Police helicopter crashes onto Glasgow pub: final AAIB report
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With regards the warning for ROTOR RPM, the report says
"The next recorded warning was rotor rpm signifying an Nr of less than 97%".
Yes, the visual warning was recorded, but without an FDR, how it is not known that all of the 4 ROTOR RPM warnings related to low Nr. It doesn't stipulate exactly.
"The next recorded warning was rotor rpm signifying an Nr of less than 97%".
Yes, the visual warning was recorded, but without an FDR, how it is not known that all of the 4 ROTOR RPM warnings related to low Nr. It doesn't stipulate exactly.
"The next recorded warning was rotor rpm signifying an Nr of less than 97%. This warning cleared, returned, cleared again and then returned and remained active. The subsequent bat disch warning indicated that the battery was providing electrical power. The final warning was related to the autopilot."
"That was why I was highlighting the similarities between the high Nr gong at 106% and the BAT DISCH gong. Without a timescale for these warnings, they could have all merged into one. That is what I meant by the sound of the gong from the Battery may have affected other audio warnings.
My point about Nr control; is that when you are trained and tested in the real aircraft, you aim to keep 100-103% Nr, to prevent damage to the head/MGB. This gets ingrained, so that when you have something for real, you don't automatically let the Nr rise, because pilots rarely/ever train full done autos in the real thing in a MET helicopter.
This has been proven is some military helicopter accidents where the pilot only flew to the practice single engine Tq figures, as opposed to the real limits (pull the lever up to your armpit) because that's what they always did in training.
(Lever up to the armpit would surely only apply at the 'cushion on' stage at the end. We cant have the General spilling his G&T now, can we!
But overall, despite all the bells and whistles sounding, and looking at the table 3 on page 33 of the report, there were a few audio warnings, any pilot under a high workload with no spare capacity gets tunnel vision. That was my point about a person's hearing being the first thing to go. (Gongs vs Low tone vs gearbox noises vs cockpit noise).
Eight Audio Warnings were acknowledged, two of which were after both engines had stopped, so they must have been heard and acknowledged during this high workload, no engine, auto scenario at 100 kts, 1000'. The only audio warnings not acknowledged were the last three in direct succession; Low Nr, Batt Disch & AP ATrim ... right at the very ,very end.
You say nothing can be proven in a case like this, but at least have the respect for everyone involved to look at the facts as presented to you.
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Sorry I couldn't count. Having recounted, the table shows there were 5 audio and visual warnings relating to ROTOR RPM. But the point I was making is what data do they have to say those were in relation to high or low Nr?
Could one of the last BAT DISCH gongs at the end have been mis-interpreted as a high Nr gong, and therefore raising the lever to contain, when the Nr was already low? By this time there were a minimum of 4 red warning lights lit.
And regarding autos, as I said, AIM for 100-103%, which therefore keeps you nicely within the power off limitations.
And I have more than enough respect for those involved, but feel there are always learning opportunities, especially when audio warnings sound the same for different warnings. I am not picking holes in anyone else who had posted but hope the points I have raised invoke thought to the aircraft system beyond the fuel tank.
Could one of the last BAT DISCH gongs at the end have been mis-interpreted as a high Nr gong, and therefore raising the lever to contain, when the Nr was already low? By this time there were a minimum of 4 red warning lights lit.
And regarding autos, as I said, AIM for 100-103%, which therefore keeps you nicely within the power off limitations.
And I have more than enough respect for those involved, but feel there are always learning opportunities, especially when audio warnings sound the same for different warnings. I am not picking holes in anyone else who had posted but hope the points I have raised invoke thought to the aircraft system beyond the fuel tank.
Purveyor of Egg Liqueur to Lucifer
Sorry I couldn't count. Having recounted, the table shows there were 5 audio and visual warnings relating to ROTOR RPM. But the point I was making is what data do they have to say those were in relation to high or low Nr?
