AAIB initial report out on BA B777 crash at LHR

[guntslapper]

Initial Report AAIB Ref: EW/C2008/01/01 Accident

Aircraft Type and Registration: Boeing 777-236, G-YMMM
No & Type of Engines: 2 Rolls-Royce RB211 Trent 895-17 turbofan engines
Year of Manufacture: 2001
Date & Time: 17 January 2008 at 1243 hrs
Location: Undershoot RWY 27L, London Heathrow Airport
Type of Flight: Commercial Air Transport (passenger)
Persons on Board: Crew - 16
Passengers - 136
Injuries: Crew - 4 (minor)
Passengers - 1 (serious)
Passengers - 8 (minor)
Nature of Damage: Substantial
Information Source: AAIB Field Investigation

Following an uneventful flight from Beijing, China, the aircraft was established on an ILS approach to Runway 27L at London Heathrow. Initially the approach progressed normally, with the Autopilot and Autothrottle engaged, until the aircraft was at a height of approximately 600 ft and 2 miles from touch down. The aircraft then descended rapidly and struck the ground, some 1,000 ft short of the paved runway surface, just inside the airfield boundary fence. The aircraft stopped on the very beginning of the paved surface of Runway 27L. During the short ground roll the right main landing gear separated from the wing and the left main landing gear was pushed up through the wing root. A significant amount of fuel leaked from the aircraft but there was no fire. An emergency evacuation via the slides was supervised by the cabin crew and all occupants left the aircraft, some receiving minor injuries.

The AAIB was notified of the accident within a few minutes and a team of Inspectors including engineers, pilots and a flight recorder specialist deployed to Heathrow. In accordance with the established international arrangements the National Transportation Safety Board (NTSB) of the USA, representing the State of Design and Manufacture of the aircraft, was informed of the event. The NTSB appointed an Accredited Representative to lead a team from the USA made up of investigators from the NTSB, the FAA and Boeing. A Boeing investigator already in the UK joined the investigation on the evening of the event, the remainder of the team arrived in the UK on Friday 18th January. Rolls-Royce, the engine manufacturer is also supporting the investigation, an investigator having joined the AAIB team.

Activity at the accident scene was coordinated with the Airport Fire and Rescue Service, the Police, the British Airports Authority and British Airways to ensure the recovery of all relevant evidence, to facilitate the removal of the aircraft and the reinstatement of airport operations.

The flight crew were interviewed on the evening of the event by an AAIB Operations Inspector and the Flight Data Recorder (FDR), Cockpit Voice Recorder (CVR) and Quick Access Recorder (QAR) were removed for replay. The CVR and FDR have been successfully downloaded at the AAIB laboratories at Farnborough and both records cover the critical final stages of the flight. The QAR was downloaded with the assistance of British Airways and the equipment manufacturer. All of the downloaded information is now the subject of detailed analysis.

Examination of the aircraft systems and engines is ongoing.

Initial indications from the interviews and Flight Recorder analyses show the flight and approach to have progressed normally until the aircraft was established on late finals for Runway 27L. At approximately 600 ft and 2 miles from touch down, the Autothrottle demanded an increase in thrust from the two engines but the engines did not respond. Following further demands for increased thrust from the Autothrottle, and subsequently the flight crew moving the throttle levers, the engines similarly failed to respond. The aircraft speed reduced and the aircraft descended onto the grass short of the paved runway surface.

The investigation is now focussed on more detailed analysis of the Flight Recorder information, collecting further recorded information from various system modules and examining the range of aircraft systems that could influence engine operation.

[old-timer]

Thumbs up for all the crew, a very professional job in extremely difficult circumstances in my opinion, well done one & all.

A deep investigation for the Avionics chaps on this one I think?
The digital FDR will be a god send for the investigators.

[Oldjet Jockey]

A Question : Does the auto throttle have to be disconected before manual inputs to the thrust levers would take effect?

OJJ

[nugpot]

If I understand the prelim report correctly, it just says that the autothrottle was engaged. It does not specifically state that the autopilot was engaged. Not that it really matters.

My question to B777 pilots ONLY (If you are not rated on the B777, this question is NOT to be answered by you):

Could you explain to a non-autothrottle (CRJ) pilot the differences in short term and long term effects of physically moving the thrust levers with the A/T engaged. Does it
1. Disengage A/T?
2. Cause an immediate thrust change which is then gradually changed back to what the A/T thinks it should be?
3. Stay at the manually commanded thrust for x time?

[Desert Diner]

So it's all about loss of throttle control at the moment.

[SuperRanger]

nugpot,

the A/T system is not a separate system on the B777 as on other 'fly-by-wire' aircrafts. when the A/Ts are engaged, the A/T servos moves the throttle levers just as a pilot will normally do, based on the A/T computer inputs. one can manually 'overwrite' the servos by physically moving the throttle levers but if you released the throttles, the A/T servos will move the throttle levers back to it's 'current commanded' position.

SR

[ETOPS Jock]

-Quote-
Could you explain to a non-autothrottle (CRJ) pilot the differences in short term and long term effects of physically moving the thrust levers with the A/T engaged. Does it
1. Disengage A/T?
2. Cause an immediate thrust change which is then gradually changed back to what the A/T thinks it should be?
3. Stay at the manually commanded thrust for x time?
-End Quote-

Answers:-
1. No
2. Yes. Physically moving the thrust levers will change the thrust. The A/T will reposition the levers to what it requires when you let them go.
3. No.

[nugpot]

Thanks SuperRanger and ETOPS Jock

Clear and concise.

[Wingswinger]

Does anyone else think that this might call into question the whole concept of the CDA?

It would depend exactly what point the critical failure occurred. Let's say it was some minutes before the point at which it became evident to the crew, with the aircraft descending to establish on the ILS and with the engines at idle.

The engines did not respond when power was applied, either by autothrust or manually. Had they responded already when the gear was selected down and landing flap lowered? We do not know yet. Let's suppose they hadn't for whatever reason - it was gusty day. If the failure was already present it could be masked at this stage.

Let us now insert a level segment in the descent at either 2500ft or 3000ft. The aircraft requires power but does not respond at this point. There is possibly earlier recognition of a serious problem and the action open to the crew is to delay lowering the gear and the flap which could result in the aircraft safely reaching the tarmac even if it touches down tail first.

Any 777 drivers care to comment? Would the 777 make a runway from 3000ft/10 miles, on the GS with power at idle?

[wobble2plank]

Had a look at this on final last night!

600'/2 miles is very late and scary to find out you have thrust lock or thrust back-off.

The interesting thing is that you are required to achieve 2 gates on the CDA. 1000' should be fully configured in the landing configuration with the Vapp within 25 knots of landing speed and reducing. The engines do not need to be spooled up to approach power by this point but they need to be stable at approach power by 500'.

These guys must have (my thoughts only) realised they had this technical fault in that 1000'-500' segment which means they dealt with it extremely quickly and very professionally at a seriously time critical point.

Curiously my colleagues and I were comparing the differences between the Boeing A/T system and the Airbus Alpha protections. In this case, as the speed came back towards the stall, would the Airbus Alpha protections kick in to giver TOGA power? Bearing in mind the protections are NOT a function of Auto Thrust.

A backup thought for the 787 maybe?

Good luck to all the crew and pax.


p.s. As Nugpot (Topgun???) has discovered the Boeing system moves the thrust levers to give tactile feedback and an early indication that power is not coming up. The Airbus system just leaves the thrust levers where they are, does its thing and leaves you to guess the power setting.

[PJ2]

wobble2plank;
Curiously my colleagues and I were comparing the differences between the Boeing A/T system and the Airbus Alpha protections. In this case, as the speed came back towards the stall, would the Airbus Alpha protections kick in to giver TOGA power? Bearing in mind the protections are NOT a function of Auto Thrust.

I've been wondering that since the AAIB report came out. Our 330's are powered by the same engine. However, as has been observed by others, the issue here looks like it is systemic and upstream of the engines, downstream of the autothrottles. There will be substantial design differences between the Airbus and Boeing installations and while the question is interesting (but hopefully not provocative), a comparison may not be possible. We'll likely hear more of this aspect as 330 operators ask the question themselves.

[Wingswinger]

would the Airbus Alpha protections kick in to giver TOGA power? Bearing in mind the protections are NOT a function of Auto Thrust.

Actually A-FLOOR is an ATHR function. A-PROT and A-MAX indications are derived from the FAC but the actual protections are done by the ELAC.

A320 protections start with ATHR at VLS and finish with ATHR at A-FLOOR which will be activated well before A-MAX.

[BorderLine]

May I politely suggest that before posting anything in this thread, people read every single last little bit of all 960 posts in the previous thread, especially the last one!

If you still feel you just HAVE to have your say, PLEASE leave out the trash.

Discussion and rumours are great but when it's the same old stuff over and over it gets a little boring. Thanks to all with constructive input.

Can't wait for the real investigation findings...

[PJ2]

Wingswinger;
Actually A-FLOOR is an ATHR function.

Fully agree, but exactly how, is the question. Because we don't know the nature of the fault(s), it may or may not be "bypassed", (not a precise term, I know), by the A-Floor response.

Like many, I anxiously await more information from the AAIB as to the failure mode(s) and whether they are endemic or limited to some msn's or to one installation.

Along with the QANTAS and Air Canada incidents, all of which were serious but with no fatalities and where experienced crews played a key role in achieving a good outcome, it will be an interesting series of reports to read when they're finally issued.

[NigelOnDraft]

Curiously my colleagues and I were comparing the differences between the Boeing A/T system and the Airbus Alpha protections. In this case, as the speed came back towards the stall, would the Airbus Alpha protections kick in to giver TOGA power? Bearing in mind the protections are NOT a function of Auto Thrust.As WS says, not quite right... ;) The Airbus (A320 anyway - rest are similar if not identical) power up is ATHR ;)

The action of going to full power is called "Alpha Floor"... WS says this occurs at VLS which, whilst it has ATHR implications (if engaged) is not Alpha Floor. Alpha Floor kicks in "at some point" prior Alpha Max (Stall), "at some point" being variable e.g. a rapid increase in Alpha (cf rapid reduction in speed) will see it kick in earlier, than gently coming back to Alpha Max.

Crucially, when related to this incident, Alpha Floor is disabled <100R on landing... as somebody found out early in the A320 days :{ So whether an Airbus would have gone for Alpha Floor would depend on what (Rad) Alt the speed decayed to the (unknown ;) ) Alpha Floor threshold.

Also interesting is the A v B flying control logic. There is talk (not really interested in discussing if true or not until the AAIB report) that the 777 stalled at @10'. There might be good reason for doing that, but the Airbus would not allow it... as it hit Alpha Max (stall AoA) it would have lowered the nose to maintain Alpha Max [in Normal Law]. In the ultimate case of "hopping over a hedge" onto a "better surface" there is a small chance that the B philosophy might just prove better here :oh:

I think the Alpha Floor etc. argument is likely somewhat spurious though... these are ATHR modes, and the AAIB have already stated the ATHR was demanding a power increase and not getting it... so at a simple level, why would Alpha Floor (or it's equivalent) get power? We shall have to wait and see where the "systems" failed, and if there is a chance that factors such as "other modes" might have bypassed the problem :uhoh:

I trust the above is seen, as intended, as a systems discussion, not speculation on Thursday...

NoD

[NigelOnDraft]

Does anyone else think that this might call into question the whole concept of the CDA?No....

