Police helicopter crashes onto Glasgow pub
The Original Whirly
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No one seems to have taken into account that the Pilot may have been taken ill? He could have had a blackout or a sudden heart attack.Have the PM's been done yet?
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As a relatively experienced commercial pilot I am not sure of the relevance of my experience to handling a complete power loss in flight. Paradoxically, a relatively inexperienced FI(H) is probably going to react better than me !!
I have not had to handle such an event in 15k. How many of us have had such an experience. I would suggest very few.
I believe, with near max pitch, the rotor would decay very quickly to a residual value.
I have not had to handle such an event in 15k. How many of us have had such an experience. I would suggest very few.
I believe, with near max pitch, the rotor would decay very quickly to a residual value.
Purveyor of Egg Liqueur to Lucifer
I would suggest that they were slowing/had slowed down to <80kts during the pre-landing stage in order to arm the floatation gear.
Pub User, Shortfinals, indeed, and I would expect any pilot, and this one in particular, to have the lever on the floor until rotor RPM was restored. Even a fully stalled rotor should still have some rotation as long as the lever was down. Surely this points towards a major mechanical failure of the transmission. Very odd.
I'm afraid this is a widely spread misconception.
A stalled rotor has a drag coefficient > 0,4 /@AoA 20°). This will even overwhelm turning engines.
For comparison in a full flare Cd will be between 0,1 and 0,2.
Without engines turning a fully developped Rotor stall will stop the rotor in very few seconds (<<10s).
Once stalled above a certain degree there is simply no way to restore RRPM and once RoD builds up, AoA (and thus stall) will progressively increase. As a result the drag will increase steeply and stop the rotor in a frighteningly short time.
Much shorter than a MGB failure will achieve (the latter one will most likekly separate before achieving similar rates of RPM reduction).
Edit:
The big question is: Why did it stall in the first place?
Last edited by henra; 9th Dec 2013 at 19:16.
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I'm wondering whether the situation served up was so full of conflicts as to give no clear indication of appropriate response. Is this terminal - dump, AR? Is this transient - heave, think and hope? Just a very few seconds of the latter response could have cut off the retreat to the former.
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Whirly
I could think of one scenario, if the ac had auto pilot activated and ran out of usable fuel whilst the pilot was in capacitated, what would happen?
engines stop, AP keeps pitch on until rotors stop...
Even if the pilot had been incapacitated, the rotors wouldn't stop. It's pretty hard to think of ANY scenario in which the rotors would stop turning in that short a time, even if you wanted them to
engines stop, AP keeps pitch on until rotors stop...
Ppruners are usually very ready to castigate the general media and their commentators for misleading and inaccurate reporting, but what about the professional media:
Glasgow helicopter crash not due to engine failure, AAIB reveals - News - Shephard
Glasgow helicopter crash not due to engine failure, AAIB reveals
The AAIB reveals no such thing. It says there was ... no evidence of major mechanical disruption to either engine.... That explicitly does not rule out engine failure, say by flame-out for a fuel-supply or FADEC reason, I think the most common causes for engine failures.
Can we please now have some of the bile usually reserved for the BBC and the daily papers?
Glasgow helicopter crash not due to engine failure, AAIB reveals - News - Shephard
Glasgow helicopter crash not due to engine failure, AAIB reveals
The AAIB reveals no such thing. It says there was ... no evidence of major mechanical disruption to either engine.... That explicitly does not rule out engine failure, say by flame-out for a fuel-supply or FADEC reason, I think the most common causes for engine failures.
Can we please now have some of the bile usually reserved for the BBC and the daily papers?
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Even if the fuel supply stopped, this does not explain the aggressive decay in rrpm - unless the response to a double engine failure was to pull maximum pitch!
Stunning that there are some who believe that "Even a fully stalled rotor should still have some rotation as long as the lever was down." As henra has said, there is a "point of no return" for every helicopter in terms of rrpm afterwhich recovery is no longer possible. You should know the minimum rrpm for the type you fly or, if you can't remember, simply do not allow your rrpm to decay beyond the bottom of the green.
In my mind I was speculating that we might have read about a catastrophic main gearbox failure but now I have no idea as to what may have happened. So many details (on the surface) don't seem to add up.
Stunning that there are some who believe that "Even a fully stalled rotor should still have some rotation as long as the lever was down." As henra has said, there is a "point of no return" for every helicopter in terms of rrpm afterwhich recovery is no longer possible. You should know the minimum rrpm for the type you fly or, if you can't remember, simply do not allow your rrpm to decay beyond the bottom of the green.
In my mind I was speculating that we might have read about a catastrophic main gearbox failure but now I have no idea as to what may have happened. So many details (on the surface) don't seem to add up.
Purveyor of Egg Liqueur to Lucifer
Google maps, just across from the pub is the 2Canvas shop. In addition to a couple of cameras around the junction, on top of the lampost facing The Victoria, is that a CCTV camera?
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Grenville
I think what we are fishing for is that in most (all?) serviceable and reasonably modern multi-engine helicopters, there is nothing you can do with the controls that will significantly droop the Nr unless the engines are set so as to permit Nr droop.
