amount of torque applied to the main rotor, and we supply the anti torque from a combo of tail rotor thrust, and the stability that comes from the vertical stabilizer. When the tail rotor fails, we must either have enough speed to allow that vertical fin to offset the torque, or we can reduce the torque to the main rotor so that the airspeed can help offset. The absolute fastest way to reduce torque is to lower the collective. By reducing torque this way, we leave the engine fully functional and available, we just remove the torque by reducing the rotor drag. We are then free to increase speed to a point at which that vertical fin can offset torque. then the pilot increases main rotor torque and flies away to a safe run on/ forced landing. If this balance is lost, the aircraft will spin... at that point, it can quickly become a ride along.

[Bell_ringer]

It largely depends on what fails and how and where.
If a driveshaft fails, or there's a gearbox failure, you could potentially also lose part of the tail. In this instance the change of CoG could make the aircraft unrecoverable.
There's theory and there's reality.
It's always better to not stick the tail somewhere it doesn't belong, since that seems to be a leading cause of "loss of thrust".

[DOUBLE BOGEY]

Army AV8R I think your explanation is spot on and very clear. Might I add some value to your post by saying, the amount of "Thrust" (antitorque) available at a specified IAS by the Fin/Tailboom varies considerably as a result of the design. I.e. fenestron fins tend to provide a lot of thrust.

And of course, the lower the IAS when the event happens the more height needed to achieve an IAS whereupon the Fin thrust can be exploited.

Sadly we tend to be at Low IAS during approaches and departures where height is often insufficient to effect recovery.

This post and AV8Rs relate only to a loss of tail rotor thrust. (All the physical components remain on the Helicopter). Flight Manual procedures generally only provide guidance for this type of failure.

As Bell Ringer points out, if a lump of mass departs the airframe at the end of the tailboom the effect on the CG could cause departure from controlled flight. The TR and its GBX are a long way from the rotor centroid so not a lot of mass needs to depart to create this loss of control. For this reason I am not aware of any flight manual that provides a solution for such a condition.

Hope this helps the original poster.

[Rotate too late]

http://www.pprune.org/military-aviation/579095-air-clues-spring-summer-2016-issue-19-a.html

FYI

[[email protected]]

Fonsini - the immediate survivability depends a lot on your height and speed at the time of failure - a low hover or highspeed, high altitude flight should, in the initial stages, be very survivable. Having said that, it depends on whether you identify the nature of the failure quickly and correctly, especially in the low hover.

Altitude and airspeed are your friends when dealing with a TR failure and you may be able to establish a power/airspeed/sideslip condition to allow you to transit to a safe area for EOL or, on some types, a fast running landing.

The EOL may in itself be an interesting one since you have no yaw control and, as you decay the Nr by pulling pitch at the bottom, the aircraft will want to yaw. The friction of the skids on the ground will help keep you pointing in the right direction and a crosswind can make things easier still.

Low speed, lowish altitude failures are usually the worst - if you can gain speed without spearing yourself into the ground then it may help you regain directional control. The worst condition would be a still air hover at 100 -500'.

[Thracian]

And besides "loss of tail" (with loss of CoG) and "loss of tail rotor thrust", you can also experience "loss of tail rotor control". In this third case, you usually will be able to fly along with the help of the vertical stabilizer and then make a running landing on any surface. This can easily be trained. Just get off the pedals and enjoy.


It gets tricky when it comes to "stuck pedal" (either low power stuck or high power stuck).


Thracian

[Fareastdriver]

Another problem with a drive failure in forward flight is that the tail rotor will go into autorotation. This could lead to flapback and large pro torque moment. The only way you can overcome this is to enter autorotation.

With old helicopters like the S55 and S58 you could get away with finding a power/speed combination to either a fast run on or an autorotation to the ground. Modern helicopters, especially those with a stabilisation system, don't have the aerodynamic qualities to continue flight so you are committed to landing fairly rapidly.

[Thomas coupling]

Probably a pilots worse nightmare.
Probably the least practiced malfunction (for obvious reasons).
Probably the least understood malfunction.
Probably a helicopter's achilles heel (unless you're NOTAR).
Probably not a lager, then................

http://www.pprune.org/rotorheads/422568-tail-rotor-failure-have-you-had-one.html?highlight=tail+rotor+failure

Enjoy.

[Hughes500]

TC

Notar has a TR but it is hidden in the tailcone ! The shaft and straps can fail !

[WillyPete]

Probably the least practiced malfunction (for obvious reasons).



I didn't realise this while practising it during training, until considering that it's always practised at height, with sufficient forward airspeed.

The discussion the other week about the "pumping" of the collective if experiencing TR failure in the hover or taxiing was a good clue as to how little the typical PPL training covers this problem.

[[email protected]]

In the hover or hover taxy, if you can recognise it, reduce the yaw (lower the lever and or close the throttle - twist grips have a distinct advantage here) and cushion the touchdown then you should survive it.

I didn't realise this while practising it during training, until considering that it's always practised at height, with sufficient forward airspeed. that's because it can be very dangerous so best done in a simulator if you can get in one.