The key for the AAIB is to discover why the engines did not respond, and then prevent that happening again (basic premise of accident investigations). We are dealing in public transport aircraft here, and we really cannot take your logic to the extent of joining LHR overhead at 3000' in a PFL pattern because of one occurence :rolleyes:

NoD

[wobble2plank]

Hiya NoD,

Good to see you still trawling the forums ;)

Sorry, just re-read my post and I didn't make my meaning all too clear! :sad:

I fully agree that the A/Thr system is responsible for applying the thrust in the case of Alpha protection (dependent upon altitude etc...), however that function is carried out irrespective of the 'armed' state of the A/THR from the cockpit. What I was wondering is whether, as with most 'Airbus'isms, that is a totally different wiring/logic route through to the activating system.

This is NOT speculation, nor have I intimated any speculation, nor do I refer any of it specifically to the 777 (a type which I have never flown), just thinking about the possibility happening on other aircraft types.

I agree about the 'gentle nose down pitch' of the airbus making a mess of your nice extended glide though.

see you soon

[Giant Bird]

I believe that there is benefit in discussing some issues which are not dependant on the technical forensic examination.
Here is a crash where everyone survived, but where luck played a big element. A difference in only seconds or a few hundred metres and there could have been total aircraft break-up and fire. The first objective is to avoid crashes the second is to make sure as few as possible are injured. What can we learn about the second objective from this crash? This post is not an exercise to point the finger, it is an exercise to discuss and learn.
Brace Instruction
Passengers are conditioned to believe that they will be instructed to go to the brace position when necessary. I think that there was good reason for passengers to be in the brace position during this crash, however no such instruction seems to be given by the flight deck or cabin crew. It seems that the SFO was handling, the Captain was trouble shooting and we have no information on what the FO was doing. I would expect that most of the cabin crew located near windows would have enough general flying experience and specific LHR approach experience to know something very abnormal and potentially dangerous was occurring in the last 30 secs of flight.
·Should the captain have taken a few seconds away from his checking to at least flash the seat belt sign to confirm to the cabin crew that any preliminary suspicions they had that things were serious were correct?
·In the absence of any communication from the flight deck, should the cabin crew have taken the initiative to instruct the passengers to the brace position?
·Does the FO in the jump seat have any ability to communicate to the cabin crew the need to get the passengers into the brace position?
·If the FO could not communicate himself should he have suggested to the Captain that he should do it?
If the answers to the above questions are no, then some other changes should be seriously debated as industry norms.
1.Passengers told to go brace instruction if instructed or if they believe that landing is abnormal. With the instruction on the seat pocket card “Any embarrassment at unnecessary brace position will be short lived, death is permanent”
2.Fit all seats with combination lap-harness belts, with passengers instructed to fit the harness portion during take-off and landing.
3.Some other change.
Evacuation
From what I have read it seems that seconds are vital in post crash evacuation. There was no fire in this case, but there could well have been. In past accidents it appears that indecision or tardiness on their own part or the part of others have cost passengers their lives, sometime by only ten seconds. Reports suggest that in this instance the flight deck never gave the order to evacuate, some passengers realising that there had been a crash and there was danger of fire headed for the exits without being instructed to do so They were told to return to their seats and sit back down. Subsequently the cabin crew commenced an evacuation.
If this information is true, I suggest that there needs to be a discussion;
·Why with three pilots on the flight deck, did not one of them initiate the order to evacuate?
·How appropriate is it that passengers end up initiating evacuation before the cabin crew?
·How appropriate is it, for the cabin crew to order passengers attempting to evacuate a plane highly likely to catch fire to return to their seats?
I repeat that I am not trying to criticise anyone, I am trying to open serious debate about some important air safety issues which deserve discussion, and which I hope will get extensive coverage in the final crash investigation report. Crashes will happen; let’s not rely on luck for high survival rates.

[Jabawocky]

NOD

Quite correct.......but you wouldn't blame any 777/Roller drivers ditching the noise abatement idea and arriving with just a little more thrust or Kinetic Energy up their sleeve:p

J:ok:

[NigelOnDraft]

GB - you are making some very unfair allegations, some of which I know are untrue... As you say, the AAIB will discuss them in detail, so why do you have to try and criticise the crew now? Especially in areas that are factually incorrect :suspect:

[NigelOnDraft]

but you wouldn't blame any 777/Roller drivers ditching the noise abatement idea and arriving with just a little more thrust or Kinetic Energy up their sleeveI might agree with you on Thrust... but in fact KE is controlled / determined by ATC, and PE is higher on the CDA ;)

[Human Factor]

·Should the captain have taken a few seconds away from his checking to at least flash the seat belt sign to confirm to the cabin crew that any preliminary suspicions they had that things were serious were correct?

No. There were more important things going on at the time I believe. If he had the chance, I'm sure he would have made the crew aware.

·In the absence of any communication from the flight deck, should the cabin crew have taken the initiative to instruct the passengers to the brace position?

No. With respect to my cabin crew colleagues, unless they have been prewarned, they have no way to know whether or not a landing is likely to be abnormal until it's finished.

·Does the FO in the jump seat have any ability to communicate to the cabin crew the need to get the passengers into the brace position?

Yes.

·If the FO could not communicate himself should he have suggested to the Captain that he should do it?

Maybe, maybe not. Perhaps he did, perhaps he didn't. There are a million reasons why it was perhaps not communicated to the cabin. All of them valid.

[Southernboy]

It is very interesting to debate all possible causes of this accident & some of it has been v enlightening but one central issue goes unadressed - if we don't know how the impossible happened why are 777s still flying & what's more on ETOPS?

Two independent engines with independent control systems, both with redundancy and still both engines "fail to respond." No cause for global concern there then? Sumat doesn't add up.

[Human Factor]

·Why with three pilots on the flight deck, did not one of them initiate the order to evacuate?

I believe one of them did.:rolleyes:

·How appropriate is it that passengers end up initiating evacuation before the cabin crew?

It isn't.

·How appropriate is it, for the cabin crew to order passengers attempting to evacuate a plane highly likely to catch fire to return to their seats?

There may be reasons why it is initially safer to stay inside than jump out. An evacuation can potentially cause more injuries than an incident. At the very least, if you have a few seconds to evaluate the situation before you initiate the evacuation, I would recommend using them.;)

[highkey]

"until the aircraft was established on late finals for Runway 27L."....

I think the report author would have prevented this line of discussion by more accurately calling it "Short Finals" or "Very Short Finals".....?:)

[NSEU]

"...the aircraft was at a height of approximately 600 ft and 2 miles from touch down. The aircraft then descended rapidly and struck the ground, some 1,000 ft short of the paved runway surface,..."

Considering the aircraft was 2 miles out and managed to get within 1000' of the runway, can this be considered a "rapid" descent? :confused:

Re fuel contamination ex-Beijing... I've been told that our airline's Airbuses (ex-China) regularly generate blocked filter messages (and have to be replaced). I didn't ask what steps have been taken to address this issue, however.

Re jet pumps getting rid of water in the tank... .Can it get rid of water if it is in the form of ice? Cold flight there, cold ground stop, cold flight back, etc.. Will it ever get the chance to thaw out?

Re FADEC

In Normal Mode (EPR), the EEC uses this data to calculate thrust ratings:
Thrust lever angle (TLA)
Inlet temperature
Altitude
Mach Number
Bleed Status

In Alternate Mode (N1) the EEC uses this...
TLA
Inlet temperature
Altitude

Some faults make the EEC switch to alternate N1 mode automatically. This is called soft reversion. When soft reversion occurs, the EEC turns on the ALTN light in the EEC mode switches. The EPR indications also go out of view.

Re P2T2 heat... (engine inlet probe heat)

There is a device called a PCU (power control unit, mounted on the side of the engine) which supplies heating power to P2T2 probe. The PCU can get it's power from the dedicated alternator (driven by engine rotation) or from ELMS (normal airplane power). There are switching circuits inside the PCU. Full details not available to me, but it seems the EEC has the ability to control what power source the PCU selects (but I don't know if this is at all times).

The EEC monitors probe heat current. There are maintenance messages for probe heat failure, but the pilots only know of probe heat failure though EEC mode EICAS and Status messages.

Information about EEC's derived from Boeing 777 Maintenance Manual (D&O).

Rgds.

[phil gollin]

Might I note :-

- This thread started off quite sensibly as a thread to discuss the AAIB initial report, it now seems to be starting to be a re-hash of the "other" thread.

- The AAIB initial report was so uninformative and SEEMINGLY deliberately so, that MAY INDICATE that the cause MIGHT at FIRST GLANCE be one that is going to be difficult to apprortion quickly. (The whole dearth of facts merely gives rise to having to be so cautious).

----------------

The only sensible comment that I can think to make is that I think that this is appalling PR, merely guaranteed to get people speculating. If the AAIB, BA and BAA want to keep public speculation, popular concern and the media feeding frenzy down, then they should be more forthcoming in their Public Relations. As a display of media control this is appalling.

.

[TyroPicard]

@wobble2plank
p.s. As Nugpot (Topgun???) has discovered the Boeing system moves the thrust levers to give tactile feedback and an early indication that power is not coming up. The Airbus system just leaves the thrust levers where they are, does its thing and leaves you to guess the power setting.

Oh for heaven's sake,here we go again..... Just how did the thrust levers give this early indication? The pilots had to look at the instruments, just like all pilots do. It's always a guess, irrespective of a/c type until you use your eyes. And your brain.

I agree about the 'gentle nose down pitch' of the airbus making a mess of your nice extended glide though.

Lots of people have died doing nice extended glides... Stalling at 100' instead of 10' might have made a huge mess of a 777 if a wing dropped - I don't know the stall characteristics or anything about the 777 Flight Control System - I think the success of this particular landing was down to the ability of the pilots and not the design of the a/c.

[Guava Tree]

Belgique's TOGA idea (posts 922 and 939 of closed BA B777 Incident @ Heathrow (merged) thread) might just have worked.
It is counter-instinctive for a pilot to attempt to go around if he knows he does not have enough power even to maintain his desired descent, and for this reason it was almost certainly not tried.
If his idea had been thought of and tried and worked the whole thing would have been hushed up and they would not have been heroes. I think they would like that trade.
Software instead of being our able assistant is really becoming our enemy.

[Wingswinger]

NoD,


The key for the AAIB is to discover why the engines did not respond, and then prevent that happening again (basic premise of accident investigations). We are dealing in public transport aircraft here, and we really cannot take your logic to the extent of joining LHR overhead at 3000' in a PFL pattern because of one occurence

I know we are dealing with a public transport aircraft, thanks. I fly them too.

If you would re-read my post #9, you'd see that I am not suggesting that absurdity. I have asked if anyone else thinks that this might call into question the practice of CDA. That is all.

[glad rag]

QUOTE

the A/T system is not a separate system on the B777 as on other 'fly-by-wire' aircrafts. when the A/Ts are engaged, the A/T servos moves the throttle levers just as a pilot will normally do, based on the A/T computer inputs. one can manually 'overwrite' the servos by physically moving the throttle levers but if you released the throttles, the A/T servos will move the throttle levers back to it's 'current commanded' position.

SR

On an approach does the AT cycle the levers constantly??

And how apparent to the PF are these lever monements???

rgds

glad rag

[ILS27LEFT]

" I would expect that most of the cabin crew located near windows would have enough general flying experience and specific LHR approach experience to know something very abnormal and potentially dangerous was occurring in the last 30 secs of flight."