I don't know what data the investigators had, but they reported that they were for the same reason, Low Nr;
"The next recorded warning was rotor rpm signifying an Nr of less than 97%. This warning cleared, returned, cleared again and then returned and remained active."
Could one of the last BAT DISCH gongs at the end have been mis-interpreted as a high Nr gong, and therefore raising the lever to contain, when the Nr was already low? By this time there were a minimum of 4 red warning lights lit.
There was only one Batt Disch activation.
When the Bat Disch Warning came on there were only three Warnings showing, the two Low Fuels and the low Rotor Rpm.
And regarding autos, as I said, AIM for 100-103%, which therefore keeps you nicely within the power off limitatio
And I have more than enough respect for those involved, but feel there are always learning opportunities, especially when audio warnings sound the same for different warnings. I am not picking holes in anyone else who had posted but hope the points I have raised invoke thought to the aircraft system beyond the fuel tank.
The Batt Disch Warning you continue to go on about to qualify your point was right at the very end of the timeline and only came on the once. Looking at the timeline this probably occurred within the last couple of seconds.
Of course I t is good to have different ways of looking at the same incident, however we should be very careful that we don't look at the published facts and shift them around to fit our version of events. When we have so many facts in front of us, opinion should start to take a back seat.
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One thing that we may wish to consider here, is the effect of the lighting being on NVG mode.
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And regarding autos, as I said, AIM for 100-103%, which therefore keeps you nicely within the power off limitations.
Sounds an eminently sensible practice - was it SOP?
I always read the FRC action as actions for a Transfer Pump failure, as it states in the FRCs. As I knew that the pumps hadn't failed, I didn't turn them off.
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Problem is....... whilst you know it isn't a failure, you don't reallyknow, do you. If the caption has come on for the 10th time, THIS time might actually be a failure.
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First of all I feel that we are dealing with a "Mickey Mouse"fuel management system, with fuel slopping between supply tanks, and supply tanks and the main tank. On top of that we have to rely on a manual intervention to ensure that vital fuel transfer pumps are switched on, using unguarded switches.
I believe that the pilot and crew thought they were dealing with spurious"Low Fuel" lights; this belief is supported by a history of in-flight fuel content defects and subsequent No Fault Founds. In addition, prior to the illumination of a Low Fuel light there should have been an amber FUEL light. However, we read that in the case of an incident on 13th Dec 2013 that the fuel quantity in the supply tanks could be overestimated and that a "Low Fuel" light could appear without any "Fuel" caution being displayed before it. So, with quantity of fuel displayed appearing OK (but overestimated), and no Fuel light, it is only reasonable to assume that any "Low Fuel" light is likely to be spurious, given the history.
But why were the transfer switches OFF? Probable because the pilot received F PUMP FWD and F PUMP AFT warning captions when the contents in the main tank became low, lower that what it ended up with. At some point, due to manoeuvring, fuel from the supply tanks found its way back to the main tank (up to 35 Kgs was possible), and created an even distribution of fuel in the supply tanks. However, fuel going back into the main tank and covering the transfer pumps would not put the F PUMP FWD and F PUMP AFT warning captions on; so no warning. An even distribution of fuel in the supply tanks would account for the time between the two flame-outs being reduced from over 4 mins to just over 30secs. Design Failure
Bottom line is, I cannot believe that three people sat there and listen to alarms going off, watching fuel contents gauges for the supply tanks reducing to zero and did nothing about it, which includes informing ATC, and police on the ground. I also belief that one prime pump switch going from ON to OFF between first responders and the AAIB examination, is a clear indication that the "crime scene" was contaminated. Having said that, the notes do say that the prime pumps are switched on for engine start and certain emergency conditions. I am not sure which prime pump switch was affected, but if it relates to the first engine to flame out then it is possible that he was trying to do are-start, believing that he still had fuel in the supply tank.
