Police helicopter crashes onto Glasgow pub
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Enough fuel on board, doesn't mean fuel was supplying the engines. Take the Guernsey SAR aircraft, I know that was pilot error and I very much doubt the Glasgow one is! But in the SAR aircraft case:
Two engines
Well maintained aircraft
Experienced crew
At night
Low level
The Pilot new he had plenty of fuel on board, one engine stops shortly followed by the other one. It's nothing short of a miracle they found the only off Airfield landing space on the Island, walked away from it and lived to tell the tale!
Otherwise we may well be discussing on this forum, how a perfectly serviceable aircraft with plenty of fuel on board had both engines quit!
If Dave's supply tanks were wrongly reading full and he got no amber warnings (as in the case of the NWAA 135, although I see that post has been pulled from this thread) then imagine his surprise when he got a red warning in a very difficult situation.
Ok shoot away! I'm ready to duck!
Two engines
Well maintained aircraft
Experienced crew
At night
Low level
The Pilot new he had plenty of fuel on board, one engine stops shortly followed by the other one. It's nothing short of a miracle they found the only off Airfield landing space on the Island, walked away from it and lived to tell the tale!
Otherwise we may well be discussing on this forum, how a perfectly serviceable aircraft with plenty of fuel on board had both engines quit!
If Dave's supply tanks were wrongly reading full and he got no amber warnings (as in the case of the NWAA 135, although I see that post has been pulled from this thread) then imagine his surprise when he got a red warning in a very difficult situation.
Ok shoot away! I'm ready to duck!
What strikes me as a key point about the faulty fuel readings scenario is that as well as having misled the pilot when determining whether to accept the Dalkeith tasking, and when calculating bingo fuel on the task, when the red light finally appeared, the gauges were still showing fuel available, and there were still no amber lights.
So his first dilemma is whether to place his faith in the gauges and amber lights or in the red light.
If you believe the gauges, you continue with plan A and head for home (which is very close) and have maintenance check the fault with the light.
If you believe the red light, and it is daytime in the countryside, maybe you park just to be sure, and call maintenance. At night, over a heavily populated area,trying to park is not without considerable risk, and being so close to home,the lesser risk might stil be to head for home (and anyway,the gauges could be right after all).
NB Two out of the three options involve continuing to head for home.
The first definitive indication that the red light is correct would be the engine with the smaller supply tank flaming out. Even then, if the manual is correct, you might still have enough to limp home, and it could still be the least bad outcome.
Yes Air Police, this is speculation, but I am not sure that it is fair to describe it as wild.
So his first dilemma is whether to place his faith in the gauges and amber lights or in the red light.
If you believe the gauges, you continue with plan A and head for home (which is very close) and have maintenance check the fault with the light.
If you believe the red light, and it is daytime in the countryside, maybe you park just to be sure, and call maintenance. At night, over a heavily populated area,trying to park is not without considerable risk, and being so close to home,the lesser risk might stil be to head for home (and anyway,the gauges could be right after all).
NB Two out of the three options involve continuing to head for home.
The first definitive indication that the red light is correct would be the engine with the smaller supply tank flaming out. Even then, if the manual is correct, you might still have enough to limp home, and it could still be the least bad outcome.
Yes Air Police, this is speculation, but I am not sure that it is fair to describe it as wild.
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falcon - I don't think your speculation is that wild, although whether the gauges were fully functioning or faulty, there are enough belts & braces in the system that it's almost certain that they set off with an accurate 400kgs, since the higher level fuel quantity will have been regularly tested & evidenced by endurance, & it 's only the lower levels that are infrequently visited and therefore tested for accuracy. In addition, the fuel flow rate, time airborne and fuel recovered all make sense.
All Police pilots re-calculate fuel remaining & distance/time to the nearest fuelling point on a very frequent basis, certainly every time they arrive on task and more frequently the further away from fuel you are!
