Tail Rotor Problems
 

Tail rotor problems can take many forms. You can have a complete loss of T/R drive, requiring an Auto or many different combinations of problems, i.e. Aux Hyd/mixing unit problems in a 61, Cable jam/failure in a 76, fixed pitch problems and so on.

So lets hear from everyone about their ideas or thoughts about these types of problems. You don't have to have any actual T/R fail experience to contribute, only a desire to learn more on the topic. All are welcome.

Let the games begin!

Cheers, OffshoreIgor http://www.pprune.org/ubb/NonCGI/eek.gif

Ok, My opinion is that anyone with only a minimum amount of hours ie less than about two hundred, is going to be very lucky to walk away from a tail rotor failure of any type unless they're very lucky.
Saying that, it wouldn't make much difference if you had thousands of hours if the conditions were against you.
What would happen while doing sling load ops, low airspeed, hilly terrain. Might not be your best days flying!!

OK, your point is well taken. However, I think a low time pilot may fair better than you think simply because he/she has probably been practicing them alot more recently than those of us who may or may not practice them once a year during recurrent training.

I for one have not had a simulated T/R drive failure in years. The closest we train to it is a jammed pedal or simulated cable failure on the 76/61.

Granted, experience may enable a calm, collected pilot to react better to a given situation, however, as you say, it may not be your day/night! i.e. Enroute to the rig at night over water and bang!!! Just look at the result of the 212 in the Maldives, that lost the T/R after the Co-Pilot's door was jetisoned in preperation for ditching! Not a good thing!

Food for thought. Cheers, OffshoreIgor http://www.pprune.org/ubb/NonCGI/eek.gif

I didn't hear of the Maldives incident but did hear of a door coming open on a jet ranger and a coat going into the tail. The pilot survived I believe.
Didn't the 76's/61's or something have a problem with corrosion on TR controls recently?

an instructor of mine once demonstrated an interesting technique for a TR failure: begin with the shallow approach, minimizing maneuvering and power application, and if possible with a left crosswind (american helos and the like). As airspeed is bled off, the nose wants to turn right but if sufficient speed is held (and hopefully if the left crosswind is present) you will be able to continue toward your spot without actually rotating. now the tricky part, as speed gets really low and you are about where you want to be, maybe at a height equivelant to a high hover (and with the nose getting close to making you wonder why you are trying at all anymore) zero the airspeed as much as possible and hold the ship level while rolling off the throttle- from here you have more or less a basic hovering autorotation- waiting for the helo to settle then applying pitch (with the throttle held at idle to prevent more spinning). The main idea is to get to your spot without the nose getting farther than 90 degrees off of your path. This maneuver seems more compilcated than necessary, but might be just the thing into an area not suited for a ground slide.

[This message has been edited by lmlanphere (edited 13 February 2001).]

Will the low time pilot scream any more than the high time pilot when it happens? Hmm, there's a study in the making hehe ....

I only hope I do react correctly WHEN it happens, somewhere down the line ....

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Marc

On paper ...when you start to read this it may come across rather fussy or complicated.

But - in practice the Loss of the TR Drive is fairly final it's going to require a bloody swift reaction, to be able to engine off from the hover in order to have a chance of being in a attitude to achieve a decent cushioned landing. In forward flight - well if you manage to contain the yaw you might be able to postion (using low power or suitable PWR/IAS combo) the helo to a safe area for an EOL or you'll just have to enter auto, shutdown the engines and accept an interest EOL at the bottom. All very challenging and something I would rather not try unless I was in a sim.....that said if I was on the NOTAR I suppose I wouldn't have the problem ....probably something else to think about though ....I'm sure.

Now - If you have a Tail Rotor control failure

There's quite alot you can achieve. If you take your time:

1. Define the problem - is it AFCS, Hydraulics, a jam, cable snap or somebody's bag rat wedged behind the pedal. It could be as simple as that - somebody's FOD.

2. Check fuel - if you've got loads we can take all the time in the world to get it right, if not then you'll have to do the same assessments but with a sensible level of alacrity.


3. You need to consider what configuration the jam or failure has left for you to deal with. Is it either:

1. low power controlled flight (pedal Positon)

or

2. High Powered controlled flight (pedal pos'n)

I make this broad assessment criteria based on the position of the applied pedal at the time of the problem first coming to light.
The pedal applied will vary as to type and MR blade rotation.

