Tail rotor drive failure video
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Where is the plane?
I watched the video over and over again but couldn't see the plane! 
I guess it must have been behind the smoking helicopter
Glad the pilot made it out ok
I guess it must have been behind the smoking helicopter
Glad the pilot made it out ok
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You can see how cool he was, punching off the load away from the building in the cleared out area, then holding it level and allowing it to turn as he lined up a clear area to land in, lowering altitude while spinning until he was about 50 feet (too high, frankly, but far far easier to judge from here then from in his shoes). He cut the throttle there, stopped rotating and then settled down, running out of rpm and control at about 25 feet, where the forward CG caused the nose to pitch over (while he was probably on the aft cyclic stops.)\Hard landing and he walked away. He gets a solid A on that whole thing!
I talked to the pilot about a week after the incident. What absolutely amazed me was his humility about the whole thing. A couple of times he expressed genuine sadness over not being able to land safely and causing the aircraft to be damaged as it was. He gave a very detailed and graphic description of what happened and how he tried to cope with it. As I recall, he was trying to make it to a flat spot but just could not get there.
The salient point of his whole story was that of "flying the machine and thinking about what he was doing".
As Nick rightly says....Grade A! Gold star...step to the front of the class!
The salient point of his whole story was that of "flying the machine and thinking about what he was doing".
As Nick rightly says....Grade A! Gold star...step to the front of the class!
Gnome de PPRuNe
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I saw this vid on TV some time back but the bu@@ers didn't say (or I missed it) what happened to the crew - it's nice to finally hear that it worked out well.
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I was impressed by how quickly the rotation stopped with the throttle chop. Sadly matched by an equally rapid Nr decay
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topendtorque asked about the phrase, "at about 25 feet, where the forward CG caused the nose to pitch over"
Some more details on the diagnosis, kind of walking through the aerodynamics of the landing:
You can see how cool he was, punching off the load away from the building in the cleared out area.
He obviously knew he was too high to just cut the throttle, and he saw that the rotation rate was not unmanageable, so he decided to ride it out by holding it level and allowing it to turn as he lined up a clear area to land in and reduced altitude. This was a conscious piloting act to just allow the turns, but also fly the aircraft down while spinning. It also means that he had to sweep the cyclic around as the aircraft rotated, so that the aircraft stayed level. Remember that the cyclic needs to be put a bit into the wind, otherwise the aircraft attitude will rise and dip and wallow as the rotor is spun around, as the part of the rotor that is upwind is lifted by the wind. That this wallowing didn't happen indicates that he was sweeping the cyclic around in the cockpit to keep the upwind part of the disk down. If you stood outside the aircraft, you would see that he was simply keeping the cyclic into the wind as the aircraft rotated. I had to do this when I did the "snap turns" in the Fantail and Comanche, it is surprisingly easy to get the hang of it with practice, and hard to do when you have to learn it while hovering over an office building!
He held this approach technique until he was about 50 feet above the ground, when he choce to cut the throttle. This was a bit too high, frankly, but is far far easier to judge from this key board then from in his shoes. He cut the throttle there, which immediately stopped the rotating. Of course it does, the turning is powered by the torque of the main rotor, take that torque away and the spin is immediately countered by the slight drag of the main transmission, which acts to make the fuselage rotate WITH the rotor.
The aircraft then settled down in a hovering autorotation, when it ran out of rpm at maybe 25 feet. The allowable CG envelope is a function of cyclic control power, where the cyclic has the control to overcome the moment from the forward (or aft) CG. In this case, the forward CG (lost tail rotor parts) required more control than the low low rotor speed could deliver at about 25 feet, so this caused the nose to pitch over (while he was probably on the aft cyclic stops.) He had a hard landing and he walked away.
He gets a solid A on that whole thing!
A similar take:
A Sikorsky Test Pilot named Cliff Brown had a tail rotor failure in an S-61N while flying with a foreign pilot, they were stabilized in a 100 foot hover over the water. He did much the same thing, riding the aircraft down to a managable 10 foot altitude before cutting the throttles and landing without further damage. He had to shout at the CP to keep him from moving the engine levers, "Stop! I will tell you when to cut them!!" he said. At ten feet above the water, he looked at the guy and said, "Now you can cut them!"
Cliff is well known in USAF circles because during a hot combat rescue in Korea, he got out of the helo to take a leak in the LZ. The rescuee fighter pilot looked in complete awe at "the bravest person" he ever met, and thus was born the Cliff's nickname, "No-Sweat Brown."
Some more details on the diagnosis, kind of walking through the aerodynamics of the landing:
You can see how cool he was, punching off the load away from the building in the cleared out area.
He obviously knew he was too high to just cut the throttle, and he saw that the rotation rate was not unmanageable, so he decided to ride it out by holding it level and allowing it to turn as he lined up a clear area to land in and reduced altitude. This was a conscious piloting act to just allow the turns, but also fly the aircraft down while spinning. It also means that he had to sweep the cyclic around as the aircraft rotated, so that the aircraft stayed level. Remember that the cyclic needs to be put a bit into the wind, otherwise the aircraft attitude will rise and dip and wallow as the rotor is spun around, as the part of the rotor that is upwind is lifted by the wind. That this wallowing didn't happen indicates that he was sweeping the cyclic around in the cockpit to keep the upwind part of the disk down. If you stood outside the aircraft, you would see that he was simply keeping the cyclic into the wind as the aircraft rotated. I had to do this when I did the "snap turns" in the Fantail and Comanche, it is surprisingly easy to get the hang of it with practice, and hard to do when you have to learn it while hovering over an office building!
