Police helicopter crashes onto Glasgow pub
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The reference to the witness being sure that he saw the aircraft "tumbling end over end" and trailing sparks is an interesting one.
A tail rotor (fenestron) drive failure in a low speed, high power situation would result in the aircraft rotating (yawing) quite suddenly and rapidly, out of control. Yaw/roll coupling may also occur. We don't know exactly what might occur because this is way beyond the flight testing done by anyone, for obvious reasons.
It should also result in the pilot rapidly (possibly instinctive for an experienced pilot) lowering the collective lever to reduce the power demand on the main rotor, in an attempt to regain some sort of control. From the hover or low speed this would obviously result in a sudden and rapid descent. If this doesn't stop the yawing motion, the next step is to shut off the engines and hopefully regain a steady, autorotative state.
As Sid has posted, by "closing the throttles" of these turbine engines in the normal way will only put the engines down to an idle setting, which will disengage the drive to the main rotor. However, once the main rotor speed droops to a low figure, they will "re-engage" and therefore provide some further torque reaction, causing further aircraft rotation in yaw. The only way to prevent or stop this is to shut off the engines fully. Personally, whatever the FRC drills say, I would prefer not to arrive at the scene of a likely hard landing accident with engines running, even at idle - they are obviously a major ignition source for any spilled fuel.
The tail rotor (fenestron on an EC135) is driven by a series of jointed shafts, much like the propshaft of a rear wheel drive road vehicle. A drive shaft failure would quite likely result in some mechanical noise, possibly some sparks from metal to metal contact (depending on the exact nature of the failure) all the way to the ground, as long as the main rotors were rotating, because the two are directly geared together.
What occurred on this tragic occasion is, of course, not yet fully understood.
A tail rotor (fenestron) drive failure in a low speed, high power situation would result in the aircraft rotating (yawing) quite suddenly and rapidly, out of control. Yaw/roll coupling may also occur. We don't know exactly what might occur because this is way beyond the flight testing done by anyone, for obvious reasons.
It should also result in the pilot rapidly (possibly instinctive for an experienced pilot) lowering the collective lever to reduce the power demand on the main rotor, in an attempt to regain some sort of control. From the hover or low speed this would obviously result in a sudden and rapid descent. If this doesn't stop the yawing motion, the next step is to shut off the engines and hopefully regain a steady, autorotative state.
As Sid has posted, by "closing the throttles" of these turbine engines in the normal way will only put the engines down to an idle setting, which will disengage the drive to the main rotor. However, once the main rotor speed droops to a low figure, they will "re-engage" and therefore provide some further torque reaction, causing further aircraft rotation in yaw. The only way to prevent or stop this is to shut off the engines fully. Personally, whatever the FRC drills say, I would prefer not to arrive at the scene of a likely hard landing accident with engines running, even at idle - they are obviously a major ignition source for any spilled fuel.
The tail rotor (fenestron on an EC135) is driven by a series of jointed shafts, much like the propshaft of a rear wheel drive road vehicle. A drive shaft failure would quite likely result in some mechanical noise, possibly some sparks from metal to metal contact (depending on the exact nature of the failure) all the way to the ground, as long as the main rotors were rotating, because the two are directly geared together.
What occurred on this tragic occasion is, of course, not yet fully understood.
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Shy, concur, but are we aware of the flight regime just prior to accident? If they were 'on a job' and hovering OGE, then your hypothesis would be bang on, but presumably if they were transiting at normal cruise speed, the effects of a TR drive failure would be offeset by the aerodynamic forces on the tail and would not necessarily result in the severe yaw/roll expected at low speed. I guess we'll have to wait and see.
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Re tumbling end over end during the descent I agree with ST and think what could have been seen was yawing and rolling during the initial rotations following a possible fenestron drive failure.
A drive shaft failure would quite likely result in some mechanical noise, possibly some sparks from metal to metal contact (depending on the exact nature of the failure) all the way to the ground, as long as the main rotors were rotating, because the two are directly geared together.
In the early days of the EC135 an ECD h/c had a driveshaftfailure in flight, which resulted in a total loss of the cover and driveshaft, but an successful landing afterwards.
Another EC135 crash was possibly discussed here in the forum some time ago. A japanese 135 lost tailrotor control due to a broken push-pull tube while on maintenance test flight. They cashed and I think, the crew of 2 perished... A vid showed them tumbling out of the sky.
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Roof Structure - Sawman
In addition to my comments on this not being a landing place of choice, I do have some experience of the construction to share.