First of all you need to do a handling check:
which should take the following form:

1. Maintain Wings level
2. Fly at Min power speed (usually 60-70kts)
3. Using collective apply a power setting that will bring the 'ball' in to the centre.
Don't concern yourself with collective and power settings too much.
Then check you RCDI and note the following

A. LOW POWER pedal situation -
for example: you find you have Wings level, Ball in middle and a ROD of 1000'/ min

This means that you could return to a large grass field in a skidded helo or a large runway in wheeled helo and carry out a pre-briefed auto or low powered descent to the ground touchng down at up to approx 60 knots and smoothly shutting down the engine(s) as you enjoy the rutted camel ride from hell across the airfield or you can differentially break if you have them fitted - Luxury. Now a 60kt touch down is very saucy but, in many aircraft a, doable get out of jail type manoeuvre. Obviously - a high wind day of 30 knots straight down your landing area is going to help immensely.

This is good news - you can now decide whether you want to do another handling check to see if you can still maintain your Wings level ball in middle at a slower speed and lower rate of descent. Who knows .....but if you have the fuel keep trying.

B. HIGH POWER PEDAL situation -

Lets do the handling check again -

WINGS LEVEL and put the BALL IN THE CENTRE with collective and find out where the power ends up. Lets say it provides the worse case scenario of a power higher than that required to hover.

We already know that the if we bring the IAS back towards a very low IAS that the PWR REQ'D will increase. As we decel we continue to try to maintain - WINGS LEVEL,BALL IN MIDDLE now by pulling collective to maintian our condition.

We see that we are climbing slowly - so what can we vary ?

1. Weight - it's reducing as we burn fuel ..so it ain't helping us
2. Even less IAS almost or even hovering .....but once we reach this we're at a point where the power req'd is now a MAX value.....but we are still climbing slowly.
3. Nr - if we vary Nr by way of a carefully controlled brief to co-pilot or crew member or self brief by the single pilot we can retard the throttle or SSL's to start a controlled reduction of Nr thus reducing Total Rotor Thrust - but maintaining useful power on Nr values. You should practice this before attemting the approach. If the Nr should decay too much too early use lever t regain Nr until you have had time to apply a little more throttle. Try to aim for a ROD around 200-300'/min

Your approach config should be practiced at altitude above your intended LS and your approach planned so that you start on an extraordinary long final (terrain dependant of course)to achieve a short final by approx 300 - 500' where you are continuing to reduce speed progressively and controlling your reduced Nr to give you a ROD around 200-300'per min at this stage on the approach the aircraft will not be pointing straight or wings level until you reach your IAS you assessed earlier. However, as you approach the hover you will have ground effect to contend with and will have to further reduce the Nr (retarding throttles and SSL's even further. As you approach the Hover or low speed you should aim to be satisfied with your heading, attitude and sink rate ...if so then smoothly retard the levers/lever or twist off the remaining power nice'n'gently and the helo will descend through the GE and you can .....shutdown and go back to the bar for several beers.


During both of these procedures you can always throw it away if you need to...... accepting the awkward manner of flight that you will achieve (out of balance wing low etc) Climb up, line yourself up again and practice it all over again - provided you haven't had to do the Engine OFf bit that is.

I have taught these techniques as have many other instructors - I'm sure, but the problems above are worth practising. If you've ever had a birdstrike that was big and it came through the perspex and wrapped it's wings and colon around your pedals ...you will want to have tried this at some point.

One important point tho' is don't get too wrapped up inside the cockpit it is possible to fly reasonably normally during the preparation and positioning. But at the end if it looks right outside the cockpit, the chances are everything will be alright so keep looking out and flying the beast.!!!

Sorry if it's long winded or if it's stuff you already know......I'm probably the only mug trying to attempt to paint the picture on paper..... back to my Guiness byeeee

[This message has been edited by eden (edited 13 February 2001).]

[This message has been edited by eden (edited 13 February 2001).]

ImIanphere,

(Sorry if I've got your ID wrong as I can't tell if they are Is or ls!)

Although your T/R drive loss technique may work on an R-22 or other small single piston-engined aircraft it might not be applicable to turbine engined ones, if only for the reason that they often don't have throttles that are within reach of a pilot with his hands full of sticks. Co-ordination then becomes a problem if a second crew member is not available (or present)to assist.

I have flown a lot of time in one aircraft type that is very likely go out of control if autorotation is not entered immediately and both throttles subsequently chopped before flaring to land; the only sure speed / power combination being nil power and 75 to 80 kts in autorotation. I did a lot of time carrying out simulator training on this type [both in the hot seat and operating the sim from down the rear] and the experiences of those unlucky enough to try it for real confirm what we found. Simulators are not always accurate because they depend on good data being programmed into them. If that's not available then an "off model" best guess is put into the software programme by the designer.

