Police helicopter crashes onto Glasgow pub
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shortfinals & Torque Tonight
My thoughts entirely. At the sort of heights police helis operate at, I wouldn't have thought it possible to stop rotation before hitting the ground, even if you were trying to do it.
Maybe someone with EC135 experience could comment on the disc loading and rate of slowdown if drive is curtailed, for whatever reason.
My thoughts entirely. At the sort of heights police helis operate at, I wouldn't have thought it possible to stop rotation before hitting the ground, even if you were trying to do it.
Maybe someone with EC135 experience could comment on the disc loading and rate of slowdown if drive is curtailed, for whatever reason.
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AAIB Observations:
1. The helicopter struck the flat roof of the single story building with a high rate of descent and low/negligible forward speed.
2. At the time of the impact [..] neither the main rotor nor the fenestron tail rotor were rotating.
3. Initial assessment [..] indicated that the main rotor gearbox was capable of providing drive [..] to the main rotor and to the fenestron drive shaft.
The bulletin also states that the no.2 engine was capable of delivering power and that this may have been the case for the no.1 engine but that this has not yet been verified due to impact damage.
So, if the main gearbox and engine or engines were capable of functioning, just what could cause such a rapid depletion of main rotor rpm?
1. The helicopter struck the flat roof of the single story building with a high rate of descent and low/negligible forward speed.
2. At the time of the impact [..] neither the main rotor nor the fenestron tail rotor were rotating.
3. Initial assessment [..] indicated that the main rotor gearbox was capable of providing drive [..] to the main rotor and to the fenestron drive shaft.
The bulletin also states that the no.2 engine was capable of delivering power and that this may have been the case for the no.1 engine but that this has not yet been verified due to impact damage.
So, if the main gearbox and engine or engines were capable of functioning, just what could cause such a rapid depletion of main rotor rpm?
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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.
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If power delivery stopped and then the collective was pulled fully up that would slow the rotor rapidly. But why would power delivery have stopped, and why would the collective be high?
We are getting down to a Fuel Problem of some kind.
If the MGB was capable of rotation by hand turning the engine drive shaft....it isn't a MGB failure which would be the most common cause of Non-Turning Rotor Blades.
The only question that needs answering now is why the Blades stopped turning....everything else is secondary.
Who has the numbers....Total Fuel Capacity (Liters), Total Useable Fuel (Liters), Un-usable Fuel (Liters)....and any Cautions or other Warnings about Aircraft Attitude and Fuel related Caution and Warning Lights?
Is it safe to assume the AAIB would have mentioned any damage to a fuel cell that would resulted in the leakage of fuel from that Cell?
Is it safe to assume there was no spilled fuel as the AAIB did not mention that?
If we assume intact fuel tanks and fuel lines....thus no spillage.....what does the Drained Fuel Amount reported by the AAIB tell us?
A Mile and a Half from Base....a low fuel level....decelerating for a landing.....nose up pitch attitude....and something happened.....What?
I will ask one more question....and the experienced folks will understand why i ask it.
Was the Pilot's Collective Lever bent upwards....indicating a maximum physical effort pull on the Collective Lever being made?
If the MGB was capable of rotation by hand turning the engine drive shaft....it isn't a MGB failure which would be the most common cause of Non-Turning Rotor Blades.
The only question that needs answering now is why the Blades stopped turning....everything else is secondary.
Who has the numbers....Total Fuel Capacity (Liters), Total Useable Fuel (Liters), Un-usable Fuel (Liters)....and any Cautions or other Warnings about Aircraft Attitude and Fuel related Caution and Warning Lights?
Is it safe to assume the AAIB would have mentioned any damage to a fuel cell that would resulted in the leakage of fuel from that Cell?
Is it safe to assume there was no spilled fuel as the AAIB did not mention that?
If we assume intact fuel tanks and fuel lines....thus no spillage.....what does the Drained Fuel Amount reported by the AAIB tell us?
A Mile and a Half from Base....a low fuel level....decelerating for a landing.....nose up pitch attitude....and something happened.....What?
I will ask one more question....and the experienced folks will understand why i ask it.
Was the Pilot's Collective Lever bent upwards....indicating a maximum physical effort pull on the Collective Lever being made?
Last edited by SASless; 9th Dec 2013 at 18:25.
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quote:
"Once removed from the building, approximately 95 litres of fuel were drained from the fuel tank system."
