Tail Rotor Problems
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Landing w/o tail rotor!?!?
A question to you rotorheads:
We had an Apache lose it's tail rotor a few weeks back, which then went on to land safely by maintaining a high speed so the tail would act as a stabilizer.
Anyone care to explain this in a bit more depth?
Cheers
DT
We had an Apache lose it's tail rotor a few weeks back, which then went on to land safely by maintaining a high speed so the tail would act as a stabilizer.
Anyone care to explain this in a bit more depth?
Cheers
DT
Guest
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DT,
can you explain in more detail what you mean by "lost" tail rotor. Did he/she lose the tail rotor gear box and blades, lose tail rotor control, or lose tail rotor drive.
The exact emergency procedure is different for all of them.
However, the vertical stablizer has a function to act as a air foil and produce thrust to help maintain streamlining of the fuselage. This unloads loads the tail rotor, the horse power that would have been used to drive the tailrotor is now avialable for the main rotor to use for lift and thrust. The streamlining is most efficent at some airspeed, probably in the neighborhood of 60kts, that the designers have determined. The streamlining should allow the helicopter to be landed with out tail rotor contol, or drive with a smaller pucker factor margin. The exact procedure is individual to the type of heliocpter, so this is a generic statement of the function of the vert stab in tail rotor failures.
can you explain in more detail what you mean by "lost" tail rotor. Did he/she lose the tail rotor gear box and blades, lose tail rotor control, or lose tail rotor drive.
The exact emergency procedure is different for all of them.
However, the vertical stablizer has a function to act as a air foil and produce thrust to help maintain streamlining of the fuselage. This unloads loads the tail rotor, the horse power that would have been used to drive the tailrotor is now avialable for the main rotor to use for lift and thrust. The streamlining is most efficent at some airspeed, probably in the neighborhood of 60kts, that the designers have determined. The streamlining should allow the helicopter to be landed with out tail rotor contol, or drive with a smaller pucker factor margin. The exact procedure is individual to the type of heliocpter, so this is a generic statement of the function of the vert stab in tail rotor failures.
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Loss of tail rotor is a big problem in any helicopter, especially since the vertical fin (which now must provide all your anti-torque) is often reduced in size to reduce blockage of the tail rotor to help increase tail thrust for better crosswind control.
The previous post that discusses the different problems depending on how much hardware is shed is correct, but only in the additional problems that a CG shift bring about, where the tail is immediately a lot lighter at the same time that the tail rotor thrust is entirely gone. For the rest of this discussion, let's assume that the tail rotor thrust is now zero, and no other problem is compounding.
The vertical fin can help in recovery from a loss of tail rotor thrust by providing some right thrust, but it will do almost no good until speeds of about 1.5 Vy, typically about 110 knots in a high speed helo (S-76, Black Hawk), maybe 80 knots is a slow Bell type machine, and maybe 60 knots in a light piston.
This is because the fin area is usually small, and it takes some forward speed for it to generate enough lift (side force) to be much help.
If you try to fly home at higher speed, the increased power you need means that you also need more anti-torque, so you might not make a powered flight situation work.
How do you know? I suggest that if you experience loss of tail thrust in cruise flight, (sharp right yaw in an American helo, left yaw in a French or Russian machine -- I will use the American convention below) get control of the yaw situation first. Lower the collective immediately enough to stop all yaw and allow a steady state descent. Carefully guard your airspeed, try to stay at a high speed autorotative glide speed (about 1.5 Vy in most helos). If all is going poorly, go to full auto and take your chances on the landing. If the glide looks good and yaw is well behaved, you MIGHT try to gently increase power to reduce the rate of descent, while maintaining speed. The aircraft will start to yaw right as power is applied, so you must cross control by applying left bank to keep the heading stabilized. You will probably have to go more nose down because you have much more drag, and you must watch for two big danger signs - excessive yaw like a flat spin, and loss of airspeed indications, where the pitot probe might give up working in the big sideslip. At the first sign of either danger sign, lower the collective pitch and the nose to get the torque down and the speed up.
For most helos, you will not be able to get to level flight because to torque you need will produce an excessive sideslip or even a flat spin (the ultimate problem in all this test pilot heroic stuff). Settle for a reduced rate of descent, since it really helps you extend your choice of landing areas. If you can get to as little as 750 feet per minute descent, and you are doing 100 knots, you can travel 3 miles from 1500 feet, almost 7 miles from 3000.
At the bottom, transition to a reduced collective flare, and make a part auto-part running landing. Don't increase the collective at touchdown unless you have decoupled the engines, as the sudden torque rise will create a big spin, and a real crack-up.
The skills needed to fly out of an anti-torque failure are not trivial, and most pilots are best served by thinking and performing an autorotation, period.
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The previous post that discusses the different problems depending on how much hardware is shed is correct, but only in the additional problems that a CG shift bring about, where the tail is immediately a lot lighter at the same time that the tail rotor thrust is entirely gone. For the rest of this discussion, let's assume that the tail rotor thrust is now zero, and no other problem is compounding.
The vertical fin can help in recovery from a loss of tail rotor thrust by providing some right thrust, but it will do almost no good until speeds of about 1.5 Vy, typically about 110 knots in a high speed helo (S-76, Black Hawk), maybe 80 knots is a slow Bell type machine, and maybe 60 knots in a light piston.
This is because the fin area is usually small, and it takes some forward speed for it to generate enough lift (side force) to be much help.
If you try to fly home at higher speed, the increased power you need means that you also need more anti-torque, so you might not make a powered flight situation work.