Incorrect, the windows on those Boeing 777 doors, by the Cabin Crew seats, are extremely small and it is nearly impossible to see what is going on outside (same as 767, windows on doors are too small!!).
This should be in fact reviewed and the window design changed. Cabin crew should always know what is happening outside (fire, etc).

Apparently those passengers seating by the "larger-normal" windows, and especially those by the wings, immediately realised that this was a crash-landing on the grass and they went straight to the exits with some degree of very understandable panic. Only after this the CSD correctly and bravely decided to evacuate.
You can do all the training you like but this was the totally unexpected "engine-throttle failure" with only a few seconds left to react. Seconds. No time to follow procedures or check-lists, just the minimum time to concentrate on your skills and istinct. This is why the absence of a side-stick (Boeing vs Airbus) might actually have helped in this case, but this just my personal speculation.

After the plane stopped, the pilots were obviously still seriously shocked after landing and they probably thought they were in the middle of a dream and all pax died at the back...it was their worst nightmare... and I applaude them for an incredible landing.
They did not know what happened behind their door until they heard the pax evacuating....our brain is not as cold as a computer...plain traditional feelings and istinct have saved this plane and those on board and those on the road and houses nearby as well.
It seems like our beloved electronic and FBW concept has failed (!) again and the only bit of "human factor" left has actually saved the plane. Unless it is fuel related.

It is impossible to understand here what they went through in the cockpit, the mental shock is extreme and they were possibly all shaking. Normal. Nobody is prepared to land on the grass just missing cars and houses on a 777...nobody. Especially so suddenly and after 12+ hours of perfect flying..

They have all done an exceptional job.:D

For all those criticising the pilots: this was not a normal, prepared, expected emergency landing but a FULLY UNEXPECTED TOTAL CRITICAL extreme EMERGENCY which happened IN THE LAST FEW SECONDS, NO TIME TO REACT, NO TIME TO TALK, NO TIME TO DO ANYTHING ELSE EXCEPT KEEPING THE MACHINE WING-LEVELLED AND TRY TO MAKE IT STALL AS LATE AS POSSIBLE INTO THE AIRFIELD. ANYTHING ELSE WAS TOTALLY IRRELEVANT AND THE MOST TINY DISTRACTION WOULD HAVE MEANT DISASTER.
The plane stalled, luckily, at the perfect stage, and in fact also stopped in an incredibly short distance. And this is exactly what the pilot should have been looking for and he made it.:ok:
Anything else is irrelevant to me.:ok:

[Mr @ Spotty M]

Ramrod2 is technically correct in his post as he did not mention the fuel tank quantity.
The reason this aircraft ended up as it did is most likely down to fuel in one way or other.
I point this out because if the engines at the time the crew demanded more power had been supplied more fuel, they would have produced more power.
The question that the AAIB has to answer is why did the engines not get this required fuel.
The point is that the FADEC along with all the other hardware and software did not supply that extra fuel when demanded.
I have read the following "The AAIB has identified that the problem seems to be connected with the avionics and and electrics which link the flight deck to the engines."
It is to early to point fingers or give praise as we do not know the facts.
The most likely to end up with some or all of the blame are going to be the following, Crew, BA, Boeing, RR or other component manufactures associated with engine controls.
Everyone has assumed that this aircraft was fully serviceable before the accident, we do not know what technical defects it was carrying prior to departure and don't know what defects it had on route.
This is why l put the crew and BA into the possible blame, as we know it sometime takes many independent items to combine to cause an accident.

[fossicker777]

AAIB quote: "the Autothrottle demanded an increase in thrust from the two engines but the engines did not respond".

An observation only: Occurring only 2 miles from touchdown at 600', is this not totally unique in commercial aviation?

[nojwod]

I know you mean well GB but your reasoning and assumptions, as well as your suggestions are incredibly hindsighted and dare I suggest what I would expect from a desk pilot or civil servant who has an excellent grasp of theory but little of reality.

Two miles out and 600' agl, engines lose power over a residential area and it takes all the skill and concentration of an experienced crew to get the aircraft onto level ground rather than the nearest road embankment or house, and you expect the crew to take time out for a message??? To anyone??? To anywhere????

There may be valid points in your second part about the evacuation order control, but once again I say that they are from the point of view of an observer, not from someone who was there at the time. Perhaps if you could qualify your statements with a statement to the effect that you are an expert crash manager, and when you brought in such and such a plane to a successful crash landing against the odds, you had the ice cool ability to do everything by the book, to the letter and per every last regulation under the cloudy London skies.

Get my point?

[NigelOnDraft]

Only after this the CSD correctly and bravely decided to evacuate.Where have you got the info that the CSD decided to evacuate :hmm: I have seen no concrete info that this occurred, rather, than say the evacuation was initiated from the Flt Deck :confused:

[Flintstone]

AAIB quote: "the Autothrottle demanded an increase in thrust from the two engines but the engines did not respond".

An observation only: Occurring only 2 miles from touchdown at 600', is this not totally unique in commercial aviation?

Do you mean is the requirement for thrust at this point in the approach "unique"? No.

If you mean 'Is it unique for the thrust not to be supplied when needed?'. Probably. I've not heard of any other crashes matching this scenario.

[Jabawocky]

Yeah

Report reads: F/O took time to address the pax to prepare for a ...........FDR/CVR stopped due stall at 300' and crashed and burned a whole suburb:ugh:

Would rather not hear a thing and actually have an aircraft .....and the physical ability to get out of it.............

Stuff the PA's......I thought .Aviate, Navigate Communicate was pretty clear, and in that order.

Regardless if they stuffed up with fuel or something, they got that last bit right.

J:ok:

[tbaylx]

The A/T will move the thrust levers if it's required to maintain selected airspeed. Most SOP's require the pilots hand to be on the thrust levers during the approach. If the approach is stable in a zero wind condition there will be little if any movement of the thrust levers by the auto throttles once the aircraft is established on final. In gusty conditions where thrust requirements change constantly the A/T will move the thrust levers quite a bit to maintain speed and movement is instantly noticable if your hand is on the thrust levers.

In CDA approach the thrust will remain near idle as the aircraft slows down to final approach speed and the aircraft is configured in the landing configuration. The thrust will then increase to maintain speed. Most airlines (BA included) have "gates"'in which the aircraft must meet certain stabilization criteria or a GA is performed. One of the last gates criteria is the aircraft is on speed and the engines are spooled up above idle. As i understand it BA's last gate is 500' so likely the thrust was coming up from an approach idle configuration to maintain speed and failed to respond at that time.

A crappy situation with very little time to recognize it and take any sort of action other than flying the aircraft. I highly doubt a PA was very likely given the amount of time they had to recognize and deal with the situation, especially considering the length of flight they had just done...you certainly aren't expecting an issue like that 600' above ground on final after a 12hr + flight.

[cwatters]

Re Giant Birds comments:

As I understand it the pilots didn't have time or were too busy even to issue a Mayday call before impact. They did that immediatly after coming to a stop and that was probabably simutaneously with the cabin crew ordering an evac. Presumably the pilots heard the cabin crew order the evac as well. Knowing that a call had been made perhaps making sure everything was shut down was higher priority. Anyway the CVR transcript will no doubt make it all clear.

I've not heard any passengers say they knew they were going to crash and they would have had a better view out of the windows. Can cabin crew even see the ground from their seats? Aren't they normally busy looking for pax standing up to retrieve hand luggage?

[aviate1138]

I do hope, when the fog of accusations has lifted, probably when the AAIB make their conclusions public, that the Blame Culture nerds do not crucify the crew for one small thing that most 777 pilots might have missed under similar circumstances and that if the crew have been proved to have taken the correct decisions then some large apologies will be posted here! And flying in a 777 can continue without any nagging doubts during the final phase of the flight!

Nothing to do with flying is 100% safe - ever!

"Never tell me the odds!" Han Solo The Empire Strikes Back

[tbaylx]

that's great WZ, when we have time we're glad to prepare the cabin, shout brace at the appropriate time and initiate and evacuation jsut like it all neatly happens in the sim.

In real life when you have seconds to analyze, fly and try and fix whatever has gone wrong before you hit the ground we instinctively try and process everything that's happening and save the aircraft or at least mitigate the damage. We'll do a PA if we have the time, in this case they didn't so it wasn't done. The cabin crew then reacted as they were trained to do and did an excellent job in getting the pax out in a controlled manner.

tell you what, next time you do a recurrent tell your instructor to give you the same situation on a random approach when you aren't expecting it and see how much time you have to do a PA. Then try and imagine you had no idea it was about to occur and you'd just done a 12hr flight from china and were about to land and see if you'd still think there was time for a PA after you figured out what the hell was going on.

[ILS27LEFT]

Just a note .:mad:
We all love our very useful electronics, including the web, car ABS, ESP etc...a lot of new cars are now built with "drive by wire" systems, e.g. the accelerator pedal communicates with the fuel injectors through wires rather than mechanically as it used to be.
Electric signals are sent. :)
...Result: more and more car-mechanics around the world have to assist clients with cars which do not respond to manual inputs as they should, either due to software failure or ECU hardware malfunction. "You push the accelerator but nothing happens...engine stays idle". The software overrides the manual input of the driver. It happens every day. I am talking about cars, including very expensive ones.:}

What I am trying to say is that rather than focusing on why the massive 777 engines did not both respond to AT and manual input (FBW), there is a high chance that the Inspectors will have to focus instead on why the software decided that more power was not needed, the glitch might be in here!
If indeed they had fuel which was not contaminated in any way, our beloved software (possibly) decided (again!) to override the manual and AP input from the throttle.
It has happened before, but never:mad: 30 secs before touchdown.
This was the 1st time.

The fact that this incident happened in the last 30 secs of a 12hr uneventful flight still points in the fuel direction first, second in a software glitch.
I am quite confident that the 2 RR engines have no responsibility in this case, they have done too well in the previous 12 hours. Fuel?...or software (outside the engine)?...the request for more fuel did not even get close to the 2 RR.:ok: I think the request for fuel stopped pretty early along the line of wires...:mad:

I think pilotless-flights projects will be put on hold for a while.:O

Just a thought.:mad:

[Whiskey Zulu]

Fair point tbalx. I was just re-emphasising the importance of a brace command from the flight deck, IF there is time, not criticising anyone.

[Gonzo]

Can we just stop speculating on whether a MAYDAY was called, or who called for evac. For those who haven't heard the R/T, either at the time or on tape, the transcript will tell you.

Superpilot.....there were a/c holding short of 27L, at S3.

However, we would very rarely hold at N1/N2E/N2W to cross southbound at the threshold when landing 27L. This would mean infringing the ILS critical area, which would fluctuate the GP signal badly. We would only do that when weather conditions were CAVOK and inbound a/c were happy to continue visually. I've seen it done maybe fifteen times in ten years.

[Mrokowski]

I did my best to browse the whole dissusion - so - sorry if I missed - any other comment on fuel contamination (rather than the one done by ILS27L)...

Software/hardware problem seems like suspect number one, but what do you think about really bad case of fuel contamination? I am trying to search data bases to find past cases. Any help on cases? Any engeener's comment on that?

[Tediek]

Is the aircraft back on her "feet" yet as I read they were suppost to lift her today?

[permFO]

If you really want to know whether the software or hardware was at fault look at the FAA website to see if they have issued any Emergency AD's. When the MAS 777 had an ADIRU fault off the coast of Western Australia in 2005 an Emergency AD was issued within a few days. That incident was caused by software and hardware faults.