[BOBAKAT]

First, you have two know about the main failure about Tail rotor :
1/ lost of control = pedal, cable, anything change the pitch of the blade but blade runing always
2/lost of part or totally Tail rotor : driving shaft, blade, tail gear box =blade no more runing properly.
Two cases totally different to manage, but you have to identify what happen first..
in case 1, you only lose the "pedal" control of your tail rotor, that'is the simpliest case. Take a look on your T/r if you can to understand whathappen, then, take your time, choice a big and flat safe place to land. On most of the helicopter manual, they say "Perform autorotation". It's trus, but you have another way : make a very flat approach, accept the yaw and keep the nose be to the right or left (depend the rotor clockwise or not). when you are nearly to the touch down low rate of descent low speed, apply slowly the pitch to put the nose "on line" with the frame and slide slowly until stop. Then put the pitch down, shut down and go to the Bar drink a Beer....
In the case No. 2, it's a little more creepy. i got a training by a pilot who's had experiment IRL .. on after the training, it and i'm not sure to do the same thing if happen really to me...
So, when you lose part or totally of the blade the CG change and you lean and you have the nose to go down . All of that happen fast...very fast.
At this time, reduce the speed if needed. Remind that to go straight and maintain altitude, you have to admit the bank and the nose down Take your time ( not too long, you don't know if the T/R maybe destroy the rest of your tail...) to choice a really good place to perform an autorotation...And do it......BUT, you have to know something : All your instrument byair managed are totally false ! Speed/rate of descent/ altitude..The bank and the nose down change the wind in the static plug and dynamic.. So if you have a GPS or another electronic system, trust him for the speed...If not : trust yourself for manage the speed, your rate of descent and perform your autorotation.....Good luck....
I never see this procedure on any manual and nobody train me on , except a old Jungle pilot who's experiment that the sling rope and the hook bump and destroy his Tail rotor. Thanks to him ;)
Sure, to explain the both procedure i take the best case : some speed, and not to close to the ground...
If no speed, try to gain some speed to put some air on your fin and be little be "online" to perform case 1 or 2.
If close to the ground, look like final approach, ( i had experiment it IRL ) PITCH DOWN ! if not you make the weathercock very fast.. It's better to crash on your skids than turning until not controlled crash...

[SASless]

Making "absolute" statements. Where generalized comments are more appropriate would be a better approach to this.

Example...a Gulf of Mexico event where a Bell 412 had a total upset at night due to a tail rotor failure in cruise flight.....the Crew regained control and successfully landed the aircraft.

It is not the presence of SAS that determines the outcome but rather the ability to match weather vaning effect to main rotor torque by reducing Collective and reaching an airspeed/Pwer setting that allows that.

The biggest hindrance probably is far too many helicopter pilots just do not understand the interaction of the flight controls and rpm control and the affect they can have "Torque" applied to the airframe.

As there are many different kinds of tail rotor failure....in all kinds of situations....in all kinds helicopters....there can be no single response.

The key training issue is to explore control reactions in controlling "Torque" without use of the Tail Rotor.

Also....one has to grasp the fact "Green Arc's" are for NORMAL OPERATIONSand there is nothing Normal about dealing with a tail rotor failure.

One has to be able to instinctively react in some situations and then be able to follow up with learned concepts.....and doing whatever it takes to control the aircraft.

I have had one tail rotor failure at a hover....we landed with no damage.

I have had one Stuck Pedal situation in flight....and landed safely.

I attribute both to the quality of training I received in the US Army.

We did lots of practice in Huey's....and got to see the effect of the controls including throttle. I used those same techniques in other aircraft I flew later.






Another problem with a drive failure in forward flight is that the tail rotor will go into autorotation. This could lead to flapback and large pro torque moment. The only way you can overcome this is to enter autorotation.

With old helicopters like the S55 and S58 you could get away with finding a power/speed combination to either a fast run on or an autorotation to the ground. Modern helicopters, especially those with a stabilisation system, don't have the aerodynamic qualities to continue flight so you are committed to landing fairly rapidly.

[Fonsini]

I have some key takeaways from your responses that I had not considered. I suspect that many pilots instinctively pull on more collective during a TR failure, exacerbating the spin and loss of control. I fully understand why perhaps only the military routinely accept the risk of training their pilots to deal with such an emergency, as it is far more likely to happen when people are shooting at your aircraft.

Gold standard information as ever - thanks guys.

[BOBAKAT]

I agree with SASless, I make my training in the French Army and we perform all kinds of T/R failure....Training is the key ;)

[gulliBell]

When teaching TR malfunctions just keep it simple. There are 2 types. Loss of drive. Loss of control (stuck pedal, broken cable, jam before or after mixing unit). Easy to diagnose which is which. Loss of drive gets your attention immediately. Loss of control you might not notice at all initially. Loss of drive = lower collective, autorotation, shut down engine/s before the landing flare. Loss of TR control, the technique is the same whatever is causing the problem. Fly at 60-70 kts adjust collective until the ball is balanced and note the power (this will be very close to the power at touchdown). If ball centered with high power, lucky, expect slow speed run-on or hover landing. If low power, bad luck, expect a faster run-on landing. With nose left of centre and aircraft aligned with runway reduce speed to 45 kts just before touchdown but don't land. Fly level 5-10', slight flare to slow down, as the aircraft slows down it will descend, but don't let it land. Slowly increase power whilst flying level and continuing to slow down (the nose will come right as you increase power). When straight, keep that attitude and power setting and the helicopter will continue to slow down and land itself. Do not let the nose go right of centre (for anti-clockwise main rotor, eg Bell). Keep it straight during any ground-run with throttle and some opposite cyclic. That's it, easy. This technique will work for most helicopters.

