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I'm surprised they'd expect an emergency transmission NS |
G0ULI,
Quote ..."My interpretation ......... The shed load switch was found still in its normal position, so the drain on the battery would have been significant with apparent attempts being made to restart an engine." If restarts were being attempted the Engine main switches would not be in the Guarded Flight positions unless both restarts had been successfull. You do make good points about the fuel system, and the fact that the transfer and prime pump switches are all the same and in a line above the pilots head does make it very possible a pilot could select the wrong pair if not monitoring the caution panel for correct operation, particularly at night. |
Please don't come on here saying "my guess was right". Someone was bound to have guessed right by the law of averages. None of us knew anything until today.
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Skysports,
Well, pending any dramatic new information, that report seems to address adequately the question of what happened, but still leaves a huge question as to why? Without any recorders onboard, is that ever now going to be resolved? |
How easy is it to confuse the operation of the transfer pump switches? They were both off, could they have got that way earlier in the flight if the pilot thought that he was putting them both on and never thought to reverse their position because they were both in the same orientation?
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So we now know what happened, but not why. Sky sport, maybe you should go back to watching the telly! Gouli, the 85kg of fuel is not unusable.
So, fuel transfer switches in the wrong place, two lots of low fuel captions ignored, failed to enter auto following the second failure. Either he was a really bad pilot or there was something else wrong - eg incapacitation of some sort. |
Feathers,
The pairs of switches are next to each other. However, when the prime pumps go on, there is a caption to tell you that you have turned them on. When the transfer pumps are off/failed, there is a caption to tell you that too. The transfer pump captions are in the centre part of the display whilst the prime pump captions are "sided" to match their respective engine. From this report, it appears that everything about the aircrafts systems worked exactly as it should. |
For those who have not yet read the report. My bold.
The contents of the non-volatile memory (NVM) from the equipment known to record data have been successfully recovered and are being analysed. The majority of the recorded data have no form of time stamp. So, whilst the order of some of the snapshots can be determined, their relative timing is unknown. Other systems use time references but ones that are not directly linked to UTC. The Warning Unit has provided information on the order in which warnings were triggered during the flight but not when they occurred. The unit recorded the normal warnings associated with starting the helicopter, followed by a warning free status. It subsequently recorded intermittent LOW FUEL 1 warnings for the left fuel supply tank, then a permanent LOW FUEL 2 warning for the right fuel supply tank. This was followed by a further temporary LOW FUEL 1 warning, before it became permanent for the remainder of the flight. These LOW FUEL warnings are triggered by thermal sensors in the supply tanks. For this helicopter build configuration, they indicate when there is approximately 32 kg and 28 kg of fuel remaining in the left and right supply tanks, respectively. On receipt of these warnings, the manufacturer’s flight manual for the helicopter instructs the pilot to ‘LAND WITHIN 10 MINUTES’. An alarm gong was also recorded followed by intermittent warnings relating to low rotor rpm. The penultimate warning recorded related to the battery discharging, which occurs when there is insufficient engine-driven generator power. The last warning related to an autopilot system failure. Investigation into the possible causes for the individual warnings is continuing. Preliminary analysis of the FADEC data indicates that the right engine flamed out, followed, a short time later, by the left engine also flaming out. Since the maintenance reports only give timings relative to the moment the FADECs were turned on (which is not recorded), the exact times at which these flameouts occurred is unknown. The recorded radio transmissions do not contain any reference by the crew to difficulties with the aircraft. The AAIB investigation continues to examine all the operational aspects of this accident and to conduct a detailed engineering investigation. In particular, the investigation will seek to determine why a situation arose that led to both the helicopter’s engines flaming out when 76 kg of fuel remained in the fuel tank group, why no emergency radio transmission was received from the pilot and why, following the double engine failure, an autorotative descent and flare recovery was not achieved. |
"From this report, it appears that everything about the aircrafts systems worked exactly as it should." Not quite....this from the report...... "A fault relating to one of the display systems was recorded and further work is being undertaken to establish the meaning and possible causes of the fault."If this fault was the CAD then fuel information should transfered to a VEMD screen, but in a very reduced format and limited warnings. So we still wait for this to be clarified by a future report. |
If this fault was the CAD then fuel information should transfered to a VEMD screen, but in a very reduced format and limited warnings. So we still wait for this to be clarified by a future report. skadi |
A double engine failure by the time of impact seems to be inferred from the state of the physical wreckage and the battery drain warning. However, that warning is reported to have followed a low-rpm warning, so was an engine still running at the time of the rpm warning (seems unlikely?).