[BorderLine]

Mrokowski

Fuel contamination would not likely manifest itself on both engines at exactly the same time, also you would expect other a/c refuelled at the same port to be showing contamination...

[Swedish Steve]

The BA Recovery team are lifting the aircraft today with jacks and four cranes. They will then put three motorised platforms under the aircraft to drive it to the maintenance base, about 500m away.
It will go in one piece.
Should be out of the way tonight.

[Lump Jockey]

Just wondering (if it was due fuel contam.) wouldn't other aircraft have been affected accordingly? I can't see it being this, surely it would've shown up earlier, not just in the last phase of flight? Also, just out of curiousity, would the crew have had time to call "Brace, brace" during all the commotion?
What a brilliant piece of operating on behalf of the aircrew though, absolutely amazing sitution to have been in with speed dropping off all the time whilst watching the ground getting closer by the second. My hat is off to you guys.
LJ.

[nukem365]

heard last night from a source that the flaps had been selected to 20.
fuel waxing being considered as the most likely cause at moment

[fossicker777]

In reply to Flintstone (see below) I did of course mean the latter. If this scenario is unique it might suggest that identifying the exact cause may not be a simple matter.

Do you mean is the requirement for thrust at this point in the approach "unique"? No.

If you mean 'Is it unique for the thrust not to be supplied when needed?'. Probably. I've not heard of any other crashes matching this scenario.
http://www.pprune.org/forums/images/statusicon/user_offline.gif http://www.pprune.org/forums/images/buttons/report.gif (http://www.pprune.org/forums/report.php?p=3849890)

[ManaAdaSystem]

Correct me if I'm wrong, but there has been a number of dual engine flameouts on Airbus 330's? I know Qatar Airways suffered one not to long ago. Ice related?

Anyways, there was an ice warning out in London FIR the same day BA 038 hit the ground. Not that I think this was the cause, but worth mentioning.

[bonajet]

NoD
As far as I remember the 330/340 is Normal law in pitch to 100RA then direct stick to elevator with no protections including Alpha Floor. Lateral is normal until the ground.
cheers B

[FlexibleResponse]

nukem365
...fuel waxing being considered as the most likely cause at moment

A thoughtful comment at last!

[Locked door]

NoD,

I think you're on about what is annunciated in the FMA's and I've disposed of my airbus manuals so an unable to give you a reference. However IIRC some background logic changes at 30R, part of that is the Alpha floor protection being inhibited which you've already alluded to. As part of that process there ceases to be any stall protection at all thus the flight crew can command as much up elevator as they want. I understood the logic being that a stall onto the main gear from below 30R is more desirable than planting it on the nosegear.

I could be wrong, it's been a while but that's how I remember it.....

LD

[ManaAdaSystem]

And the airtemp over UK at the time was some of the coldest I've ever experienced with OAT at higher levels down to -70 degrees celcius.

[Mrokowski]

Thank you!
I wait for more on this when available. Maybe there is a big lesson coming in -on, let's say, QA side of GH ops...

[Teal]

Question for the experts: is fuel waxing a common occurrence in aviation, and if so, under what circumstances?

[FE Hoppy]

whats the certified environmental envelope for a 777?

Some one questioned CDA earlier in the thead.

Long descent at idle may have masked a fuel problem until thrust demand at 600'

New air traffic systems may well have introduced new failure modes previously unknown.

[BorderLine]

The fuel freezing point is the temperature at which wax crystals, which form in the fuel as it cools, completely disappear when the fuel is rewarmed. (This should not be confused with the fuel becoming cloudy upon cooling, which results when water dissolved in the fuel freezes, forming a suspension of very fine ice crystals. Airplane fuel and engine systems are designed to handle water ice crystals safely.)

The Jet A fuel specification limits the freezing point to a maximum of –40°C; the Jet A-1 limit is –47°C maximum.

The 777 has a fuel temperature probe located between ribs 9 and 10 of the left main tank. The probe is approximately 12.6 in from the lower wing skin and is located one rib over, approximately 40 in outboard, from the aft boost pump inlet. Because the left wing tank contains a single heat exchanger, its fuel can be slightly colder than that in the right wing tank, which contains two hydraulic heat exchangers.

Fuel temperature on the 777 is displayed in white on the primary EICAS in the lower right corner. If the fuel temperature reaches the established minimum, the indication turns amber in color and the FUEL TEMP LOW advisory message is displayed.

http://www.boeing.com/commercial/aeromagazine/aero_16/images/polar_fig5.jpg

[DAYAVAAN]

Until the AAIB determine the cause of the accident it would be prudent for all operators to advise pilots to disconnect/reconnect the auto pilot & auto-throttles before commencing the approach. Also in view of limited landings (due long sectors) performed pilots must carry out manual approaches in VFR conditions. This is from an old timer who commanded DC-3, F-27, B-737 & A-300 types.

[greekdalek]

In the days of the Comet 1 fuel waxing was a problem!:}

[woodpecker]

With regard to fuel temperatures, Flight Planning on the B767 on long sectors (Heathrow-Vancouver/Seattle) often required the cruising height in the latter part of the sector to be reduced to maintain he fuel temperature above the minimum.

The B777 however, on simular sector lengths and OAT's didn't seem to have the same problem. The fuel never seemed to get as cold as it did on the B767.

At least the data will be available on the fuel temperature and one would assume some fuel remained (on board) on which tests can be carried out.

[Wornout Rubber]

Fuel waxing I believe is rare indeed.

Also the chances of simultaneous engine failures or engines failing to respond simultaneously due to waxing must be very small.

One interesting point that may be worth mentioning is fuel crossfeeding.

The Boeing 777 FCOM states that "Fuel balancing may be done in any phase of flight".

I am not implying in any shape or form that the 777 was balancing fuel at the time of the incident, but would it be more prudent NOT to balance fuel close to the ground, when you would be feeding both engines from one tank, and raising your chances of power losses due to contaminated fuel etc. in that specific tank?

I do not know whether fuel balancing on the approach, landing or go around is permitted on other Boeing or Airbus types. Perhaps someone can comment.

What is the fuel balancing/crossfeeding policy of Airlines in the UK?

[pilotpilot]

two quick points:

1. At 600 feet (if they were @ the usual 750 ft p. min on the glide), they only had less than 48 seconds to recognize and react.

Probably much less, since at the very last bit, they were just falling (stalling), so the rate of descent increased.

2. If the pilots had extended the gear only a very few seconds earlier, the demand for the thrust would have been earlier, and the crash would have occurred abit furthur back from the runway!!!!! So everyone involved was really really really lucky!

[BorderLine]

Dayavaan

Until the AAIB determine the cause of the accident it would be prudent for all operators to advise pilots to disconnect/reconnect the auto pilot & auto-throttles before commencing the approach. Also in view of limited landings (due long sectors) performed pilots must carry out manual approaches in VFR conditions. This is from an old timer who commanded DC-3, F-27, B-737 & A-300 types.


Why? It appears the auto throttle didn't have any problem at all...

[rubik101]

This has been a bug-bear of mine for many years in my piloting life.

A few posts mention the fact that there was apparently no command from the flight deck to initiate an evacuation. While this may or may not be the case, it might be worth considering another aspect of the incident while we wait for the AAIB report.

It may not be appropriate, as has been queried earlier, for passengers to initiate an evacuation but they will, whatever the Cabin Crew try to tell them to the contrary.
If you are sitting over the the trailing edge of the port wing and see large chunks of raggedy metal sticking through the once smooth wing, mud and debris flying past your window along with the fact that it is grass underneath you and not the usual tarmac/concrete, then you might be forgiven for thinking that something is very wrong. Any spilled liquid will only add to your sense of unease and you will try to get away from the surrounding situation just as soon as you can. Hence, if nothing is heard or even 'Stay in your seats', you will ignore them, self preservation will be paramount. Indeed, passengers have a much better view from their nice big windows and so have a better understanding of what is going on outside than the cabin Crew with their needlessly tiny door windows. Cabin Crew need to be aware that the passenger panicking near the over-wing might well be doing so for a very valid reason!

Evacuation studies carried out since the very survivable Manchester BA B737-200 fire in 1985 have some interesting results. Cranfield University, using a Trident fuselage and more recently a B737 Cabin Simulator along with a two deck wide-body simulator have shown that passengers, me amongst them on the Trident, behave in many and varied ways to such a situation. At one extreme, a number will be moving towards the exits even before the aircraft has come to rest, others will sit and do nothing no matter how hard you shout at them.

Incidentally, the command from the cockpit found to be the most use in our multi-lingual era is 'Open your seat belts and get out.' Any other form of words, particularly the use of, 'unfasten', 'evacuate', 'exits,' were all found to be confusing and less well understood. If your company uses anything other than this form of words,get them to change them, now!

I suspect that perhaps half of the passengers on BA038 have English as a second language or perhaps speak little or even none at all. In this instance, everyone survived. I shudder to think how long the other thread would have been if even a few unlucky passengers had perished in any fire there might well have been.

Philosophy 101

In this instance, the aircraft touched the ground 'relatively' gently and the fuselage stayed intact, the grass was wet and soggy, so slowing the aircraft rapidly and causing no sparks, the fuel spilt was very cold, so less inclined to vapourise, there was no smoke in the cabin, all exits were usable, there were many empty seats and the Cabin crew were very well trained.

You can rewrite the previous paragraph with all the positives as negatives and see for yourselves how the outcome could well have been different.

My point is that no matter how hard we all train to be as professional in our aviating lives as we possible can be, no matter how skilled we are and how hard we try to influence the outcome of an event, fate/schiksal/karma/God, in all his forms, is the final arbiter of the outcome of so much that occurs in our lives. The slimmest margins make the difference between good and bad outcomes to so many things in our lives that we will never know just how lucky we are to be alive!

Happy Landings!

[woodpecker]

To reinforce Borderlines comments could I suggest that anyone commenting on the auto throttle performance refer firstly to NSEU's excellent factual post (No.38).

The response of the electronic control of the engines is (amongst other things) from data obtained regarding TLA (thrust lever angle). Whether the movement of the TLA forwards was from the autothrottle system or a manual input/override the resulting demands for more power was exactly the same.

Perhaps all posts should be made, as with other forums, through moderators who could remove these red herrings before they are posted and (by some) taken up as fact! Just a thought.

[Flight Safety]

Borderline wrote:

The 777 has a fuel temperature probe located between ribs 9 and 10 of the left main tank. The probe is approximately 12.6 in from the lower wing skin and is located one rib over, approximately 40 in outboard, from the aft boost pump inlet. Because the left wing tank contains a single heat exchanger, its fuel can be slightly colder than that in the right wing tank, which contains two hydraulic heat exchangers.

It's interesting the ground evidence (photos of fan blades) suggests the left engine was still making some power when it hit the dirt, while the right engine was not, the opposite of what you might expect from a fuel freezing incident with this heat exchanger arrangment. Sounds like the temp probe is in the colder tank, which was a good design choice. Is the fuel temp recorded on the FDR?

[stranex]

Rubik101.....thats got to be the best post here since this all "kicked off"! :D :D

We, all of us, are human (I hope!) and naturally will speculate and draw conclusions based on our knowledge and the evidence we are presented with, be it a 777 pilot, engineer, controller, eye witness or a drunken Aussie!

However, to post your personal speculation and cause the old wildfire to spread throughout the aviation fraternity and other "members of the public" who read this is plain irresponsible.