In addition, pilots will/should have briefed their endurance to MLA at each shift brief, and re-briefed if they've changed fuel loading in the interim. As a result, all crew/pax will know when they took-off & therefore when they should be back on the ground. This endurance will form part of a pilots calculation back-stop when looking at his apparent remaining fuel.
There was enough fuel recovered, albeit below MLA, to have got them back to base. The critical thing is that we don't know which tank/s it was in.
All Police pilots re-calculate fuel remaining & distance/time to the nearest fuelling point on a very frequent basis, certainly every time they arrive on task and more frequently the further away from fuel you are!
In addition, pilots will/should have briefed their endurance to MLA at each shift brief, and re-briefed if they've changed fuel loading in the interim. As a result, all crew/pax will know when they took-off & therefore when they should be back on the ground. This endurance will form part of a pilots calculation back-stop when looking at his apparent remaining fuel.
There was enough fuel recovered, albeit below MLA, to have got them back to base. The critical thing is that we don't know which tank/s it was in.
Last edited by zorab64; 17th Jan 2014 at 12:14. Reason: typo
Thanks Zorab.
You highlight something which I was assuming, ie that the fuel recovered by AAIB was not in a location where it could be used, and therefore as far as the engines were concerned didnt exist.
A couple of other thoughts which you have prompted:
-Would the various en route fuel checks and recalculations not be corrupted by invalid fuel contents readings?
-Would they be able to reliably perform "seat of the pants" fuel consumption assessments on a bifurcated sortie like this? When they took of (and remembering we dont know this, I am assuming it) they were just tasked to travel a very very short distance to an incident on a railway line. 400Kgs would have been more than they could conceivably use, and in any event they could refuel in minutes. I doubt whether any undue attention was paid to fuel ( and I dont intend any criticism by that remark). The Dalkeith request changed everything, and I have to question whether the crew could reliably retrospectively reconstruct fuel consumption characteristics without reference to the fuel gauges.
- Prior to April 2013 and the formation of Police Scotland, this aircraft was a Strathclyde resource, and would not have operated many west east west sorties like this. I have no insight as to how it was operated thereafter, but there may not be the body of operational endurance information which you suggest in relation to this flight.
- I know I am assuming tasking for the Dalkeith leg arose after takeoff, but if it did, it would throw much of the preflight briefing out of the window, certainly the parts relating to fuel requirements for the mission.
- you state that the fuel remaining was below MLA, (which suggests that like me, you believe all fuel remaining was drained by the AAIB). Does this not confirm that all of the checks to which you refer had gone seriously pear shaped?
You highlight something which I was assuming, ie that the fuel recovered by AAIB was not in a location where it could be used, and therefore as far as the engines were concerned didnt exist.
A couple of other thoughts which you have prompted:
-Would the various en route fuel checks and recalculations not be corrupted by invalid fuel contents readings?
-Would they be able to reliably perform "seat of the pants" fuel consumption assessments on a bifurcated sortie like this? When they took of (and remembering we dont know this, I am assuming it) they were just tasked to travel a very very short distance to an incident on a railway line. 400Kgs would have been more than they could conceivably use, and in any event they could refuel in minutes. I doubt whether any undue attention was paid to fuel ( and I dont intend any criticism by that remark). The Dalkeith request changed everything, and I have to question whether the crew could reliably retrospectively reconstruct fuel consumption characteristics without reference to the fuel gauges.
- Prior to April 2013 and the formation of Police Scotland, this aircraft was a Strathclyde resource, and would not have operated many west east west sorties like this. I have no insight as to how it was operated thereafter, but there may not be the body of operational endurance information which you suggest in relation to this flight.
- I know I am assuming tasking for the Dalkeith leg arose after takeoff, but if it did, it would throw much of the preflight briefing out of the window, certainly the parts relating to fuel requirements for the mission.
- you state that the fuel remaining was below MLA, (which suggests that like me, you believe all fuel remaining was drained by the AAIB). Does this not confirm that all of the checks to which you refer had gone seriously pear shaped?
