JetRanger crash Honolulu HI
ersa, I would calm down if some people didn't spout garbage!
He is into wind, got forward airspeed, he is decending in what looks like a normal but maybe cautious approach.
Helicopters make this type of approach all day everyday and don't get into the dreaded VRS. Why do you think he did?
However, on this occasion something mechanical went wrong it lost the RPM required to fly and dropped like a stone. They are very lucky to have had no fatalities at this stage.
He is into wind, got forward airspeed, he is decending in what looks like a normal but maybe cautious approach.
Helicopters make this type of approach all day everyday and don't get into the dreaded VRS. Why do you think he did?
However, on this occasion something mechanical went wrong it lost the RPM required to fly and dropped like a stone. They are very lucky to have had no fatalities at this stage.
Heliringer...
I never did ....just take a chill pill....hope you don't work in a multi crew environment
I never did ....just take a chill pill....hope you don't work in a multi crew environment
Last edited by Senior Pilot; 19th Feb 2016 at 10:31. Reason: Delete unnecessary profanity
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I'm a fixed wing student pilot so don't have a huge amount of knowledge on helicopters. Just wondering if one of you guys could answer a question? If that was indeed a drive shaft failure, and he had more altitude, say a couple of hundred feet, would he have been able to perform an autorotation? Was the biggest problem here his lack of altitude while making his approach and it all went wrong at the worst time?
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TR flicker shown on video reverses its direction, sound of drive train change - TRF, methinks.
If I were to bet my chips on it, Drivetrain failure would be it, notice how the MR slows down too.
I'm a fixed wing student pilot so don't have a huge amount of knowledge on helicopters. Just wondering if one of you guys http://www.bing.com/images/search?q=...jaxhist=0could answer a question? If that was indeed a drive shaft failure, and he had more altitude, say a couple of hundred feet, would he have been able to perform an autorotation? Was the biggest problem here his lack of altitude while making his approach and it all went wrong at the worst time?
Do not assume that the apparent change in tail rotor RPM is because it is slowing down. Perhaps it is speeding up? The 206 produces a very distinctive tail rotor growl. Listening to the audio portion of that clip, it appears - at least to me - that the tail rotor is increasing in RPM. The video itself shows the nose yaw to the left. The helicopter drops like a rock.
These three things persuade me that it was an input drive shaft failure (the one that goes from the engine to the transmission). 206 drivers know that when you lose this drive shaft the engine is now powering the tail rotor, not the transmission. We are told that the N2 governor will hold the engine rpm at 100%, and that may be so. But I'd still bet that there are some RPM excursions while the governor plays catch-up.
An IDS failure would account for the apparent speed-up of the tail rotor, the left yaw of the nose, and the sudden, violent vertical descent.
To answer Rob Melvini's question... Yes, if the pilot had more altitude he certainly could have autorotated to a safe landing. But having all that beating and banging going on back there would have been disconcerting to say the least! In such an emergency, 206 pilots are cautioned to not roll the throttle off; doing so would remove power to the tail rotor, giving you yet another emergency on the way down! (I wonder if Bell has rectified this peculiarity with the 505?) But as one with "more than a couple" hours in 206's, even I would be sorely tempted to impulsively roll it off, and in my highly-stressed state of mind I might do just that.
These three things persuade me that it was an input drive shaft failure (the one that goes from the engine to the transmission). 206 drivers know that when you lose this drive shaft the engine is now powering the tail rotor, not the transmission. We are told that the N2 governor will hold the engine rpm at 100%, and that may be so. But I'd still bet that there are some RPM excursions while the governor plays catch-up.
An IDS failure would account for the apparent speed-up of the tail rotor, the left yaw of the nose, and the sudden, violent vertical descent.
To answer Rob Melvini's question... Yes, if the pilot had more altitude he certainly could have autorotated to a safe landing. But having all that beating and banging going on back there would have been disconcerting to say the least! In such an emergency, 206 pilots are cautioned to not roll the throttle off; doing so would remove power to the tail rotor, giving you yet another emergency on the way down! (I wonder if Bell has rectified this peculiarity with the 505?) But as one with "more than a couple" hours in 206's, even I would be sorely tempted to impulsively roll it off, and in my highly-stressed state of mind I might do just that.