I appreciate this is a RUMOUR network but that doesn't mean we should all try and out do each other with our theories and level of knowledge....leave it to the experts to come up with the facts and present them in a timely and accurate manner.

Despite my suspicions of BA, AAIB, Boeing, I am sure that if they had ANY indication so far that the problem was fleet wide, they would have been grounded or at the least, SBs issued.

In the meantime lets have an informed discussion about the a/c systems and intelligent questions regarding evacuation procedures etc but from those discussions let pleassssssssseeeeeeeeee stop speculating in public

[kuningan]

Where have you got the info that the CSD decided to evacuate I have seen no concrete info that this occurred, rather, than say the evacuation was initiated from the Flt Deck

The pax testimony I heard was that after they came to a halt some pax jumped up and were told to sit down - 'then a red light came on over the doorway' and the crew evacuated the pax. I don't know whether that refers to the red Exit sign or one of the crew signals.

Whatever else happened the co-pilot remembered rule #1 - 'fly the plane' - had he attended to other things some seem concerned about (mayday calls, brace instructions) then this might be a very different thread indeed.

[peacock1]

Could we have an idea of the 777's environmental envelope temperature limits please?

[GMDS]

Stranex
To have a informed discussion about aircraft systems includes inherently some speculation. If everything would be crystal clear, why discuss it??

Therefore and nevertheless now another hypothesis concerning systems: If i go about the RR Trents on the T7, there is a possibility of no malfunction but still having the effect described. The engine anti-ice is mostly switched to "AUTO". I have witnessed its reluctance to go to "ON" more than once. Lets assume the inlet PT probe was iced up, apparently a ice warning was out that day and prolonged holding in the FL80 to 120 is a ice prone region. As the EEC uses EPR as parameter for thrust setting, in conjunction with the thrust lever angle, a demand either by the auto throttle or the pilots might have been ignored by the EEC, simply because with a PT inlet iced up and PT outlet not, the difference would fake "differential pressure", thus thrust, to the EEC. It would say "I am already giving you what you're asking for", not increasing FF and the result would be the low thrust setting persisting with a functioning and happy EEC.
Far fetched?

[Wornout Rubber]

Woodpecker,

The reason why 767s get colder fuel temperatures than 777s in the same enviroment, is that fuel temperatures are closely (but not exactly) related to the TAT and not the OAT. The higher speeds on the 777 keep the fuel warmer. :ok:

[astonmartin]

As an A330 pilot I am most interested in the aspect of 'pitch control' during the seconds after the double flame out.

I do not want to start another A vs B discussion but want ask a question about the 777 flybywire.

1. I do not think that pulling your aircraft (any aircraft) into a stall will postpone your impact. The impact will be earlier instead.

2. Loss of all engines during approach is not trained in the simulator, because it is regarded as negative training; there is no way you can prevent a crash landing.

3. The confrontation with loss of all engines in real life will make your brains and thus body go into survival mode; only the very most essential tasks will be executed. (Making a PA call is certainly not one of them)

4. While in survival mode, I can imagine the brain has difficulties with smooth control inputs. (Just like too much brake application during an emergency stop in your car.) I think on the Airbus the FlybyWire system would give you a "superhuman" postponement of the impact in this situation, just by pulling the stick fully backwards all the time. (This is why you have to do exactly this after a terrain warning)

While waiting patiently on the investigation what caused the engine problems, my question is: Is it possible to stall a B777 with manual inputs?

[BorderLine]

Straight from Boeing Web

Operations and procedures with low fuel temperatures.

During long-range operations at high altitudes, fuel tank temperatures can approach the freezing point of fuel. On long flights, the fuel temperature tends to adjust to the temperature of the aerodynamic boundary layer over the wing skin. This boundary layer temperature is slightly lower than the TAT because theoretical TAT is not achieved. Initially, TAT is much lower than the fuel probe temperature because of the thermal lag of the fuel. Thermal analysis of the 747-400, 777, and MD-11 airplanes shows that the fuel tank temperature is driven more by TAT than airplane configuration.

In flight, a temperature differential must be maintained between the observed temperature indication and the freezing point of the fuel. For the 747-400, 777, and MD 11, the observed fuel temperature must remain at least 3°C above the specified freezing point. (The actual fuel freezing point may be used if known.)
When fuel temperature decreases to 3°C above the freezing point, a message of FUEL TEMP LOW displays in the 747-400 and 777 flight decks; the message FUEL TEMP LO is displayed in the MD-11 flight deck. If this condition is reached, the flight crew must take action, as described below, to increase the TAT to avoid further fuel cooling.

In consultation with airline dispatch and air traffic control, the flight crew decides on a plan of action. If possible, the action should include changing the flight plan to where warmer air can be expected. Another action is to descend to a lower altitude. The required descent would be within 3,000 to 5,000 ft of optimum altitude. In more severe cases, a descent to 25,000 ft might be required. Recent experience on polar routes has shown that the temperature may be higher at higher altitudes, in which case a climb may be warranted. The flight crew also may increase airplane speed; an increase of 0.01 Mach results in a TAT increase of 0.5° to 0.7°C. (It should be noted that any of these techniques increases fuel consumption, possibly to the point at which refueling becomes necessary.)
It takes approximately 15 min to 1 hr for a change in TAT to affect the fuel temperature. The rate of cooling of the fuel is approximately 3°C/h. A maximum of 12°C/h is possible under the most extreme cold conditions.
A minimum in-flight fuel temperature advisory message provides a margin of safety under all atmospheric and operational conditions to ensure that the fuel will continue to flow to the boost pump inlets. Besides the 3°C margin between the advisory message temperature and fuel freezing point, there typically is a 6°C difference between the freezing point and pour point of fuels, which provides an additional margin. A review of the service history of transport airplane operations worldwide for the past 40 years does not show a single reported incident of restricted fuel flow because of low fuel tank temperatures. This service history affirms that the criteria used to establish the advisory message are adequate and conservative.

[Domi]

It is not normal that the a modern 200T twin jet as the 777 simply "shut off" at the last 10s of a 11hrs flight. Here are the facts. This event is fascinating us but we must not speculate until AAIB report is issued. AAIB staff has everything to do its job: plane, crew, witnesses. But it does not mean it will be easy unless basic cause explains the failure.

In the other case, the more complex the systems, the more complex may be the causes. Event if a 1.50$ piece of copper might crash a system, the job is to find the evidence.

While waiting the report, may I suggest to remember the following events:
- Dual engine failure of an Austrian Fokker 70 on approach in Munich in january 2004 - landing on a field - mechanical failure of ice impact panels.
- Nearly stall of a B777 at FL390 in 2005 - ADIRU failure - see AD 2005-18-51
- Byzantine faults of complex systems - google 'Flight Control System Software Anomalies'

I mean, we all try to do our job to our best of knowledge, but we will always learn about flying from experience.

[vikena]

Giant Bird,

Really your questions indicate a position that bears distant relation to the real world of commercial aviation.

Its not a perfect world and these guys did a fantastic job. The result is more important than the method in cases like this.

So it's provocative and inappropriate of you to start your introspective judgemental thing at this time so please don't.

V

[FE Hoppy]

Therefore and nevertheless now another hypothesis concerning systems: If i go about the RR Trents on the T7, there is a possibility of no malfunction but still having the effect described. The engine anti-ice is mostly switched to "AUTO". I have witnessed its reluctance to go to "ON" more than once. Lets assume the inlet PT probe was iced up, apparently a ice warning was out that day and prolonged holding in the FL80 to 120 is a ice prone region. As the EEC uses EPR as parameter for thrust setting, in conjunction with the thrust lever angle, a demand either by the auto throttle or the pilots might have been ignored by the EEC, simply because with a PT inlet iced up and PT outlet not, the difference would fake "differential pressure", thus thrust, to the EEC. It would say "I am already giving you what you're asking for", not increasing FF and the result would be the low thrust setting persisting with a functioning and happy EEC.
Far fetched?

Are the T2P2 probes only heated when ice is detected? I think not. Does the FADEC only use EPR or does it use N1 also?

[astonmartin]

As an A330 pilot I am most interested in the aspect of 'pitch control' during the seconds after the double engine loss.

I do not want to start another A vs B discussion but want to ask a question about the 777 flybywire.

1. I do not think that pulling your aircraft (any aircraft) into a stall at the last moment, will postpone your impact. The impact will be earlier instead.

2. Loss of all engines during approach is not trained in the simulator, because it is regarded as negative training; there is no way you can prevent a crash landing.

3. The confrontation with loss of all engines during approach in real life, will make your brain and thus body go into survival mode; only the very most essential tasks will be executed. (Making a PA call is certainly not one of them)

4. While in survival mode, I can imagine the brain is having difficulties making smooth control inputs. (As with making a smooth and firm brake application during an emergency stop with your car.) I think on the Airbus the FlybyWire system would give you a "superhuman" postponement of the impact in this situation, just by pulling the stick fully backwards all the time. (This is why you have to do exactly this after a terrain warning)

While waiting patiently on the investigation what caused the engine problems, my question is: Is it possible to stall a B777 with manual inputs?

[GMDS]

Hoppy, you're right, the inlet PT is heated anyway. However the Potomac incident showed us that icing in the inlet region can lead to misreadings of the inlet pressure. That intrigued me then aswell, leading to my raising the issue today.
The Trent takes only EPR in the nomal mode, N1 when reverted (soft or hard) to the alternate mode. On the GE it takes N1 for normal.

[sky9]

The AAIB initial report did not say that there was a flame out, only that the thrust levers failed to respond to a demand for increased power. A couple of newspapers made the same statement today.

As I read the AAIB statement the engines were still running at some at preset indeterminate (low?) power setting. This raises the question as to when the APU started up automatically and what caused it to do so, and did the RAT extend and for what reason. If they had both activated during the approach rather than on touchdown it might just identify the cause of the "hung" engines. I remember some years ago on the 767 someone had malfunctioning N1guages pulled the CB to reset them and the RAT fell out as it sensed a double engine failure.

AAIB report:-
"At approximately 600 ft and 2 miles from touch down, the Autothrottle demanded an increase in thrust from the two engines but the engines did not respond. Following further demands for increased thrust from the Autothrottle, and subsequently the flight crew moving the throttle levers, the engines similarly failed to respond."

[BorderLine]

Don't know if the APU did start or not. APU inlet door is open, APU wont start until it's open, maybe loss of busses AFTER 'landing' caused APU to attempt auto start...

[PEHowland]

BBC News has (http://news.bbc.co.uk/2/hi/uk_news/england/london/7198598.stm) the following quote from a Sunday Mirror interview with the SFO:

"Suddenly there was nothing from any of the engines, and the plane started to glide," he said.

"I didn't think we'd clear the fence at first. As we landed I was bracing myself for an enormous thud. But instead of one thud, there was a series of thuds as it bounced along the grass."

He added: "Eventually it shuddered to a halt. While I was trying to stop the plane. I struggled to try and keep it in a straight line."

He said that after the crash "there was no sound at all. No sound from the engines, no sound from behind.

"I turned around and composed myself and heard a lot of commotion behind me. I realised that staff were trying to carry out the drills to evacuate all the passengers."

[Ian W]

Wingswinger:
Does anyone else think that this might call into question the whole concept of the CDA? The intent of Continuous Descent Approaches (CDA) was initially to reduce noise and has morphed to include reduction in fuel usage (and therefore emissions). Trials by SAS and others in Australia have show savings of between 500Kg and 1000Kg of fuel are possible per approach for some CDA variants (obviously dependent on aircraft type and the normal non-CDA procedure with which it is compared).

