Tail Rotor Problems
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I had a quick look at Section 8, Training. It makes a big thing of the use of simulators, preferably with 6 DOF (Degrees Of Freedom). Fine for the military with the Lynx, but do CHC or Bristow have anything so elaborate? And coming down the pecking order, I have yet to come across an R-22 sim with any DOF at all.
Page 155 names several schools that describe TRF at least in passing, but - for a report released in November 2003 - I thought it strange that SouthernAir were mentioned. Didn't they go the way of all good things a little while ago? Like, two years?
But fantastic spot, Nr. You also beat me to it with the December bulletins.
Page 155 names several schools that describe TRF at least in passing, but - for a report released in November 2003 - I thought it strange that SouthernAir were mentioned. Didn't they go the way of all good things a little while ago? Like, two years?
But fantastic spot, Nr. You also beat me to it with the December bulletins.
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What a tome! A most impressive body of work, with many things to learn and more to ponder. The discussion by Steve O'Collard at the end is worth the price of admission!
Some concerns I have:
The failure rate appears all out of whack to me. I see the rate of approximately 20 per million hours on the tables (notably P. 40) but that seems awefully high, based on the failures I know of for the aircraft I follow. For example, at 20 per million, I would have expected about 50 TR failures on S-76 fleet, but I can only recall maybe 5 if I stretch. For Black hawk, that would have to be about 80 tail rotor failures, again a big number.
Introducing a new and potentially eye-watering system like a parachute that always deploys when the tail rotor fails and never ever deploys otherwise is an interesting concept. It is kind of like the guy who carries a bomb aboard all airliners that he flys on, because, "The odds of there being two bombs aboard is so very low, I am completely safe!"
The study does survey lots of options, and does call for more and better design attention for TR systems, certainly important if those pesky data are accurate. And the call for monitoring for failures is positively 21st century, as the S-92 has about 20 vibration monitors for the drive train alone, all reporting through a Level A software system.
Thanks for the steer, Nr. Good stuff.
Some concerns I have:
The failure rate appears all out of whack to me. I see the rate of approximately 20 per million hours on the tables (notably P. 40) but that seems awefully high, based on the failures I know of for the aircraft I follow. For example, at 20 per million, I would have expected about 50 TR failures on S-76 fleet, but I can only recall maybe 5 if I stretch. For Black hawk, that would have to be about 80 tail rotor failures, again a big number.
Introducing a new and potentially eye-watering system like a parachute that always deploys when the tail rotor fails and never ever deploys otherwise is an interesting concept. It is kind of like the guy who carries a bomb aboard all airliners that he flys on, because, "The odds of there being two bombs aboard is so very low, I am completely safe!"
The study does survey lots of options, and does call for more and better design attention for TR systems, certainly important if those pesky data are accurate. And the call for monitoring for failures is positively 21st century, as the S-92 has about 20 vibration monitors for the drive train alone, all reporting through a Level A software system.
Thanks for the steer, Nr. Good stuff.
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Tail Rotor failures
Summary:
The report contains what the CAA describes as the "deliverable" from from the QinetiQ research project ‘Helicopter Tail Rotor
Failures’ carried out for the CAA under a contract awarded to the Defence Evaluation and Research Agency (DERA) in 1997. The project was co-funded by the Ministry of Defence.
The project studied tail rotor failures and their consequences and was carried out because of overwhelming evidence gathered by the UK Tail Rotor Action Committee that TRFs were occurring at rates much greater than the airworthiness design standards require. This was true for both tail rotor drive and control systems, and applied to both civil and military types.
The principal aims of the study were to analyse and quantify the nature and extent of the problem, and explore ways to reduce failure/accident rates and/or mitigate their effects in the future. In addition, existing training procedures and handling advice
were examined and means of improvement suggested to prepare aircrew better for the effects of TRFs.
The study looked into the nature and extent of helicopter tail rotor failures, techniques/technologies to reduce occurrence and/or mitigate consequences, existing emergency procedures and handling advice, current pilot training practice and simulators, existing airworthiness requirements. It included piloted simulation-based experimental work.
(If you're not on broadband, it may be easier to download the file first.)
The report contains what the CAA describes as the "deliverable" from from the QinetiQ research project ‘Helicopter Tail Rotor
Failures’ carried out for the CAA under a contract awarded to the Defence Evaluation and Research Agency (DERA) in 1997. The project was co-funded by the Ministry of Defence.