In the Sea King, the highest matched torque I ever saw in flight in the real aircraft (we did appalling things to the sim) was 135%, which is 12% over the gearbox transient limit. The Nr and both engines were perfectly happy (it was dark, in the mountains, going down rather fast, before NVG and I was the co-pilot staring rather hard at the engine gauges - the captain was a bit busy Aviating). I find it difficult to believe that a 35-yr-younger design wouldn't do better. And personal experience tells me that the rotor brake has no chance against the engines. So I'm assuming that, regardless of how the controls were handled, if the transmission was serviceable and the engines were running at governed Nf/Nr, the rotor would have been turning. Ergo, as the rotors were stopped at impact the engines must have been below governed Nf/Nr, and quite likely stopped, whether because wound back, shut down or for some other reason.
I think what we are fishing for is that in most (all?) serviceable and reasonably modern multi-engine helicopters, there is nothing you can do with the controls that will significantly droop the Nr unless the engines are set so as to permit Nr droop.
In the Sea King, the highest matched torque I ever saw in flight in the real aircraft (we did appalling things to the sim) was 135%, which is 12% over the gearbox transient limit. The Nr and both engines were perfectly happy (it was dark, in the mountains, going down rather fast, before NVG and I was the co-pilot staring rather hard at the engine gauges - the captain was a bit busy Aviating). I find it difficult to believe that a 35-yr-younger design wouldn't do better. And personal experience tells me that the rotor brake has no chance against the engines. So I'm assuming that, regardless of how the controls were handled, if the transmission was serviceable and the engines were running at governed Nf/Nr, the rotor would have been turning. Ergo, as the rotors were stopped at impact the engines must have been below governed Nf/Nr, and quite likely stopped, whether because wound back, shut down or for some other reason.
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Does it rule out that the engines were shut down deliberately(as in drills for tail rotor drive failure). Main gear box and mechanical failure of engines ruled out. Makes no mention of tail rotor/fenestron though...??
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So is there such a setting on the EC135 which will configure the engines in such a manner so as to permit a catasprophic droop in Nr?
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"In my mind I was speculating that we might have read about a catastrophic main gearbox failure"
I was fully expecting the same.
The AAIB report specifically states the main rotor and tail rotor were not rotating at impact. Witness reports indicate "misfiring" sounds.....presumably engine surges. So presumably the engines were running very shortly before the accident.
How do you go from engines running to rotor stopped in such a short time frame.......you'd need both engines to stop more or less at the same time (pretty unlikely) and for the pilot to grossly mishandle the collective (even more unlikely). It beats me.
I really hope we don't end up with a final report where the cause "could not positively be determined".
I was fully expecting the same.
The AAIB report specifically states the main rotor and tail rotor were not rotating at impact. Witness reports indicate "misfiring" sounds.....presumably engine surges. So presumably the engines were running very shortly before the accident.
How do you go from engines running to rotor stopped in such a short time frame.......you'd need both engines to stop more or less at the same time (pretty unlikely) and for the pilot to grossly mishandle the collective (even more unlikely). It beats me.
I really hope we don't end up with a final report where the cause "could not positively be determined".
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High Spirits
AAIB say "No evidence of mechanical failure".
Now I am quite aware that absence of evidence does not equal evidence of absence. But AAIB are the most conservative of bodies in their statements. I may be wrong, but given that they say that they can't find anything broken, I would bet a lot of money that they can prove that the fenestron would have been going round if the main rotor had been going round.
Further to that, a quick check of the report shows that they have explicitly said so:
providing drive from the
No 2 engine power turbine to the main rotor and to the
fenestron drive shaft.
And that, of course, only says that the fenestron drive shaft could have been going round, not the fenestron itself. However, given the "no mechanical failure" statement, we can be confident that the fenestron would have been turning if drive had been provided.
AAIB say "No evidence of mechanical failure".
Now I am quite aware that absence of evidence does not equal evidence of absence. But AAIB are the most conservative of bodies in their statements. I may be wrong, but given that they say that they can't find anything broken, I would bet a lot of money that they can prove that the fenestron would have been going round if the main rotor had been going round.
Further to that, a quick check of the report shows that they have explicitly said so:
providing drive from the
No 2 engine power turbine to the main rotor and to the
fenestron drive shaft.
And that, of course, only says that the fenestron drive shaft could have been going round, not the fenestron itself. However, given the "no mechanical failure" statement, we can be confident that the fenestron would have been turning if drive had been provided.
Last edited by Jetdriver; 10th Dec 2013 at 22:20.
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How do we know for sure that one engine was not already out and the pilot was expediting the trip home, perhaps on AP and then when the second engine quit the AP just tried to continue the flight?
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One of the smallest spaces on any aircraft is the one between the pilots ears. We've spent decades reducing the capacity of that space to be the root of disaster, but what we can do little to do is to increase the capacity of that space to respond to chaos.
The one man we would wish we could consult is no longer available to us.
I think we are all glad not to have been where he was.
But I wish I could have observed what he saw, in a sim.
The one man we would wish we could consult is no longer available to us.
I think we are all glad not to have been where he was.
But I wish I could have observed what he saw, in a sim.