Unfortunately, the definition of CDA is vague in the extreme. Some CDA like those at LHR are effectively interceptions of the glide slope at well above normal heights after a normal descent. Others involve continuous descent from last en-route fix at flight idle (or more) to intercept the glide slope from above. AFAIK once established on the glide slope the aircraft will fly the descent according to operators SOPs or the ANSP requirements for that airport. In all cases that I am aware of the aircraft would thus be stabilized in descent as they are now with sufficient power to fly a normal 3 or 2 1/2 degree glide slope at least at the same distance from touchdown as they are now.

Therefore I do not see that CDA per-se would have any bearing on this although it is possible that the BA or NATS procedures for flying them at LHR might have some impact. However, as these procedures have been flown successfully by B777s for some time - including apparently the aircraft landing ahead - I doubt that there is anything in these procedures that had a direct causative relationship to the accident.

[fg32]

I make no apology for posting what some of you may brand "speculation" on a website named "Rumour Network". Surely every rumour is speculative.

I have read and considered every single post in both threads, and frankly I feel I have suffered just as much wasted bandwidth (and irritation) from the self-congratulatory pomposity of the "in-crowd" criticising the garbage of the ignorant as from the garbage of the ignorant itself.

Particularly inappropriate, in my opinion, was the endless praise for flight and cabin crew. Until we know what happened it is no more appropriate to broadcast such assumptions as truth than it is to broadcast technical assumptions about failure modes as truth. Those blindly praising colleagues on no evidence, and even castigating others who fail to do likewise, are really just praising themselves, no ?

I agree that once we learned of the simultaneous double "failure to respond" it did begin to look likely that the flight crew did well from that point on, but it is not yet totally certain that the problem was not exacerbated by crew actions or omissions. Only the report can tell us how much praise or blame is due, and until then anything else is correctly categorised as what you all so hate - "speculation".

Enough of that - here is my very own bit of "speculation" :

Did anyone else notice post 59, and think it might be significant ?

Here it is :
"And the airtemp over UK at the time was some of the coldest I've ever experienced with OAT at higher levels down to -70 degrees celsius."

This sounds as though this was pretty abnormal. How abnormal ? Could the fuel have got below freezing point ? Is there only one fuel temperature sensor ? Could it (or even both) have failed ?

Alternatively, we have heard doubts expressed about the quality of Chinese fuel. Could it have been out-of-spec, so that it froze at, say -40degC instead of the required -47degC ? Presumably the sensor would have no way of knowing this, and if it works on a 3deg margin, it would have issued no warning.

Do these two things, taken together (or even the first point on its own), suggest fuel waxing as a cause?

Previous posters have judged it unlikely that fuel waxing or other contamination could cause two engines fed from different tanks to suffer flow restriction more or less simultaneously, and ruled it out of consideration on the basis of that simultaneity.

But perhaps they didn't get into difficulty simultaneously. If they had been close to idle or at fairly low fuel flow for several minutes, they could have got into difficulty that many minutes apart. Only the call for power which revealed the problem was simultaneous on both. The actual fuel flow restriction need not have commenced simultaneously at all.

So you see, I am hypothesising about possible causes. I am inviting a discussion of evidence for and against. Perhaps what I suggest can be demolished by the more knowledgeable at a stroke, in which case thats fine, the picture becomes a little clearer.

I understand that for too many here the rule is

"What I post is calm analysis, what you post is inappropriate speculation, what he posts is ignorant rubbish"

...and yes, there is much rubbish and (inevitably) much duplication (not everyone can read every word of both threads)...... but in my opinion the policy of allowing open posting gives us more than we lose - and the truly useless postings would waste less bandwidth if others could refrain from adding to the dross by complaining about them. If you watch you will see that the worst do get periodically culled.

So what do you think ?

Freakily cold conditions? Poor fuel freezing too easily? Fuel waxing not simultaneous, but simultaneously revealed ?

[I Just Drive]

With a fuel issue, albeit 1) lack of 2) contaminated or 3) cold soaked, I can't see how they would fail almost simultaneously. I would have thought there to be at least a couple of minutes between them. Each engine doesnt burn the exact same amount at the exact same time so I would have expected a lag.

[nlarbale]

as fg32 said, if fuel waxing occured and affected the engines ability to recieve fuel, it's likely that the situation developed at different times in each engine during descent, but it was only readily apparent when a large thrust increase was demanded, which the engines where then unable to comply with due to restricted fuel flow

seems well within the realm of the possible

[A32A]

It is not at all unplausible that ATC at LHR has "maintain 160 to 4" which means that at 4 You slam the throttles back to idle to reduce to, what, maybe 138 for the landing. The autothrottle is as stupid as the train (it only follows the track) it only demands more power when the speed drops below placard speed. If by some mysterious reason a spurious signal has told the engines to spool down to ground idle instead of flight idle it takes a considerable time to accelerate them up to full power, and they will most likely not do that in syncron. And when the speed drops below minmum for flaps full, 5 seconds is like an eon, if You try to maintain glidepath You will get too high angle of attack and then loose even more speed, so, unless there is something untold, They did a good job flying the airplane onto the ground rather letting it fall out of the air.

[bsieker]

[...]
my question is: Is it possible to stall a B777 with manual inputs?

Yes.

The Flight Manual states in the section about pitch envelope protection:


Stall protection reduces the likelihood of inadvertently exceeding the stall angle of attack by providing enhanced crew awareness of the approach to a stall or to a stalled condition.

[...]

The pilot must apply continuous aft column force to maintain airspeed below the minimum maneuvering speed. Use of the alternate pitch trim levers does not reduce the column forces.



Mernaing with sufficient force on the column the handling pilot can stall the machine, the protection system only provides enhanced crew awareness against inadvertent stall by pilot inputs.

In addition, at the Introduction to the Flight Control System Overview (FM, Section 6.9) it states that

The pilot always has ultimate control authority; the flight control computers cannot override a pilot command.

I'm not judging the different systems, only noting that this is different from Airbus FBW pitch protection, which will not allow stalling the aircraft by pilot input.


Bernd

[hawk37]

Would the crew have had the ability to assume any manual or secondary control over the engines? Is there any option to disengage the FADEC, or use it in a degraded mode? I realize they had very little time, but am just trying to understand whether this would even have been possible. Hawk

[Hand Solo]

I've been flying in that cold air mass (-69C at worst) and was faced with low fuel temperatures (-40C at one stage) but noted that the fuel was considerably above this temperature by the time we arrived in the London area. Given the aircraft in question also spent some time in the LAM hold below FL150 I'd be rather surprised if fuel waxing was present.

[Lemain]

Waxing seems plausible. Do we know how similar engines and fuel systems accommodate waxing?

For a moment, let's assume that waxing was the problem. - What needs to be done now, to prevent it happening again on the next flight from China?

[moggiee]

I've been flying in that cold air mass (-69C at worst) and was faced with low fuel temperatures (-40C at one stage) but noted that the fuel was considerably above this temperature by the time we arrived in the London area. Given the aircraft in question also spent some time in the LAM hold below FL150 I'd be rather surprised if fuel waxing was present.
Once cold soaked, fuel can stay cold for a VERY long time. It takes a long time to cool down and a long time to warm up (I´ve seen the underside of the wing on my aeroplane covered in ice for some considerable time after landing in the Arizona desert).

I'm not speculating here - I'll wait for the report. However, low quality fuel or the use of Jet A as opposed to Jet A1 has caused me some "inconvenience" in the past.

[Hand Solo]

I've seen the ice too, but there's a big difference between underwing icing (fuel below 0C) and fuel waxing (fuel a loooong way below 0c). I flew largely the same route and profile as the accident aircraft and made a point of noting the fuel temperature once we landed, which was around the -25C mark. If fuel waxing occurs at this high a temperature then I'll stand corrected but it was always my understanding you'd need to be well on your way to -40C before waxing was an issue. For info top of descent on this route to touchdown is a typically 40 mins in increasingly warm air.

[TyroPicard]

astonmartin
Don't know about the 330, but a double engine failure in the A320 (i.e. AC Bus 1+2 fail as well) leads to Alternate Law - so bang goes your stall protection. Is the 330 different?
But if one/both engines are running but fail to respond, Normal Law protections would still be there.
TP

[You Gimboid]

I have total confidence in the 777.

In the sim we did a deadstick autoland from 13 miles out, 6000ft and 250kt. It tracked the 3deg ILS all the way down, we just dropped flaps and gear on the speed schedule. It has a max landing weight in the region of 195 tons, yet the Vref at this weight is less than a 737. It has superbly efficient wings, & is very slippery for a big beast.

It is a superb piece of kit, I've had a very happy flying career to date on it. Believe me when I tell you this is going to be a (dramatic!) glitch which will most likely never be seen again.

[beaglecp]

As I watch, she's trundling along at a surprisingly good lick on an array of huge trailers

[Human Factor]

The 777 will fly a three-degree glideslope engines-off clean at 220kts. The art of getting it on the threshold is when to configure. I wouldn't fancy losing (or partially losing) both engines at 600ft though. Fantastic job.

(MLW is either 201t or 208t, depending on the version - MM was 208.6t)

[misd-agin]

You Gimboid (post #100) -

The parameters you gave, 13 miles at 6000' and 250Kts, is an energy state higher than almost every approach we do in real life. Therefore, IMO, it's not quite realistic and is obviously a completely different scenario then the BA 38 incident.

Every airline I've 'dead sticked' in the sim makes it to the runway from 2000' on G/S at 250 kts. If you're FMC is working you can program that into the box or just do the math in your head (727, DC-9, etc).

The newer jets, being much 'slicker', arrive with more than enough airspeed while 727's just barely made it.

Based on my observations, without very strong winds aloft, I think, almost every jet tracking a glideslope @ 250 KTS has a fairly high chance of success. Next sim session I'll try it from 20 DME and 250kts and figure out how high I have to be to have enough energy to reach the field.

Modern airlines glide at about 18:1. In simple pilots talk that's your altitude in thousands x 3 IE, 30,000 becomes 30 x 3 = 90 n.m.

[A good headin]

Lets say the fuel was contaminated with a large quantity of water:sad:.

The water sinks to the bottom of the fuel tank and after 11 hours in the air you would be getting pretty close to powering Rolls Royce's finest on Evian.

Sabotage or HF?

Interesting times ahead for the AAIB.:hmm:

[willnotcomply]

If this was due to a possible electronic/software glitch??????? Why have all 777's not been grounded, pending a more defnitive cause? I would suggest more than a few nervous 777 crews operating at the moment, not to mention pax!

[sanjosebaz]

The water sinks to the bottom of the fuel tank and after 11 hours in the air you would be getting pretty close to powering Rolls Royce's finest on Evian.
OK I'll bite! Are you insinuating that fuel is somehow drawn from the top of the tanks during flight? :confused:

[Pinkman]

At last something I can comment on with authority. Yes, Teal, it can happen but it is incredibly rare. I cant remember the last time I heard of it happening. Moggiee is correct - Jet A (US) has a higher freeze point than Jet A-1 (i.e. it freezes more readily). The current spec for the UK is what used to be called DERD 2494 now renamed DefStan 91-91. The spec is - 47 degrees Celsius. The problem with the freezing /waxing theory is that Chinese jet A-1 equivalent (used to be RP-3, now called jet fuel number 3) typically has a lower freeze point (-52C) than Jet A-1.