As long as the TRGB or components haven't departed the scene and put you out of CofG limits, and you have a suitable landing site, you should be able to land without a scratch. I've practiced this many hundreds of times. The key to stuffing it up is letting the nose go right of centre when you're close to the ground. When this happens students tend to react by increasing power, and when you do that it very quickly becomes unrecoverable and you'll turn it into a mangled mess.

[[email protected]]

Gullibell - you should also stress how helpful a crosswind from the (left in your case) is as it helps keep the nose from swinging right for longer and gives a slower touchdown speed. The bigger the fin/vertical stabilisers, the more effective this becomes.

[JohnDixson]

F.E.D. re your post #9. I can add a historical data point.

During initial commercial S-61 FAA testing at the forward CG limit, the test crews had trouble making the required control delay time after a forward AFCS pitch channel hardover at max power, min speeed ( 40KIAS as I recall ).

The Ch Exp. Pilot got involved and went out to get the data point. Set up the condition right after takeoff, hardover was introduced and nose went down.....and down. Well, the aft stick input was finally made ( with authority ), easily meeting the required delay time, but the tail drive shaft suffered an intervention by a main blade, and an autorotation into an open field with 2 inches of snow resulted. A picture exists showing a perfectly straight line thru the snow made by the tail wheel. Instrumentation indicated a tail rotor Nr that could only be explained by autorotation.

So, the tail rotor autorotative state may not be all bad. The copilot for the flight was Dmitri ( Jimmy ) Viner for the historians out there.

[Gordy]

DtpG8oIvbZQ

[jellycopter]

My personal soapbox. Why do we insist on calling completely unrelated malfunctions virtually the same name? Tail Rotor Drive Failure versus Tail Rotor Control Failure.
In the heat of the moment, it's easy to jump down the wrong rabbit hole. I've seen multiple crews open up the cards to the wrong section and start the wrong drills because of this.

My suggestion; Tail Rotor Failure = Loss of drive/TGB detached

Yaw Control Malfunction = Stuck/Sloppy pedals.

Simples

[[email protected]]

I've seen multiple crews open up the cards to the wrong section and start the wrong drills because of this. Often because they are not as familiar with the cards as they should be.........I have seen the same for the same reason

[Zaxis]

This makes interesting viewing

https://www.youtube.com/watch?v=fNkwk2d_DJ8

fNkwk2d_DJ8

[jellycopter]

Often because they are not as familiar with the cards as they should be.........I have seen the same for the same reason
Agreed Crab. But a simple change in nomenclature from the outset would effectively stop any confusion before it has time to start.

I can't remember what the latest flight safety just culture management buzzword this kind of thing fits into, but there's got to be some systemic failing. We have for years, collectively, set up a man trap that we repeatedly see crews fall into, but don't do anything about it. Stating that people should be more familiar with the cards/drills doesn't fix anything.

[albatross]

Newbie question here, so please forgive my ignorance.

All the tailrotor failures I have seen training videos of, invariably seem to show a high sink rate often accompanied by a spiralling nose down attitude until impact.

Is there a best practice recommendation for cyclic and collective use in such a situation, or are you really just along for the ride at that point?

Well, looking at the title of your post, if all tailrotor failures were "Unrecoverable" there would be no Emergency Procedures called for. Just as there are no "Wing Falls Off" checklists in fixed wing nor "Loss of Main Rotor" in helicopters.
There are procedures that must be carried out...initial actions are "Memory Items" Reaching for a checklist as you spin like a Kid's top will not lead to a optimal outcome.
You must be fully aware of the initial actions and carry them out.
FYI I had a friend who had the tailrotor and gearbox of a Hughes 500 depart the airframe in cruise flight ..he got it down OK ..his underwear and seat cushion were unrecoverable!

[MightyGem]

A Twin Squirrel landing after a TR drive failure. Not good quality video, but the stationary TR can be seen.

z3oVw6_0MEU

[treadigraph]

I recall a Met Police Bell 222 had a TR failure around 1980 and made a run-on landing at Hatfield. I think it rolled over but all walked away.

[[email protected]]

Jellycopter - I just think it is down to training - and that includes knowing the cards through self-study and practice in the simulator.

I think the difference between a TR drive failure and a TR control failure is quite clear, perhaps because I have taught it quite a lot.

TR drive and TR control failures were mandatory parts of the 6-monthly sim on the Sea King as I am sure they are on many other types.

I don't know what you would call the two conditions that would be any clearer.

[jellycopter]

Jellycopter - I just think it is down to training - and that includes knowing the cards through self-study and practice in the simulator.

I think the difference between a TR drive failure and a TR control failure is quite clear, perhaps because I have taught it quite a lot.

TR drive and TR control failures were mandatory parts of the 6-monthly sim on the Sea King as I am sure they are on many other types.

I don't know what you would call the two conditions that would be any clearer.

Crab, if I had a Euro for every misguided helicopter pilot that glibly stated that they'd autorotate in the event of a TRCF I'd be quite a bit better off than I am now.

If you turn the problem through 90 degrees, no one ever gets the drills for stuck collective mixed up with MGB/input drive failure. But we're talking, effectively, the same thing. Why do less well trained crews continue to make the same mistake?