From the lack of timestamp information in the FADEC memory, it doesn't seem to be clear what the interval was between the two engines stopping ("a short time"), although the AAIB seem confident that the right engine stopped first, presumably based on some unstated concrete information, rather than just by being consistent with the relative supply tank sizes. The difference between the engines' run times is known, but will it ever be known which was started first, and the gap between the start times? Whether there was time to land with one engine still running after the first one failed seems to be unclear. The eyewitness reports of low flying before the crash seem to be incorrect, given that the report says the steady radar returns before the accident were from 1000 feet and 105kt. This report seems to rule out some dramatic mechanical issue, so the focus now falls on the mysteries of human factors, and, as stated by "Art of flight", whether the failed display system might have prevented the recorded warnings, and perhaps the state of the pumps?, from being appreciated onboard. |
Guys
For those of us that are not familiar with the EC135 is there any chance of a little more clarity, in factual terms, as to the exact nature of the incident. If I understand it correctly, there were two low fuel warning indicators which illuminated (along with aural indications) to warn to the pilot that fuel was becoming critically low. The procedure in the FM is to land within 10 minutes and there was sufficient fuel in the tank for a safe landing to have taken place. I'm guessing that the Fuel Transfer Pumps should have been ON to assist with the transfer of the remaining fuel from the tanks, through to the header tanks, and that because these were not on there was not sufficient fuel flow to the engine(s) and they subsequently flamed out. I'm also guessing that there was not sufficient time for the pilot to react to the double flame out and as a result the RRPM decayed to an un-recoverable level resulting in the crash. I have no interest in blame I just want to understand if I'm correct in what and why it happened. Thanks Joel |
The report says " This Special Bulletin is published to provide more factual information and an update on the progress of the investigation. No analysis of the facts is attempted." I think it remains a mystery.
The one thing they haven't covered at all so far is the capacity of the pilot. Might he have been incapacitated by injury or illness? The presumption has to be that he wasn't otherwise something would have been flagged and maybe the funeral would have been delayed. |
Sky sport, maybe you should go back to watching the telly! With regard to "A fault relating to one of the display systems was recorded and further work is being undertaken to establish the meaning and possible causes of the fault."
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What I found noteworthy was the following
The penultimate warning recorded related to the battery discharging, which occurs when there is insufficient engine-driven generator power. The last warning related to an autopilot system failure.
Not knowing the EC135 A/P system some questions do come to mind: Would this warning also be submitted if the A/P was deactivated? Or would the A/P still have to be engaged to receive this warning? If the latter: What are the conditions for the A/P to completely disengage? Would the A/P completely diengage in case of any significant Control input or could there be situations where it would only be temporarily overridden? |
pilot not incapacitated
To answer Lemain's comments re the pilot's capacity, I do recall reading a page on the net shortly after the time of the pilot's funeral which gave some (very little) information from his post mortem regarding cause of death. The official post mortem had to be filed somewhere according to law -seem to recall it was Rutherglen Health authority or Rutherglen District Council -sorry I cannot re-find the link -which stated that cause of death was, not surprisingly, injuries sustained in the crash and importantly (IMO) noted that they found no indication of a heart attack, stroke or that type of injury which would have caused him to be incapacitated prior to the crash. I was surprised this was not more widely reported at the time, but perhaps, out of respect for the pilot and the gravity of other's injuries at that time, reporters chose to ignore. I am further surprised that I cannot re-find the link, despite my searches. It seems to have vanished. But it does exist somewhere for a digging journo to find as the post mortem itself surely is a matter of public record. I know it was also briefly reported before his funeral that the pilot had not long returned to work after recuperating, over the previous months, from a very serious illness (no idea what) which fits in with his decrease of pilot hours during that period.
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The autopilot warning will possibly just be the final act of the basic function disengaging due perhaps to loss of electrical power to it, not to be confused with any drop-out of upper mode functions (selected options) such as alt/AS/hdg hold etc.
Annoying that the media are reporting this as a fuel problem, and double engine failure. The report quite clearly states that the fuel system as tested was fully functional, the engines did NOT fail, they simply stopped due to lack of fuel. There was fuel available, just that for whatever reason the pilot had de-selected the only method of getting it to the engine supply tanks. |
Perhaps transitioning from Hover during the last task to forward flight the aft Xfer pump was switched off as per RFM (or once the caution was activated due to no flow) but the FWD pump was missed, quite how is unknown.
The A/P could have disconnected for several reasons, excessive attitude, power failure are just two, my money is on power failure due to the Gen dropping off. I would expect the rotor rpm to fall before the Gen goes off line, N1 spinning at around 90%+. |
Perhaps someone could enlighten me, but do we have a similar situation to the 206L/407 where a fuel low light could come on even though plenty of fuel is indicated on board? Where are the FUEL LOW transmitters on this machine? Or does it have any at all?
phil |
FS,
I would expect to have deselected and reselected at least one , perhaps both, transfer pumps given that sortie profile and fuel remaining. fairly standard fare for police flying, still a mystery why both low cautions were ignored along with the master caution, and the prime pumps were selected on unless, say the CAD had failed and confusion had set in. Once you accept the facts of the switch positions it is an easier conclusion that it was simply mis-selection, but the ignoring of cautions remains a mystery. Paco, you've got a lot of reading to do, lots of previous posts on your question. |
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