Being around Construction in Glasgow for 25 years, I wouldn't expect to find any steel in that roof, indeed all I can see is timber in the photo's. (in fact the open lattice type purlin beams described in earlier posts are a raretity in the UK, used only in steel framed industrial buildings)
There is a massive stone wall in the middle of the pub, this is intact and its this that the aircraft 'slid' down as it went through the rest of the roof structure to the North, it also explains why the South end of the pub was relatively unscathed.
The original first floor timber floor is likely to have been in place, these joists being up to 12 inches deep and at centres of 18 inches, they would not be on hangers or bolted, but set into pockets in the masonry. On top of this would have been further counter joists to support the (1970's?) original flat roof, and there appears to have been a further batten and board layer to support a later over-roofing.
The AC condensers on the roof, I cant see having caused extensive damage to the aircraft if it had made a semi controlled landing and 'bumped' one with its tail. These units are not fixed down (as to do so breaches the roofing membrane) so they are usually sitting on plastic feet or bolted to a loose paving slab - you could easily push one over.
You might also notice a Flue to the South which is about a 1.5 metres or so above the roof, its fragile and completely intact, so the aircraft must have came in nose down at a steep angle to have avoided it and the first AC condenser, only taking out the second one.
From a building perspective, that wasn't a progressive collapse due to overloading, it was impacted hard, I suspect the nose went straight through the timber structure as the dividing wall crushed the port side of the underbody, it may simply have got wedged here momentarily until one further joist broke or slipped from its pocket, allowing further forward and downward movement.
This is just taken from the photo's I have seen and works on similar buildings.
Sorry for my laymans terms descriptions of the aircraft.
Being around Construction in Glasgow for 25 years, I wouldn't expect to find any steel in that roof, indeed all I can see is timber in the photo's. (in fact the open lattice type purlin beams described in earlier posts are a raretity in the UK, used only in steel framed industrial buildings)
There is a massive stone wall in the middle of the pub, this is intact and its this that the aircraft 'slid' down as it went through the rest of the roof structure to the North, it also explains why the South end of the pub was relatively unscathed.
The original first floor timber floor is likely to have been in place, these joists being up to 12 inches deep and at centres of 18 inches, they would not be on hangers or bolted, but set into pockets in the masonry. On top of this would have been further counter joists to support the (1970's?) original flat roof, and there appears to have been a further batten and board layer to support a later over-roofing.
The AC condensers on the roof, I cant see having caused extensive damage to the aircraft if it had made a semi controlled landing and 'bumped' one with its tail. These units are not fixed down (as to do so breaches the roofing membrane) so they are usually sitting on plastic feet or bolted to a loose paving slab - you could easily push one over.
You might also notice a Flue to the South which is about a 1.5 metres or so above the roof, its fragile and completely intact, so the aircraft must have came in nose down at a steep angle to have avoided it and the first AC condenser, only taking out the second one.
From a building perspective, that wasn't a progressive collapse due to overloading, it was impacted hard, I suspect the nose went straight through the timber structure as the dividing wall crushed the port side of the underbody, it may simply have got wedged here momentarily until one further joist broke or slipped from its pocket, allowing further forward and downward movement.
This is just taken from the photo's I have seen and works on similar buildings.
Sorry for my laymans terms descriptions of the aircraft.
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cenzo, I totally agree. I added the final sentence on my post for precisely that reason.
This, on the face of it, is a highly unusual accident scenario (with unusually tragic result). I'm sure all the evidence exists and can eventually be pieced together by the AAIB, whilst we here are merely trying to make something of the puzzle without all the pieces.
Skadi, yes, a loss of tail rotor authority (to low anti-torque power) could of course give similar symptoms to a loss of drive, albeit without sparks and no unusual noise. But if that was the case here, it wouldn't explain the witness report. Also the loss of drive at either end of the shaft could have occurred and this would be perhaps less obvious from the photo. I did notice that the entire tail empennage was no longer fully attached to the tail boom. Close mechanical examination would soon make this clear and I'm sure this is/was a priority.
This, on the face of it, is a highly unusual accident scenario (with unusually tragic result). I'm sure all the evidence exists and can eventually be pieced together by the AAIB, whilst we here are merely trying to make something of the puzzle without all the pieces.
Skadi, yes, a loss of tail rotor authority (to low anti-torque power) could of course give similar symptoms to a loss of drive, albeit without sparks and no unusual noise. But if that was the case here, it wouldn't explain the witness report. Also the loss of drive at either end of the shaft could have occurred and this would be perhaps less obvious from the photo. I did notice that the entire tail empennage was no longer fully attached to the tail boom. Close mechanical examination would soon make this clear and I'm sure this is/was a priority.