The fact that someone on this thread decided to bring stuck pedals/TRCF into it shows the depth and universal nature of the problem.

I wish, for the good of Rotary aviation, people would stop using the term 'Tail Rotor' when referring to a control malfunction. Call it what it is, a Yaw Control Malfunction.

[gulliBell]

My personal soapbox. Why do we insist on calling completely unrelated malfunctions virtually the same name? Tail Rotor Drive Failure versus Tail Rotor Control Failure...

Because that is what they are. It is not possible to be confused which of the 2 you have, whatever you care to call them. They are so obviously different malfunctions.

TR drive failure don't even bother getting out the emergency checklist, the immediate actions are all memory items. If it's an impending failure e.g. vibration in pedals or airframe, TGB/IGB chip light on, grinding noise etc, but you still have pedal authority then sure, turn towards a suitable landing area and get out the ECL and review the procedure. Maintain height, slow down to best rate of climb speed. Do not descend until you arrive at a point in space where you can execute an autorotation to the landing area.

TR control malfunction there are no memory ECL items, this is a far more sedate problem to deal with. You have time to get out the ECL. The next thing is put your test pilot hat on and diagnose the problem as per the checklist. But as I said before, it doesn't matter whether stuck pedal, broken control cable etc, the landing technique is the same for all of the causes of TR control problem.

Whether TR drive failure or TR control malfunction, if you have a suitable landing area to aim for you should be able to execute a safe landing without putting a scratch on the aircraft.

[NumptyAussie]

One could always ask the TOLL Chief Pilot on the NSWA AW139s if a tail rotor strike is unrecoverable. By all accounts, they did recover, but by truck to Bankstown!

[Fonsini]

As the OP on this, I really was only referring to tail rotor failure in the sense that it has failed completely for reasons of a broken driveshaft or blade failure or hub/bearing failure etc etc.

This video would best illustrate the failure type I was thinking of - with the best video quality I can find showing the TR condition. I also chose this as the pilots survived the forced landing.

6s8Ahcxg84g&feature=related

[jellycopter]

Because that is what they are. It is not possible to be confused which of the 2 you have, whatever you care to call them. They are so obviously different malfunctions.

I find it hard to believe that it is possible to confuse the two malfunctions too. It shouldn't be possible.
However, after decades as an instructor and examiner I have had many pilots that have. I believe that when pilots give either malfunction the 'tail rotor' label all too often they opt for the dump the lever option when it's exactly the wrong thing to do.

Crab has experienced the same. Are there any other instructors/examiners out there that have seen this from time to time?

[Palma]

I remember Dennis Kenyon demonstrating Tail Rotor Failure recovery whilst doing his display at an airshow at Cranfield in the 1980s. He was flying his normal, excellent, display in an Enstrom when something "went a bit wrong"! He then flew a couple of low passes down the active runway and, on the third pass, did a run-on landing. Everything was OK - apart from the broken TR cable!

[[email protected]]

Palma - that is exactly what Jellycopter is talking about - it wasn't a TR failure, it was a loss of TR control.

It is straightforward, with a TR failure, the TR is producing no thrust in any direction and probably not turning at all. With a TR control failure, the TR is still turning and may be producing thrust one way or the other, depending on the nature of the failure, or none at all if it has gone to flat pitch.

[PPRuNeUser0211]

I never understood the obsession with tail rotors.... Just fly a tandem rotor, at least then all the bits that can break aren't in places where you are going to put them into a tree...

[[email protected]]

Except that hitting/losing one of those rotors is guaranteed to be catastrophic:ok:

[gulliBell]

One could always ask the TOLL Chief Pilot on the NSWA AW139s if a tail rotor strike is unrecoverable. By all accounts, they did recover, but by truck to Bankstown!

Karma. Toll was reluctant to let me do any training in their NSWA AW139. They got to bend one first with their own people before I ever got close to one.

[gulliBell]

....Crab has experienced the same. Are there any other instructors/examiners out there that have seen this from time to time?

Confusion reigns for many recurrent trainees when diagnosing TR control malfunctions. But for TR drive failure they don't have time to get confused before they need to carry out an immediate action in response to their predicament. What that immediate reaction is can be surprising...I've seen a pilot just take his hands off the controls and leave the outcome of TR drive failure entirely up to the will of Allah. Needless to say it didn't end well.

[Thomas coupling]

http://www.pprune.org/rotorheads/508810-tr-malfunctions-beginners-refresher-lesson.html?highlight=tail+rotor

[megan]

Was extremely surprised at the training available from even highly respected organisations. In the sim, single pilot -76, drive failure in the hover, climb the rotating aircraft to 1,000 ft, nose over to gain airspeed, and fly to a suitable landing area. Assumed performance permitting. Having only ever seen one drive failure* in my life thought it suss teaching. Perhaps it is possible, I don't know.

* Huey stuck its tail into the ground in the flare at slow speed. That sucker whipped around so fast I found it unbelievable. Trouble was the tail took out permanently some of the troops waiting.

[Ascend Charlie]

In the sim, single pilot -76, drive failure in the hover, climb the rotating aircraft to 1,000 ft, nose over to gain airspeed, and fly to a suitable landing area. Assumed performance permitting.

Megan, I hope you were suitably disappointed that they said such a thing was possible?

