Xlsky, I absolutely agree that all too often pilot error is blamed unfairly. I’d put AF447 in the same category.

Paco and SilsoeSid, I agree; TR failure is (apart from double engine fire) the only scenario in which I can see a pilot would need to shut down both engines.

In photographs of the scene, the fenestron appears to have separated from the boom at the ring frame on impact.

Hypothetically, if a progressive failure at that point had occurred in flight, could it bend the fenestron drive shaft enough to slow the main rotor below the point of no return?

I’m not suggesting this is what actually happened, I’m just trying to make a list of possible failures that could have caused this tragic accident.

SASless #1312.

I wondered about the effect of freewheel problems. A couple of points; many years ago I had a freewheel unit drive itself into re-engagement in a Hiller when established in an auto about 500', just after I had closed the throttle fully for an EOL exercise, .... the RRPM were "snatched" down dramatically to about 70% of their normal auto RPM and we "fell like a stone". Onlookers asked later why I didn't hear the backfiring going on behind me, perhaps I was too busy trying to wind the RPM back on with the ground rapidly approaching, but anyway a Doc later told me that hearing is the first sense to shut down in stressful situations. Also, like you, I remember the rotors turning very slowly after I completed the "EOL", but then that was because the rotors were trying to turn over a stopped piston engine (I even closed the ICO in the flare!). That can't happen with a turbine can it? I have every faith that the AAIB will come up with a full and detailed report in due course.

Sid,

I think that you may be getting a little off track with your assumptions -

Nr & N2
This is actually close to min flow on the fuel schedule. At that N1 the resulting N2/NR is what you would end up with at the current pitch setting. i.e if only one engine was running it would be lower and if you pulled the collective up N2/NR would reduce further. N2 is not governed in any way.

True but as these engines are FADEC controlled - N2 IDLE in this position IS controlled by the FADEC.

Nominal depending on DA.

100% is flight idle with high Nr selected

103% is flight idle on application of collective

100% is flight above 55kts

103% is flight when reducing below 50kts

Sid I understand your attraction to a TR problem theory followed by a deliberate in flight shotdown. However, as Henra points out, there is really only one way to have zero NR at impact. I cannot see how the pilot would choose to chop throttles without already having lowered the lever and at leat prepared for the autorotation.

Seized or jammed engines/gearboxes I believe would lead to destruction of the drivetrain in flight. It would appear that this did not happen.


DB

Imagine you're not a pilot. Or an engineer, or even particularly knowledgeable about aviation. You're a wealthy celebrity. A singer/songwriter, perhaps. Aircraft are just a means of travel to you.

You've read this thread and the others related to the Glasgow tragedy. You've read many conflicting versions about how to fly a helicopter. Would you get into a helicopter with any one pilot on this thread? Which one?

Do you think the singer is justified in feeling uncomfortable about flying in a craft that even the most experienced pilots cannot agree how to fly in an emergency?

Could this disagreement about how to fly the machine be at least a contributory factor in the Glasgow tragedy?

:zzz:RVDT,

This incident occurred in the UK at the end of November at just above sea level. (5 degrees, QNH 1025 DA -1520')

Let me assure you that if anyone in the UK today (my local DA -56') were to start up a 135, the ground idle selection would see the Nr & N2 settle at 75%. I can also assure you that if that they were then to move the twist grips to the red button position, the Nr & N2 would decrease and settle at 60%. On repositioning the twist grips into their detent'd and then selecting flight, the Nr & N2 would stabilise at 97%.

No assumptions, fact!


DB, I would suggest that the pilot took the action of fully closing the twist grips in order to prevent the engines running post impact, thereby saving a lot more lives.

Electric John,

We cannot answer your question because there are just too many variables.

DB

There isn't disagreement on how to handle emergencies, there is following the flight manual and not following the flight manual. Most operators act within the manufacturers guidance. Handling notes from eurocopter are pretty good, most drills are straightforward. I am snoozing reading the crappy arguments about autorotation entry. On Central Flying School, we used to chop the throttle on people without notice. I have seen many varied entry techniques under pressure, most work as long as the lever goes down. At the bottom you have a sliding scale of survivability depending how many of the landing techniques you attempted. I used to send people first solo of they could lower the lever at the top and attempt a flare/check at the bottom. The rest was icing on the cake that I would expect by half way through the course.