Scoobydroo: thanks for taking the time to inform us of this unique piece of witness evidence: I hope your son isn't too traumatised.
In concert with another witness statement about the flight path of said a/c and also the footage of the crash scene, we can be as certain as one can in these circumstances that the a/c was near stationary when the descent was initiated. I woul also postulate that because Post 534 indicates the blades were stationary, that something very very quick and very devastating took place seconds earlier.
I would suggest that by the time Post 534 saw the incident - the pilot was a already a passenger and no longer in control of the helo.
Ag B has a valid point which I think shouldn't be ignored in that a multiple bird strike may have possibly been a cause (although he did go onto say that the a/c may have been in transit and I don't agree with this).
I am going to use post 534 as the basis for the following revised theories:
(No particular order): These are obviously alleged scenarios.
Catastrophic failure of the MGB. Rotor decay, pilot accepts the hopelessness of the situation and does what he can to minimise damage on impact by switching engines and fuel off.
(The other side of the argument would suggest that any hint of mechanical problems would ground the fleet - which didn't happen).
A pilot suffers a severe and serious incapacitation (TIA for eg). Passing in and out of consciousness, they attempt to descend to land, roll the throttles off to FI and inadvertently raise the collective thinking they are close to the ground, when in fact they are still hundreds of feet up in the air.
Sabotage.
1 x other.
I simply cannot think of any other scenarios. (That's probably why I never worked for ther AAIB
).
am a frequent visitor to the site, but infrequent poster. My youngest son wants to be a pilot and is mid-application to join the navy to train as a helicopter pilot and I usually read the wannabe section and military threads. I spotted this thread and have read it with considerable interest as my middle son is the editor of the Scottish Sun who witnessed the fall of the helicopter on Friday night from the top floor of the multistorey car park, about 250metres West from the crash site. Despite his journalistic background and being a hardened hack, he has been severely traumatised by what he saw. Gordon's reports have been well published on all of the TV channels and newspapers but I think it is fair to say that he believes that the helicopter was out of control. He was on the phone to a colleague in London and was about to get his the car to drive home when he became aware of a loud noise above him - when Gordon is on the phone, like many young people, it is difficult to distract him so the noise must have been considerable. He describes the night as being crystal clear and was aware of the helicopter starting its fall. He initially thought the helicopter was falling towards him and dived behind the car but continued to watch the helicopter fall. He describes the helicopter tumbling - not sure if this is what you are describing as autorotating - but he does not think that this was controlled. The helicopter, as we know, did not hit the car park but landed 250m away on the other side of a block of flats and the Holiday Inn Express and he did not see the impact. He was able to see the police signs on the helicopter as it came down and stated that he was 80% certain that it was the police helicopter that had been involved long before it was officially announced. He is also clear that the helicopter was eerily quiet, that the rotors did not seem to be rotating and was amazed that there was no explosion. He struggled to get his car out of the car park and by the time he got to the site on foot, which is not far away, the emergency services were already arriving and blocking off the scene. He ran round the corner into Argyll Street to get back to his office in Queen Street. He spoke to a policeman in Argyll Street who was totally unaware of the helicopter coming down and initially did not believe him until he called into control.
I appreciate that Gordon is no expert but he is clear that the helicopter could not have landed gently on the roof of the pub, or that the pilot was trying to find a safe landing place. He has been interviewed by the authorities and told that in due course will be required to give evidence at any subsequent Fatal Accident Inquiry.
I hope that this helps and that the reason for the crash is ascertained sooner rather than later.
I appreciate that Gordon is no expert but he is clear that the helicopter could not have landed gently on the roof of the pub, or that the pilot was trying to find a safe landing place. He has been interviewed by the authorities and told that in due course will be required to give evidence at any subsequent Fatal Accident Inquiry.
I hope that this helps and that the reason for the crash is ascertained sooner rather than later.
I would suggest that by the time Post 534 saw the incident - the pilot was a already a passenger and no longer in control of the helo.
Ag B has a valid point which I think shouldn't be ignored in that a multiple bird strike may have possibly been a cause (although he did go onto say that the a/c may have been in transit and I don't agree with this).
I am going to use post 534 as the basis for the following revised theories:
(No particular order): These are obviously alleged scenarios.
Catastrophic failure of the MGB. Rotor decay, pilot accepts the hopelessness of the situation and does what he can to minimise damage on impact by switching engines and fuel off.