The AFM usually gives some guidance but can't be relied on as gospel 'cos manufacturers don't often practice it deliberately for obvious reasons.
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In the case of a cable jam /partial loss of control of T/R pitch where a powered approach is being considered:

As one who has flies American and European aircraft (different directions of main rotor rotation), to help prevent any confusion with phrases such as "Lucky Left" or "Right is Right" (depending which type I am flying) I now simply remember which side the retreating blade is on (I tend to remember this from the start-up)! This side is then the good side to have the nose "cocked off" towards on the approach. As collective is increased to cushion the (powered)touchdown, the nose will come round, from increased Tq reaction, to point straight ahead. The retreating blade side is also the good side to have the crosswind coming from.

Hope this helps the discussion.

ShyT.

Hey Offshore: Do you know why the F/O in the Maldives accident would jettison the door while still airborne. I've always been taught to wait till you were on the water and the motion has stopped.

Helimutt,

I might not have put over my point too well
(on the thread this disccusion began).

I wanted to start it the right place, which is to take a look at the often misused term
'TR failure' but it appears to be getting done now.

I have to say that the difference between a
true TR failure and a TR drive failure would be completely unoticeable and agree with you on that point, as the result would still be zero TR thrust to balance torque whether the blades are still on the Heli. or not.

But I think the difference between the above and jammed pedals/controls or control disconnection WOULD be clear because the Heli would not yaw right at anything like the initial rate, even if its pitch reduced to minimum. Easy on paper though, quite different in the heat of the moment and if that is where you were going then I agree with that too.

But all good training begins with fully understanding what is going on first, and that is where I began.

A good thread which I will read fully and contribute to when I have finished work.

The last time I renewed by Inst. rating in UK We did TRUE TR failure in the hover and it was surprisingly easy to master. Intersting for me because I have witnessed a
loss of TR control on an R22 in UK but more of that later.

Lovely sunny day, slingloading is today's order and I'm off to help a very able student take a heap of tyres for a flying lesson of their own! (Yes, using an R22, and within MAUW and C of G!) :)

IHL:

The CoJo was a long time friend of mine and his background was Mil. The only thing that has come out of the inquiry is that he had been trained to jettison the door prior to water contact in an imminent ditching situation. Knowing his background, I can't figure out who would advocate the door being jettisoned above translational.

From what has been published by TSB in Canada, the aircraft appeared to be returning to shore, when it went down. The initial report points to the door jettison as the cause of the loss of T/R. The door went throught the mast and then through the T/R.

As to why it was jettisoned, I guess we'll never know. I guess the best question to ask in this forum is, When should you jettison the doors. My opinion is only when you have a controlled ditching situation and only at a reduced airspeed i.e. less than 35 KIAS.

As for the responses to this topic, I think we've found a winner. No shortage of expertise here. I think this will be a real benefit to all pilots as the techniques we use on mediums and heavies are not always taught to those flying SE Light Helis. Although the same procedures will generaly work on all types.

One procedure I haven't heard yet is for a jammed pedal situation. On the 76 we teach our pilots to 'Beep Up' for a stuck right pedal and to 'Beep Down' for a stuck left pedal. The logic being, more power to reduce for the RPF (i.e. nose swings left) and more power available for the LPF (i.e. nose swings right). This technique can be equally useful for a 206, 500, 355 etc. Remember, the engine will still help you in the recovery whether it is a power reduction or power increase.

Cheers, OffshoreIgor http://www.pprune.org/ubb/NonCGI/eek.gif

The procedure I have tried to put across will work for jammed pedals, problems arising from cabling and negative force gradient spring residual problems, stuck or jammed pitch setings on the TR - in short any CONTROL you might get. We all obviously pray that we don't get the extremes of left or right - but that could be the way the cookey crumbleth.

If you run back to looking outside and seeing what the different combinations of airspeed, wings level and ball in middle as a result of lever position(thus power being used) you can determine the type of approach you need to consider.

I obviously didn't explain it very well ....never was good at this writing thing! I'll have to stick to the frantic egg whisk flying I reckon!

Offshore: Good on you to start this one. It would be great to hear from a 'novice' about their views on such a sinister malfunction. We always seem to hear from the same 'pro's'....
Eden: Guess who's been thru beefers school then!! Brilliant contribution..if only it was so predictable in real life!!
SPS: How on earth can you 'practice' real TR failures in the hover. Do you have a disconnect coupling in the drive train??

Thing to remember, in addition to the effects of surviving the initial bang....if the TR decides to take off, you're left with a major C of G problem [as per the story of the vietnam helo pilot who got his tail blown off with a SAM 7].
Different a/c types have their pros and cons too. Fenestrons offer advantages w.r.t. some TR problems. Can someone out there offer observations on the 902 series with TR problems (equivalent).


What goes round...comes round.


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Thermal runaway.