Finally, Autorotation. The lack of RAD ALT and spot light must have been major contributing factors to the failure. The report and I think the pilot's notes, state that the power change over switch could be difficult to locate in an emergency. So why was it left like that? Why wait until someone tells you to have an automatic system? And how long does it take for the Rad Alt to run up and give accurate readings once the switch is found; probably a lot longer than the time taken to fall 300ft. DesignFailure.
DV
I believe that the pilot and crew thought they were dealing with spurious"Low Fuel" lights; this belief is supported by a history of in-flight fuel content defects and subsequent No Fault Founds. In addition, prior to the illumination of a Low Fuel light there should have been an amber FUEL light. However, we read that in the case of an incident on 13th Dec 2013 that the fuel quantity in the supply tanks could be overestimated and that a "Low Fuel" light could appear without any "Fuel" caution being displayed before it. So, with quantity of fuel displayed appearing OK (but overestimated), and no Fuel light, it is only reasonable to assume that any "Low Fuel" light is likely to be spurious, given the history.
But why were the transfer switches OFF? Probable because the pilot received F PUMP FWD and F PUMP AFT warning captions when the contents in the main tank became low, lower that what it ended up with. At some point, due to manoeuvring, fuel from the supply tanks found its way back to the main tank (up to 35 Kgs was possible), and created an even distribution of fuel in the supply tanks. However, fuel going back into the main tank and covering the transfer pumps would not put the F PUMP FWD and F PUMP AFT warning captions on; so no warning. An even distribution of fuel in the supply tanks would account for the time between the two flame-outs being reduced from over 4 mins to just over 30secs. Design Failure
Bottom line is, I cannot believe that three people sat there and listen to alarms going off, watching fuel contents gauges for the supply tanks reducing to zero and did nothing about it, which includes informing ATC, and police on the ground. I also belief that one prime pump switch going from ON to OFF between first responders and the AAIB examination, is a clear indication that the "crime scene" was contaminated. Having said that, the notes do say that the prime pumps are switched on for engine start and certain emergency conditions. I am not sure which prime pump switch was affected, but if it relates to the first engine to flame out then it is possible that he was trying to do are-start, believing that he still had fuel in the supply tank.
Finally, Autorotation. The lack of RAD ALT and spot light must have been major contributing factors to the failure. The report and I think the pilot's notes, state that the power change over switch could be difficult to locate in an emergency. So why was it left like that? Why wait until someone tells you to have an automatic system? And how long does it take for the Rad Alt to run up and give accurate readings once the switch is found; probably a lot longer than the time taken to fall 300ft. DesignFailure.
DV
Distant Voice,
When I went through type rating for the 135 it was emphasized to me by both my instructor and TRE that there was no such thing as a "Spurious" LOW FUEL caption. It's either in fuel or it isn't. If it comes on believe it, follow the actions required by the FRC's, LAND within 10 minutes and argue the toss afterwards.
Also, if the Transfer Pumps are switched off the captions are ON - and, if you want to do a restart, the first thing that needs to happen is the ENG MAIN Switch to off - not put a Prime Pump to ON.
As for the FUEL caption, that illuminates when the fuel level Indicated reaches approx 40 in the PT and 35 in the STBD Supply Tanks. However, if the Supply sensors are faulty and constantly reading Full, (47 & 43), then the FUEL Caption won't appear.
When I went through type rating for the 135 it was emphasized to me by both my instructor and TRE that there was no such thing as a "Spurious" LOW FUEL caption. It's either in fuel or it isn't. If it comes on believe it, follow the actions required by the FRC's, LAND within 10 minutes and argue the toss afterwards.
Also, if the Transfer Pumps are switched off the captions are ON - and, if you want to do a restart, the first thing that needs to happen is the ENG MAIN Switch to off - not put a Prime Pump to ON.
As for the FUEL caption, that illuminates when the fuel level Indicated reaches approx 40 in the PT and 35 in the STBD Supply Tanks. However, if the Supply sensors are faulty and constantly reading Full, (47 & 43), then the FUEL Caption won't appear.