(The other side of the argument would suggest that any hint of mechanical problems would ground the fleet - which didn't happen).
A pilot suffers a severe and serious incapacitation (TIA for eg). Passing in and out of consciousness, they attempt to descend to land, roll the throttles off to FI and inadvertently raise the collective thinking they are close to the ground, when in fact they are still hundreds of feet up in the air.
Sabotage.
1 x other.
I simply cannot think of any other scenarios. (That's probably why I never worked for ther AAIB
).
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I can think of another scenario and again one that could fit the eye witness report.
Are there any previous instances of a fenestron tail rotor assembly shedding a blade? What would the be result on the tail structure of an out of balance fenestron assembly?
Are there any previous instances of a fenestron tail rotor assembly shedding a blade? What would the be result on the tail structure of an out of balance fenestron assembly?
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ST
Surely if a fenestrom blade came off it would depart the scene at a fair lick and go a distance so AAIB would be looking for it and there appears to be no such action
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Shy, don't know of any fenestron blade shedding incidents, but we did have the rather unproven phenomena of the 'fenestron stall' which led to a couple of Gazelles arriving in a snotty heap. Thankfully no major injuries and I can't really remember whether this was a disruption to the airflow due to being IGE a la recirculation or not. Not relevant to this one though, I think. Any operators aware of this phenomena in the EC135?
Sorry whodictus, clearly typing and thinking of the same thing at the same time.
Sorry whodictus, clearly typing and thinking of the same thing at the same time.
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cenzo,
Yes I've heard of it and read the accident reports, as an ex Shawbury AFTS Gazelle QHI.
The photos of the fenestron assembly showed some blades missing. Presumably all of these missing blades have been located and accounted for in the wreckage.
Yes I've heard of it and read the accident reports, as an ex Shawbury AFTS Gazelle QHI.
The photos of the fenestron assembly showed some blades missing. Presumably all of these missing blades have been located and accounted for in the wreckage.
IMO, any "tumbling-end-over-end" report would have to treated with reserve. As an anorak, I've been observing a/c of all kinds from the ground all my life, and even in broad daylight it's easy completely to misread the attitude and trajectory of an a/c - even during a simple steep turn.
What I find more interesting is that, according to his father, the Scottish Sun editor was at one point in fear that the a/c might be crashing on to a car park 250m from its subsequent impact site. That strikes me as significant.
Quote from Scoobydroo (my emphasis):
He was on the phone to a colleague in London and was about to get his the car to drive home when he became aware of a loud noise above him - when Gordon is on the phone, like many young people, it is difficult to distract him so the noise must have been considerable. He describes the night as being crystal clear and was aware of the helicopter starting its fall. He initially thought the helicopter was falling towards him and dived behind the car but continued to watch the helicopter fall. He describes the helicopter tumbling - not sure if this is what you are describing as autorotating - but he does not think that this was controlled. The helicopter, as we know, did not hit the car park but landed 250m away on the other side of a block of flats and the Holiday Inn Express and he did not see the impact. He was able to see the police signs on the helicopter as it came down and stated that he was 80% certain that it was the police helicopter that had been involved long before it was officially announced. He is also clear that the helicopter was eerily quiet, that the rotors did not seem to be rotating and was amazed that there was no explosion.
Taken on face value - and ignoring the "tumbling" reference - the a/c was initially very noisey, and then eerily quiet. And, during that relatively short period, the a/c may have travelled a considerable distance horizontally.
What I find more interesting is that, according to his father, the Scottish Sun editor was at one point in fear that the a/c might be crashing on to a car park 250m from its subsequent impact site. That strikes me as significant.
Quote from Scoobydroo (my emphasis):
He was on the phone to a colleague in London and was about to get his the car to drive home when he became aware of a loud noise above him - when Gordon is on the phone, like many young people, it is difficult to distract him so the noise must have been considerable. He describes the night as being crystal clear and was aware of the helicopter starting its fall. He initially thought the helicopter was falling towards him and dived behind the car but continued to watch the helicopter fall. He describes the helicopter tumbling - not sure if this is what you are describing as autorotating - but he does not think that this was controlled. The helicopter, as we know, did not hit the car park but landed 250m away on the other side of a block of flats and the Holiday Inn Express and he did not see the impact. He was able to see the police signs on the helicopter as it came down and stated that he was 80% certain that it was the police helicopter that had been involved long before it was officially announced. He is also clear that the helicopter was eerily quiet, that the rotors did not seem to be rotating and was amazed that there was no explosion.