Last edited by falcon900; 17th Jan 2014 at 13:20.
All that happpens when you run out of fuel is that the engines stop.
When either the last engine or all of the engines quits....a lot of things happen in addition to it getting awfully quiet.
Generators cease providing power, lots of electrical powered systems stop working, and the Pilot's workload becomes extremely intense. Throw in flying over a big city....and darkness.....and it gets complicated for sure.
You are factually correct to the extent when the engine(s) stop getting fuel....they cease operating.
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From various sources of information, it seems clear neither engine was producing power in the moments leading up to the accident. That's rather unusual. Possible causes?
1) Lack of fuel to the engines.
2) Damage to the engines.
3) Closing down the engines.
Scenarios:
1) Since a significant amount of fuel was drained from the aircraft, (presuming no contamination) we have to assume a fault occurred causing inadequate delivery to the engines. Combined with a separate indication fault which would have disguised the developing deficiency in the supply tanks. Even in such a situation the system is designed in such a way that one engine should stop some minutes before the other. I forget the precise time, but I would anticipate all EC135 pilots would know what it was?
2) Engine damage can be caused by both external, and internal issues. An example of externally initiated damage would be Birdstrike. Internal damage would very likely be due to mechanical causes. To be a complete explanation here, any damage would have to have been caused to both engines, even if one engine's problems caused damage to the other - not unheard of.
3) Closing down the engine(s) might occur in two scenarios: Most obviously when an engine was unreliable/misbehaving/damaged. But also to remove torque during a tail rotor problem. Removing torque by closing down both engines would require an immediate entry into autorotation. Torque itself is of course not a problem when the aircraft is in forward flight, as aerodynamic forces on the fuselage flying 'sideways' balance the power required to fly level. Closing down of both engines is essential only when a tail rotor failure occurs in or very close to the hover.
How does this fit with what very little we (joe public) currently know?
The witness statements referred to by 4listair are very revealing. Everyone interested should read them. They might be taken to suggest that, within seconds of the accident, the aircraft was in forward flight, at very low level, making odd noises, and producing sparks?
Any aviator will be familiar with the phrase; aviate-navigate-communicate. It seems the "communicate" phase was never reached?
Finally, it seems very likely that autorotation was (for some reason) not successfully established?
Which of 1) 2) or 3), or combination thereof might explain such an event?
It is possible the clues are there?
1) Lack of fuel to the engines.
2) Damage to the engines.
3) Closing down the engines.
Scenarios:
1) Since a significant amount of fuel was drained from the aircraft, (presuming no contamination) we have to assume a fault occurred causing inadequate delivery to the engines. Combined with a separate indication fault which would have disguised the developing deficiency in the supply tanks. Even in such a situation the system is designed in such a way that one engine should stop some minutes before the other. I forget the precise time, but I would anticipate all EC135 pilots would know what it was?
2) Engine damage can be caused by both external, and internal issues. An example of externally initiated damage would be Birdstrike. Internal damage would very likely be due to mechanical causes. To be a complete explanation here, any damage would have to have been caused to both engines, even if one engine's problems caused damage to the other - not unheard of.
3) Closing down the engine(s) might occur in two scenarios: Most obviously when an engine was unreliable/misbehaving/damaged. But also to remove torque during a tail rotor problem. Removing torque by closing down both engines would require an immediate entry into autorotation. Torque itself is of course not a problem when the aircraft is in forward flight, as aerodynamic forces on the fuselage flying 'sideways' balance the power required to fly level. Closing down of both engines is essential only when a tail rotor failure occurs in or very close to the hover.
How does this fit with what very little we (joe public) currently know?
The witness statements referred to by 4listair are very revealing. Everyone interested should read them. They might be taken to suggest that, within seconds of the accident, the aircraft was in forward flight, at very low level, making odd noises, and producing sparks?