Last edited by Fortyodd2; 1st Nov 2015 at 15:27.
Purveyor of Egg Liqueur to Lucifer
Not according to what others on here say that they do. In fact I didn't know that other people were turning the pumps off and on until after this accident.
I always read the FRC action as actions for a Transfer Pump failure, as it states in the FRCs. As I knew that the pumps hadn't failed, I didn't turn them off.
I always read the FRC action as actions for a Transfer Pump failure, as it states in the FRCs. As I knew that the pumps hadn't failed, I didn't turn them off.
As Dg says, you can't know that the pump hasn't failed can you? So apart from not following the 'correct actions', which I know are not etched in stone, you could have been in the situation where should you have had an incident where your pump had failed (related or not) and the switch was found in the wrong position, we would be discussing that incorrect switchology in a new thread as a possible factor.
Purveyor of Egg Liqueur to Lucifer
More Questions.
Distant Voice, I think we've heard from 'users' that the system isn't anything like as MM as people are making out. Perhaps not the best but certainly not unmanageable or unsafe when operated correctly as trained.
The issue of the time between 2 & 1 failing certainly needs to be looked at, perhaps it was the change of attitude that made the fuel move away from the pump. How long does it take a cell of fuel to move from the pump to the combustion chamber?
As mentioned previously, the NVG lighting was on, how much of a difference to the CAD reading did that make?
Totally agree with the disbelief that three people just sat there with all the cautions and warnings presented to them, which must raise the question, what was going on in that cockpit that evening, where there any CRM issues and what culture existed at the unit?
I can't think for a minute that a restart would have been attempted. That's purely my opinion as I know that I would rather have been looking at a landing site than a restart, especially given what the report says was being presented to me.
As far as the Rad Alt and Steerable LL are concerned. Ok, the ergonomics could be better, however there are ways that we have of making it a little easier to identify. The operators instructions say that the switch should be used, "if time is available once the auto has been established and Nr stable" (p.67) in this case perhaps time wasn't available. It has to be added though, over the city what accurate use would the Rad Alt have and how useful would the steerable landing light be? Some here have even said the lights of the city would be bright enough to make the Naster Caution not stand out!
Fundamentally though I agree with what you say.
The issue of the time between 2 & 1 failing certainly needs to be looked at, perhaps it was the change of attitude that made the fuel move away from the pump. How long does it take a cell of fuel to move from the pump to the combustion chamber?
As mentioned previously, the NVG lighting was on, how much of a difference to the CAD reading did that make?
Totally agree with the disbelief that three people just sat there with all the cautions and warnings presented to them, which must raise the question, what was going on in that cockpit that evening, where there any CRM issues and what culture existed at the unit?
I can't think for a minute that a restart would have been attempted. That's purely my opinion as I know that I would rather have been looking at a landing site than a restart, especially given what the report says was being presented to me.
As far as the Rad Alt and Steerable LL are concerned. Ok, the ergonomics could be better, however there are ways that we have of making it a little easier to identify. The operators instructions say that the switch should be used, "if time is available once the auto has been established and Nr stable" (p.67) in this case perhaps time wasn't available. It has to be added though, over the city what accurate use would the Rad Alt have and how useful would the steerable landing light be? Some here have even said the lights of the city would be bright enough to make the Naster Caution not stand out!
Fundamentally though I agree with what you say.
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Fortyodd said
I don't think this is correct, ref AAIB report:
"An algorithm is built into the CPDS software to prevent intermittent fuel transfer pump captions appearing during dynamic manoeuvres in flight, as the fuel moves about in the main tank. This inhibits the caption until there has been a continuous period of three minutes during which the pump has run dry. If, within the three-minute period, the pump becomes re-immersed in fuel, the three-minute delay is reset to zero to await the next dry running condition. The f pump aft and f pump fwd caution captions will also illuminate after three minutes if the fuel transfer pumps are switched off while immersed in fuel or become blocked. A message is not provided for the situation where a pump has been switched off, after running dry, and is then re-submerged in fuel.