The project studied tail rotor failures and their consequences and was carried out because of overwhelming evidence gathered by the UK Tail Rotor Action Committee that TRFs were occurring at rates much greater than the airworthiness design standards require. This was true for both tail rotor drive and control systems, and applied to both civil and military types.
The principal aims of the study were to analyse and quantify the nature and extent of the problem, and explore ways to reduce failure/accident rates and/or mitigate their effects in the future. In addition, existing training procedures and handling advice
were examined and means of improvement suggested to prepare aircrew better for the effects of TRFs.
The study looked into the nature and extent of helicopter tail rotor failures, techniques/technologies to reduce occurrence and/or mitigate consequences, existing emergency procedures and handling advice, current pilot training practice and simulators, existing airworthiness requirements. It included piloted simulation-based experimental work.
(If you're not on broadband, it may be easier to download the file first.)
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I've browsed through this weighty tome, and was impressed by the detailed work.
More specific comments will have to wait for a thorough review, but aside from generating more TLA (three letter acronyms) that will probably cause confusion, there is little to fault with the work done.
We do need to simplify things here so that we can help to train everyone
for example - for engine fuel control problems, the advice of 'high Rotor RPM, high engine bad (for multi-engine machines) and Low Rotoro RPM - low engine bad' helped to simplify a very complex subject.
Does anyone have any thoughts on this - like (for N. American direction of rotation main rotors) - yawing right, no sinking- loss of tail rotor, yawing left plus sinking= loss of engine (on the assumption that your tail rotor control system is unlikely to give you a hardover, but could perhaps jam)
More specific comments will have to wait for a thorough review, but aside from generating more TLA (three letter acronyms) that will probably cause confusion, there is little to fault with the work done.
We do need to simplify things here so that we can help to train everyone
for example - for engine fuel control problems, the advice of 'high Rotor RPM, high engine bad (for multi-engine machines) and Low Rotoro RPM - low engine bad' helped to simplify a very complex subject.
Does anyone have any thoughts on this - like (for N. American direction of rotation main rotors) - yawing right, no sinking- loss of tail rotor, yawing left plus sinking= loss of engine (on the assumption that your tail rotor control system is unlikely to give you a hardover, but could perhaps jam)
Avoid imitations
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Shawn,
For pilots who fly both American and European types (opposite main rotor rotations) and I am one, there is a big danger of confusion during the initial stages of a T/R malfunction, which can jeopardise the recovery. At a simulator for the S-76 I attended, there was constant reference to the terms "Lucky Left & Rotten Right", I'm sure you will have heard this used, too. I don't like this term because for a european helicopter it is "rotten left & lucky right".
I thought myself through this during my RAF time carrying out instruction on the Puma Sim. I came up with the following maxim:
The LUCKY side, no matter what the direction of blade rotation, is the RETREATING side!
Much easier to remember, as most pilots do actually remember which way the rotors went on start up!
For pilots who fly both American and European types (opposite main rotor rotations) and I am one, there is a big danger of confusion during the initial stages of a T/R malfunction, which can jeopardise the recovery. At a simulator for the S-76 I attended, there was constant reference to the terms "Lucky Left & Rotten Right", I'm sure you will have heard this used, too. I don't like this term because for a european helicopter it is "rotten left & lucky right".
I thought myself through this during my RAF time carrying out instruction on the Puma Sim. I came up with the following maxim:
The LUCKY side, no matter what the direction of blade rotation, is the RETREATING side!
Much easier to remember, as most pilots do actually remember which way the rotors went on start up!
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T/R failure in forward flight....
All you experts out there - If T/R failure occours in foward flight and enough forward speed and height is available to enter autorotation after chopping the throttle - should the aircraft be flared before making a fast run on landing or not? I am very interested to see what advice is given here by ye old lags. Thanks.
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some-ones going to ask
the question some one will throw back, is, "what type of failure"
- loss of component (t/r departed)
- loss of t/r control (pedal inputs do nothing)
- fixed pitch failures (how much pedal at failure and which pedal)
type of failure dictates recovery, autorotation may not be necessary
i guess that someone was me
- loss of component (t/r departed)
- loss of t/r control (pedal inputs do nothing)
- fixed pitch failures (how much pedal at failure and which pedal)
type of failure dictates recovery, autorotation may not be necessary
i guess that someone was me
As he's chopped the throttle I would think it's a drive failure. Can't recall anyone telling me not to flare. It would be useful to get rid of some excess speed. Of course there may well be yaw in the direction of the blade rotation, due to friction in the transmisssion.