Any aviator will be familiar with the phrase; aviate-navigate-communicate. It seems the "communicate" phase was never reached?
Finally, it seems very likely that autorotation was (for some reason) not successfully established?
Which of 1) 2) or 3), or combination thereof might explain such an event?
It is possible the clues are there?
Last edited by Tandemrotor; 17th Jan 2014 at 14:01.
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what I am getting at is, that were the fuel gauge problem problem present, the calculations regarding viability of the Dalkeith trip, and of bingo fuel on task would have been invalid as they would have been based on incorrect (optimistic) contents readings
What strikes me as a key point about the faulty fuel readings scenario is that as well as having misled the pilot when determining whether to accept the Dalkeith tasking, and when calculating bingo fuel on the task, when the red light finally appeared, the gauges were still showing fuel available, and there were still no amber lights
You highlight something which I was assuming, ie that the fuel recovered by AAIB was not in a location where it could be used, and therefore as far as the engines were concerned didnt exist
If the fuel was not in the main or supply tanks where was it then?
skadi
Bladecrack,
prompted by your comments, I have re-read the thread regarding the Bond ec135 groundings in connection with the fuel probes. I may yet be missing something, but they clearly are concerned with quantity readings and the amber warnings. I know that the red warnings are separate, and indeed this fact plays an important role in my hypothesis of how events may have unfolded.
I would also refer you to earlier posts on this thread discussing "unuseable" fuel quantities in this type of aircraft. To summarise, there will always be fuel in the tank which cannot be accessed by the supply tanks and hence the engines. The quantity varies depending on aircraft attitude, and can be increased by incorrect transfer pump settings or pump/valve failures.
prompted by your comments, I have re-read the thread regarding the Bond ec135 groundings in connection with the fuel probes. I may yet be missing something, but they clearly are concerned with quantity readings and the amber warnings. I know that the red warnings are separate, and indeed this fact plays an important role in my hypothesis of how events may have unfolded.
I would also refer you to earlier posts on this thread discussing "unuseable" fuel quantities in this type of aircraft. To summarise, there will always be fuel in the tank which cannot be accessed by the supply tanks and hence the engines. The quantity varies depending on aircraft attitude, and can be increased by incorrect transfer pump settings or pump/valve failures.
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Dipping the tanks.
I've searched the thread and not spotted this being discussed. My experience has been that despite gauges, calculations and paperwork one should always dip the tanks regularly to see how much is actually in there.
OK fixed wing not rotary but on annual we always drained the tanks and "started again".
Is this point worthy of discussion?
SGC
I've searched the thread and not spotted this being discussed. My experience has been that despite gauges, calculations and paperwork one should always dip the tanks regularly to see how much is actually in there.
OK fixed wing not rotary but on annual we always drained the tanks and "started again".
Is this point worthy of discussion?
SGC
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Bladecrack wrong I'm afraid, the Amber warning doesn't trigger because the supplies show permanent full
Falcon900
I may yet be missing something, but they clearly are concerned with quantity readings and the amber warnings. I know that the red warnings are separate
To summarise, there will always be fuel in the tank which cannot be accessed by the supply tanks and hence the engines. The quantity varies depending on aircraft attitude, and can be increased by incorrect transfer pump settings or pump/valve failures.
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Failure of the FWD pump can result in an unusable quantity of as much as 59 kg if above 80 KIAS and is 3.6 kg if below which is effectively the same as normal unusable fuel in this cell.
Failure of the AFT pump can result in as much as 71 kg in the hover reducing to 7.5 kg above 80 KIAS increasing the unusable by 4 kgs.
With a little arithmetic the maximum increase in unusable at the failure of BOTH pumps could be as much as 215 kg in the level attitude. This would be the maximum that you couldn't get to by being a little bit cunning. This of course depends on when both pumps become inactive.