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My reaction was "what a strange way for the helicopter to behave". Even assuming an engine failure, I would expect a collective pull at the bottom to greatly reduce the sink rate which made me think that one of two things was going on:
1) Something aerodynamic like VRS was causing a sink rate .... or
2) RPM was already very low and there wasn't much left to pull.
So, I did some counting of RPM. In the early part of the video we see the rotor taking 7 frames to make a main rotor revolution. Later, as the sink rate dramatically increases it's taking 10 to 11 frames for the rotor to make a revolution. That works out as:
(f/r = video frames per revolution)
(sec/rev = seconds/revolution)
7 f/r @ 30 fps = 0.23 sec/rev = 257 RPM = 65% Nr
10 f/r @ 30 fps = 0.33 sec/rev = 180 RPM = 46% Nr
11 f/r @ 30 fps = 0.36 sec/rev = 163 RPM = 40% Nr
So, by the time the video starts, he's already below the recommended touchdown RPM (70%). Most of his pull is already used up (and remember that energy in this case is a squared function of rotor RPM so there's not much energy in decelerating the rotor from 65% to 40%).
So, seeing that the rotor speed is that low, the video makes a lot of sense. He's had some kind of a power train failure (engine, short shaft) and at the time we first see it, he's already bled most of his RPM (early flare and pull, or hasn't lowered the collective enough to maintain flight rpm). Given all that, it's not surprising that we're seeing a dramatic acceleration towards the ground. By 40% Nr, the main rotor is providing little lift and gravity kicks in with a vengeance.
Happy to hear from you if I'd made any errors in my calculations...
1) Something aerodynamic like VRS was causing a sink rate .... or
2) RPM was already very low and there wasn't much left to pull.
So, I did some counting of RPM. In the early part of the video we see the rotor taking 7 frames to make a main rotor revolution. Later, as the sink rate dramatically increases it's taking 10 to 11 frames for the rotor to make a revolution. That works out as:
(f/r = video frames per revolution)
(sec/rev = seconds/revolution)
7 f/r @ 30 fps = 0.23 sec/rev = 257 RPM = 65% Nr
10 f/r @ 30 fps = 0.33 sec/rev = 180 RPM = 46% Nr
11 f/r @ 30 fps = 0.36 sec/rev = 163 RPM = 40% Nr
So, by the time the video starts, he's already below the recommended touchdown RPM (70%). Most of his pull is already used up (and remember that energy in this case is a squared function of rotor RPM so there's not much energy in decelerating the rotor from 65% to 40%).
So, seeing that the rotor speed is that low, the video makes a lot of sense. He's had some kind of a power train failure (engine, short shaft) and at the time we first see it, he's already bled most of his RPM (early flare and pull, or hasn't lowered the collective enough to maintain flight rpm). Given all that, it's not surprising that we're seeing a dramatic acceleration towards the ground. By 40% Nr, the main rotor is providing little lift and gravity kicks in with a vengeance.
Happy to hear from you if I'd made any errors in my calculations...
VRS etc is nonsense ! Also I don't see TRF either as your instinct would be to pull pitch ( which didn't happen .......or IF it did the blades were already about to stall ) coupled with the fact there was no serious yaw to left , 30 deg at most .
I think it was possibly a slow reduction of power /drive to the blades with subsequent rotor decay . Probably lucky to not reach the land and the tourists also thank God it was doors off . Let's hope the kid is going to be ok .
My money is governor failure .
I think it was possibly a slow reduction of power /drive to the blades with subsequent rotor decay . Probably lucky to not reach the land and the tourists also thank God it was doors off . Let's hope the kid is going to be ok .
My money is governor failure .
Reported as being five on board, including a 15-year-old boy who was taken to the hospital in critical condition. He had been trapped in the wreckage, and cut free by bystanders. A 50-year-old man and a 45-year-old woman also were treated at the scene by Honolulu Emergency Medical Services and taken to the hospital in stable condition.
My money is on drive failure.
My money is on drive failure.
Paul Cantrell,
If your numbers are right, and I expect they are, then i think that the actual mechanical failure, what ever it was, occurred before the start of the video. Look at the google maps link I posted previously to where the accident occurred. There isnt a helipad near by but a largeish green park that is part of the pearl harbor monument national park.