Your brain would ooze out your ears while pulling pitch to get to 1000', and the "roll coupling" effect where the fuselage no longer stays level and the spin goes more vertical than horizontal would disorient even our mate Nick.

When I did the sim on the 76B at West Palm, the only thing taught for a drive failure from any altitude was throttles-idle auto. I was able to show the sim instructor a different technique (from Huey days, and applying to B206 as well) leading to a running landing - had to show it to him twice before he really believed it - but he insisted that the tried-and-true auto be performed to pass the course.

[[email protected]]

The only problem with relying 100% on techniques 'perfected' in the sim is that the aircraft modelling might not be accurate enough to 'prove' the technique in the real world.

Having said that, I have valued all the sim training I have received over the years but hope I never have to try it out for real!

[Thomas coupling]

Everyone needs to be aware that sim programmes rely on OEM algorithms to simulate TR failures et al.
Currently it has been found that one major global helicopter manufacturer has not got his ducks in a row when it comes to the "data in" on their TR programme.

It has thrown up some serious questions by test pilots on the efficacy of it all.

The ONLY way to 'manage one's expectations' when it comes to handling TRF and TRCF is to talk to seasoned vets and those who have had one.

[ShyTorque]

Having been part of the team that set up one of the RAF's first helicopter sim. training programmes, I was pleased to hear feedback from one of our pilots who stated that he was of the opinion his life was saved by guidance and training given to him regarding T/R malfunctions.

His aircraft suffered a tail rotor control failure over the sea (limited tail rotor power). He managed to spiral down and safely ditch the aircraft, which was later recovered. He said that without the training he would probably have chopped the engines, which would have been a big mistake; things would undoubtably have gone very badly wrong.

I also know of another pilot (of a non RAF Puma, not given our training) who suffered a tail rotor drive failure in the 140 kt cruise. He initially tried to slow down without chopping the engines but it began to go wrong so he accelerated back to 140 kts, flew back to an airfield and carried out a running landing at that speed. He apparently got away with it, too!

[gulliBell]

..In the sim, single pilot -76, drive failure in the hover, climb the rotating aircraft to 1,000 ft, nose over to gain airspeed, and fly to a suitable landing area..

Having done, and seen demonstrated, many TR drive failure in S76 sim, nothing has ever come close to that technique mentioned there. The only way to carry out a successful recovery from TR drive failure in S76 sim is to follow the procedure as per the RFM. Real life might be different, but I'd be very surprised if any S76 pilot who climbed to a 1000' from a real TR fail in hover would have any sensibilities left to do anything after such a wild ride which it certainly would be. Especially in a B or C variant.

[Thomas coupling]

In the course of my varied professional life, I have been fortunate to debrief literally dozens of pilots who have survived various catastrophic experiences. Apart from making my decision making process more comprehensive, it has made others more aware as I cascaded this information at every opportunity.
In this particualr instance (TRF and TRCF) research, revision and calm - were the common factors with all the debriefers.

Shy - I'm struggling with a 140+Knot running landing on a narrow tricycle undercarriage I am afraid - it's just not going to happen.

And I concur with gullibell - no sane pilot would ever 'knownigly' transition out of a hover after a real TR failure because he would be completely disorientated within seconds as the G foces and dizziness and blurred vision overcame him - again this leaves a lot to be believed.

A TRF in the hover is dead easy - lower the lever. The end.

It requires little or no thinking. You simply take your chance with the impact.
[Chopping throttles and cushioning the landing is a very very nice luxury and tends to be the option available only to the lightning quick and very calm driver).

[ShyTorque]

Shy - I'm struggling with a 140+Knot running landing on a narrow tricycle undercarriage I am afraid - it's just not going to happen.Unfortunately, for once, you are wrong - it did.

However, I would definitely NOT recommend the technique, for the same reasons you quoted!

[Thomas coupling]

Shy - so you want other peers to believe that a Puma touched down at 162mph with a major malfunction in the knowledge that the very instant he lowered the lever (to stay on the runway) his aircraft would have commenced a side slip due to the yaw differential?

C'mon Shy - perleeeeeeze smell the coffee.:rolleyes:

[megan]

When I did the sim on the 76B at West Palm, the only thing taught for a drive failure from any altitude was throttles-idle autoTwas taught in that very same building AC, A sim.

A thread I started some time ago.

http://www.pprune.org/rotorheads/579762-apache-tail-rotor-failure.html

Page 46 of the attached, Apache loss of tail drive.

https://www.raf.mod.uk/rafcms/mediafiles/3EEA9B62_5056_A318_A88B016F60697008.pdf

Wessex drive failure.

cDj6oYaYrR8

and

5kXUZQYFu18

and

cgi8WPfq46k I'm struggling with a 140+Knot running landing on a narrow tricycle undercarriageRecall a 76 making a somewhat high speed landing as a result of T/R issues. Drive or control don't recall, went off the side of RW, kept it upright. Written up in R & W I think, many years ago.

[SASless]

Shy - so you want other peers to believe that a Puma touched down at 162mph with a major malfunction in the knowledge that the very instant he lowered the lever (to stay on the runway) his aircraft would have commenced a side slip due to the yaw differential?

C'mon Shy - perleeeeeeze smell the coffee.:rolleyes:


I cannot attest to the particular event but I know of similar landings post tail rotor problems.