I'm presuming that from the way the rescue services were operating, there was no fuel deposition in the building? If so, that doesn't seem to be a whole lot of juice? 75 kilos? Is that not lights and bells territory?
"Once removed from the building, approximately 95 litres of fuel were drained from the fuel tank system."
I'm presuming that from the way the rescue services were operating, there was no fuel deposition in the building? If so, that doesn't seem to be a whole lot of juice? 75 kilos? Is that not lights and bells territory?
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Ok, come with me for a moment.
Total or marked reduction in power, drop the collective. No brainier. Instinct to captain of this experience.
I get intermittent partial power loss (fuel pump problem? Low fuel - sucking alternat slugs of fuel/air?). Oh no, this can't be happening. But power comes back, so I pull for height - even if only to buy time if it deteriorates further. Power never fully restored, rotor rpm reducing fast. Boats burned.
I must emphasise that I know NOTHING. This is all pure pprune speculation, and those with deep type knowledge may be able to comment on possibility of such a partial/intermittent power loss scenario which, at v low level, urban, night, single crew, could suggest to a highly experienced captain that pull and hope looked a better bet than precautionary dump the collective and ar.
Total or marked reduction in power, drop the collective. No brainier. Instinct to captain of this experience.
I get intermittent partial power loss (fuel pump problem? Low fuel - sucking alternat slugs of fuel/air?). Oh no, this can't be happening. But power comes back, so I pull for height - even if only to buy time if it deteriorates further. Power never fully restored, rotor rpm reducing fast. Boats burned.
I must emphasise that I know NOTHING. This is all pure pprune speculation, and those with deep type knowledge may be able to comment on possibility of such a partial/intermittent power loss scenario which, at v low level, urban, night, single crew, could suggest to a highly experienced captain that pull and hope looked a better bet than precautionary dump the collective and ar.
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Arkroyal
I'm sure that when the ac was removed from the building and placed on the road, one of the first things that I saw happen was the fuel sample being taken. Given the angle of the ac on the strops, this would certainly be an 80+ kts attitude. With the fuel sample point being where I think it is, near to the fwd transfer pump, I would assume that the fuel in the forward part of the main tank wasn't drainable. With the fwd transfer pump u/s above 80kts, the fuel unusable is 59kgs.
This link shows a video of the recovery and at around 30 seconds it seems to me that the sample is being taken with the ac still on the strops at that angle;
Vid - The Independent
Is this the fuel sample being taken?
In conclusion, in addition to the 76kg litres drained (95 litres @ sg0.8) I suggest that there was at least another 60 litres in the system. 136 kgs would still give at least another 10 minutes before a night time MLA of 90kgs, which in itself would still leave another 25-ish minutes until the tanks are dry. So all in all over half an hour remaining before it ran out of fuel.
Sid
Not sure what you mean by the angle of the aircraft when fuel was taken.
It was taken after the helo was removed from the building, so probably substantially level.
How far was there to go to the helipad, and at what distance would one expects to commence a speed reducing flare?
Not sure what you mean by the angle of the aircraft when fuel was taken.
It was taken after the helo was removed from the building, so probably substantially level.
How far was there to go to the helipad, and at what distance would one expects to commence a speed reducing flare?
This link shows a video of the recovery and at around 30 seconds it seems to me that the sample is being taken with the ac still on the strops at that angle;
Vid - The Independent
Is this the fuel sample being taken?
In conclusion, in addition to the 76kg litres drained (95 litres @ sg0.8) I suggest that there was at least another 60 litres in the system. 136 kgs would still give at least another 10 minutes before a night time MLA of 90kgs, which in itself would still leave another 25-ish minutes until the tanks are dry. So all in all over half an hour remaining before it ran out of fuel.
Last edited by SilsoeSid; 9th Dec 2013 at 18:38.
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"Be interesting to know where the rotor brake lever position was".
If the rotor brake had been inadvertently deployed there would be very obvious overheating indications all around the rotor brake calipers and vicinity. Probably a fire as well. You can't miss it.
If the rotor brake had been inadvertently deployed there would be very obvious overheating indications all around the rotor brake calipers and vicinity. Probably a fire as well. You can't miss it.
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"Does the EC135 have a rotor brake?"
It does, but surely any rotor brake in a certified helicopter would be nowhere near powerful enough to actually cause an incident like this.