If the pilot had engine failure at height before the video started, auto rotated to the park but then saw all obstacles/people and tried to arrest the decent and ran out of options.
If your numbers are right, and I expect they are, then i think that the actual mechanical failure, what ever it was, occurred before the start of the video. Look at the google maps link I posted previously to where the accident occurred. There isnt a helipad near by but a largeish green park that is part of the pearl harbor monument national park.
If the pilot had engine failure at height before the video started, auto rotated to the park but then saw all obstacles/people and tried to arrest the decent and ran out of options.
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My 2 cent : Freewheel failure
Why ?
1 / it's a normal approach =no VRS or other
2 /you listen clearly engine runing all the time = no engine failure,
3 / you listen clearly engine overspeed...It's mean, no more power transmitted to the rotor and T/R but engine runing
4 / The helicopter fall down like a block of concrete during a normal appproach = no power transmitted to the main rotor AND no reaction from the pilot (no time to react !)
5 / the briefly yaw is not due to an engine failure, but overspeed of the T/R
All of that = = no more free wheel runing ! it's a know defect on the 206
But, i was not on board.....
Why ?
1 / it's a normal approach =no VRS or other
2 /you listen clearly engine runing all the time = no engine failure,
3 / you listen clearly engine overspeed...It's mean, no more power transmitted to the rotor and T/R but engine runing
4 / The helicopter fall down like a block of concrete during a normal appproach = no power transmitted to the main rotor AND no reaction from the pilot (no time to react !)
5 / the briefly yaw is not due to an engine failure, but overspeed of the T/R
All of that = = no more free wheel runing ! it's a know defect on the 206
But, i was not on board.....
I mentioned in posts No's 7 & 9 that it appears to be an approach to a precautionary landing at a suitable open space. This would indicate (as I mentioned) an existing fault indication and the freewhel fits this scenario, whereas a drive shaft failure is very unlikely to have given any prior indication.
Again putting on my Monday morning umpire's hat, I would have set up a far steeper approach to allow for the possibility of it turning into an auto with only the landing area as a suitable destination. It happened to me once (compressor failure on short finals to a floating pontoon) and I make the point long and loud to anyone who will listen: a steep approach is the only guard against losing power on short final that will assure a landing at the planned site for a single engine helicopter.
Rotor flicker/speed on a smartphone video is totally unreliable. Search for videos of stationary blades in flight, what you see on the video is unlikely to have any similarity to what actually happened.
Again putting on my Monday morning umpire's hat, I would have set up a far steeper approach to allow for the possibility of it turning into an auto with only the landing area as a suitable destination. It happened to me once (compressor failure on short finals to a floating pontoon) and I make the point long and loud to anyone who will listen: a steep approach is the only guard against losing power on short final that will assure a landing at the planned site for a single engine helicopter.
Rotor flicker/speed on a smartphone video is totally unreliable. Search for videos of stationary blades in flight, what you see on the video is unlikely to have any similarity to what actually happened.
John are you suggesting to disregard the HV chart in the RFM?
Of course there are obstacle/wind/terrain considerations that necessitate a steep approach for operational purposes in some instances, however I think Bell would disagree with your technique of flying well and truly in the shaded section of the HV chart for just about every approach.
** only talking about single engine aircraft here.
Of course there are obstacle/wind/terrain considerations that necessitate a steep approach for operational purposes in some instances, however I think Bell would disagree with your technique of flying well and truly in the shaded section of the HV chart for just about every approach.
** only talking about single engine aircraft here.
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I am just making guesses like everyone else and I keep leaning toward VRS because how else could it drop so fast .
VRS could also explain the rpm increase because of unloaded blades and unloaded engine during the VRS
As far as I can tell MR pitch was never reduced ... so if it was a shaft or sprague failure a 206 should have mushed down as MRRPM decayed , not the sudden drop we saw.
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I am just making guesses like everyone else and I keep leaning toward VRS because how else could it drop so fast .
VRS could also explain the rpm increase because of unloaded blades and unloaded engine during the VRS
As far as I can tell MR pitch was never reduced ... so if it was a shaft or sprague failure a 206 should have mushed down as MRRPM decayed , not the sudden drop we saw.
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Turning into a really boring thread by wannaabees. How about something went wrong and since i didn't have floats i was in the wrong place at the same time.... S..T happens.