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FS,
You still have some very differnent problems. Loss of component ie: GB or T/R departed , life becomes extreme very fast, due to cg change. You gonna spin , buck and it'll be a wild ride (more than likely) Do what ever you can to keep it flying , even in an auto. It aint gonna be pretty.
snapped driveshaft, or gb fails, use airspeed and or collective pitch adjustments to keep it flying if possible, to a spott where you can auto to or run it on without a scratch if your lucky. Lot of this depends on AC , gross wieght, other enviromental factors, etc.
Every one will be differnt....
like some of these salty old guys around here say. Thousands of hours of sheer boredom, moments of stark terror.
RB
You still have some very differnent problems. Loss of component ie: GB or T/R departed , life becomes extreme very fast, due to cg change. You gonna spin , buck and it'll be a wild ride (more than likely) Do what ever you can to keep it flying , even in an auto. It aint gonna be pretty.
snapped driveshaft, or gb fails, use airspeed and or collective pitch adjustments to keep it flying if possible, to a spott where you can auto to or run it on without a scratch if your lucky. Lot of this depends on AC , gross wieght, other enviromental factors, etc.
Every one will be differnt....
like some of these salty old guys around here say. Thousands of hours of sheer boredom, moments of stark terror.
RB
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lets say an auto is required --
i've been told (no personal experience), and it makes sense to me, that a flare just before touchdown, besides loosing forward speed, and held (mild flare, not standing it on it's end) so that the stinger makes contact with the ground will have the efect of straightening out the airframe before the skids touch.
having the heels of the skids touching first will also help keep you aligned
wouldn't want to touchdown full skid with a 45 deg nose angle
i've been told (no personal experience), and it makes sense to me, that a flare just before touchdown, besides loosing forward speed, and held (mild flare, not standing it on it's end) so that the stinger makes contact with the ground will have the efect of straightening out the airframe before the skids touch.
having the heels of the skids touching first will also help keep you aligned
wouldn't want to touchdown full skid with a 45 deg nose angle
If it's a Squirrel and a simple drive failure, then you should be able to maintain control, fly to a suitable field and carry out a powered run on landing. As one of my colleagues did a few years ago.
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There is no straightforward answer. The main variables are aircraft type and landing area condition. If the only place to touch down is full of obstacles (the pilot might have little choice) obviously one needs to reduce forward speed by flaring as much as possible. Shame to survive the impact but at high groundspeed and subsequently watch a stone gatepost get closer to the "between the legs" position.... 
Some aircraft are best engines shutdown (most I have flown are), some are OK at engine ground idle, and some may be better placed with regard to a speed / power combination. Reading the Flight Manual is always good advice and simulator training helps too.
At night I would want to reduce g/s as much as possible, even at the expense of a higher rate of descent.
Some aircraft are best engines shutdown (most I have flown are), some are OK at engine ground idle, and some may be better placed with regard to a speed / power combination. Reading the Flight Manual is always good advice and simulator training helps too.
At night I would want to reduce g/s as much as possible, even at the expense of a higher rate of descent.
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Flying Squirrel,
In answer to your question -which, if I'm not mistaken is - "If I've entered autorotation after a T/R failure should I flare at the bottom?"
Yes under most circumstances. If you have rolled the throttle off to achieve aircraft control after T/R failure and the area where you are about to land is not a runway then flare. In a crash forward speed kills so reducing the forward speed to zero just prior to touch down will significantly improve your chances of survival. Directional control should not be too much of a problem through the flare if you have a fin. Expect some yaw in the direction of rotation as you intial the collective. This is due to you imparting a decelerative force on the blades when you initial. The torque reaction of the fuselage is to turn in the direction of blade rotation. The attitude now must be levelled prior to cushioning at touch down. During the touch down you will be rotating but much less wildly than if the throttle was open. Fly to touch down in a level attitude. Hopefully the aircraft will remain upright but even if it doesn't the lack of forward speed will hopefully ensure minimal injuries.
However, depending on the aircraft type an autorotation is not always the immediate solution to a T/R malfunction. The manufacturer's recommended solution is probably most appropriate.
