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Helicopter down outside Leicester City Football Club

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Helicopter down outside Leicester City Football Club

Old 31st Oct 2018, 14:57
  #361 (permalink)  
 
Join Date: Aug 2001
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Originally Posted by jeepys View Post
The autopilot will only have max 10% authority.
Hi Jeeps
An autopilot with only 10% authority wouldnt be much use as an autopilot. Individual series actuators typically have 10-15% authority with two actuators in series giving 30% (ish), this is then usually extended to 100% authority by use of parallel actuators. I totally agree an actuator runaway will be limited by its authority.
Im not suggesting any of this is relevant in this case.
Cheers TeeS
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Old 31st Oct 2018, 15:08
  #362 (permalink)  
 
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Originally Posted by Torquetalk View Post
Without any implication with respect to the current accident, the pilot in the Wessex Welsh lake video seems to have done an outstanding job given the circumstances. Looks as though they managed to check some of the yaw and get some directional control before accepting more yaw and a reduced ROD and forward speed.

All the videos all show that once the yaw has accelerated following a serious anti-torque problem, stopping it is going to be extremely difficult, even with a lot of height.
Aircraft type would also appear to play an important role in the rate of yaw development and prospects for recovery. The lake and hoist videos show quite rapid yaw arrest in response to control inputs. It makes me wonder if some aircraft are harder to get back, with the AW139 & AW169 more at that end of the spectrum.
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Old 31st Oct 2018, 16:01
  #363 (permalink)  
 
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Just worth noting that I know someone who was still at the game and has been to several and seen the helicopter take off.

apparently, it was all normal (including that first initial yaw input when it first looks controlled). You cannot make it out too well in the video, but the gear retracts and it begins a rotation - apparently as it always did.. At that point it never seems to recover.

im no expert and could be coincidence - but could that suggest a peddle / input problem. He stated that it actually didnt sound too out of the ordinary. The strange noise people seem to be referring to from what he saw was the pitch of the blades against the air as it began to rotate seemingly uncontrollably.

just thought Id share to maybe shed some insight from someone who has some basic understanding of aircraft / rotors rather than just a regular member of the public.

it maybe a result of the cause rather than the cause itself, but thought Id share it with people much more knowledgeable than myself.

Last edited by RiSq; 31st Oct 2018 at 16:09. Reason: spelling
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Old 31st Oct 2018, 16:05
  #364 (permalink)  
 
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I ,can say that if a rotor blade departs,then the remaining blades and gearbox will have departed too; this will likely take the Cof G past the nose,and the stick fully back...
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Old 31st Oct 2018, 16:09
  #365 (permalink)  
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Originally Posted by ShyTorque View Post
Have you personally experienced this particular failure, or practiced it in a simulator? Thirty years ago I was a QHI involved in a full motion helicopter simulator project for the UK military and was part of a team (of two) tasked to expand the then current teaching on tail rotor malfunctions, which was woefully inadequate. We did some practical test flying (hours costed by MOD on behalf of Boscombe Down) and developed a syllabus. We then began teaching both "ab initio" and experienced squadron pilots alike. I saw many highly experienced pilots fail to arrest the yaw rate in time, despite being pre-briefed and pre-warned that the T/R was about to malfunction. Bear in mind that this was in a simulator lesson doing nothing but tail rotor malfunctions.

Given that it takes a second or two to diagnose the failure in the real case, the pilot probably did as well as anyone could have in the circumstances. Note the slight pause in the yaw rate - it's likely that full opposite pedal was applied in an attempt to stop the yaw, probably a pilot response.Then once the tail rotor blades produced no more effective thrust, round it went again at an increased rate of yaw. Once a rapid fuselage spin develops, response to cyclic inputs may not be what is normally expected and that effective rotor rpm is reduced.

Other things that could cause a sudden yaw are a gust of wind, an autopilot/SAS malfunction, or an inadvertent foot touching a yaw pedal. Dumping the lever and chopping the engines would be an inappropriate immediate response.