Besides, on the EC135 I believe the rotor brake disc is mounted to the tail rotor shaft, so even if it did manage to jam somehow, the tail rotor shaft would break long before the engines were overcome.
It does, but surely any rotor brake in a certified helicopter would be nowhere near powerful enough to actually cause an incident like this.
Besides, on the EC135 I believe the rotor brake disc is mounted to the tail rotor shaft, so even if it did manage to jam somehow, the tail rotor shaft would break long before the engines were overcome.
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Rotor brakes
Sanus
Agreed. You do not need a fully applied rotor brake or anything like it to cause a fire. There will be people on here who know / recollect far more than I do, but how about the Merlin Mk1 that went in the Sound of Raasay?
And, I have very personal experience of the results of cocking up the rotor brake action sequence. The result is unmistakeable.
Agreed. You do not need a fully applied rotor brake or anything like it to cause a fire. There will be people on here who know / recollect far more than I do, but how about the Merlin Mk1 that went in the Sound of Raasay?
And, I have very personal experience of the results of cocking up the rotor brake action sequence. The result is unmistakeable.
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Rotor brake applied intentionally ..... wouldn't the other person in the front fight to release it?
People, when you're thinking up your theories, don't forget, there were 3 people on board!
People, when you're thinking up your theories, don't forget, there were 3 people on board!
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If the rotor brake was deployed after the engines were stopped and RRPM had reduced with collective say not being lowered, there would be no fire. Extremely unlikely,of course. But then so is everything else.
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Rotor brake applied intentionally ..... wouldn't the other person in the front fight to release it?
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Fuel faults
I throw this in for one of the EC135 operators / engineers to comment, as I can't readily lay my hands on a LP fuel system schematic.
In the Sea King, we had a vaguely similar fuel system, in that all the working bits were in the collector tank (I suspect equivalent to the supply tank). Now one of the things that could go wrong was that if the pipework between the back and the front (where the collector tank was) became disconnected inside the tank, then the collector tank could be at the same level as the main tanks. In a Sea King, which held 6000 lbs of fuel (american aircraft) and had a minimum when I started of 85 lbs / side, the result of a pipe disconnect downstream of the transfer pumps and a leaky collector tank inlet valve would be absolutely nil, just as long as you didn't manoeuvre the aircraft hard at a low fuel state. There was, when I became the MTP for the RAF SAR fleet in the mid-90s, no check at all for these two pre-existing failures, and no cockpit indication direct or indirect that they were present.
Where I am headed with this boring old duffer's discourse on an unrelated and otherwise quite dissimilar type is:
What mechanical failures could cause the EC135 supply tank to be near empty, when the lack of failure indications could give the pilot the impression that it should be full? Are any of those failures of a type that could lie dormant for long periods? Could such mechanical failures (splits in feed pipes within the tank system, for example) be hidden from a post-crash inspection by the gross disruption of the lower fuselage?
I lack the knowledge to offer an opinion in respect of the EC135, but I have seen several dormant faults of this type on the Sea King once we went looking for them.
Sven
In the Sea King, we had a vaguely similar fuel system, in that all the working bits were in the collector tank (I suspect equivalent to the supply tank). Now one of the things that could go wrong was that if the pipework between the back and the front (where the collector tank was) became disconnected inside the tank, then the collector tank could be at the same level as the main tanks. In a Sea King, which held 6000 lbs of fuel (american aircraft) and had a minimum when I started of 85 lbs / side, the result of a pipe disconnect downstream of the transfer pumps and a leaky collector tank inlet valve would be absolutely nil, just as long as you didn't manoeuvre the aircraft hard at a low fuel state. There was, when I became the MTP for the RAF SAR fleet in the mid-90s, no check at all for these two pre-existing failures, and no cockpit indication direct or indirect that they were present.
Where I am headed with this boring old duffer's discourse on an unrelated and otherwise quite dissimilar type is:
What mechanical failures could cause the EC135 supply tank to be near empty, when the lack of failure indications could give the pilot the impression that it should be full? Are any of those failures of a type that could lie dormant for long periods? Could such mechanical failures (splits in feed pipes within the tank system, for example) be hidden from a post-crash inspection by the gross disruption of the lower fuselage?
I lack the knowledge to offer an opinion in respect of the EC135, but I have seen several dormant faults of this type on the Sea King once we went looking for them.
Sven
Last edited by Sven Sixtoo; 9th Dec 2013 at 19:13. Reason: speeling