How do you know? I suggest that if you experience loss of tail thrust in cruise flight, (sharp right yaw in an American helo, left yaw in a French or Russian machine -- I will use the American convention below) get control of the yaw situation first. Lower the collective immediately enough to stop all yaw and allow a steady state descent. Carefully guard your airspeed, try to stay at a high speed autorotative glide speed (about 1.5 Vy in most helos). If all is going poorly, go to full auto and take your chances on the landing. If the glide looks good and yaw is well behaved, you MIGHT try to gently increase power to reduce the rate of descent, while maintaining speed. The aircraft will start to yaw right as power is applied, so you must cross control by applying left bank to keep the heading stabilized. You will probably have to go more nose down because you have much more drag, and you must watch for two big danger signs - excessive yaw like a flat spin, and loss of airspeed indications, where the pitot probe might give up working in the big sideslip. At the first sign of either danger sign, lower the collective pitch and the nose to get the torque down and the speed up.
For most helos, you will not be able to get to level flight because to torque you need will produce an excessive sideslip or even a flat spin (the ultimate problem in all this test pilot heroic stuff). Settle for a reduced rate of descent, since it really helps you extend your choice of landing areas. If you can get to as little as 750 feet per minute descent, and you are doing 100 knots, you can travel 3 miles from 1500 feet, almost 7 miles from 3000.
At the bottom, transition to a reduced collective flare, and make a part auto-part running landing. Don't increase the collective at touchdown unless you have decoupled the engines, as the sudden torque rise will create a big spin, and a real crack-up.
The skills needed to fly out of an anti-torque failure are not trivial, and most pilots are best served by thinking and performing an autorotation, period.
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Guest
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Nick, I'd like to ask you a rather odd question, given your test pilot background. Would a small drogue chute help with a loss of tail rotor problem?
My thinking is that the drogue could be released from the extreme end of the tail boom (below the tail rotor), and the chute would also need a jetison mechanism. I was wondering if you've ever heard of such an idea.
My thinking is that following the loss of tail rotor thrust, and once the yaw has been stabilized and a descent rate with good forward airspeed established, then the drogue could be released. It seems to me this could help to add additional stability to the yaw so more power and collective could be re-applied. Of course good forward airspeed would have to be maintained for the chute to remain affective in contolling the yaw.
If the chute were effective enough at controlling the yaw so that a small climb rate could be established, then you'd have your choice of landing areas. A run on landing might be easier to accomplish with the chute, and at the very least perhaps you could choose the spot to perform an autorotative landing, which is much safer to perform if you can be selective about the landing area.
Does this idea make any sense?
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Safe flying to you...
[This message has been edited by Flight Safety (edited 01 July 2001).]
My thinking is that the drogue could be released from the extreme end of the tail boom (below the tail rotor), and the chute would also need a jetison mechanism. I was wondering if you've ever heard of such an idea.
My thinking is that following the loss of tail rotor thrust, and once the yaw has been stabilized and a descent rate with good forward airspeed established, then the drogue could be released. It seems to me this could help to add additional stability to the yaw so more power and collective could be re-applied. Of course good forward airspeed would have to be maintained for the chute to remain affective in contolling the yaw.
If the chute were effective enough at controlling the yaw so that a small climb rate could be established, then you'd have your choice of landing areas. A run on landing might be easier to accomplish with the chute, and at the very least perhaps you could choose the spot to perform an autorotative landing, which is much safer to perform if you can be selective about the landing area.
Does this idea make any sense?
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Safe flying to you...
[This message has been edited by Flight Safety (edited 01 July 2001).]
Guest
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I have had two T/R malfunctions. The last one was in an A-Star while on final to an offshore platform. Prior training had taught me how to land after experiencing a T/R malfunction, but not how to get out of the spin. I increased the collective, which initially increased the spin, but I had to avoid the crane on the platform. Started feeding in forward cyclic and eventually got it under control. Not easy on any day, but a little more trying with two passengers screaming like girls. Flew back to the beach with a slight slideslip. Above 40 kts. the aircraft will streamline. This goes for a 206 also. Did a running landing in the grass. Slowed down to 40 kts. on final and slowed it up some more. This initially increases the yaw rate. At the bottom, pulled on power, the nose aligned, and ran it own. I wouldn't do an auto unless you have loss of components. Why give yourself another emergency to deal with.
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GulfPLt, you're experience reminds me of an idea I've often had regarding loss of T/R.
I saw a video about a year ago of an ANG Blackhawk performing a rescue of an injured climber in a small but deep rocky ravine (if I remember this correctly). The ravine was too small to land the helo in, and the rocky sides were so narrow they would have caused rotor contact if a landing were attempted. Surrounding this small ravine on 3 sides was fairly flat terrain.
In the video, the Blackhawk had just gotten into position to lower the winch cable, when suddenly it lost tail rotor thrust. The Blackhawk began to spin, and for some reason that was not clear to me, it went straight down into the ravine in a slow flat spin, destoying the main rotor in the process as it contacted the rocky walls. The airframe landed right side up at the bottom and all the crew survived (some with injuries), and another Blackhawk had to arrive on the scene to winch all persons out of the ravine.
What puzzled me was why the pilot didn't apply more collective and climb, so he could straighten it out with a little altitude and attempt a landing on the surrounding flat terrain. I know this would have increased the spin rate, but as long as the airframe structure can tolerate the increased spin, this would have been far better than destroying the helo in the rocky ravine.
So that's my idea, why can't pilots do what "GulfPLt" did, and just climb if needed while enduring a higher spin rate, if that's what it takes to get out of trouble following the loss of T/R, especially at low altitude above an uninviting landing area?
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Safe flying to you...