Taken on face value - and ignoring the "tumbling" reference - the a/c was initially very noisey, and then eerily quiet. And, during that relatively short period, the a/c may have travelled a considerable distance horizontally.
Last edited by Chris Scott; 4th Dec 2013 at 11:39. Reason: "attitude" added in 1st para. Last sentence added.
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Bladecrack, Sven,
I think you are being slightly unrealistic in expecting a single pilot to be able to remember the exact location of a small non-descript building, among many other larger buildings and obstructions, while dealing with (probably) a major emergency, at night! Yes of the course the pilot (RIP) was familiar with that part of the city, but what tends to stick in our minds from local area knowledge is the features which are either a hazard to us as we go about our business, or useful landmarks (in many cases, one feature can be both at once). The Clutha was neither of these.
In fact, your mention of 'prominent buildings' kind of makes my point for me!
I think you are being slightly unrealistic in expecting a single pilot to be able to remember the exact location of a small non-descript building, among many other larger buildings and obstructions, while dealing with (probably) a major emergency, at night! Yes of the course the pilot (RIP) was familiar with that part of the city, but what tends to stick in our minds from local area knowledge is the features which are either a hazard to us as we go about our business, or useful landmarks (in many cases, one feature can be both at once). The Clutha was neither of these.
In fact, your mention of 'prominent buildings' kind of makes my point for me!
Last edited by Jetdriver; 5th Dec 2013 at 16:16.
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Chris, agree. In a tradititional helo, most of the noise comes from the interaction between the air from the main rotor onto the tail rotor blades. This is not the case in a shrouded fan, where there will of course be some noise from the MRB, and I seem to remember the fenestron being quite noisy as well. This combined with the engine noise makes quite a racket. For it to be 'eerily quiet' would appear to intimate that the engines were off and the noise of the fenestron assembly and rotor were absent.
Many factors will affect this though, for example, if the wind was relatively strong, this may alter the individuals perception of the noise. Too many variables, but food for thought.
Many factors will affect this though, for example, if the wind was relatively strong, this may alter the individuals perception of the noise. Too many variables, but food for thought.
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If a flock of birds had blocked the engines (
), I for one, would like to see how they managed to do it. With the 135s intake position and bits in the way, they must have been pretty flexible birds..........
), I for one, would like to see how they managed to do it. With the 135s intake position and bits in the way, they must have been pretty flexible birds..........
In pictures: Glasgow helicopter crash tragedy pt 2 - Daily Record
Looking at the photos posted by the newspaper....any suggestion that the top of the Pub was the intended point of landing during an autorotation just does not hold water.
Compare the obstacles around the roof top....on the roof top...and then look at all the pavement and open areas that surround the Pub on two sides and all the obstructions on the other two sides.
Normally, one aims for the largest, most flat,least obstructed area when doing a forced landing.
Looking at the photos posted by the newspaper....any suggestion that the top of the Pub was the intended point of landing during an autorotation just does not hold water.
Compare the obstacles around the roof top....on the roof top...and then look at all the pavement and open areas that surround the Pub on two sides and all the obstructions on the other two sides.
Normally, one aims for the largest, most flat,least obstructed area when doing a forced landing.
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Just some insigth to the fuel system for ec-135;
- In hover you will normally get a Fuel pump Aft light around 71kg (15-20min), this is unusable fuel until acc. speed above 80kts.
- Low fuel light and gong when 8-10 min fuel remaining
- The supply tanks have a 5 kg difference to avoid flame out of engines at the same time!
That´s if system is a´ ok!
This machine is strong enough to hover OEI at current config. 3 crew police version, with 60 min of fuel remaining. Understand it had been airborn for almost 2 hr´s.
Birdstrike is ulikely the way the air intake is built passing cooling fan, MGB and changing 90´direction to a protected compressor. That´s also why flame out due to snow/icing is highy unlikely on theese machines.
Hover at night can cause SWP.
Still a mystery to me!
- In hover you will normally get a Fuel pump Aft light around 71kg (15-20min), this is unusable fuel until acc. speed above 80kts.
- Low fuel light and gong when 8-10 min fuel remaining
- The supply tanks have a 5 kg difference to avoid flame out of engines at the same time!
That´s if system is a´ ok!
This machine is strong enough to hover OEI at current config. 3 crew police version, with 60 min of fuel remaining. Understand it had been airborn for almost 2 hr´s.
Birdstrike is ulikely the way the air intake is built passing cooling fan, MGB and changing 90´direction to a protected compressor. That´s also why flame out due to snow/icing is highy unlikely on theese machines.
Hover at night can cause SWP.
Still a mystery to me!