Thats not to say it could not have happened or that the particular delivery could not have been waxy. But there will have been retention samples taken and freeze point is a test that will have been carried out by an approved lab. BA do take a keen interest in the fuel that goes into their aircraft and I remember being on the recieving end of an assessment visit in Nairobi with painful clarity. It resulted in us buying a whole bunch of new equipment.

The problem is that the normal freeze point for Kerosene is minus twenty or so. Dual purpose kerosine, which can be used in both aircraft and in domestic appliances has both a low freeze point and a high smoke point.

Mistakes can happen.....

P

[slink]

In the sim we did a deadstick autoland from 13 miles out, 6000ft and 250kt. It tracked the 3deg ILS all the way down, we just dropped flaps and gear on the speed schedule. It has a max landing weight in the region of 195 tons, yet the Vref at this weight is less than a 737. It has superbly efficient wings, & is very slippery for a big beast.

No doubt the 777 has efficient aerodynamics, but as I am sure you're all too well aware that as ATC we're rather limited against allowing you to fly at 6000 feet to capture an ILS at 13D, and you'll probably be back at 180kts or thereabouts. In fact, if I have any pilot close to 3000' at 10 miles, they're asking for further descent, so I am not sure this is a relevant example.

Now, I also have a question - from 13D, the 3 degree glide you state your sim tracked all the way down would still have you around 1866' AGL at the threshold (13Nm x 318' per mile descent = 4134 feet of descent). I take it you didn't track the glide at all, just happened to intercept it at around the TDZ, so meaning in this case the 777 DID NOT maintain a 3 degree slope with a double engine failure (which, in this accident, was not what happened anyway). In fact, 6000' in 13 miles is nearer 4.4 degrees (tan-1 461'/6076). The point I am trying to make here is that in the example you gave, using your figures, it was not a 3 degree path that was followed, and in a real world example where you are lower and slower (3000 AGL and 180kts or less, and just about to intercept the glideslope), I doubt the 777 could maintain a power off 3 degree glide.

Finally, correct me if I am wrong (I left engineering without 777 experience), but in every other type I have known, for an autoland, the buses need to be separated, which means 2 independant forms of power. In a twinjet, I would take this to mean a "deadstick autoland" is not possible?

The last point I'd make is that the a 737 at 195 tons would, no doubt have a very high Vref, but I guess Boeing haven't stretched it this far yet? ;)

[Airways B]

All I have to say in the matter is "Thank God For good old ILS"

All ILS localiser antenna arrays, need a large protected sterile 'Critical Area' in front of them for the guidance beam to correctly form. Usually this is nothing more than an expanse of grass on which the airport operator can do nothing but regularly mow when operations permit. It is, in this case, the 09R Loc Critical area which presented this 777 with a forgiving, spark supressing, fuel absorbing, cushion.

MLS however, which everyone thought would have replaced ILS years ago, should be able to operate with a much reduced critical area, allowing who knows what to be done with these patches of valuable real estate.

Sometimes the non progress of technology is safer.:oh:

[slink]

The point here is that, according to the program, the Russian accident investigator maintained that there is more than 1 reason in every accident. In this case, the thing which strikes me was the discovery that the Autopilot on A310's is partially disconnected (some control surfaces) if you "fight" against it for more than 30 seconds-


Well, not sure about the A310, but with every other type I have experienced, the autopilot disconnect is immediate once breakout force is exceeded - ie, give the controls a good heave, and the autopilot will be disconnected. It's something we used to test on the 737s in the hangar with a good old fashioned fishing spring balance!

[Dropp the Pilot]

... and we crashed exactly where they did...

gross weight 200 tons, 143 knots on the glide at 2 miles exactly and shut down the engines. neither the RAT nor the APU has time to start before impact which means only the captains flight instruments are showing. if the f/o was indeed flying, at least one engine was pulling enough power to keep a generator on line and give him flight instruments to look at. sim visual data base has three low buildings at about 1 mile and we cleared those by maybe 10 feet ....don't know if those exist in the real world.

[misd-agin]

http://www.pprune.org/forums/images/statusicon/post_old.gif Today, 08:59 #76 (http://www.pprune.org/forums/showpost.php?p=3850270&postcount=76) Wornout Rubber (http://www.pprune.org/forums/member.php?u=212371)
Instead of being 'just another number' I could order a Personal Title (http://www.pprune.org/ptorder/ptorder.htm) and help support PPRuNe

Join Date: Jan 2008
Location: Dubai
Posts: 8


Woodpecker,

The reason why 767s get colder fuel temperatures than 777s in the same enviroment, is that fuel temperatures are closely (but not exactly) related to the TAT and not the OAT. The higher speeds on the 777 keep the fuel warmer. :ok:
http://www.pprune.org/forums/images/statusicon/user_offline.gif http://www.pprune.org/forums/images/buttons/report.gif (http://www.pprune.org/forums/report.php?p=3850270)

Fuels system engineer working on new jet a/c about 10 yrs ago told me wing thickness was important.

777's typically cruise 2-4000' higher on the same stage length. That temperature difference, below FL370 typically, is warmer for the 767.

You TAT theory can be tested. Fly the same altitude at increasing Mach speeds and note the temperature rise. I'll try it on my next flight. I'm guessing the difference will be very small.

[misd-agin]

Dropp the pilot -

A more accurate scenario would have been to leave the engines at idle. The engines were running, they just 'didn't respond' when increased power was called for.

[I Just Drive]

I need more convincing on the cold fuel theory. Even super cold soaked fuel from a long sector has warmed a fair bit once you have been through the stepped descent of the London TMA. I never have a cold soaked fuel problem in the UK, its always elsewhere when you get large straight in descents and the fuel doesnt get a chance to warm.

[NigelOnDraft]

slink.... somne good/interesting points you make, which I shall try to answer. Not really relevant to this incident, so we'll probably sent to the "stupid questions" thread ;)

At "idle" most modern jet airliners plan a 3 degree descent from Cruise altitude. We tend to be above optimum speed, so changing the "idling engines" to "stopped engines" then a 3 degree glide is just about possible, clean (1 in 3 i.e. 3 miles / 1000').

For Engine Out planning, we'd rather go for somewhere 1 in 2, so keeping something in hand for maneouvre... and plan on ~2500' for a 180 degree turn. We then hold the 1:2 approach with some flap ~180K and this needs some speedbrake.... and then ~1500' think about gear, rest of flap and flare. It is eye opening the change at this point i.e. the effect of the gear and extra flap and you do not want to this bit too early :{

Finally, correct me if I am wrong (I left engineering without 777 experience), but in every other type I have known, for an autoland, the buses need to be separated, which means 2 independant forms of power. In a twinjet, I would take this to mean a "deadstick autoland" is not possible?
You are correct, but only as far as the rules go ;) Airbus AP will quite happily fly engines out, APU on, and really gives you some "capacity". You would normally want do the landing manually, but 1 trainer with too much time on his hands used (in the Sim) to show you could do the 1:2 profile, when the gear went down, also increased RoD and picked up the 3 degree ILS slope (very late!) to an Autoland...

NoD

[Rover90]

Just a thought. On the 747-400 at the end of a sector in the normal fuel config, you basically have the four engines each feeding off four independent tanks.

Don't know the tank layout of the 777 but the basic philosophy would still hold true, each engine would be feeding off its own independent tank.

If you are suggesting fuel contamination or water droplets, it would mean that this manifested itself at virtually the same time in each tank?

As an aside, I agree with the suggestions that if it had happened further up the slope the keeping 200 plus kts and intermediate flap and gear up would allow you to basically fly the glide slope or more sensibly, a few dots high, and drop the gear at 500ft.

For this to happen at 600ft, gear down and land flap, there are very few options......sometimes god is a real ****.
See ya

[ByteJockey]

I'm puzzled by the concentration on fuel problems as the most likely cause of this accident. I'm a software engineer and not an aeronautical one, but it seems to me that the failure of both the engines to respond to either autothrottle or manual throttle input is just as likely (if not more likely) to be caused by a fault in some common hardware/software subsystem. I started doing a bit of digging around to try to find some details of the architecture of the systems on the 777, and found some interesting references which I've given below. There is at least one large, centralised component that has a part to play in thrust management - the AIMS (Airplane Information Management System). I'm not saying that the AIMS *is* the cause of the problem, just that there *are* common subsystems involved in managing the engines.


BOEING 777 AIRPLANE INFORMATION MANAGEMENT SYSTEM OPERATIONAL EXPERIENCE
http://ieeexplore.ieee.org/iel3/5023/13779/00635042.pdf?arnumber=635042

The 777 AIMS combines primary flight display, navigation display, EIC.AS display, flight planning, navigation, performance management, guidance, thrust management, central maintenance, airplane and engine monitoring, communications management, digital flight data acquisition, and data conversion gateway functionality into a single integrated system.

[...]

Thrust Management
The thrust management function sends commands to the autothrottle servo motors to move the airplane throttle levers, displays the thrust limit and autothrottle mode, and sends trim commands to the electronic engine controllers.

[...]

AIMS contains more than 600,000 lines of software

Developing the 777 Airplane Information Management System (AIMS): A View from Program Start to One Year of Service
http://ieeexplore.ieee.org/iel4/7/12850/00588382.pdf

The robust partitioning provided by the architecture allows applications to use common resources without any adverse interactions. This is achieved through a combination of memory management and deterministic scheduling of application software execution. Memory is allocated before run time, and only one application partition is given write-access to any given page of memory. Scheduling of processor resources for each application is also done before run time, and is controlled by a set of tables loaded onto each CPM and IOM in the cabinet.
I'm sure the system has been written extremely carefully and tested thoroughly, but there's always the potential for bugs in any piece of software.

[JimBall]

Some unique shots here (http://gallery.mac.com/gpixx#100033)

[Morpheme]

Why are some people still going on about fuel icing, contamination etc etc.

It is clear from the report that the engines did NOT fail - they just did not respond to autothrottle / thrust lever commands when the thrust was supposed to come up at 600ft.

I for one will wait for the official report and see what BA tells us in the meantime. I agree that this will probably turn out to be a one-off event - the 777 is a well engineered and very well thought out aeroplane.

[A4]

I'm not familiar with the chemistry but when the fuel waxes, does it then remain in that waxed stated regardless of an increase in its temperature? i.e. does the wax remain in suspension within the fuel? Logically, as the fuel temperature increases during descent, it will revert back to its non-waxed state - but is the transition linear or does it have to be warmed "more" to change back compared to the amount of cooling originally required?

The reason I ask is that a period of time in the LAM hold requires a thrust setting probably above final approach thrsut and the fuel will only be getting warmer by the time it's on approach.

A4

[tubby linton]

My old Airbus is prone to ice on the exterior of the Outer fuel tanks.This happens on even quite temperate days and we don't fly very high so are not exposed to very low temperatures or for 10 hours!The only way to stop it forming is to create an air gap in the tank by feeding fuel from that tank,so that some warming can take place in the descent.Many times I have sat on a very warm ramp an hour after landing and still seen ice on the skin in the tank area.There is no indication of fuel temperature in the cockpit.Cold soaked fuel takes a long time to warm-certainly more than the 30 minutes a 777 would take to get from top of descent to the ground.

[Pinkman]

Morpheme

People are going on about waxing and icing etc, because those are valid possibilities at the end of a sector especially one flown through the especially cold upper air conditions found on that day over the UK. Water and wax crystals sink in fuel, they are not homogenously distributed throughout the fuel. If they were to be an issue, it would be at the end of the sector. I agree its a very remote possibility but until the AAIB do their 30 day announcement, it remains as equally strong a contender as electronics, RFI, etc.