This unfortunate pilot probably experienced a T/R drive failure at the most critical stage of flight imaginable. I say "probably" because AAIB haven't yet released initial findings and I am quite possibly wrong; obviously I'm only an amateur compared to some experts here.
An fascinating post from a QHI experienced in Tail Rotor failures in the sim.
In what follows I assume it was a tail rotor failure and the usual caveats to hasty judgement apply.
If I'm reading you correctly and not reading too much between the lines your sim experience tells you if you really do have a tail rotor failure, tail rotor control failure or failure in the drive train to the tail rotor by the time the handling pilot has evaluated all cues and eliminated other malfunctions; yaw trim actuator hard over, other pilots boots, or whatever then the situation is perilously close or already beyond effective recovery action. Put simply if you have a tail rotor failure especially at high power settings with low air speed, zero weathercock stability, then the collective lever has got to lowered immediately and swiftly, how long a second, two at the outside. Then given the T/O flight profile the nose must be lowered aggressively to recover airspeed for flare, check level. Do Flight Manuals even have graphs for this nightmare?
 
Old 31st Oct 2018, 16:44
  #366 (permalink)  
 
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Another 'expert' who should know better...

Tony Cable

Tony Cable, a former senior investigator at the Air Accident Investigations Branch (AAIB), has watched footage and said: 'The takeoff looked normal but as it hovered above the stadium you can see pieces falling away. It looks like from the rear rotor blades.'It is consistent with a tail rotor breaking off. There are lots of pieces flying around. If you lose a large proportion of the blade you get a very large imbalance and pull the whole tail rotor off the aircraft'.
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Old 31st Oct 2018, 16:50
  #367 (permalink)  
 
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The significance of the anti collision light extinguishing in the video could be a sign of both generators going off line, this could be due to both engines being shut down, in turn suggesting the pilot shut them down in reaction to a tail rotor drive failure? Speculation on my part following a logical chain of events if the anti coll was extinguished.
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Old 31st Oct 2018, 17:05
  #368 (permalink)  
 
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Another 'expert' who should know better...
Why? You think they're insects, he thinks they're pieces of tail rotor.
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Old 31st Oct 2018, 17:08
  #369 (permalink)  
 
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Originally Posted by Geoffersincornwall View Post
When teaching TR Fail (drive fail or worse) in the 139 sim I first caution the candidates about taking care not to take too much detail away with them after this exercise - the sim cannot be relied upon to truly replicate the real event. ...
etc etc Yep, I agree with all of that, 100%.
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Old 31st Oct 2018, 17:09
  #370 (permalink)  
 
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The anti-collision light mounted on top of the vertical fin is still flashing. You can see it still flashing as it disappears behind the stadium.
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Old 31st Oct 2018, 17:10
  #371 (permalink)  
 
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Surely the time between seeing the so called object and the loss of control is way too long, would be instant.

His interview on Sky is shocking, implying that a simple lowering of the collective and cutting engines would have quickly brought the aircraft under control! He has either been seriously misquoted or lost the plot!
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Old 31st Oct 2018, 17:15
  #372 (permalink)  
 
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He has either been seriously misquoted
​​​​​​​Given his credentials and it's Sky, I'm guessing he's been seriously misquoted....but maybe experts here know better....
Tony Cable:
B.Sc., M.R.Ae.S
University of London BSc Honours Degree in Aeronautical Engineering
Powerplant Design Engineer with Boeing Aircraft on large public transports
Systems and Safety Engineer with BAe, including Tornado and Concorde
Aircraft Engineering Accident Investigator full-time since 1976
Visiting Fellow at Cranfield University
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Old 31st Oct 2018, 17:20
  #373 (permalink)  
 
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Originally Posted by clareprop View Post
Why? You think they're insects, he thinks they're pieces of tail rotor.
Surely he should know better than to pronounce the cause of the accident from a Sun video...