With regard to jettison before contacting the water. Some aircraft have flotation gear which may prevent a door being jettisonned once inflated and supporting the aircraft's weight. Not a good idea at speed for obvious reasons!

Shytorque,

Glad you pointed that one out. We use to use a B222 on marine pilot transfers and the norm was to lose the door on short final due to the floats. We now use a BK117, which seems to be a little more forgiving when it comes to the doors. Although the rear sliding doors do come into contact with the floats whilst jettisoning, it dosn't stop the pax from getting out.

On the single engine stuff, I am under the impression that you will most likely need a small amount of power during the auto and flare if you have a 'basic' drive failure. All got to do with drag etc from the transmission.

One other thing to nut over. Does the tail rotor go into auto itself if you boot in right pedal during a drive failure (American heli's)? Maybe it could give an additional, albeit small, amount of stability to an unstable situation. (could you overspeed a T/R)

Food for thought if nothing else.

As a low timer, my only experience of TR problems is my CPL instructor's boot on the pedals (I never practiced or had this demonstrated at PPL). All I can say is that I would NOT like to do it for real! Things were stressful enough and wild enough close to the ground in the practice situation.
Eden's post is great, and I'm printing it off for future reference. One thing, though, I was briefed to aim for a runway if poss, as the concrete is somewhat more forgiving if the touchdown is made pointing more sideways than might otherwise be prudent. Having practiced to grass, I was hoping concrete would be slightly easier.

I've decided, reading this thread, to grab my old instructor and have him jam his boot on the pedal again and see how I get on.

Thomas Coupling -

I wrote 'The last time I renewed by Inst. rating in UK We did TRUE TR failure in the hover'

I used 'true' in preference to 'real' as I thought the latter unsuitable.

I can see your point, we can only simulate having no TR thrust but cannot disconnect the TR so we have to get as close as possible
by using full right pedal.

Isn't this actually a very accurate simulation though? The TR has to be capable of making thrust in both left and right directions, one of the main reasons for that requirement being that friction effect in autorotation (nose yaws left) must be balanced by TR thrust in the opposite direction to powered flight.

(The neutral position for TR thrust on the ground in an R22 is with the right pedal a good deal forward, not with the pedals level with each other. The TR is rigged to give more control range to the left for powered flight)

Somewhere inbetween full left pedal and full right pedal there is a completely neutral TR pitch setting which is the same as having no TR thrust at all. If you use full right pedal you are actually PAST the zero TR thrust to the right value and into the (narrower)thrust to the left range. That must be ADDING to the speed of right yaw that would result from having no TR thrust due to a true (true making the distinction between a complete loss of TR thrust and other problems such as control failure or jamming) TR failure.

So it seems to me that full right pedal in the hover is a very realistic way of simulating a complete loss of TR thrust in the hover. It gives a greater yaw rate than a complete loss of TR thrust would do in the same profile.

I agree that it would be good to hear from any low hours pilots reading on the sideline, I think that the forum would benefit if more of that were to happen.

Moving on, The control failure in the hover (UK) that I saw was caused by a TR swashplate bearing siezure. The swashplate then wanted to rotate with the TR driveshaft which broke the horn control connection and left the TR in a fixed pitch state. The Instructor got it down fine although it was yawing slowly, I cant remember in which direction but guess that it must have been to the left as the lever was lowered to land.

It is important to note that this was a machine left outside in all UK weathers and had done around 1200 hrs. The bearing is lifed for 2000 hrs but leaving it to be ravaged by those conditions can do it no good at all.

To Offshore
Great Subject, lots of experienced pilots "experiences" for novices to learn something from, however putting this into practice real time for us novices is another matter.

To Thomas Coupling

I think I fit in to the novice category very well (PPLH gained 10 months and some 200 hours ago in the UK)So here goes on my experiences/thoughts on the prospect of a TR failure.
When doing my PPL H experience of Simulated TR failure was limited to approximately 10 minutes of demonstration by my instructor, at this point the following thoughts sprung to mind.
1. Sh**
2. I hope that never happens to me.
3. How on earth can you Practic TR failure in its various forms.
4. I now know enough to make me think that if it happened to me I had NO chance.

Luckily after gaining my PPL H (which after all is only a licence to learn) I had to go to the US to do a conversion course onto a NOTAR helicopter(more of that later) but during the course we covered TR (fan) failures in all their various forms Fan failure and or fixed left pedal in the hover being my particular favourite. These failures proved very realistic (I guess) and only required flying the heli with your instructor working the pedals (the factory test pilots who have actually had the failures for real)This then gave me the following thoughts.
1.The PPL H course in the UK should either not cover it at all(ignorance is bliss!)or do it properely(maybe this was just my instructors and not the course ?)
2.I still have a lot to learn.
3.OK while it was only simulated, I now feel more comfortable with TR failures.
4.I would react better to the situation.
5.If it does happen I won't just be waiting for the crash , I will be trying to do something about it when I crash !!!!!!
6.BUT no one told life/situations to follow what it says in the book!