Straight over his head. If he had been listening at school then he'd have got a proper job.

Electric John - join the queue :ooh: We're thinking the same.

JayT2: Excellent post.

None of us are saying it isn't pilot error, but we are saying he isn't here to defend himself. That means you have to be respectful, my last little rant tried to cover that. People saying 'in the absence of major mechanical failure it must be the pilot' are disrespectful. The mull of McIntyre accident and Hillsborough disaster show the folly of assumption. Also, newspapers aviation sources are often pprune, they don't care about facts. If a professional pilot says something outrageous, they print it as aviation sources.
Not one of you knows what happened, not one. The people who do know certainly won't post here. I agree on freedom to speculate, I do! But I imagine the paper talk comes from here, consider the consequences of blaming Dave.
Consider how statements are written, 95 litres on board.... if that was in the main tank it was unusable. An engine capable of supplying drive doesn't mean it was connected to the drive train. Blades not turning at impact may have been turning just before impact. What were the positions of the engine controls? If they were normal, what stopped the engines? We're they stopped? Eye witness reports are often bullshot, one told a news station a piston might have gone in the engine!. So many of you have not considered the wording of the statement issued. ANY OF YOU could be correct, good luck

Jayteeto - I would go further and say whatever happened I would bet my years wages Dave tried his very best to overcome the adversity that he and his crew faced that night! Sometimes your best is not enough.

DB

Sid,

I may be asleep according to you but -

Care to elaborate as I don't understand what you are on about.

Explanation of engines and Nr, not autorotations.
 

No worries RVDT,

Ok, for explanation purposes, you enter autorotation and once stabilised, lets say at 90kts and 100%Nr, you twist off the throttles to the red button stop. This causes the N2s to run down to 60%.

At 100' you start your flare and have a nice little cushioned run on, slowly lowering the collective to slow yourself down. With the collective fully down the Nr decays to 60% whereupon the free wheels re-engage and keeps driving the gearbox at 60% until you do something to affect it.

Hope that explains it along with the help of a picture, with the triple tachometer (Nr Needle, with #1 N2 & #2 N2 needles behind), top right.

http://i52.photobucket.com/albums/g1...ps429db98e.jpg

Jayteeto, lest you be in any doubt, I do not think this was in any way pilot error, hence my comment:
"...but until all possible mechanical failures have been exhausted I'd be tempted to give any pilot, and especially this one, the benefit of the doubt."
You are right in saying that no one knows what caused the accident, and I'm glad you accept our freedom to speculate.
My possible scenario (post 1350) is one such speculation based on having read all I can and examined all the pictures I can. The first picture in: Glasgow helicopter crash: Investigation begins into why chopper 'fell like a stone' | UK | News | Daily Express appears to show separation at the ring frame.
On 6th December, the CAA issued: http://www.caa.co.uk/docs/33/2013120...D20130289E.pdf
Before anyone asks, I don't know the part number of the ring frame installed in this particular EC135, and it may be just an unfortunate coincidence.
But, like DB, I'd wager that the pilot did all anyone could to control the helicopter and minimise loss of life.

Roseland,

I have seen the photographs as well. The failure was not at the ring frame as far as I can see but behind it.

It would be pretty obvious to blind Freddie wrt the AAIB, ECD, BFU etc etc.

NO INFORMATION from any of them?

Know the area pretty well after installing 3 reinforcements.

RVDT, Many thanks. I defer to your superior knowledge. As I said, it was just one possible scenario.

Er Sid,

Fairly aware of the technicals thanks - agree with you fully.

Maintenance and Pilot licence on type.

I was just having a hard time with the context you were putting forward considering your assumptions versus the range of possibilities.

Yes your assumption could well be correct - or not.

Context is that it shows that the engines were shut down prior to impact.

Aye, I can think of one, Flt Lt (Retd) David Traill RAF...

I didnt know the guy but having been a passenger in one of Her Majesty's flying machines on more than a few occasions I always had total confidence in the driver, that view continues. Very well trained and professional to the N'th degree.