Also, if the Transfer Pumps are switched off the captions are ON -"
"An algorithm is built into the CPDS software to prevent intermittent fuel transfer pump captions appearing during dynamic manoeuvres in flight, as the fuel moves about in the main tank. This inhibits the caption until there has been a continuous period of three minutes during which the pump has run dry. If, within the three-minute period, the pump becomes re-immersed in fuel, the three-minute delay is reset to zero to await the next dry running condition. The f pump aft and f pump fwd caution captions will also illuminate after three minutes if the fuel transfer pumps are switched off while immersed in fuel or become blocked. A message is not provided for the situation where a pump has been switched off, after running dry, and is then re-submerged in fuel.
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DV said
your theory is very much along my lines of thinking.
Yes, the pilot made errors of judgement, we all have at some time. I believe however that there were significant contributory factors and in all likelihood many in his position would have done the same. Not only was he assessed as an 'above average" pilot but he was also the RAF Chinook display pilot in 2007.
lots of stuff that made sense
Yes, the pilot made errors of judgement, we all have at some time. I believe however that there were significant contributory factors and in all likelihood many in his position would have done the same. Not only was he assessed as an 'above average" pilot but he was also the RAF Chinook display pilot in 2007.
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Some things need to be made clear;
The ac was at 'approximately' 1000' AMSL and 100 kts GS when the engines stopped.
The biggest red herring that has been latched on to in this whole thread is the Nr Warning.
Remember that the power off Nr range is from 80% to 112% putting the point at which the Low Nr Warning activates (<97%) just above the mid range point.
As can been seen in my picture below the Power off Nr range is the inner green band. The needle is pointing at 97%, the point at which the Low Nr Warnings both aural and visual are activated.
The first low Nr warning did not come on until late in the Warning Unit indicators timeline on page 33.
The warning came on, went off, came on, came on went off and then came on again.
This to me would probably suggest that the Nr was indeed being controlled in the middle of the band and well within the power off limits ... right until the very end.
The ac was at 'approximately' 1000' AMSL and 100 kts GS when the engines stopped.
The biggest red herring that has been latched on to in this whole thread is the Nr Warning.
Remember that the power off Nr range is from 80% to 112% putting the point at which the Low Nr Warning activates (<97%) just above the mid range point.
As can been seen in my picture below the Power off Nr range is the inner green band. The needle is pointing at 97%, the point at which the Low Nr Warnings both aural and visual are activated.
The first low Nr warning did not come on until late in the Warning Unit indicators timeline on page 33.
The warning came on, went off, came on, came on went off and then came on again.
This to me would probably suggest that the Nr was indeed being controlled in the middle of the band and well within the power off limits ... right until the very end.
Lets make an adjustment as it needs to be read in conjunction with the rest of the info -
The last part of the statement was just to clarify your assumption.
"An algorithm is built into the CPDS software to prevent intermittent fuel transfer pump captions appearing during dynamic manoeuvres in flight, as the fuel moves about in the main tank. This inhibits the caption until there has been a continuous period of three minutes during which the pump has run dry. If, within the three-minute period, the pump becomes re-immersed in fuel, the three-minute delay is reset to zero to await the next dry running condition. The f pump aft and f pump fwd caution captions will also illuminate after three minutes if the fuel transfer pumps are switched off while immersed in fuel or become blocked. A message is not provided for the situation where a pump has been switched off, after running dry, and is then re-submerged in fuel.
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Skyrangerpro, to clear that one up;
If the transfer pumps are switched off, within three minutes, the CAD bars flash, the F Pump Aft/ F Pump Fwd captions illuminate and the Master Caution illuminates. When this is acknowledged the CAD bars and Master Caution light extinguish, leaving the F Pump Aft/F Pump Fwd captions remaining on.
If the pumps are then reimmersed in fuel, the captions remain on because the pumps are switched off. If you then switch the pumps back on the captions will clear.