I saw a video about a year ago of an ANG Blackhawk performing a rescue of an injured climber in a small but deep rocky ravine (if I remember this correctly). The ravine was too small to land the helo in, and the rocky sides were so narrow they would have caused rotor contact if a landing were attempted. Surrounding this small ravine on 3 sides was fairly flat terrain.
In the video, the Blackhawk had just gotten into position to lower the winch cable, when suddenly it lost tail rotor thrust. The Blackhawk began to spin, and for some reason that was not clear to me, it went straight down into the ravine in a slow flat spin, destoying the main rotor in the process as it contacted the rocky walls. The airframe landed right side up at the bottom and all the crew survived (some with injuries), and another Blackhawk had to arrive on the scene to winch all persons out of the ravine.
What puzzled me was why the pilot didn't apply more collective and climb, so he could straighten it out with a little altitude and attempt a landing on the surrounding flat terrain. I know this would have increased the spin rate, but as long as the airframe structure can tolerate the increased spin, this would have been far better than destroying the helo in the rocky ravine.
So that's my idea, why can't pilots do what "GulfPLt" did, and just climb if needed while enduring a higher spin rate, if that's what it takes to get out of trouble following the loss of T/R, especially at low altitude above an uninviting landing area?
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Safe flying to you...
Guest
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Regarding the T /R loss. Two cases are to take into account: loss of the T/R itself or loss of the control ( linkage between pedals and rotor).
The first case is worst because, there is no more thrust anymore and the stability of the fuselage is ensured only by the fin, if the helicopter is equipped with such device. In such a case, if the failure occurs in hover, there is no chance to recover the helicopter as the torque, at the occurrence is too high. If the failure occurs in flight, the helo is flyable but the only solution to rejoin the ground is autorotation.
In case of loss of control, the case is less dramatic as there is a remaining thrust. I remind my instructors teaching me the high side loss or low side loss, with specifics procedures according to the case. Modern helicopters have sometimes a damper located on the T/R system which set the T/R blade pitch angle at a standard angle in order to provides a permanent thrust. In such a case, running landing can be attempted with good chances of success.
Take a Dauphin. With its huge fin, loss of T/R control in flight could be unnoticced. It is possible, but not advised, to land such helo in hover while experiencing a T/R loss of control if the helo is light and there is a 15+ knots of wind set exactly on the RH side of the helo during a low flat approcah to land.
Cheers
The first case is worst because, there is no more thrust anymore and the stability of the fuselage is ensured only by the fin, if the helicopter is equipped with such device. In such a case, if the failure occurs in hover, there is no chance to recover the helicopter as the torque, at the occurrence is too high. If the failure occurs in flight, the helo is flyable but the only solution to rejoin the ground is autorotation.
In case of loss of control, the case is less dramatic as there is a remaining thrust. I remind my instructors teaching me the high side loss or low side loss, with specifics procedures according to the case. Modern helicopters have sometimes a damper located on the T/R system which set the T/R blade pitch angle at a standard angle in order to provides a permanent thrust. In such a case, running landing can be attempted with good chances of success.
Take a Dauphin. With its huge fin, loss of T/R control in flight could be unnoticced. It is possible, but not advised, to land such helo in hover while experiencing a T/R loss of control if the helo is light and there is a 15+ knots of wind set exactly on the RH side of the helo during a low flat approcah to land.
Cheers
Guest
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Ancient Pelican-he lost the rotor completely, it detached itself from the tail.
The crew got a reading saying it was stuck, but saw it fall/spin away.
you all keep saying that you can still fly the helo. At high speeds I can understand this, but how can you keep it straight during landing?
The only landing I can see is a running one-yes?
Thanx for the replies-very interesting.
DT
The crew got a reading saying it was stuck, but saw it fall/spin away.
you all keep saying that you can still fly the helo. At high speeds I can understand this, but how can you keep it straight during landing?
The only landing I can see is a running one-yes?
Thanx for the replies-very interesting.
DT
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See these recent threads which have appeared on Rotorheads :
Tail Rotor Problems
Tailrotor Fun $#@! - Harry, did you get any responses and have you had a chance to collate them ?
As I've never had a t/r failure for real, I don't suppose there's someone out there who has access to the right people and the right toys to play with this sort of stuff in the sim, is there ? Perhaps a bottle of whisky for the best answer ?
[This message has been edited by The Nr Fairy (edited 01 July 2001).]
Tail Rotor Problems
Tailrotor Fun $#@! - Harry, did you get any responses and have you had a chance to collate them ?
As I've never had a t/r failure for real, I don't suppose there's someone out there who has access to the right people and the right toys to play with this sort of stuff in the sim, is there ? Perhaps a bottle of whisky for the best answer ?
[This message has been edited by The Nr Fairy (edited 01 July 2001).]
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I think you will get a dozen different answers to the same question with this one, depending on individual's experience.
Touch wood, I have not experienced a tail rotor problem though I have spoken to several pilots who have and I also include stuck pedals occasionally on Proficiency checks.
What is evident, with a stuck pedal, is that the transition from seemingly controlled flight to loss of control can be very rapid and with little warning. In the event, disciplining your actions against your instincts can be dificult.
The yaw rate that could develop with total loss of thrust must be huge and extremely disorientating. I suspect that if you were to exacerbate it by pulling collective to climb, you could get yourself really 'lost in space' and the rate of yaw may not beacome recoverable despite any actions. Throw in loss of componants and the ensuing C of G shift and things get really interesting. I could imagine that with a teetering head there would be a real risk of blade strike to trying to dive on speed while rotating like a Derbisher.