At one Operator I had the misfortune to hire on with.....flying BK's....the procedure taught was exactly that. In training I saw Approach speeds in excess of 100 KTS.....but no touch downs.

When I inquired if the TC was making a very bad joke....he had quite a sense of humor failure and demanded to know what I would do differently.

Up we went...established the same setup....and I did an autoration and accepted some yawning at the bottom with zero ground speed.....which seems far safer an arrival than getting to the bottom at over a hundred knots ground speed and full chat on the rotor system....very limited yaw control....and thoughts that following through with Cyclic might prove to be a bit of a challenge!

But then what do I know?

[SASless]

I never understood the obsession with tail rotors.... Just fly a tandem rotor, at least then all the bits that can break aren't in places where you are going to put them into a tree...



From experience.....that is not a true statement!:(

[John R81]

Don't know about 140knt - I can't go that fast.

I did however once do a 70knt running landing in a skid-equipped machine; scary beyond belief.

[SASless]

I once talked with the pilot of the 58T doing the Underslung Load....he said he was trying to get the aircraft to a cleared area and was accepting the yawing and once close enough to the clearing....he cut the Throttles...and entered autorotation and when he tried to move forward a bit....the nose dropped a bit too much and that is when it all went pear shaped.

He was not seriously hurt.....and he did opine he felt very badly about the damage to the aircraft.

[Hot and Hi]

He was not seriously hurt.....and he did opine he felt very badly about the damage to the aircraft.
And I feel bad that the guys carrying him out of the wreck dropped him twice...

[[email protected]]

TC - very fast running landings are quite possible in tricycle undercarriage aircraft with TR malfunctions as long as you have enough real-estate to make a very gradual lowering of the lever once the wheels are on.

A lockable nose-wheel helps directional stability and lateral cyclic combined with differential braking help keep you straight-ish.

Not saying you would stay on the runway but I wouldn't dismiss Shy's story out of hand:ok:

[treadigraph]

A Met Police Bell 222 did a run on landing at Hatfield after a tail rotor failure many years ago. I think it rolled on to its side but the crew were ok.

[Thomas coupling]

Crab - howdie.
Have you been on the crystal meth too?

Just picture a running landing at 160mph - just for a few seconds will you?

Picture a runway of - on average 2 miles long. You can't use brakes at that speed and as you lower the lever you will need someone standing between the pilots bringing the SSL's back at a very co-ordinated and precise rate according to your instructions.
The helo presently is travelling at 2.7 miles per minute. You have 80 seconds to stop before you run out of runway. Any side slip will result in a catastrophic rollover. Once the cab starts to deviate from anything other than straight ahead at any considerable speed, your corrections will almost certainly cause divergence and pilot oscillations.

You would only survive because of pure unadulterated luck. Choosing to do this voluntarily is crass stupidity and gross ignorance of the limits of your a/c.
Low speed handling checks at height (1000') would offer you the ability to atleast halve this speed whilst still maintaining directional control.
The comment from Shy that it "started to go wrong when he slowed down", suggests mishandling.
Next time you're airborne, shoot an approach to your runway at your Vmax and let me know what it feels like if you had to follow thru and land without brakes and a dodgy steering wheel!!!!!

[SASless]

Amen! TC gets a Gold Star!

If one is confronted with such an option.....why not do an autorotation as I suggested?

Is not the problem too little “tail rotor thrust”?

[[email protected]]

TC - I'm not saying it was the right thing to do but I'm not rubbishing someone else's story just because I haven't done one myself.

Some thoughts - in an emergency situation, why would you worry about brake speed limits or running landing limits? If you have a pilot who is not confident of surviving an EOL without the TR (and I suspect there are more than a few of those out in the big wide world) then adapting something you already know (and may well have practiced in the sim) might seem a more attractive option.

The modern twin-driver will likely have very few EOLs under his belt and may have only ever done one in the Sim.

What if your RFM doesn't even give you the option of a EOL - only a high speed running landing?

He may have made the approach at 140kts but that doesn't mean he touched down at 140 or anything like it.

If 140kt is what you need straight and level to keep straight then in a descent of say 500'/min that speed will be a lot less as you have less Tq to oppose.

As you get to the ground you can flare a little more speed off as well - if you can get the touch down speed below 100kts, that is reasonably manageable as long as you have lots of runway and are gentle with the lever/throttles. personally I would consider shutting down one engine on the approach so I only had one throttle to worry about on the ground.

I regularly do 80-100Kt landings in the sim and 50-60Kt running landings in the aircraft as part of TR failure drills.

You and I would conduct a low speed handling check (exactly what I teach at the moment) but a lower-time pilot may not have been shown that or not understand it has to be done VERY gradually at a safe height.