He held this approach technique until he was about 50 feet above the ground, when he choce to cut the throttle. This was a bit too high, frankly, but is far far easier to judge from this key board then from in his shoes. He cut the throttle there, which immediately stopped the rotating. Of course it does, the turning is powered by the torque of the main rotor, take that torque away and the spin is immediately countered by the slight drag of the main transmission, which acts to make the fuselage rotate WITH the rotor.
The aircraft then settled down in a hovering autorotation, when it ran out of rpm at maybe 25 feet. The allowable CG envelope is a function of cyclic control power, where the cyclic has the control to overcome the moment from the forward (or aft) CG. In this case, the forward CG (lost tail rotor parts) required more control than the low low rotor speed could deliver at about 25 feet, so this caused the nose to pitch over (while he was probably on the aft cyclic stops.) He had a hard landing and he walked away.
He gets a solid A on that whole thing!
A similar take:
A Sikorsky Test Pilot named Cliff Brown had a tail rotor failure in an S-61N while flying with a foreign pilot, they were stabilized in a 100 foot hover over the water. He did much the same thing, riding the aircraft down to a managable 10 foot altitude before cutting the throttles and landing without further damage. He had to shout at the CP to keep him from moving the engine levers, "Stop! I will tell you when to cut them!!" he said. At ten feet above the water, he looked at the guy and said, "Now you can cut them!"
Cliff is well known in USAF circles because during a hot combat rescue in Korea, he got out of the helo to take a leak in the LZ. The rescuee fighter pilot looked in complete awe at "the bravest person" he ever met, and thus was born the Cliff's nickname, "No-Sweat Brown."
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Excellent thread! First class lesson in how to do it if it ever happens, and great explanations and backup info from some experienced pilots - I have printed this one out for my prune folder and students... well done to the pilot involved.
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If you look at the frames around 1:33 into the video you see four intact tail rotor blades. I don't think there was a shift in the cg.
My guess is that he chopped throttles to stop the yawing and then used cyclic to try to make it to a more desirable LZ. I wouldn't be surprised to hear the pitch forward was commanded. If you look where he came to rest, it looks like just short of that ledge was a larger drop so it was probably a good thing he pitched forward.
In any case, what matters the most is that he walked away. Well done!
My guess is that he chopped throttles to stop the yawing and then used cyclic to try to make it to a more desirable LZ. I wouldn't be surprised to hear the pitch forward was commanded. If you look where he came to rest, it looks like just short of that ledge was a larger drop so it was probably a good thing he pitched forward.
In any case, what matters the most is that he walked away. Well done!
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Question
Hi All,
wonderful thread.. However I do have a question. Please no real abuse replies but.... I saw a clip on here prevoiusly it was a sky crane with LTE and the pilot dumpped the water and continued to fly away. Nick explained what happened which was to me , extremely informative. However, the case in question above, why couldn't the pilot, once the load was released, lower collective, reducing power and fly out of it, any which way possible, or am I totally missing something here... Thanks in advance for your help...
wonderful thread.. However I do have a question. Please no real abuse replies but.... I saw a clip on here prevoiusly it was a sky crane with LTE and the pilot dumpped the water and continued to fly away. Nick explained what happened which was to me , extremely informative. However, the case in question above, why couldn't the pilot, once the load was released, lower collective, reducing power and fly out of it, any which way possible, or am I totally missing something here... Thanks in advance for your help...
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If you look carefully at the time of original failure, you can see the tail wiggle a few times and the aircraft yaw to the LEFT. Then the TR stops and the fun begins with the classic right yaw. I have a suspicion that the failure was due to loose control cables, which can cause an instability in the tail rotor controls that causes a rapid divergent TR pitch problem that eventually leads to very high left pedal, then failure.
Why not just fly away? There was no antitorque as the right yaw developed, and fly away was simply not possible. This case is far different from the Skycrane, which had merely pulled the rpm low enough to swamp the tail thrust with the main torque.
Why not just fly away? There was no antitorque as the right yaw developed, and fly away was simply not possible. This case is far different from the Skycrane, which had merely pulled the rpm low enough to swamp the tail thrust with the main torque.
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Does this helicopter have a collective mounted power control grip? (throttle)
He chops the power while still quite high, I'm GUESSING he must have hurried to take his hand, off the collective, put it up there where the lever is pushed it back, then go back to collective to cushion landing.
He must have seen the ground come up really fast so he decided to do it early or else he wasn't going to have time to cushion landing.
Of course all of the above could only be remotely correct if this particular helicopter hasn't a collective mounted power control, if it does forgive my ramblings.
One more reason to have collective mounted power control in my tired opinion.
He chops the power while still quite high, I'm GUESSING he must have hurried to take his hand, off the collective, put it up there where the lever is pushed it back, then go back to collective to cushion landing.
He must have seen the ground come up really fast so he decided to do it early or else he wasn't going to have time to cushion landing.
Of course all of the above could only be remotely correct if this particular helicopter hasn't a collective mounted power control, if it does forgive my ramblings.
One more reason to have collective mounted power control in my tired opinion.
Nick, I'm not sure why you think that a loose TR cable would lead to a total loss of drive (the TR blades are stationary in the descent). If it were a broken or loose cable the ability to change the pitch of the TR would have been reduced or lost completely but the TR would still be driven. I don't know if this model had the same folding tail pylon as our military Wessex did but if so, the disconnect coupling would be a prime culprit - the profile looks exactly like a friend of mine had a few years ago in a SAR Wessex.
BTW Blender, the only civilian S58 I have seen did have collective mounted throttles.
BTW Blender, the only civilian S58 I have seen did have collective mounted throttles.