I know, personally, 4 pilots who have experienced loss of tail rotor componants and thrust in 4 different Puma and Super Pumas. In every case they were in the cruise or a shallow descent, with good speed. In every case they rotated rapidly about three axes and in two case crashed/ditched out of control. The other two were recovered to autorotation only after closing the speed select levers (collective insufficient on its own) and successful ditchings followed.
I also read an article in the Navy's flight safety magazine, written by the crew of the EH101 that crashed following a tail rotor control failure at 10,000. The 4 crew bailed out after all attempts to regain control were lost. The description of the rotational g forces and attendant escape problems was particularly interesting!
So, basically, I think it would be true to say that a tail roror failure may not be the end of the world and there are many cases of successful recoveries from such problems (eg Gulfplt). However, I think it is niaive to think that it is a straight forward problem that can be recovered from using a standard technique. Glib remarks like "I don't understand why they didn't JUST pull power and gain height" seem to show a lack of understanding of the nature and seriousness of the problem.
BTW, I don't know if you are at the FSI Bell facility,FSI, but if so I do think the simulation of tail rotor problem in the 212/412 sim is a touch optimistic. You come away (or could do) thinking it would be no problem at all.
Like the idea of the drogue shoot, FW have used them for years for spin testing.
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Another day in paradise
Touch wood, I have not experienced a tail rotor problem though I have spoken to several pilots who have and I also include stuck pedals occasionally on Proficiency checks.
What is evident, with a stuck pedal, is that the transition from seemingly controlled flight to loss of control can be very rapid and with little warning. In the event, disciplining your actions against your instincts can be dificult.
The yaw rate that could develop with total loss of thrust must be huge and extremely disorientating. I suspect that if you were to exacerbate it by pulling collective to climb, you could get yourself really 'lost in space' and the rate of yaw may not beacome recoverable despite any actions. Throw in loss of componants and the ensuing C of G shift and things get really interesting. I could imagine that with a teetering head there would be a real risk of blade strike to trying to dive on speed while rotating like a Derbisher.
I know, personally, 4 pilots who have experienced loss of tail rotor componants and thrust in 4 different Puma and Super Pumas. In every case they were in the cruise or a shallow descent, with good speed. In every case they rotated rapidly about three axes and in two case crashed/ditched out of control. The other two were recovered to autorotation only after closing the speed select levers (collective insufficient on its own) and successful ditchings followed.
I also read an article in the Navy's flight safety magazine, written by the crew of the EH101 that crashed following a tail rotor control failure at 10,000. The 4 crew bailed out after all attempts to regain control were lost. The description of the rotational g forces and attendant escape problems was particularly interesting!
So, basically, I think it would be true to say that a tail roror failure may not be the end of the world and there are many cases of successful recoveries from such problems (eg Gulfplt). However, I think it is niaive to think that it is a straight forward problem that can be recovered from using a standard technique. Glib remarks like "I don't understand why they didn't JUST pull power and gain height" seem to show a lack of understanding of the nature and seriousness of the problem.
BTW, I don't know if you are at the FSI Bell facility,FSI, but if so I do think the simulation of tail rotor problem in the 212/412 sim is a touch optimistic. You come away (or could do) thinking it would be no problem at all.
Like the idea of the drogue shoot, FW have used them for years for spin testing.
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Another day in paradise
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Nick Lappos
Thanks for the post. Hope to read more contributions from you from time to time.
Nick Lappos is Sikorsky's Assistant Chief Test Pilot. A former U.S. Army Warrant Officer and a combat veteran of Vietnam, he flew Cobra attack helicopters in D Troop, 1st Squadron, 1st Cavalry. An Aerospace Engineering graduate of Georgia Tech, he came to Sikorsky Aircraft in 1973. Since then, he has flown in the YUH-60 Black Hawk program, flown the first flight and structural shakedown of the S-76, the "Shadow" cockpit research aircraft, the adaptive fuel control experimental aircraft, and the "Fantail" fan-in-fin demonstrator. He is now assigned to the RAH-66 Comanche project, where he is part of the pilot team flying the shakedown and envelope expansion.
In 1988, the Society of Experimental Test Pilots awarded Nick their Tenhoff Award for the most outstanding paper at the Annual Symposium. The American Helicopter Society awarded Nick their Feinberg award as most outstanding pilot for his contribution to the understanding of maneuverability in 1989 and again in 1998 (as part of the Comanche Team), and in 1994 he was named a Fellow of the Society. He was a member of the American Helicopter Society's Handling Qualities committee and AGARD Working Group #19 (Functional Agility), and is currently a member of the NASA/FAA Air Traffic Management R&D Executive Steering Committee.
Nick has written a number of technical papers, and articles for magazines such as "Rotor and Wing," "Interavia," and "Defense Helicopter." He holds 15 U.S. and a number of foreign patents on flight and engine controls and cockpit displays.
Photo of Apache during initial flight tests.
Thanks for the post. Hope to read more contributions from you from time to time.
Nick Lappos is Sikorsky's Assistant Chief Test Pilot. A former U.S. Army Warrant Officer and a combat veteran of Vietnam, he flew Cobra attack helicopters in D Troop, 1st Squadron, 1st Cavalry. An Aerospace Engineering graduate of Georgia Tech, he came to Sikorsky Aircraft in 1973. Since then, he has flown in the YUH-60 Black Hawk program, flown the first flight and structural shakedown of the S-76, the "Shadow" cockpit research aircraft, the adaptive fuel control experimental aircraft, and the "Fantail" fan-in-fin demonstrator. He is now assigned to the RAH-66 Comanche project, where he is part of the pilot team flying the shakedown and envelope expansion.