And a cursory glance at the wreckage shows the tail rotor roughly where it should be, albeit sans half of one blade.
Surely the imbalance of losing half a blade would have put the TRGB somewhere in the next county...?
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Old 31st Oct 2018, 17:22
  #374 (permalink)  
 
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Originally Posted by Art of flight View Post
The significance of the anti collision light extinguishing in the video could be a sign of both generators going off line, this could be due to both engines being shut down, in turn suggesting the pilot shut them down in reaction to a tail rotor drive failure? Speculation on my part following a logical chain of events if the anti coll was extinguished.
doesnt the battery kick back in and supply power at that point?
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Old 31st Oct 2018, 17:24
  #375 (permalink)  
 
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I'm amazed by the low quality of the (Sun) video, and I've assumed that they have a higher quality version but have opted to share a highly compressed version online. The sun has now updated their video (watch from 1:18) where they replay the "interesting" part in slow motion.

I now doubt that they have a higher quality version, as I think they would have used that as the source for the replay. It's a shame, because it would have made it much easier to tell
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Old 31st Oct 2018, 17:26
  #376 (permalink)  
 
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Surely he should know better than to pronounce the cause of the accident from a Sun video...
Evidence is evidence no matter where it comes from. Given he was a senior guy with the AAIB engineering section for 40+ years and during that time investigated many infamous rotary accidents, I'm thinking that he probably still has the odd chat with them from time-to-time.
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Old 31st Oct 2018, 17:34
  #377 (permalink)  
 
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Originally Posted by Mitchaa View Post
Unburnt fuel, oil or water.
The change in direction of the rising puff of smoke from the engine whilst it was being started suggests to me the initial climb was with a tail wind....granted, maybe the wind was swirling inside the stadium but that smoke did catch a bit of tail wind...I don't think it was sucked in to some inflow into the rotor disc as the rotor had only just started to turn.

I'm still suspicious about that smoke...perhaps caused by oil momentarily getting past a labyrinth seal and burning in the hot engine? I'm not familiar with that particular engine, but it does look unusual.
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Old 31st Oct 2018, 17:38
  #378 (permalink)  

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Originally Posted by runway30 View Post
Im not defending Learmount but as someone who has done his fair share of punditry let me tell you what the media is looking for. They want a very complicated subject explained in two minutes in a way that 99% of the population will understand. This is while, depending on where you are being interviewed, someone is talking in your ear and youre trying not to think of how many million are listening to you making an ar*e of yourself. Not as easy as you think.
Exactly! Speaking as someone who has been approached by the media to appear in such interviews, thought about it and declined, he does have my sympathy - especially as his personal experience was as a fixed wing pilot. One small slip of the tongue in the harsh spotlight of the media and you'll be pilloried here forever!
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Old 31st Oct 2018, 17:50
  #379 (permalink)  
 
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As a former helicopter maintenance engineer, I can confidently say that if an AW169 lost a tail rotor blade then the gearbox will rapidly break free and depart from the airframe.
Helicopters with 4-bladed tail rotors might, with luck, throw the opposite blade too, thus putting the rotor back into some form of balance, but a 3-bladed tail rotor has no chance.
The pictures I have seen suggest that a tail rotor blade loss is highly unlikely to be the cause of this accident.
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Old 31st Oct 2018, 18:13
  #380 (permalink)  
 
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Originally Posted by gulliBell View Post

I'm still suspicious about that smoke...perhaps caused by oil momentarily getting past a labyrinth seal and burning in the hot engine? I'm not familiar with that particular engine, but it does look unusual.
The smoke coming from the engine is nothing to be concerned about, if engineers got twitchy every time we saw a start with white smoke, none of us would ever go flying! It's too thick and too soon in the start cycle to be oil, it is almost certainly fuel - perhaps unburnt from the last shutdown being kicked out, or a small purge coming through prior to the ignitors cracking off, but most certainly not an issue to flight safety
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