If the F Pump Aft/ F Pump Fwd captions illuminate of their own accord, along with the CAD bars flashing and master Caution coming on, the pump(s) have either failed or have been running dry for longer than three minutes. At this point (illumination of the cautions) the respective pumps should be switched off iaw the FLM procedures.
Acknowledging the caution will extinguish the CAD bars and Master Caution.
If the pumps are not switched off and the pump is then reimmersed in fuel, the F Pump Aft/F Pump Fwd will extinguish.
I know others will have different opinions based on flying in different aircraft where you don't have to think about the fuel system too much, but it is quite straight forward.
If the transfer pumps are switched off, within three minutes, the CAD bars flash, the F Pump Aft/ F Pump Fwd captions illuminate and the Master Caution illuminates. When this is acknowledged the CAD bars and Master Caution light extinguish, leaving the F Pump Aft/F Pump Fwd captions remaining on.
If the pumps are then reimmersed in fuel, the captions remain on because the pumps are switched off. If you then switch the pumps back on the captions will clear.
If the F Pump Aft/ F Pump Fwd captions illuminate of their own accord, along with the CAD bars flashing and master Caution coming on, the pump(s) have either failed or have been running dry for longer than three minutes. At this point (illumination of the cautions) the respective pumps should be switched off iaw the FLM procedures.
Acknowledging the caution will extinguish the CAD bars and Master Caution.
If the pumps are not switched off and the pump is then reimmersed in fuel, the F Pump Aft/F Pump Fwd will extinguish.
I know others will have different opinions based on flying in different aircraft where you don't have to think about the fuel system too much, but it is quite straight forward.
Skyrangerpro,
Sorry, my bad England - What Sid says is correct and there is a 3 minute delay. However, also from the report, the Tx pumps must have been off for more than 3 mins before the "Low Fuel" Captions came on - even more clues that all was not well.
Sorry, my bad England - What Sid says is correct and there is a 3 minute delay. However, also from the report, the Tx pumps must have been off for more than 3 mins before the "Low Fuel" Captions came on - even more clues that all was not well.
Or alternatively Sid,
Engine 2 stops - N1 tops -> NR droops <97% RRPM -> 1st NR Warning (OEI HIGH event recorded in the FADEC) Low NR OEI would imply topping?
Collective lowered NR recovers
Engine 1 stops - NR decays < 97% RRPM 2nd NR Warning
Collective lowered NR recovers
Low NR - ????? 3rd NR Warning
Low NR snapshot captured due to BAT DISCH
Low NR snapshot captured due to AP A.TRIM
Although the report differs apparently implying that Low NR was not experienced until the second engine failure but I cannot find where that is substantiated.
The next recorded warning was rotor rpm signifying an Nr of less than 97%. This
warning cleared, returned, cleared again and then returned and remained active
warning cleared, returned, cleared again and then returned and remained active
Collective lowered NR recovers
Engine 1 stops - NR decays < 97% RRPM 2nd NR Warning
Collective lowered NR recovers
Low NR - ????? 3rd NR Warning
Low NR snapshot captured due to BAT DISCH
Low NR snapshot captured due to AP A.TRIM
Although the report differs apparently implying that Low NR was not experienced until the second engine failure but I cannot find where that is substantiated.
After the second engine had flamed out, the rotor rpm warning caption
illuminated, accompanied by its aural tone. This indicated that the speed of the
rotor had decreased below 97%. This warning then extinguished, re‑illuminated
and extinguished again. It finally re-illuminated and stayed on for the remainder
of the flight, as the helicopter descended.
illuminated, accompanied by its aural tone. This indicated that the speed of the
rotor had decreased below 97%. This warning then extinguished, re‑illuminated
and extinguished again. It finally re-illuminated and stayed on for the remainder
of the flight, as the helicopter descended.
not switching them off isn't the norm
what else did you do that wasn't the norm
List all the things that were the norm.
As Dg says, you can't know that the pump hasn't failed can you?