In the case of a loss of T/R Drive or loss of control linkage it is probably advisable to fly the aircraft to a runway. Enter autorotation by lowering collective and only roll the throttle off after achieving a slow enough run on speed and lined up with the runway.
In the case of catastrophic failure and loss of components, the longitudinal CofG problem is now going to dictate whether the aircraft can be controlled and therefore whether the throttle should be rolled off straight away.
There's not enough room here to go through what to do for a jammed pedal.
Note these are general solutions and may vary from type to type and configuration to configuration. ie wheels vs skids, PCL vs twist grip etc
Your best bet is to sit down for a long chat with a crusty old instructor and satisfy yourself you can identify the type of T/R emergency and the best way to deal with it.
PS The suggestion that friction in the transmission is the cause of rotation after initial at the bottom of an autorotation is a myth. It belongs in Mr Lappos' thread about urban myths. The rotation is due to the decelerative force on the blades at initial.
In answer to your question -which, if I'm not mistaken is - "If I've entered autorotation after a T/R failure should I flare at the bottom?"
Yes under most circumstances. If you have rolled the throttle off to achieve aircraft control after T/R failure and the area where you are about to land is not a runway then flare. In a crash forward speed kills so reducing the forward speed to zero just prior to touch down will significantly improve your chances of survival. Directional control should not be too much of a problem through the flare if you have a fin. Expect some yaw in the direction of rotation as you intial the collective. This is due to you imparting a decelerative force on the blades when you initial. The torque reaction of the fuselage is to turn in the direction of blade rotation. The attitude now must be levelled prior to cushioning at touch down. During the touch down you will be rotating but much less wildly than if the throttle was open. Fly to touch down in a level attitude. Hopefully the aircraft will remain upright but even if it doesn't the lack of forward speed will hopefully ensure minimal injuries.
However, depending on the aircraft type an autorotation is not always the immediate solution to a T/R malfunction. The manufacturer's recommended solution is probably most appropriate.
In the case of a loss of T/R Drive or loss of control linkage it is probably advisable to fly the aircraft to a runway. Enter autorotation by lowering collective and only roll the throttle off after achieving a slow enough run on speed and lined up with the runway.
In the case of catastrophic failure and loss of components, the longitudinal CofG problem is now going to dictate whether the aircraft can be controlled and therefore whether the throttle should be rolled off straight away.
There's not enough room here to go through what to do for a jammed pedal.
Note these are general solutions and may vary from type to type and configuration to configuration. ie wheels vs skids, PCL vs twist grip etc
Your best bet is to sit down for a long chat with a crusty old instructor and satisfy yourself you can identify the type of T/R emergency and the best way to deal with it.
PS The suggestion that friction in the transmission is the cause of rotation after initial at the bottom of an autorotation is a myth. It belongs in Mr Lappos' thread about urban myths. The rotation is due to the decelerative force on the blades at initial.
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"However, depending on the aircraft type an autorotation is not always the immediate solution to a T/R malfunction. The manufacturer's recommended solution is probably most appropriate.
In the case of a loss of T/R Drive or loss of control linkage it is probably advisable to fly the aircraft to a runway. Enter autorotation by lowering collective and only roll the throttle off after achieving a slow enough run on speed and lined up with the runway."
First paragraph of that advice =
I agree with you there, but the second paragraph =
I have to strongly disagree with the second paragraph. It is VITAL to know your aircraft type because on some aircraft, after a loss of tail rotor drive, any attempt to "fly to a runway" other than in autorotation may result in loss of control. This technique may be a good one if the tail rotor is still producing thrust, i.e. control of the pitch angle has been lost.
We must be very careful with this subject. Trying to give general advice on how to handle a tailrotor malfunction may be inappropriate.
In the case of a loss of T/R Drive or loss of control linkage it is probably advisable to fly the aircraft to a runway. Enter autorotation by lowering collective and only roll the throttle off after achieving a slow enough run on speed and lined up with the runway."
First paragraph of that advice =
I agree with you there, but the second paragraph =
I have to strongly disagree with the second paragraph. It is VITAL to know your aircraft type because on some aircraft, after a loss of tail rotor drive, any attempt to "fly to a runway" other than in autorotation may result in loss of control. This technique may be a good one if the tail rotor is still producing thrust, i.e. control of the pitch angle has been lost.
We must be very careful with this subject. Trying to give general advice on how to handle a tailrotor malfunction may be inappropriate.