If the fuel is no longer being transferred to the Supply tanks by either gravity or pumps there is 92 kgs remaining of which 86.7 is usable. Due to the shape of the tanks Engine 2 will stop after approximately 23 minutes and then engine 1 after 27 minutes. The "LOW FUEL 1" and "LOW FUEL 2" Warning indications come on at the minimum of 24kg per cell. Hence the procedure "Land within 8 minutes."
The above is based on manufacturer's fuel flow data of 65% Q at SL ISA - give or take.
Failure of the AFT pump can result in as much as 71 kg in the hover reducing to 7.5 kg above 80 KIAS increasing the unusable by 4 kgs.
With a little arithmetic the maximum increase in unusable at the failure of BOTH pumps could be as much as 215 kg in the level attitude. This would be the maximum that you couldn't get to by being a little bit cunning. This of course depends on when both pumps become inactive.
If the fuel is no longer being transferred to the Supply tanks by either gravity or pumps there is 92 kgs remaining of which 86.7 is usable. Due to the shape of the tanks Engine 2 will stop after approximately 23 minutes and then engine 1 after 27 minutes. The "LOW FUEL 1" and "LOW FUEL 2" Warning indications come on at the minimum of 24kg per cell. Hence the procedure "Land within 8 minutes."
The above is based on manufacturer's fuel flow data of 65% Q at SL ISA - give or take.
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A spokesman for Eurocopter, a unit of European aerospace and defence company EADS, said tests by Bond and two other EC135 operators in Europe found possible similar supply-tank fuel gauging errors that overestimated the fuel on board.
"The first analysis shows that the indication of the fuel quantity in the supply tanks could be overestimated," the company said in a statement.
"All crews should be aware that in the worst case a red warning "Low Fuel" could appear without any amber FUEL Caution before."
Eurocopter said it was issuing a safety notice to remind all EC135 operators to follow the safety procedures already in place and outlined in the flight manual, regardless of the aircraft's fuel quantity indication.
It's that last paragraph that niggles me!
"The first analysis shows that the indication of the fuel quantity in the supply tanks could be overestimated," the company said in a statement.
"All crews should be aware that in the worst case a red warning "Low Fuel" could appear without any amber FUEL Caution before."
Eurocopter said it was issuing a safety notice to remind all EC135 operators to follow the safety procedures already in place and outlined in the flight manual, regardless of the aircraft's fuel quantity indication.
It's that last paragraph that niggles me!
If something is causing a capacitance gauge to read an incorrect capacitance for the actual fuel level, then an incorrect reading would be displayed, and the amber light would not come on at the correct time. The red light which, as I have learned on this thread, is operated by a sensor using a different method of detection.
Bacteria growth in the fuel probe can cause a change in the fuel's capacitance properties or water to be retained between the concentric tubes of the probe. Eurocopter did state that most of the removed faulty EC135 fuel probe worked correctly after cleaning.
In 'Aviation Fuel Quality Control Procedures', a contribution by P. Martin states, 'In aircraft, microbial contamination of the fuel may lead to fuel gage (sic) malfunction...'
Bacteria growth in the fuel probe can cause a change in the fuel's capacitance properties or water to be retained between the concentric tubes of the probe. Eurocopter did state that most of the removed faulty EC135 fuel probe worked correctly after cleaning.
In 'Aviation Fuel Quality Control Procedures', a contribution by P. Martin states, 'In aircraft, microbial contamination of the fuel may lead to fuel gage (sic) malfunction...'
Last edited by Mechta; 17th Jan 2014 at 17:54. Reason: Link didn't work
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Due to the shape of the tanks Engine 2 will stop after approximately 23 minutes and then engine 1 after 27 minutes.
that means 3.33Kg per minute being burnt or 1.67KG per engine per minute. with a 4KG difference between the two tanks that would give you 2.4 Minutes. If you also factor in that once OEI the working donk will be at a higher Tq then the fuel burn will also increase reducing this time even further. So in fact if you think that you have 4 minutes to silence it may come as an even greater surprise when No. 2 stops within half that time!