So, no crystal meth, just not prepared to decry a story which might just turn out to be true:ok:

[albatross]

Ok here is my 2 cents worth.
If you have a full blown TR drive failure you are going to be in "Immmediate Actions" mode and will most likely have to enter full Autorotation ( engines off ). This will severely impact your options. Best or luck!
If you are dealing with loss of tail rotor control or stuck pedals ...things are looking up.
If the aircraft is controlable ....
Slow to 80 knots in level flight. Look at the Ball...is it off to the left or right? Go to the opposite side then ..Lucky Left- Rotten Right . ( basically ball to the LEFT = rotten right, Ball to the Right = Lucky Left.) NB. The further the Ball is out..the worse your problem is.
If Lucky Left you will be able to land with higher torque perhaps even bring it to the hover. Rotten Right landing will be at a lower torque and run on will be required.
(Oh this is for North American machines, EU folks use "Lousy Left ...Righteous Right)
Truck on back to your "suitable forced landing area".
Set up an normal approach starting at 80 knots initialy with a 2-300fpm descent rate ( use cross wind to your best advantage. Left xwind for Rotten Right..Right xwind for lucky left.)
Slow down but keep it at a speed/ torque setting that keeps the nose aligned with the runway.
At the slowest possible speed land be prepared to shut down engines if Rotten Right.

Some smart person wrote a very nice blurb on this with diagrams and it used to be in our OPS Manual.
Worked well. Actually I believe he posts here from time to time. Great training guy and a darn fine pilot.

[Thomas coupling]

http://www.pprune.org/rotorheads/508810-tr-malfunctions-beginners-refresher-lesson.html?highlight=tail+rotor

[airpolice]

Mighty Gem, I remember the night that "Lucky" told me the story of that landing, as we approached Speke, at 500 feet in the dark. I asked which crew it was, and he laughed and said "Us" so that made me feel better, or something.

Looking at the video later that evening. I decide to check the door latches myself before getting back in.

What an awesome bit of flying, by an awesome pilot.

[ShyTorque]

Albatross,

Yes, "Lucky left/rotten right" is only so for counter-clockwise rotor rotation, e.g. Sikorsky, Agusta. For French helicopters, it's the other way round.

As someone who has had to fly helicopters of different main rotor blade directions, the thing I taught myself and my students to remember is that the "lucky" side is the retreating blade side. Hopefully most pilots remember that from when they started up the "aircraft of the day"!

I don't blame TC's scepticism about the very high speed running landing. I just wish he could be slightly less rude about it. Just to reiterate, I never taught him that, no-one taught him that and by all accounts he was very lucky to survive.

[gulliBell]

...
Set up an normal approach starting at 80 knots initialy with a 2-300fpm descent rate ( use cross wind to your best advantage. Left xwind for Rotten Right..Right xwind for lucky left.)
Slow down but keep it at a speed/ torque setting that keeps the nose aligned with the runway...

No, you don't want to be aligned with the runway. You want a power/speed configuration where the nose is pointing left of the runway direction (for anti-clockwise main rotor). Reason being, when you are in the process of terminating the approach with application of power, the nose will then come into alignment with the landing direction. If the nose is already straight when you start to apply power you're going to mess up that which would have otherwise been a scratch and dent free landing.

Once the nose is pointing straight you can't be applying any more power.

[Gray 14]

Had a cargo door come loose on a UH-1H. Took out the T/R and 90 deg gear box. Did a running landing in a rice paddy. No further damage.

[SASless]

I don’t care where the nose is pointing except no where on the non-power pedal side.....for a situation where I have an excess of tail rotor thrust that affords a left of center to aligned orientation.

Maneuver the aircraft to arrive at the minimum forward speed with the nose aligned with the direction of travel.

Excess thrust can be minimized by reducing MR rpm to the bottom of the power on green arc.

Making a long shallow approach to a foot or so off the surface and decelerating very slowly till the nose is aligned or the aircraft is in a stablehover....the landing and then carefully reducing rpm to idle/flat pitch....makes a Bobby yer Mum’s brother!

[[email protected]]

Gullibell - agreed, in fact it is the anticipation of that swing into alignment that is the difficult thing to teach, if you wait until it swings before you land it is already too late. The control inputs are very subtle and each knot of speed and each degree of collective are very important.

Also, unless you have done a low speed (breakaway) handling check, 80Kts might still be too slow for the initial stages of the approach.

A crosswind from the 'lucky' side will help enormously.

At the start of the approach, I teach my students to look at how far out of alignment the nose is from the runway - the further away it is the slower the speed for the run on will be.

If at the start you are already aligned with the runway then you are already at your absolute minimum speed for the approach and need to be very careful not to let 'ground-rush' make you wash speed off in the descent.

[Non-PC Plod]

I agree with what you are saying crab - speed control is the key. The students who get it wrong are the ones who are not scanning the airspeed constantly.

A slight variation on the technique, which seems to work well in my experience:
Start as already discussed, ideally nose slightly left, and as you approach the landing area, adjust the speed carefully until it is stabilised with the nose straight and with the aircraft flying maybe 10 or 20 feet above the runway. At this point, be prepared to change your brain to think about steering with the collective. If you pull up- nose goes right ( in normal helos!) if you push down, nose goes left.
To initiate the descent for the last 10 or 20 feet, just raise the nose a tad, and as the speed washes off, the helo will descend. You just need to keep steering with the collective as you touch the runway with the main wheels. If you hold the nose up off the ground, you will brake aerodynamically until the nose falls naturally, and you can slowly lower the collective.

[[email protected]]

I think it depends on some degree whether you are flying wheeled or skidded helicopters.

We get down to 5 or 6' above the runway before reducing speed, you have almost maximum ground effect to reduce your power required and it enables you to land far more promptly as the nose starts to swing. The additional benefit is that you usually need to lower the lever slightly to land which, if you haven't anticipated the nose swinging round early enough, gives you a little help in controlling the Tq reaction.