To Eden
You mentined the NOTAR system in one of your posts, and the fact it may be better with a failure. In my experience if the fan fails its jsut like any loss of TR, except for maybe above 35 Knots IAS when the steerable verticals are in effect, but then if you have a fixed pedal scenario they make it even worse in certain cases. The drive to the fan can fail just the same as a TR, the big bonus is that the fan is less likely to strike anything to cause the failurein the first place! Wether in flight or in the hover.

To All Novices like Me
Remember this in your quest for flying knowledge:
"In the life that is helicopter flying we start off with 2 Bags, One bag of LUCK which is FULL, the other bag is for EXPERIENCE and is EMPTY, Make sure you FILL the bag of EXPERIENCE BEFORE your bag of LUCK runs OUT"

Cant remember who told me this/wrote it but they are very wise.

Regards
hoverbover

I think the big thing to remember here is that with the exception of a total drive failure or actual loss of complete T/R assembly, the one thing you will have lots of, is time.

Don't be in a mad panic to get down. Take your time and experiment with power and airspeed combinations that will give the best profile for landing.

On wheel equipped A/C, you will be able to run the A/C on at a considerably higher than published speed i.e. S76 60-70 Kts! Skid equipped A/C, if recovered at a runway, can also run on at a fairly higher than normal speed (obviously not great for the skids but at least you get down in one piece).

Someone asked about the T/R being 'Auto'd'. The SH/UH60 has the tail rotor mounted on an angle (I forget the exact amount). If a total loss of T/R drive is experienced it is recommended that the aircraft be banked 20-30 degrees (I think to the left). This causes the T/R to autorotate to some extent returning, I believe about 50% tailrotor control.

Well keep it coming as I do believe this may turn into a very educational topic for all.

Cheers, OffshoreIgor http://www.pprune.org/ubb/NonCGI/eek.gif

hoverbover:

Thanks for that info' I was kind of alluding to the fact that I wasn't really aware or sure of what happened with these beasts, having never flown one. I felt that they might present a different set of problems and was kind of hoping that someone would jump on my ignorance a sort me out - so I am grateful for your advice.

Out of interest: for those who may have had a TR CONTROL problem (as opposed t failure) the techiques I describe work - having had a cockpit floor full of Seagull and derision wedged firmly amongst the pedals of a Gazelle during a low level sortie. Luckily -the problem it gave me enabled me to return for a slow speed running landing which was all very benign .....the greatest shock is a facefull of feathers, a facewash of Seagull blood but the remains made for good burgers at lunch!

I mentioned this on a different topic, but Rotorque mentioned throttle control in autorotation on the previous page and so I thought I'd mention it again. In singles with throttle on the collective, reducing pitch but leaving the throttle alone and Nr in the normal range may produce just the right amount of torque to balance the transmission bearing drag at normal auto airspeed. However, during the collective application at the end, throttle will have to be held at idle to prevent the correlator from sending the power back up, and in the case of TR failures, this will leave a healthy yaw to contend with as the transmission bearing drag becomes unopposed. I suppose that a near zero speed landing would be something to consider in this case, if possible.

I've had a tail rotor control jam on me, the wires jumped the control run guide pulleys and the pitch setting luckily was jammed to a +ive setting. Luckily we were shore side at the time otherwise I would have had to recover to 3000 tons of moving deck the size of a car parking slot!!!

One of two things will happen to you if it is going to happen:

1. There will be an almighty bang accompanied with the inherent yaw in oppostion to the direction of the main rotors. If you are in fwd cruise then the rate will be in proportion to your speed. [In the hover, you will rotate very very quickly, so much so that you will become very disorientated and if not strapped in properly, will be flung outboard of the rotation. Should this be away from the throttle(s) then you won't be able to chop it/them]. The simple solution here is dump the lever and land, accept the very hard landing!!
In fwd flight you will also get a fwd pitch of the a/c dependant on the moment arm of the TR x weight (of chunk)lost! If a/c is still flyable: YOU MUST ENTER AUTO AND CHOP THOSE THROTTLES ASAP. At the bottom, the flare will assist with yaw correction but not fully, you will be committed to a zero spd landing if you don't want to flip head over heels. Keep the Nr up at max throughout, this too helps with yaw correction.