There has also been a lot of questions on how two engines can be lost at the same time. Unless I have missed something we do not know that is what happened and If fuel starvation for whatever reason was the cause then the above scenario of Two followed by one would be more likely.
If after No.2 stopping you run through the drills establish OEI check for other problems fire etc and then assess and address the problem you could find yourself working the overhead panel ultimately. Making the emergency shed bus then checking pump circuit breakers switch config. etc. If whilst doing this and left hand is holding flip cards or working above your head on panel when No.1 stops allowing for Pilot intervention time the Nr may well have been below recoverable before the lever was lowered. Even if only close to it the only way to increase Nr is to accelerate (not easy with not a lot of height below you) or load the disc (hard to flare when already probably at 60Knts or so OEI and still trying to asses the situation). This will leave you with a slow forward speed no Nr situation ending up with all on board as pax.
There is very little rotation at all once blades are fully stalled as anyone who has seen the video of the R22 falling completely level with only a couple of RRPM on till it impacted can tell you. The 135 is a low inertia system and if the lever is not lowered quickly or fully pulled up to early without any drive the system will effectively stop.
Just the rambling thoughts of an idiot who will now duck for cover.
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PieChaser, Mechta, & MaxTakeoff - good informative posts there guys 
That is the statement that concerns me most...
Dipping the tanks.
SGC - a question for an engineer to answer, its not something the pilot can do.
tests by Bond and two other EC135 operators in Europe found possible similar supply-tank fuel gauging errors that overestimated the fuel on board.
Dipping the tanks.
I've searched the thread and not spotted this being discussed. My experience has been that despite gauges, calculations and paperwork one should always dip the tanks regularly to see how much is actually in there.
OK fixed wing not rotary but on annual we always drained the tanks and "started again".
OK fixed wing not rotary but on annual we always drained the tanks and "started again".
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Here's a scenario:
Fuel gauges showing a modest amount of fuel in tanks, but just from sphincter sensations you knew you couldn't have a great deal on board. Then two red fuel low level lights unexpectedly illuminate. Next thing that happens is that, inexplicably one engine runs down. What would you suspect may be the cause?
In that scenario, would you be running through flip cards or working through the overhead panel? Indeed is there a memory drill for a simple engine run down?
Anyone ever heard of (T)DODAR? Where 'T' stands for time?
Experienced pilots can frequently 'skip' steps that a robot, or inexperienced pilot would be obliged to perform. SOMETIMES being human is a good thing. SOMETIMES being human is not!
Personally, I'd be sh1tt1ng myself, looking for an IMMEDIATE (and I MEAN immediate) landing. I would also be mentally preparing myself to dump the lever at the slightest cough from the running engine.
Finally, where do the witness statements of 'fireworks' or 'sparks' fit into this scenario?
I have no real answers. Just throwing it out there for debate, that's all.
Fuel gauges showing a modest amount of fuel in tanks, but just from sphincter sensations you knew you couldn't have a great deal on board. Then two red fuel low level lights unexpectedly illuminate. Next thing that happens is that, inexplicably one engine runs down. What would you suspect may be the cause?
In that scenario, would you be running through flip cards or working through the overhead panel? Indeed is there a memory drill for a simple engine run down?
Anyone ever heard of (T)DODAR? Where 'T' stands for time?
Experienced pilots can frequently 'skip' steps that a robot, or inexperienced pilot would be obliged to perform. SOMETIMES being human is a good thing. SOMETIMES being human is not!
Personally, I'd be sh1tt1ng myself, looking for an IMMEDIATE (and I MEAN immediate) landing. I would also be mentally preparing myself to dump the lever at the slightest cough from the running engine.
Finally, where do the witness statements of 'fireworks' or 'sparks' fit into this scenario?
I have no real answers. Just throwing it out there for debate, that's all.
Last edited by Tandemrotor; 17th Jan 2014 at 21:05.