In 1988, the Society of Experimental Test Pilots awarded Nick their Tenhoff Award for the most outstanding paper at the Annual Symposium. The American Helicopter Society awarded Nick their Feinberg award as most outstanding pilot for his contribution to the understanding of maneuverability in 1989 and again in 1998 (as part of the Comanche Team), and in 1994 he was named a Fellow of the Society. He was a member of the American Helicopter Society's Handling Qualities committee and AGARD Working Group #19 (Functional Agility), and is currently a member of the NASA/FAA Air Traffic Management R&D Executive Steering Committee.
Nick has written a number of technical papers, and articles for magazines such as "Rotor and Wing," "Interavia," and "Defense Helicopter." He holds 15 U.S. and a number of foreign patents on flight and engine controls and cockpit displays.
Photo of Apache during initial flight tests.Guest
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this is a video clip of a t/r failure at hover. Its pretty sobering.
http://www.helis.com/movies/taiwan.rm
http://www.helis.com/movies/taiwan.rm
Guest
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Ties in with what I was trying to say. "why didn't they just pull pitch and fly away?" Yeah, right!
In fact the initial problem wasn't a tail rotor one. The a/c had a P2 leak due to a maintenance error, when it tried to come to the hover the power loss meant it started to sink and the Nr drooped. The pilot tried to arrest the descent by pulling more collective and they settled on to the water, at which point the tail rotor drive shaft failed as the fenestron started sucking water rather than air. The newly released power to the main transmission was sufficient for the a/c to get airborne again, with the pilot still pulling, at which point the a/c started rotating freely. Sadly, one of the pilots drowned.
Now you can see why check lists for a failure in the hover often say; "lower the collective immediately and accept the yaw". If you don't, it's going to get a lot worse very quickly.
PS The Taiwan 365 info came directly from Eurocopter in response to a question about fenestron power consumption in the hover (I'm writing from Marignane)
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Another day in paradise
In fact the initial problem wasn't a tail rotor one. The a/c had a P2 leak due to a maintenance error, when it tried to come to the hover the power loss meant it started to sink and the Nr drooped. The pilot tried to arrest the descent by pulling more collective and they settled on to the water, at which point the tail rotor drive shaft failed as the fenestron started sucking water rather than air. The newly released power to the main transmission was sufficient for the a/c to get airborne again, with the pilot still pulling, at which point the a/c started rotating freely. Sadly, one of the pilots drowned.
Now you can see why check lists for a failure in the hover often say; "lower the collective immediately and accept the yaw". If you don't, it's going to get a lot worse very quickly.
PS The Taiwan 365 info came directly from Eurocopter in response to a question about fenestron power consumption in the hover (I'm writing from Marignane)
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Another day in paradise
Guest
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212man, where did I EVER suggest a modification to SOPs, WHERE?
My ideas run along the line that I'm convinced that more can be done in helo design to make loss of T/R more survivable (both for pilots and airframes). Obviously this puts the ideas in the realm of experimental flight test, where they belong. Clearly ANY new procedure has to be thoroughly understood through analysis and flight test before incorporating them into ANY SOP or emergency procedure. You're not foolish enough to violate this fundamental wisdom of flight, and neither am I. Enough said.
Anyway, FWIW, I was already having second thoughts about the drogue chute idea, as I see 2 problems already. One, a tether of any length could allow the chute to get caught in either the tail rotor or the main rotor with bad results following. Second, in forward flight with any airspeed, the chute could get caught in the rotor downwash causing an interesting pitch problem.
A third idea is that it might be helpful to design the tailboom as a structure that's both fairly narrow with broader flatter sides. This might help in 2 areas. One, it could add more keel area to the rear of the airframe, thus augmenting the vertical stabilizer in yaw control in forward flight after T/R loss occures. Second, if you added collective to climb out of a bad situation, the broad flat sides could help control the spin rate by offering significant drag in the spin (all to be tested and validated in fligh test of course). The tailboom and remaining airframe structure would have to be stressed for the spin rate produced by a slow climb after loss of T/R, if such a capability were to be designed into an airframe.
The main subject of this thread was landing after a loss of T/R. I think its fair to discuss both ways to accomplish this with current SOPs, and what could possibly be done in the future to improve this particular situation in helo airframes.
All I know is that climbing out with increased spin rate after T/R loss is a reasonable idea with some merit in certain circumstances, as it surely kept GulfPLt from getting tangled up with a crane. His passengers may have been screaming like girls, but at least they were able to safely clean out their drawers after he landed.
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Safe flying to you...
[This message has been edited by Flight Safety (edited 02 July 2001).]
My ideas run along the line that I'm convinced that more can be done in helo design to make loss of T/R more survivable (both for pilots and airframes). Obviously this puts the ideas in the realm of experimental flight test, where they belong. Clearly ANY new procedure has to be thoroughly understood through analysis and flight test before incorporating them into ANY SOP or emergency procedure. You're not foolish enough to violate this fundamental wisdom of flight, and neither am I. Enough said.
Anyway, FWIW, I was already having second thoughts about the drogue chute idea, as I see 2 problems already. One, a tether of any length could allow the chute to get caught in either the tail rotor or the main rotor with bad results following. Second, in forward flight with any airspeed, the chute could get caught in the rotor downwash causing an interesting pitch problem.
A third idea is that it might be helpful to design the tailboom as a structure that's both fairly narrow with broader flatter sides. This might help in 2 areas. One, it could add more keel area to the rear of the airframe, thus augmenting the vertical stabilizer in yaw control in forward flight after T/R loss occures. Second, if you added collective to climb out of a bad situation, the broad flat sides could help control the spin rate by offering significant drag in the spin (all to be tested and validated in fligh test of course). The tailboom and remaining airframe structure would have to be stressed for the spin rate produced by a slow climb after loss of T/R, if such a capability were to be designed into an airframe.