2. You will experience an undemanded yaw input proportional to collective input and possibly slight mechanical noises. This baby should give you time to change your underwear and hand over to the commander!!!
This scenario has been superbly described by others earlier. Time is on your side.
Concrete is better for landing because the skids/undercarriage can scrape more easily over concrete. Don't land on grass if possible. Do as many approaches as necessary before the real Mcoy, as long as you don't go below min pwr speed on each approach you won't lose heading control...Get rid of fuel,if possible. If you can limp to a major airport, get them to foam a strip of runway.

Go thru what you would do, every month or so, get a feel for your craft, play with stuck pedal/speed/collective/wind...this is what makes a professional stand out from a joy rider. Last but not least: DO A GOOD WALKROUND EVERY TIME.


http://www.gograph.com/Images-7298/A...if/redstar.gif
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Thermal runaway.

[This message has been edited by Thomas coupling (edited 14 February 2001).]

Chaps,
Loads of very interesting, well formulated hypothesis and real experiences alike. For my ha'peth worth there is no substitute for simulation. Most see the merits of a half decent sim for practicing those failures that we dare not try in reality (bearing in mind for the bean-counters present; we wreck more aircraft in training than in Operations!). This was certainly true of my experience with FSI's 212 sim at Fort Worth. Among the many any other failures, we underwent simulated T/R drive-shaft failures. The Company policy was 'find big space - enter auto - live happily ever after! The FSI instructors however had a different idea - they advocated and trained the 'find some sort of flight attitude with forward speed, run on to runway with power, gently rolling off throttle and lowering collective, to a gentle if graunching stop.' First try, I managed several pirouettes culminating in a nice little roll (no 10/10 from the judges there then!). After a couple of attempts I could get down in one piece but it still frightened me to death. My conclusion was that if confronted with the reality, I would tow the Company line - I truly felt that I would have a far better chance of walking away as autos are far more regularly practiced. I would would maybe reconsider if sim training was the 'norm' and I got to practice the FSI way on a yearly basis.

To all who responded to my request for a discussion on TR failure, a great thanks. Lots of food for thought here. Thanks particularly to Eden for his book on the subject. I am more sure than ever that at 75 hrs of heli time, I do NOT want to face a TR problem. But, like autos, I will try to practice it regularly. The repetition won't necessarily help, but, at least, there will likely be less of a feeling of panic if it occurs. Keep the thread going, please!

Little finger rule-

When your left hand is curled around the throttle stretch out your little fimger (LH!)

As you decrease throttle (the nose would yaw
more left) your finger will point left. Apply the reverse to increasing throttle.
The nose will yaw right as your finger points right.

Good for trimming up for a run- on from jammed controls (depending on the nature of the problem).

To Eden

Sorry if my response to you sounded as if I was telling you it wasn't intended that way at all. Its just that most of my flying has been on the NOTAR system, and most people have never had the chance.(I'll send you an email)As said before its very similar to a tail rotor but with some particular differences (some good some bad). Again sorry if my response sonded like I was setting you straight "I'm here to learn not preach"

Reagrds

hoverbover

SPS :

That's only good for anti-clockwise rotating helicopters, though, no ?

I have posted this on several other threads and on another forum. Although there was no actual tailrotor failure the pilot perceived that the tailrotor gearbox had suffered a failure and as a result took corrective action which only made things worse. This could also be posted on the wire strike thread.

I was flight mechanic on a Bell HTL-1 (early model 47) and we were returning to base in Traverse City, Michigan from a stint on an Ice Breaker on Lake Superior. We had a leaky tail rotor gearbox so every fifty miles or so we would land and I would fill up the gearbox with of all things, fish oil. Very smelly stuff. My pilot, Dave Gershowitz, who incidentally was the first helicopter pilot to hit 1000 hours, was easily freaked out.
While flying in the left seat I was holding the oil can between my legs and reading a map. We were about twenty minutes out when Dave saw a bear. He very excitedly told me to look. When I leaned over, my legs spread and the can hit the deck making a loud noise. Dave thought there was something wrong with the tail rotor gearbox and he made a quick turn looking for a spot to land. In the process of making his maneuver he really made a hard over. On that particular helicopter type when there was an excessive side load on the mast it would cause the planetary gears to really growl.
Upon hearing that, he really wanted to get on the ground. He picked out a landing spot in front of what we later found out was a veterinarians office. To get from where we were to that landing spot we had to pass over a turkey farm and in the process we made the turkeys stampede and over 100 birds were killed in the pileup at the fence surrounding the turkey farm.

Oh yes, in the process of landing, we took out the vets' telephone line
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The Cat

Hoverbover: no bad feeling taken - I was being very genuine about my ignorance and I am grateful for your info' - I look forward to your email and hope you can provide me with some more detail as to how the thing works.

