Police helicopter crashes onto Glasgow pub
Join Date: Apr 2008
Location: scotland
Posts: 29
Likes: 0
Received 0 Likes
on
0 Posts
Well, it's been a disappointing day for those of us that hoped the interim report might provide some clarity, some of the posts this evening have been frankly ridiculous.
A couple of pages ago I asked if the 135 has 'crash handles', similar to other EC types. Could someone in the know please clarify for me?
Ta.
A couple of pages ago I asked if the 135 has 'crash handles', similar to other EC types. Could someone in the know please clarify for me?
Ta.
Purveyor of Egg Liqueur to Lucifer
Sven Sixtoo
No it didn't, it said ...
"Initial assessment provided no evidence of major mechanical disruption of either engine and indicated that the main rotor gearbox was capable of providing drive from the No 2 engine power turbine to the main rotor and to the fenestron drive shaft."
... which suggests to me that there is the possibility that there may be something to find in the tail rotor drive shaft department.
High Spirits
AAIB say "No evidence of mechanical failure".
AAIB say "No evidence of mechanical failure".
"Initial assessment provided no evidence of major mechanical disruption of either engine and indicated that the main rotor gearbox was capable of providing drive from the No 2 engine power turbine to the main rotor and to the fenestron drive shaft."
... which suggests to me that there is the possibility that there may be something to find in the tail rotor drive shaft department.
Join Date: Oct 2011
Location: bora scirocco
Age: 50
Posts: 280
Likes: 0
Received 0 Likes
on
0 Posts
A couple of pages ago I asked if the 135 has 'crash handles', similar to other EC types. Could someone in the know please clarify for me?
... It doesn't!
Last edited by Jet Ranger; 9th Dec 2013 at 21:40.
Purveyor of Egg Liqueur to Lucifer
MG
Where do you get that from Sid?
Quote:
I suggest that there was at least another 60 litres in the system.
I suggest that there was at least another 60 litres in the system.
The amount of fuel drained would be limited to the level of the drain point, (near to the pump). Much like those boxes of wine, when the level of the wine gets to below the tap you can't pour any more wine out unless you tip the box.
In the scenario of the fwd transfer pump failing above 80 kts, ( greater nose down attitude), the unusable fuel is 59 kgs. Therefore if the ac on the strops is at an angle equal to or greater than the 80 kt attitude, that fuel will not be able to be drained until the ac is level. The same drain point/fuel level explanation applies for the smaller amount not accessible in the supply tanks.
Mind you, the report said that "approximately 95 litres of fuel were drained from the fuel tank", which doesn't necessarily mean that they drained it until it was empty, perhaps that's as much as their container could hold.
Based on awblain's explanation, rapid loss of Nr is possible if power is absent meaning that in order to achieve the AAIB's initial findings of a high speed impact with nil apparent Nr we are looking at a total power failure followed by sustained pitch on the main rotor? 
Probably yes. I have difficulties conceiving many other ways to end up with a fully stalled rotor and thus close to 0 RRPM on impact
Join Date: Oct 2011
Location: bora scirocco
Age: 50
Posts: 280
Likes: 0
Received 0 Likes
on
0 Posts
... which suggests to me that there is the possibility that there may be something to find in the tail rotor drive shaft department.
Join Date: Jan 2008
Location: Hampshire
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
I saw earlier that the 'rotor brake' had been discounted in an earlier reply but can't find where that was mentioned in the thread. Is it as simple as the rotor brake being locked out in flight?
It also seems very close to the engine controls from the panel diagrams I saw and I wonder if trying to shut down an engine in an emergency situation could also have resulted in accidental application of the rotor brake. Removing power from a misbehaving engine and applying the rotor brake might explain everything observed from the ground.
It also seems very close to the engine controls from the panel diagrams I saw and I wonder if trying to shut down an engine in an emergency situation could also have resulted in accidental application of the rotor brake. Removing power from a misbehaving engine and applying the rotor brake might explain everything observed from the ground.
We should stay on solid ground. Therefore I am going to steer clear of any (so far) mechanical faults as mentioned in the AAIB prelim from now on.
The usual caveat: can a current operator confirm the feasability of this please as it's been a while since I drove the old girl? However my current experience on heavies should transfer across hopefully.
The pilot is coming to the end of his task having spent some considerable time doing the same old, same old. I recall getting bored/tired towards the end of some monotonous sorties and my mind wandering.
At some challenging stage in his flight he experienced a potentially benign run down or torque fluctuation caused by one of the ECU's stalling/surging (as witnessed by outsiders). "Normally" one determines the duff engine by comparing Nr movement with the suspect engine Ng. The duff engine drives the Nr out of its governed range thus enabling the pilot to select the correct engine for shut down. Perhaps this time the wrong engine was shut down whilst tired/confused. This left the duff engine driving the Nr and if that engine was providing less than nominal output the Nr will droop or even worse. He may have instinctlively raised the collective to maintain his cruise height anyway (or tried to stop his increasing descent) and the Nr would continue to decay - ever closer towards its point of no return (what is it in the 135? 82%?). He sees this and tries in vain to salvage the decaying Nr by chopping the remaining engine and lowering the collective but too late, he sees the looming deck and pulls for all its worth to salvage some of the RoD. By then there is very little Nr left, but what is left is washed out by that final application of lever. RoD continues unchecked and the cab hits hard with no engines or little minimal Nr.
The usual caveat: can a current operator confirm the feasability of this please as it's been a while since I drove the old girl? However my current experience on heavies should transfer across hopefully.