The main subject of this thread was landing after a loss of T/R. I think its fair to discuss both ways to accomplish this with current SOPs, and what could possibly be done in the future to improve this particular situation in helo airframes.
All I know is that climbing out with increased spin rate after T/R loss is a reasonable idea with some merit in certain circumstances, as it surely kept GulfPLt from getting tangled up with a crane. His passengers may have been screaming like girls, but at least they were able to safely clean out their drawers after he landed.
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Safe flying to you...
[This message has been edited by Flight Safety (edited 02 July 2001).]
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Army grounds Apache fleet for safety checks
WASHINGTON (Reuters) - The U.S. Army has grounded its entire fleet of Apache attack helicopters to inspect the tail rotors on the aircraft, an Army spokesman said Thursday.
The inspection was ordered as a precautionary measure following a June 11 incident involving a faulty tail rotor on an Israel Apache, spokesman Thomas Collins said.
"This action is a precautionary result of an Israeli AH-64A aircraft incident where the tail rotor head assembly separated from the aircraft in flight,'' Collins said.
Collins said each inspection would take about 30 minutes and would determine whether the tail rotor needed to be replaced. He could not say when the inspections began or how long they would take to complete.
"We're trying to accomplish the inspection as quickly as possible, but we also have to be as thorough as possible because the safety of our soldiers is of paramount importance,'' he said.
Collins said the tail rotor on the Israeli helicopter came apart during a routine flight. The aircraft landed safely at an Israeli air base, he said, adding that an investigation was under way to determine the cause of that incident.
The AH-64 Apache attack helicopters, built by Boeing Co (BA.N), have been grounded twice before, both times to check potentially dangerous tail rotor problems. The tail rotor controls the aircraft's ability to turn left or right.
The fleet was grounded in December 2000 after the discovery of a faulty tail rotor "swashplate'' assembly and in November 1999 after the Army found suspect rotor bearings and transmission problems following crashes.
Six Army Apaches crashed in 1999. Army officials said investigators found that a heating process used by Boeing to make the bearing assembly extra hard led to stress corrosion fractures in the bearings. ^ REUTERS
WASHINGTON (Reuters) - The U.S. Army has grounded its entire fleet of Apache attack helicopters to inspect the tail rotors on the aircraft, an Army spokesman said Thursday.
The inspection was ordered as a precautionary measure following a June 11 incident involving a faulty tail rotor on an Israel Apache, spokesman Thomas Collins said.
"This action is a precautionary result of an Israeli AH-64A aircraft incident where the tail rotor head assembly separated from the aircraft in flight,'' Collins said.
Collins said each inspection would take about 30 minutes and would determine whether the tail rotor needed to be replaced. He could not say when the inspections began or how long they would take to complete.
"We're trying to accomplish the inspection as quickly as possible, but we also have to be as thorough as possible because the safety of our soldiers is of paramount importance,'' he said.
Collins said the tail rotor on the Israeli helicopter came apart during a routine flight. The aircraft landed safely at an Israeli air base, he said, adding that an investigation was under way to determine the cause of that incident.
The AH-64 Apache attack helicopters, built by Boeing Co (BA.N), have been grounded twice before, both times to check potentially dangerous tail rotor problems. The tail rotor controls the aircraft's ability to turn left or right.
The fleet was grounded in December 2000 after the discovery of a faulty tail rotor "swashplate'' assembly and in November 1999 after the Army found suspect rotor bearings and transmission problems following crashes.
Six Army Apaches crashed in 1999. Army officials said investigators found that a heating process used by Boeing to make the bearing assembly extra hard led to stress corrosion fractures in the bearings. ^ REUTERS
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I wanted to try and summarize these weird ideas on loss of T/R I've posted, and relate them to what I think is the current state of dealing with the loss of T/R in the helo industry. My opinion is that dealing with the loss of T/R thrust is not nearly as well developed as it can be, and this poses some safety problems.
In the Penny Farthing helo configuration, we all know that the loss of T/R thrust is a significant failure that no pilot wants to face, but all pilots should be prepared for. For this discussion I'll focus mainly on total loss of T/R thrust and exclude jammed pedals, stuck cables, etc, and those failures with CG changes.
There are 3 basic methods of responding to this failure, which deals with the loss of the anti-torque required for directional control of a Penny Farthing helo.
Method 1 Reduce the Main Rotor torque to zero. This is the "reduce the collective, chop the throttle and autorotate to a landing" method. It is the method of choice for failure in the hover, and for inexperienced pilots. This is taught by all flight instructors to new pilots, and all new pilots learn autorotative techniques in training.
Pros: Stops the airframe from experiencing severe yawing. Relies on the autorotative ablility of the airframe for a "safe" landing. All pilots have a degree of training in autorotation. Most simple recovery technique.
Cons:Technique varies by airframe type. Not all airframes are created equal in autorotative landing ability. The choice of landing area is severely restricted.
Method 2 Low to mid range Main Rotor torque method. This is the run-on landing method where forward flight with a controlled descent rate at sufficient airspeed provides enough anti-torque for directional control, to allow a run-on landing in either grass or on concrete.
There seems to be a lot a gray area in this method. Not all airframes are well suited to this method. Not all pilots are trained in this method. This method also generally requires a lot of skill from the pilot (Nick Lappos spoke eloquently on this in his earlier post). This method is generally not well developed (with certain exceptions), in either airframe capability or in pilot training.
Pros: The pilot has much greater choice of landing areas. The airframe usually suffers far less damage upon landing.