I am going to have a look at a Notar machine in the next week or so and would appreciate as much background info on tail rotor snags that you can provide about it.

I too am here to learn and I hope never to preach too hard - cheers

eden - energy driven eccentric nirvana

NOTAR itself really has moved the tail "rotor" into the body of the machine itself. A fan unit run off the trannie sends high pressure air into the boom, the air is then forced out thru two slots on the side, and due to coranda effect helps to offset torque, the rest of the air is coming out of the variable nozzle at the aft end, in which the amount can be adjusted by the pilot.
The vertical vins are also controlled by the bilot and the SAS.


A basic description. But as hoverbover was saying, since the fan is now inside the fuse you could sit all day with the boom in a tree (McD loves pics of this) with no problems :) Yopu are less likely to have things hit the fan too.

Boy what a great thread! Lot's of stuff to absorb. My hope is that if I suffer a tail issue, it's a control one with time to sort it out, if not them I'm into auto and hope for the best.

SPS: Like your 'lil pinkie trick!


------------------
Marc

To Eden

Hope you got the email, so that everyone can understand(hopefully I might even understand it myself one day)I am posting my thoughts about the NOTAR here(I dont wish to divert the thread,but I dont think it warrants its own one and is kind of related)

The NOTAR system basically works from air pressure created by a fan at the front of the Tail Boom (Tube)This fan is driven by the turbine in the same way as any TR drive.
The fan is very similar to A FENESTRON in looks but with very short blades (about 60mm in length)The fans pitch is increased and decreased/coupled to the pedal inputs(Strangely enough it increases pitch in both directions) and consequently greater pedal input creates greater pressure in the tube.
at the end of the Tail Boom there is (for want of abetter expression) a rotating dustbin which allows the air pressure in the tube (from memory its around 3psi)to be directed for pedal turns in the hover.

There are also two long slots on one side of the boom (and a diffuser on the otherside)which are configured so that air continually comes out of the slots in a downward direction,so that in the hover the downwash from the Main Rotor Flows over the boom and using the principal of there then being a low pressure one side and highpressure the otherside of the boom (Coanda effect I think)This also creates some of the anti torque in the hover (think its 20 %)

Obviously as you move into forward flight the downwash is not flowing over the boom and the air pressure from the bucket is less effective so the 2 Rear verticals are also connected to the pedals (either by cable or in some configurations by linear motor)so in forward flight you have rudders!

And there you have it simple,a bit like me.

Flying it is very similar to a normal TR but the following are what I find to be the differences.
1.Firstly in the hover the pedals need a lot of movement,but in forward flight they are VERY sensitive (unless AC is YSAS equipped)
2.When its windy the pedal movements are quite big in the hover,but still plenty of power.
3.As the tail goes thru the wind there is no snap like a TR, everything seems far smoother
4.When you are coming into the hover from forward flight you actully have to apply more right pedal (as the downwash sticks to the boom)before a big boot of left.
5.In flight the vibrations/resonance of a tailrotor is non existant so its very smooth
With these in mind its just like any helicopter it has quirks,but I guess you learn to live with them and being a low hour pilot and having spent 50/50 in TRs and Notars I havent built up any great aversion to them. But when you land in a forest or in fact anywhere (even an airfield) not having to worry about people walking into(airfields) or things hitting the tail rotor does allow some comfort(I know the LZ is always checked and scrutinized but this thread would be here if accidents didnt sometimes happen,and its amazing how a running TR looks like a bicycle wheel to our canine friends who shouldnt be off alead but sometimes appear from nowhere.)
Autos:
These feel very similar to a normal TR.
TR Failures:
Again very similar but if the fan fails in forward flight you can actually land (at 40 knots ) using the rudders, having tried this to the concrete and to the grass it is a wild ride! (ever tried slowing down on skids on concrete with no TR authority form 40 Knots?and yes using the throttle/finger pointing method helps but you have to be quick to make it stay on the runway and not go pirouetting onto the grass)
As said before stuck pedals can be alot worse than normal TR because of the effect of the rear verticals
Problems:
Havent really found any yet, some people say that in heavy rain the fan has problems but having flown in heavy(maybe not american heavy)rain I have not found any problems.

Just make sure no one has thrown a bag of bolts in the fan intake on the walk round (can you believe this has actually happened to one, and it still flew,not as quietly though and there were a few red faces)

This is how I understand it,and have tried to make it as understandable as possible with goinginto the real tech side of it (that would tax my brain too much)and Im sure other NOTAR pilots will hopefully have more to add,with differing opinions I should think
Unfortunately some LOVE it some HATE it,me I just enjoy flying it.

