Police helicopter crashes onto Glasgow pub: final AAIB report
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Originally Posted by [email protected]
so, since the thread is about a double engine flameout in the hover and subsequent fatal EOL then your teaching of the EOL iaw the RFM isn't relevant, even though it might be for other occasions.:
"The helicopter tracked towards GCH at an altitude of about 1,000 ft amsl, with a ground speed of approximately 100 kt. Between 2221:35 hrs and 2221:45 hrs, when the helicopter was about 2.7 nm east of GCH, the right engine flamed out, leaving the pilot with one engine inoperative (OEI). Approximately 32 seconds later, about 1.8 nm east of GCH, the left engine flamed out."
No, you are right - my error - point conceded
To confirm - Flightpath derived from Glasgow Airport and Lowther Hill radar. Not much hovering.
https://assets.publishing.service.go...015_G-SPAO.pdf
https://assets.publishing.service.go...015_G-SPAO.pdf
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Originally Posted by [email protected]
No, you are right - my error - point conceded
Guilty as charged your honour
At what point and for what duration did the aircraft last hover prior to reaching the start point in the graphic?
The dual engine flameout due to fuel starvation might not have happened during a hover....but the last bit of hovering set up the outcome for sure.
Was that last hover commanded by Police Ops or did the Crew take it on outside of direction from Central Control?
Why is the Aircraft/Police Ops radio conversation(s) being withheld?
The dual engine flameout due to fuel starvation might not have happened during a hover....but the last bit of hovering set up the outcome for sure.
Was that last hover commanded by Police Ops or did the Crew take it on outside of direction from Central Control?
Why is the Aircraft/Police Ops radio conversation(s) being withheld?
SASless,
You have hit the nail on the head.
The absence of any input from police comms in the latter stage if the flight is glaring. The rationale for those last orbits of motorway junctions seems central to understanding how the aircraft came to grief.
You have hit the nail on the head.
The absence of any input from police comms in the latter stage if the flight is glaring. The rationale for those last orbits of motorway junctions seems central to understanding how the aircraft came to grief.
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At what point and for what duration did the aircraft last hover prior to reaching the start point in the graphic?
The dual engine flameout due to fuel starvation might not have happened during a hover....but the last bit of hovering set up the outcome for sure.
Was that last hover commanded by Police Ops or did the Crew take it on outside of direction from Central Control?
Why is the Aircraft/Police Ops radio conversation(s) being withheld?
The dual engine flameout due to fuel starvation might not have happened during a hover....but the last bit of hovering set up the outcome for sure.
Was that last hover commanded by Police Ops or did the Crew take it on outside of direction from Central Control?
Why is the Aircraft/Police Ops radio conversation(s) being withheld?
That is my understanding.
It looks to me that the first engine flamed out whilst he was routing back to his home base and 32 seconds later the second flamed out. Looking at the distance covered in those 32 seconds, it would indicate a fast cruise (100kts+).
Unless anyone else has another synopsis to offer.
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SAS, once the transfer pumps are selected OFF (Which the evidence pointed to in this case), and the fuel in the main tanks is below the level of the overspill, the supply tanks begin to empty in isolation of the main tank. The attitude of the helicopter from this point onwards makes no real difference to the eventual outcome once the supply tanks become depleted. Fuel starvation is inevitable. The helicopter was recovered with virtually zero fuel in the supply tanks and around 78 KGS left in the main tank.
That is my understanding.
It looks to me that the first engine flamed out whilst he was routing back to his home base and 32 seconds later the second flamed out. Looking at the distance covered in those 32 seconds, it would indicate a fast cruise (100kts+).
Unless anyone else has another synopsis to offer.
That is my understanding.
It looks to me that the first engine flamed out whilst he was routing back to his home base and 32 seconds later the second flamed out. Looking at the distance covered in those 32 seconds, it would indicate a fast cruise (100kts+).
Unless anyone else has another synopsis to offer.
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gevans35, how do you know he didnt enter autorotation?
He arrived at the ground with low NR, but if he misjudged his height to flare (no radalt remember), he may have just used it all up at 1-200 feet. That would still produce the outcome we saw.
He arrived at the ground with low NR, but if he misjudged his height to flare (no radalt remember), he may have just used it all up at 1-200 feet. That would still produce the outcome we saw.
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There is little doubt that at the point of impact with the pub roof, the blades were all but stationary. The lack of leading edge or indeed any other rotational damage would support that supposition. If we accept that then we have to understand how the aircraft ended up with no Nr. The answer almost certainly lies in the deep stall of the blades, associated with zero torque driving them, a high angle of attack and a high rate of descent. Its hard to accept that such conditions could arise by a poorly judged flare height. Added to the testimony of eyewitnesses (of course cannot be relied upon) but their testimony supports a deep stall at significant height.