Cons: Requires a lot of pilot skill to accomplish. Can only be used when some altitude is present at failure. Not all helos are well suited to this method. Not all pilots are capable of this method. Maintaining altitude (or a slight climb) may only be possible with significant forward airspeed, and only in certain airframes.
Method 3 High Main Rotor torque method. This is the climb out from either low speed or a hover method. This method is used to climb out of a bad landing area at low altitude, so a transition to method 2 can be made. This is the method GulfPLt used in the event of his earlier post.
This method is not well understood at all, and presents considerable dangers. Anecdotal evidence suggests that this method does work at times, but accident investigations show that it often does not work.
There is usually not enough alternative anti-torque available with this method to prevent spinning of the airframe, as spinning of the airframe is considered quite dangerous in a helo.
Pros: Can prevent a forced landing in an inhospitable area during a low altitude failure.
Cons: Requires great skill from the pilot. Requires an airframe, avionics, engines, fuel system, etc, that can tolerate a high torque induced flat spin. Persons can be thrown out of the airframe while spinning if not belted in. (Added in edit) A pilot can become disoriented in a spin. Structural failure of the airframe could occur in a spin. Collision with an obstacle might occur in the spin.
Conclusion
I guess my final conclusion is that not enough has been done to help helo pilots deal with the issue of loss of T/R. Most new or low time pilots are at a loss as to what do if a loss of T/R event occures except to use Method 1 discribed above, and the results of this method are not always satisfactory. Method 2 is highly useful in certain circumstances, but many pilots are not trained for it, and some airframes are not built to use this method without making great demands on the skills of the pilots.
Method 3 does have some merits in my opinion, but the demands on both pilot and airframe are even greater than in method 2. When I posted some of the ideas previously, it was an attempt to think of ways to better improve the ability of all pilots (through airframe improvements) to perfrom a satisfactory recovery from a loss of T/R event. I also don't understand several things related to method 3. Why does a spinning airframe HAVE to be dangerous (apart from not being belted in, and poor directional control near obstacles). FW pilots practice spin recovery all the time. But as GulfPLt pointed out in his post, he had no training in how to recover a helo from a spin. Why are pilots not trained for this? Are there methods to prevent (or at least limit) the pilot disorientation of a spin? Is there any aero-medical research on this?
Reading the other thread referred to by "The Nr Fairy" demonstrates just how daunting this event is to nearly all helo pilots, and it's my opinion that more can done to improve both helo airframes and a pilot's training to help a pilot get through a loss of T/R event safely.
To vfrpilotpb, I took the word "some" out of the text, as you are correct.
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Safe flying to you...
[This message has been edited by Flight Safety (edited 02 July 2001).]
In the Penny Farthing helo configuration, we all know that the loss of T/R thrust is a significant failure that no pilot wants to face, but all pilots should be prepared for. For this discussion I'll focus mainly on total loss of T/R thrust and exclude jammed pedals, stuck cables, etc, and those failures with CG changes.
There are 3 basic methods of responding to this failure, which deals with the loss of the anti-torque required for directional control of a Penny Farthing helo.
Method 1 Reduce the Main Rotor torque to zero. This is the "reduce the collective, chop the throttle and autorotate to a landing" method. It is the method of choice for failure in the hover, and for inexperienced pilots. This is taught by all flight instructors to new pilots, and all new pilots learn autorotative techniques in training.
Pros: Stops the airframe from experiencing severe yawing. Relies on the autorotative ablility of the airframe for a "safe" landing. All pilots have a degree of training in autorotation. Most simple recovery technique.
Cons:Technique varies by airframe type. Not all airframes are created equal in autorotative landing ability. The choice of landing area is severely restricted.
Method 2 Low to mid range Main Rotor torque method. This is the run-on landing method where forward flight with a controlled descent rate at sufficient airspeed provides enough anti-torque for directional control, to allow a run-on landing in either grass or on concrete.
There seems to be a lot a gray area in this method. Not all airframes are well suited to this method. Not all pilots are trained in this method. This method also generally requires a lot of skill from the pilot (Nick Lappos spoke eloquently on this in his earlier post). This method is generally not well developed (with certain exceptions), in either airframe capability or in pilot training.
Pros: The pilot has much greater choice of landing areas. The airframe usually suffers far less damage upon landing.
Cons: Requires a lot of pilot skill to accomplish. Can only be used when some altitude is present at failure. Not all helos are well suited to this method. Not all pilots are capable of this method. Maintaining altitude (or a slight climb) may only be possible with significant forward airspeed, and only in certain airframes.
Method 3 High Main Rotor torque method. This is the climb out from either low speed or a hover method. This method is used to climb out of a bad landing area at low altitude, so a transition to method 2 can be made. This is the method GulfPLt used in the event of his earlier post.
This method is not well understood at all, and presents considerable dangers. Anecdotal evidence suggests that this method does work at times, but accident investigations show that it often does not work.
There is usually not enough alternative anti-torque available with this method to prevent spinning of the airframe, as spinning of the airframe is considered quite dangerous in a helo.
Pros: Can prevent a forced landing in an inhospitable area during a low altitude failure.
Cons: Requires great skill from the pilot. Requires an airframe, avionics, engines, fuel system, etc, that can tolerate a high torque induced flat spin. Persons can be thrown out of the airframe while spinning if not belted in. (Added in edit) A pilot can become disoriented in a spin. Structural failure of the airframe could occur in a spin. Collision with an obstacle might occur in the spin.
Conclusion
I guess my final conclusion is that not enough has been done to help helo pilots deal with the issue of loss of T/R. Most new or low time pilots are at a loss as to what do if a loss of T/R event occures except to use Method 1 discribed above, and the results of this method are not always satisfactory. Method 2 is highly useful in certain circumstances, but many pilots are not trained for it, and some airframes are not built to use this method without making great demands on the skills of the pilots.