The pilot is coming to the end of his task having spent some considerable time doing the same old, same old. I recall getting bored/tired towards the end of some monotonous sorties and my mind wandering.
At some challenging stage in his flight he experienced a potentially benign run down or torque fluctuation caused by one of the ECU's stalling/surging (as witnessed by outsiders). "Normally" one determines the duff engine by comparing Nr movement with the suspect engine Ng. The duff engine drives the Nr out of its governed range thus enabling the pilot to select the correct engine for shut down. Perhaps this time the wrong engine was shut down whilst tired/confused. This left the duff engine driving the Nr and if that engine was providing less than nominal output the Nr will droop or even worse. He may have instinctlively raised the collective to maintain his cruise height anyway (or tried to stop his increasing descent) and the Nr would continue to decay - ever closer towards its point of no return (what is it in the 135? 82%?). He sees this and tries in vain to salvage the decaying Nr by chopping the remaining engine and lowering the collective but too late, he sees the looming deck and pulls for all its worth to salvage some of the RoD. By then there is very little Nr left, but what is left is washed out by that final application of lever. RoD continues unchecked and the cab hits hard with no engines or little minimal Nr.
Where does this obsession with the rotor brake come from?
It is a rather flimsy device compared to the aerodynamic forces involved and is strictly manual.
It is a rather flimsy device compared to the aerodynamic forces involved and is strictly manual.
Join Date: Nov 2007
Location: It's very flat around here...
Posts: 9
Likes: 0
Received 0 Likes
on
0 Posts
Jetranger, there may not be evidence of the Fenestron failure, but here's one to think about - pilot reacts to a PERCEIVED TR malfunction, which may have actually been some strange disruption to TR efficiency (Fenestron Stall?) and carries out TR drive failure drill, secures both engines and makes a very good stab at an EOL, but difficulty in judging height at night causes him to flare early with subsequent long fall raising collective to the stops. Would the Nr decay all the way? Dunno, but this may have happened before.
Join Date: Nov 2000
Location: Grobelling through the murk to the sunshine above.
Age: 60
Posts: 562
Likes: 0
Received 0 Likes
on
0 Posts
and tries in vain to salvage the decaying Nr by chopping the remaining engine and .............
Join Date: Nov 2000
Location: Grobelling through the murk to the sunshine above.
Age: 60
Posts: 562
Likes: 0
Received 0 Likes
on
0 Posts
cenzo
That's a good theory, and should be apparent to the AAIB by the position of the engine controls.
I've done EOLs at night, to a lighted and clear grass strip, and can easily perceive massive height misjudgements over a built-up area.
That's a good theory, and should be apparent to the AAIB by the position of the engine controls.
I've done EOLs at night, to a lighted and clear grass strip, and can easily perceive massive height misjudgements over a built-up area.
Purveyor of Egg Liqueur to Lucifer
To sum up, the AAIB have said that nothing departed the ac prior to impact and that there is no evidence of major mechanical disruption of either engine and indicated that the main rotor gearbox was capable of providing drive from the No 2 engine power turbine to the main rotor and to the fenestron drive shaft.
So, all is well up to the point at which the mrgb is connected to the trds. Anything beyond that point could still present the cause for the incident, such as the trds, bearings and the trgb itself.
I hope some people sleep well tonight believing the papers and their own consciences, I'll be dropping off going through tail rotor scenarios.
Glasgow pub tragedy prompts West Midlands helicopter checks « Express & Star
So, all is well up to the point at which the mrgb is connected to the trds. Anything beyond that point could still present the cause for the incident, such as the trds, bearings and the trgb itself.
I hope some people sleep well tonight believing the papers and their own consciences, I'll be dropping off going through tail rotor scenarios.
Glasgow pub tragedy prompts West Midlands helicopter checks « Express & Star
From the aerodynamic side this will not be an absolute number. It will depend on weight and RoD. Edit: and altitude but this wouldn't have played a role here.
Stall (drag) depends strictly on AoA.
So, while in horizontal flight, a momentary drop to 75% might be recoverable at a certain mass, the same at a higher mass may not. Same applies, once a descent has started. This will increase AoA and thus increase the likelyhood of a stall at an RPM which was still recoverable in horizontal flight.
In a stabilised descent with collective fully down, somewhere in the mid to high 70s, maybe 80 should be about it for most helicopters with relatively high power/disc loading and thus range of collective movement.
Join Date: Aug 2008
Location: Warminster, UK
Age: 73
Posts: 25
Likes: 0
Received 0 Likes
on
0 Posts
A very puzzling and perturbing scenario from the AAIB report. And no scenario that I can imagine that can be aligned in any way with the (at least two, I believe) reports from inside the pub of a brief period between some "minor" ceiling collapse and the main impact.
Purveyor of Egg Liqueur to Lucifer
TC
If the Nr goes up, there's no engine switching off going on!
The duff engine drives the Nr out of its governed range thus enabling the pilot to select the correct engine for shut down.
Join Date: Jan 2001
Location: The Burrow, N53:48:02 W1:48:57, The Tin Tent - EGBS, EGBO
Posts: 2,297
Likes: 0
Received 0 Likes
on
0 Posts
Any radio hams out there - listening in?
Last edited by DX Wombat; 11th Dec 2013 at 23:43.
Join Date: Aug 2006
Location: nice house
Age: 57
Posts: 53
Likes: 0
Received 0 Likes
on
0 Posts
Mind you, the report said that "approximately 95 litres of fuel were drained from the fuel tank", which doesn't necessarily mean that they drained it until it was empty, perhaps that's as much as their container could hold.