Another option is to just fly with between 3 - 500'/min RoD all the way to the ground, with just a gentle flare at the very end - this is definitely more suited to wheeled helos with nice big oleos to soften the impact, but it does reduce your power required and therefore the amount of Tq reaction you are opposing with speed.

With a wheeled aircraft it helps to 'plant' the nosewheel (if it is a lockable one) as that also helps with directional control - just don't dump the lever as soon as you are on the ground.

[albatross]

No, you don't want to be aligned with the runway. You want a power/speed configuration where the nose is pointing left of the runway direction (for anti-clockwise main rotor). Reason being, when you are in the process of terminating the approach with application of power, the nose will then come into alignment with the landing direction. If the nose is already straight when you start to apply power you're going to mess up that which would have otherwise been a scratch and dent free landing.

Once the nose is pointing straight you can't be applying any more power.

Quite right I made a mistake in my post.
Thanks for the correction.
Cheers
Albatross

[chopjock]

gullibell
Once the nose is pointing straight you can't be applying any more power.

But you could apply pitch to cushion the touch down without applying more power...

[212man]

I must say I find the Puma story a little tall too. In my previous company we had three Super Puma tail rotor failures and one (that I am familiar with - could have been more before that) on a 330J. One of the 332 ones was at low power and the pilot (it was effectively SP as using a foreign co-pilot and a translator) was able to successfully autorotate to a ditching without too much initial drama. A second one happened at a moderate cruise speed/power following a lightning strike, with the crew poised to react. When the TR 'let go' the subsequent motion was described by the handling pilot as like a Lomcovák and only stopped with the throttles off. The third was at the bottom of an ILS (in VMC), so less than cruise power at slightly less than cruise speed, at around 200 ft and was an uncontrolled impact with serious injuries. The 330J event was in the cruise, and the aircraft tumbled so violently that at least one of the pilots lost his headset and it was not a controlled ditching that resulted in fatalities.

So, none of the above lends itself to the idea that you can have a TR failure at 140 kts and then take the aircraft to land on a runway - unless we are talking about TRCF not loss of thrust.

[[email protected]]

Would you notice a loss of TR thrust at 140 kts in the cruise? The TR can't be at that high a pitch with all the tail boom and vertical fin working for you.

I know the Brit Mil Puma was not brilliant in terms of directional stability but I thought that had been addressed with extra area on the tail on the civil versions.

Is it so bad that you can't achieve any power/speed/sideslip configuration to make a powered approach?

[gulliBell]

gullibell
But you could apply pitch to cushion the touch down without applying more power...

I teach S76C++. Applying pitch without applying more power can only happen with a double DECU failure, which is beyond the capability of most recurrent students. And in any event, you can't purposely put both engines in manual control mode in a C++. It's just not physically possible. The only way both engines can be in manual control mode is if both DECU channels of both engines failed, it is not something the pilot has any control over. Unlike a Bell 212 or 412, for example, where a pilot can put one engine in manual control, and then the other.

If you had a TR control malfunction and a double DECU at the same time....well, the likelihood of that happening is zero.

[Thomas coupling]

Fonsini. Have you slit your throat yet.
Look how far we've come from the humble beginnings of the OP.

The words 'plot' and 'lost' spring to mind.

[[email protected]]

Gullibell - I think chopjock is talking about light singles with a twistgrip throttle.

[Paul Cantrell]

Would you notice a loss of TR thrust at 140 kts in the cruise? The TR can't be at that high a pitch with all the tail boom and vertical fin working for you.

Crab, I was told long ago that if the TR stops rotating (as opposed to a TRC failure where it goes flat pitch but keeps turning) that you lose the same amount of weathercock stability as if you had lost a chunk of your vertical stabilizer of equal area to the TR area. I have no idea if that's true, perhaps someone else here knows for sure.

On the subject of controllability if the TR gearbox comes off, I was talking with Pat Cox at Robinson a year or two ago about the fact that I seemed to remember the R22 manual originally calling for a running landing for TR failure, and that I think it changed to calling for an auto in the 90's sometime. He said that they believe the R22 is uncontrollable (due to CG shift) if the gearbox departs, but that the R44 and R66 are probably controllable. My only point is that it's probably highly aircraft specific which ones are controllable if you lose the gearbox. I guess it also helps if you're not at the forward CG limit when it happens :(

[chopjock]

I guess it also helps if you're not at the forward CG limit when it happens

What about if you ask the front seat passenger to jump out?

[SASless]

Gullible,

In a 212/412/58T.....rolling the throttles back manually achieves the same thing as I recall. No need to move either/both Gov Sw’s.

[SASless]

Quite right I made a mistake in my post.
Thanks for the correction.
Cheers
Albatross

If the nose comes around to the right(Left turning rotor systems).....accelerate using power you need and repeat the process...till no scratch/dent landing is accomplished.

[ShyTorque]

What about if you ask the front seat passenger to jump out?

Please jump out!

[gulliBell]

Gullibell - I think chopjock is talking about light singles with a twistgrip throttle.

Fair enough...point being, some helicopters don't have twist grip throttles or pilot option to control power/RRPM independent of collective position.

[SASless]

What about if you ask the front seat passenger to jump out?


I always preferred an aft cog for that reason and some other considerations.