Method 3 does have some merits in my opinion, but the demands on both pilot and airframe are even greater than in method 2. When I posted some of the ideas previously, it was an attempt to think of ways to better improve the ability of all pilots (through airframe improvements) to perfrom a satisfactory recovery from a loss of T/R event. I also don't understand several things related to method 3. Why does a spinning airframe HAVE to be dangerous (apart from not being belted in, and poor directional control near obstacles). FW pilots practice spin recovery all the time. But as GulfPLt pointed out in his post, he had no training in how to recover a helo from a spin. Why are pilots not trained for this? Are there methods to prevent (or at least limit) the pilot disorientation of a spin? Is there any aero-medical research on this?
Reading the other thread referred to by "The Nr Fairy" demonstrates just how daunting this event is to nearly all helo pilots, and it's my opinion that more can done to improve both helo airframes and a pilot's training to help a pilot get through a loss of T/R event safely.
To vfrpilotpb, I took the word "some" out of the text, as you are correct.
------------------
Safe flying to you...
[This message has been edited by Flight Safety (edited 02 July 2001).]
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Flight Safety,
I am a reasonably low time Heli pilot covering the range from R22,R44 and B206, here in the UK in order for you to get your Licence you must be able to demonstrate to the Flight Examiner that you are fully capable of enterings and controling autorotaion and to land from that Auto,as opposed to your comment that some knowledge of Auto is taught, however it seems that because of the complexity of simulating T/R failure the only thing that is covered during civillian training is the Cfi jamming the control's so you get some feel of what is going to be the problem of directional control as speed decays, you soon realise that engine speed is the solution to keeping straight, but in the main we civvie pilots are not able to do much more than ask, read and talk to very experianced pilots about the problem of tail rotor failure.
Being interested in this from a selfish , safety of my backside point of view, I would ask that "Ancient Pelican or Nick Lappos" PLEASE give us the benifit of their huge experience in this area (T/R Failure) so some of us less experienced pilots could benifit from their knowledge , possible AP has more than anyone , as this thread has ben told of the total loss of his TR, and he is still posting here, that indicates his ability to comment with authority.
My Regards
I am a reasonably low time Heli pilot covering the range from R22,R44 and B206, here in the UK in order for you to get your Licence you must be able to demonstrate to the Flight Examiner that you are fully capable of enterings and controling autorotaion and to land from that Auto,as opposed to your comment that some knowledge of Auto is taught, however it seems that because of the complexity of simulating T/R failure the only thing that is covered during civillian training is the Cfi jamming the control's so you get some feel of what is going to be the problem of directional control as speed decays, you soon realise that engine speed is the solution to keeping straight, but in the main we civvie pilots are not able to do much more than ask, read and talk to very experianced pilots about the problem of tail rotor failure.
Being interested in this from a selfish , safety of my backside point of view, I would ask that "Ancient Pelican or Nick Lappos" PLEASE give us the benifit of their huge experience in this area (T/R Failure) so some of us less experienced pilots could benifit from their knowledge , possible AP has more than anyone , as this thread has ben told of the total loss of his TR, and he is still posting here, that indicates his ability to comment with authority.
My Regards
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Flight Safety,
Your goal is an admirable one, but one critical reaction of a spinning helicoper is the force of airframe drag. When a helicopter spins, in particular, the tail boom and vertical fin (but also the cabin area) act to roll the helicopter over. This is due to the fact the boom and fin are positioned below the level of the rotor head producing a coupling that is detrimental to the control of the helicopter. In nearly every case the helicopter will bank over, as it spins, to the point where either blade / boom contact is made or the disk is tilted to near vertical where it cannot support the weight of the aircraft.
One other point is that in most cases you could not posibly translate from your method 3 to method 2 in a developed spin. The ability of a human to make the control inputs necessary to keep a helicopter upright and accelerating at the same time whilst spinning is basically out of our reach. Not only that, but the rate at which our pilot will be required to go from cyclic stop to cyclic stop will be faster than the rate the control servos will allow, he will now be fighting the hydraulics as well.
The last point may not be as relevent on our modern machines now with hingless or rigid rotor systems etc, but more often than not you will come to grief if you try it in a 206 or 47 or similar.
Enough said, my point really is to highlight the fact that the helicopter will most likely NOT stay spinning in one plane, if power is applied during a tail rotor failure in the hover or at slow speed.
Cheers
Your goal is an admirable one, but one critical reaction of a spinning helicoper is the force of airframe drag. When a helicopter spins, in particular, the tail boom and vertical fin (but also the cabin area) act to roll the helicopter over. This is due to the fact the boom and fin are positioned below the level of the rotor head producing a coupling that is detrimental to the control of the helicopter. In nearly every case the helicopter will bank over, as it spins, to the point where either blade / boom contact is made or the disk is tilted to near vertical where it cannot support the weight of the aircraft.
One other point is that in most cases you could not posibly translate from your method 3 to method 2 in a developed spin. The ability of a human to make the control inputs necessary to keep a helicopter upright and accelerating at the same time whilst spinning is basically out of our reach. Not only that, but the rate at which our pilot will be required to go from cyclic stop to cyclic stop will be faster than the rate the control servos will allow, he will now be fighting the hydraulics as well.
The last point may not be as relevent on our modern machines now with hingless or rigid rotor systems etc, but more often than not you will come to grief if you try it in a 206 or 47 or similar.
Enough said, my point really is to highlight the fact that the helicopter will most likely NOT stay spinning in one plane, if power is applied during a tail rotor failure in the hover or at slow speed.
Cheers