Regards
hoverbover

To R W1
You posted while I was typing mine to EDEN sorry mine took so long to say what yours did.
However great the pictures with the NOTAR tail in the tree may look great, ask the guy who stuck his tail into a bush changed pedal input/rotated dustbin caught branches in hole that closed due to bin roating to let air out other side.
Result:cat caught by tail syndrome,and change of underwear for pilot.
Luckily he got away with it but the notar isn't infallable.!!!!!!!!!!!
Regards
hoverbover

Hover,

Heard about that one myself ..... :)

Nothing perfect hehe ....

Liked your description, I had left out the variable aspect of the fan for simplicity, but you are right. Mine was a Q&D response.

The slots and high pres air add energy to the boundry layer of the airflow going around that side of the boom delaying separation, thus as I understand it intensifying the coanda effect.

I think you meant Florida heavy rain hehehe ...

Now if they could make it so that the heli doesn't look like it has a hige cigar stuck into it's A$$ .......

[This message has been edited by RW-1 (edited 15 February 2001).]

what keeps the fan of the notar system running when the engine fails? or is it even necessary?

To Imlanphere

The drive to the fan is coupled to the main transmission in the same way as any TR drive,so providing ONLY engine failure and you enter auto its driven in just the same way as normal.
You do actually require the fan to work because after all it is just like losing an normal TR.(NOT GOOD)
Hope this clears it up.
Any other questions on the NOTAR fire away
and I'll try and answer them.

Regards
hoverbover

Nr fairy -

Hadn't even considered it to be abs. frank, don't fly them often. Good point and we'll leave it to the forum to see what they think (code for I don't know and I have to dash right now!)

RW -

Glad you like the little finger rule - It is just amazing what you can do with one!
:)

Rotorque -

Your thoughts on the tail rotor and the possibility of it entering autorotation are very interesting. I was similarly intrigued when making a study of the TR and I concluded with this –

<i>(Basic facts are established for the benefit of sideline readers and not to patronize anyone)</i>

‘Autorotation’ is a term used for MR harnessing of an incoming airflow to maintian RPM in much the same way as a windmill sails would (except that a windmill is static and the incoming airflow moves to it as wind but the Helicopter moves to the incoming airflow).

In this autorotative state the MR is not driven (rotated) by any power applied through its driveshaft from an engine but by the effect of the airflow, i.e. it is driven in reverse, driving the gearbox and anything connected to it.

The TR never enters autorotation in forward flight as it continues to be driven by the MR through the gearbox. It always receives shaft power for rotation. Whether that power is developed and delivered by an engine or autorotative force from the MR makes no difference at all. The TR is always driven by shaft power transmitted from a power source.

If this is taken one step further it is apparent that the TR is always making some thrust in one direction or another (unless TR blade angles of attack are truly zero or RPM are insufficient, etc.).

A Helicopter (of conventional design) in autorotation experiences ‘friction effect’ on the fuselage which tends to twist it in the opposite direction to torque, i.e. yaw to the left. This means that the TR must be capable of making thrust to either the left or right of the tail. It must balance torque during powered flight (by producing thrust to the right) and friction effect during autorotation (by producing thrust to the left).

So it’s a busy little thing eh?!


SPS

http://www.helicopterpilotsguide.com...e_steering.GIF

First experiment.....Thanks to all who posted advice for graphic image placement.

Hope it is of use.

(Hope it works !!)

:) SPS

If you can see no light at the end of the tunnel then get down there and light it yourself.

Just caught up on three pages of this thread after a week away, and off for another week in a couple of hours so will have to leave it for now. But one thing now really really bothers me. In company with someone else a page or so back, I never practised anything concerning tail rotor failure for my PPL, or while practising emergency procedures with an instructor sometime afterwards. I once mentioned stuck pedals to an instructor at some point, and got a quick little demo, but that was all. The fact that I'd read about what to do seemed to keep everyone happy. Doesn't keep me happy, now I think about it. Think I might find another instructor, or another school, and learn about this.

What are other PPLs' experiences on this? And many thanks to all who've contributed to this most interesting thread.

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Whirly

To fly is human, to hover, divine.

Sorry, been away - excellent thread.

Going back to a comment on page 1 by ShyT concerning throttle position in turbine helis, I'm pleased to say that the layout in the Bell 205 (throttle on the collective) saved an oppo of mine in Oman in 1983. He was in the hover over an underslung load at Saiq (6,300 ft amsl, OAT 20 deg...) when the tail rotor decided it didn't want to play any more. He rolled the throttle shut, kept the aircraft level and cushioned the touchdown with no damage to aircraft, aircrew, ground hook-up party or even the load. Top stuff - proves that what's been written in this forum really works.