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That is why for me, maximum efforts should be made to afford MEH pilots time to become fully comfortable with the second engine failing. I go back to what I said at the start. After OEI, the Nr gauge is your only real reference as to what may happen next. Nothing else matters until the remaining engine convinces you it is not going follow its mate.
After OEI, the Nr gauge is your only real reference as to what may happen next.
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Gevans35, If you have sat in the back of a simulator, introduced a double engine failure, cold, to crew in the first hours of their recurrent with no previous practice, you would understand how this can occur. Sadly and possibly to any one of us! For those of us employed on regular CAT we do not ever really have any opportunity to play at autorotation until our arse is dumped in the Recurrent seat each 6 month interval. For GA and FIs its a different story.
That is why for me, maximum efforts should be made to afford MEH pilots time to become fully comfortable with the second engine failing. I go back to what I said at the start. After OEI, the Nr gauge is your only real reference as to what may happen next. Nothing else matters until the remaining engine convinces you it is not going follow its mate.
That is why for me, maximum efforts should be made to afford MEH pilots time to become fully comfortable with the second engine failing. I go back to what I said at the start. After OEI, the Nr gauge is your only real reference as to what may happen next. Nothing else matters until the remaining engine convinces you it is not going follow its mate.
As a (lapsed), night rated, PPL(H), I was fortunate never to have to execute a night EOL for real, but I was current in EOLs. Had I had an engine failure at night it would have been a case of... NR, NR, wind, NR and hike the lever under my armpit when I saw something that looked like the ground, 50/50 chance of limping away from it? Perhaps this pilot did enter autorotation after the second engine stopped and mistook something, perhaps a tall building, for the ground. Lever under armpit... game over.
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When one engine has inexplicably failed, the most obvious indication that the remaining engine has suffered the same fate is a sudden collapse of Nr. There is nothing else of immediate value to look at until you have convinced yourself that the remaining engine will not suffer the same fate.
https://assets.publishing.service.go...015_G-SPAO.pdf
There is nothing else of immediate value to look at until you have convinced yourself that the remaining engine will not suffer the same fate.
Is this something you teach in the Sim?
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My team all teach this in the FSTD for nearly a decade and it works. I can be 100% certain that if the candidate is looking at the Nr Gauge he will react quickly and appropriable. We go to significant lengths to prove this to each pilot by doing it in slow time so they understand the extra margin they have to avoid slamming the lever to the floor which inevitably cause handling issues. I also demonstrate this in the AC as the second engine is cut to idle. It works. Obviously the story is bigger than what I am describing here. Flight path management is paramount but we start by getting the pilot to invest in the idea that the Nr gauge is his most reliable indication of a complete power loss. From that concept he can build a strategy that works around the Nr gauge.
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SAS The justification for reference to Nr as a priority after an OEI event is born from the AAIB report para below. If the collective is not lowered quickly enough and the NR decays to the figure indicated with a High ROD, a deep stall occurs and the rotor stops very quickly. The OEM testing indicated this can happen in around 2 seconds when the conditions have been met. Its scary and it is the major lesson from this accident. Our teaching practices are expressly aimed at providing a strategy to prevent this from happening whilst at the same time building resilience to overcome the startle effect. The simpler the response the more likely the pilot will follow. "OEI - Look at the Nr, if it remains stable after 1 minute, you can start to breathe again. If it remains stable after 5 minutes, you can allow you attention to go elsewhere momentarily"
Main and tail rotor system
Total loss of rotational speed of the rotor system during the subsequent unpowered descent is consistent with a higher than optimum main rotor blade pitch being applied and maintained during some part of the descent.
The physical damage identified on the main rotor blades was typical of lead-lag resonance. This occurs when the main rotor speed decays through the region of 60%-70% Nr. and can be brought about when significant main rotor blade pitch is applied to an unpowered rotor system.
Evidence of blade coning during lead-lag resonance also confirmed that the latter occurred before impact. Ear-witness evidence was also consistent with lead-lag resonance occurring whilst the helicopter was still airborne. Lead-lag resonance in flight occurs at a rotor speed below the minimum Nr (75% Nr) from which it is irrecoverable in autorotation.
Main and tail rotor system
Total loss of rotational speed of the rotor system during the subsequent unpowered descent is consistent with a higher than optimum main rotor blade pitch being applied and maintained during some part of the descent.
The physical damage identified on the main rotor blades was typical of lead-lag resonance. This occurs when the main rotor speed decays through the region of 60%-70% Nr. and can be brought about when significant main rotor blade pitch is applied to an unpowered rotor system.
Evidence of blade coning during lead-lag resonance also confirmed that the latter occurred before impact. Ear-witness evidence was also consistent with lead-lag resonance occurring whilst the helicopter was still airborne. Lead-lag resonance in flight occurs at a rotor speed below the minimum Nr (75% Nr) from which it is irrecoverable in autorotation.