A4., no, it changes phase and resolubilises (sp?) as the temperature increases, but it takes temperature AND motion (jiggling around) to do it (I have done it in the test tube with both Jet and Diesel). Tubby is right - it does not revert instantaneously - there is a lag. Additionally, the smaller the volume of fuel, the quicker the initial icing would be.

P

[PJ2]

Bernd;

Re stalls and autothrust on the B777, the AOM provides the following, from 2.27.20:

Pitch Envelope Protection
The pitch envelope protection functions include:
• stall protection
• overspeed protection.
Stall Protection
Stall protection reduces the likelihood of inadvertently exceeding the stall angle of attack by providing
enhanced crew awareness of the approach to a stall or to a stalled condition.
Stall protection limits the speed to which the airplane can be trimmed. At approximately the minimum
maneuvering speed, stall protection limits the trim reference speed so that trim is inhibited in the nose
up direction. The pilot must apply continuous aft column force to maintain airspeed below the
minimum maneuvering speed. Use of the alternate pitch trim levers does not reduce the column
forces. When flying near stall speed, the column force increases to a higher level than would occur
for an equivalent out–of–trim condition above the minimum maneuvering speed.
The autothrottle can support stall protection if armed and not activated. If speed decreases to near
stick shaker activation, the autothrottle automatically activates in the appropriate mode (SPD or THR
REF) and advances thrust to maintain minimum maneuvering speed (approximately the top of the
amber band) or the speed set in the mode control panel speed window, whichever is greater. The
EICAS message AIRSPEED LOW is displayed.
Note: When the pitch mode is FLCH or TOGA, or the airplane is below 400 feet above the airport
on takeoff, or below 100 feet radio altitude on approach, the autothrottle will not automatically
activate.
Note: During a descent in VNAV SPD, the autothrottle may activate in HOLD mode and will not
support stall protection.

[Morpheme]

Well sorry if I sound dismissive (which I am) but even several hours in very low temps won't send 30-odd tons of fuel below -47degC.

As well the obvious question - why didn't all the Far East-originating westbound traffic fall out of the sky together?

[PPRuNe Towers]

PPRuNe is writing to the Salvation Army to thank them for being on site hour after hour. They arrived with a catering van to make sure the all those involved in the investigation and recovery were fed and watered.

Rob

[Duck Rogers]

PPRuNe is writing to the Salvation Army to thank them for being on site hour after hour. They arrived with a catering van to make sure the all those involved in the investigation and recovery were fed and watered.

Rob

Soup sir? BIG ISSUE!!:}

Seriously though. They might be a bunch of God bothering biddies but well done.

[Sunfish]

Can people please forget about water in the fuel, waxing etc.? It's unlikely to be valid, otherwise jets would be dropping out of the sky daily all over the world.

For a start, Beijing is holding the Olympics shortly and they have thoroughly renovated everything aviational. As for waxing, the cloud point (at which wax freezes out of the fuel) for Jet fuel is very low and its tested when the batch is approved.

As for water, (as a former terminal engineer before joining an airline), I can tell you that oil companies are paranoid about water in jet fuel storage tanks. Furthermore, the fuel will have traveled through at least THREE filter/coalescer units (terminal, receiving station and final loader) which remove dirt and water before it is loaded into the aircraft tanks that should leave it clear and bright. So absent massive water contamination, that would by now have affected dozens of aircraft, in all probability this is a non-issue.

[Hand Solo]

My old Airbus is prone to ice on the exterior of the Outer fuel tanks.........There is no indication of fuel temperature in the cockpit.Cold soaked fuel takes a long time to warm-certainly more than the 30 minutes a 777 would take to get from top of descent to the ground

My old 744 is prone to ice on the fuel tanks too, but we have fuel temperature indications in the cockpit and the 30 mins it takes us to get from top of descent to ground is more than enough to significantly warm fuel above -40C. Once again, ice on the exterior bears no relation to waxing in the fuel. Ice will form as long as the fuel temp is below 0C. Wax won't form in the fuel until it's much much colder than that.

Edited to add that the freeze point is the temperature at which was starts to form, not the temperature at which it freezes, so the fuel in question would need to be close to -47C to support waxing. There's no way on earth the aircraft landed with fuel anything close to that temperature.

[chksix]

Also, there would have been an alert about fuel filter bypass if there had been an issue with fuelclogging.

[pax2908]

Are there previous instances (lets say on this A/C type+engine) of _one_ engine failing or being unexpectedly slow to respond during the approach?

[Contacttower]

It is clear from the report that the engines did NOT fail - they just did not respond to autothrottle / thrust lever commands when the thrust was supposed to come up at 600ft.



There does seem to be a lot of confusion over this, the AAIB report does seem rather at odds with what John Coward apparently told Sky News:

"The adrenaline kicked in when I realised I had to land the plane with absolutely no power at all. There are drills for a power failure at 30,000ft, when you have time to reset and restart engines, but there are no drills for this. As I approached the runway, I thought that this was going to be a catastrophic crash."

[looseobject]

Extracts from an AD issued after an A330 (QR i think) experienced a dual engine flameout.

Several A330 aircraft equipped with General Electric (GE) CF6-80E1 engines
experienced an engine flame out during descent, 2 to 3 seconds after engine
acceleration upon aircraft altitude capture, under inclement weather conditions. In all
cases, the engines restarted and then operated normally.
Analysis has shown that at high altitude an accretion of the conventional ice or ice
crystals in the engine fan or booster stages during descent at low engine power can
shed in significant amount into the core inlet upon engine acceleration when the
variable bleed valve doors close. This ice ingestion will then increase the water/air
ratio leading to flame smothering.
This situation if not corrected can lead to the temporary loss of both engines thrust in
flight which constitutes an unsafe condition. In order to mitigate the risk of a dual
engine flame out in flight, the original issue of this Directive mandated the
operational procedure which increases the fuel/air ratio in the engine during the
descent and under inclement weather conditions.

“ICING CONDITIONS EXPECTED DURING DESCENT
• If icing conditions (including ice crystals) are expected during descent:
• At top of descent, or at the latest before entering the expected icing
conditions:
Select ENG ANTI ICE and WING ANTI ICE to ON.
Select PACK FLOW at HI.
• Below 10 000 ft:
Resume normal operation.”

[bsieker]

PJ2,

Thanks, yes, that's exactly the same wording as in the Flight Manual, which I abridged.

So the B777 protection system only reduces the likelihood of inadvertent stall, but will not absolutely prevent the pilot from pulling the column fully back. And since the engines did not respond in this case, Autothrottle would not have been able to do anything, either.

Whether or not this is relevant or whether or not being able to stall the aircraft in from the last 10' actually helped in this case, I'm basically trying to understand the Triple's systems, since up to now I'm more familiar with Airbus, but always like to know as much as I can about the machine.

This leads to another (possibly only marginally related) question: It says in the Manual that Autothrottle will support stall protection by increasing thrust as needed, when armed but not active:

How common is it in a Boeing to have the Autothrust neither active nor armed?

(The Alpha-Floor protection in Airbus goes to, and locks, TOGA thrust regardless of previous Autothrust setting (off/armed/engaged)).

Please, again, I'm not judging either over the other, just wanting to learn.

The inhibition altitudes for autothrust/-throttle supporting stall protection seems to be the same for both B and A, namely up to 400' at takeoff, and from 100' down during landing.


Bernd

[PJ2]

Morpheme;
Well sorry if I sound dismissive (which I am) but even several hours in very low temps won't send 30-odd tons of fuel below -47degC.

I concur. I would be very surprised (shocked is more like it) if this turns out to be an issue. The case of "fuel out of China" may have a tiny bit more legitimacy but as someone else has pointed out, polar and overseas routes are done out of Beijiing all the time with nil problems in terms of fuel-jelling etc. Now when things get down to, say, a steady -70C enroute, there are procedures including descent, diversion etc which are in place to handle such issues. Fuel freezing is not a significant industry issue but of course cannot be dismissed here because we just don't know yet.

[lefthanddownabit]

There does seem to be a lot of confusion over this, the AAIB report does seem rather at odds with what John Coward apparently told Sky News:

"The adrenaline kicked in when I realised I had to land the plane with absolutely no power at all. There are drills for a power failure at 30,000ft, when you have time to reset and restart engines, but there are no drills for this. As I approached the runway, I thought that this was going to be a catastrophic crash."
If an engine hangs and does not respond to acceleration demand, one way to reset it is to shutdown and relight. Maybe that's what the F/O meant.

The AAIB report does not go into any detail, so there is not necessarily any conflict between it and any statement the crew might make (though I'd rather they didn't talk to the media to be honest).

[PJ2]

looseobject;

FYI, re the AD for the GE CF6-80E1, a similar bulletin was issued for the RB211, requiring the selection of engine anti-ice as part of the pre-descent checklist.

That bulletin was rescinded in July, 2005 and is no longer applicable to the RB211.

Cheers,
PJ2

[Pinkman]

Sunfish

I have no idea whether fuel specification and freezing is an issue in this case or not. And actually, neither do you. I did say I thought it unlikely. But you just dont know. And by the way, cloud point isnt a typical specification used for Jet - its used for diesel, along with cold filter plugging point (CFPP).

But what do I know, I'm just an ex lab-rat fuel-analyst....

[Riverman]

GMDS
Granted the following AD applied to GE90's but does appear to confirm that there are paths where FADEC signals can be corrupted.


SUPPLEMENTARY INFORMATION: The Federal Aviation Administration (FAA) has received seven reports of loss of thrust control (LOTC) on General Electric Company (GE) Model GE90 turbofan engines installed on Boeing 777 series aircraft. Five LOTC events occurred in-flight and two occurred on the ground. The five in-flight LOTC events were temporary in that the engine recovered and continued to operate normally for the remainder of the flight.

Investigation

The investigation revealed that water can accumulate in the Ps3 and P3B pressure sensing system, which can freeze in the full authority digital engine control (FADEC) sensing ports or pressure line. Frozen water can result in a restriction or a blocked signal to the FADEC. This blocked signal can cause a corruption of the FADEC signal and result in abnormal engine start characteristics on the ground or lack of engine response to commanded thrust levels in flight. Although there have been no LOTC events attributed to icing of the P3B sensing system in the field, inspections have identified moisture in this system, which could freeze and corrupt the P3B signal to the FADEC as well. This condition, if not corrected, could result in LOTC due to blockage of the FADEC sense lines, which if it occurs in a critical phase of flight, could result in loss of aircraft control.

Simultaneous LOTC Events

The FAA is especially concerned about the possibility of simultaneous LOTC events on both engines installed on the Boeing 777 series aircraft due to common mode threats, such as certain atmospheric conditions that may result in ice in the Ps3 or P3B pressure sensing system and causing corrupted signals to the FADEC in both engines.

SUMMARY: This amendment adopts a new airworthiness directive (AD) that is applicable to certain General Electric Company GE90 series turbofan engines. This action requires visually inspecting Ps3 and P3B sense lines and full authority digital engine control (FADEC) Ps3 and P3B sensing ports and fittings, cleaning Ps3 and P3B fittings and sensing ports, purging the Ps3 and P3B systems of moisture, and, if necessary, blending of high metal, nicks, burrs, or scratches on Ps3 and P3B fitting threads. This amendment is prompted by seven reports of loss of thrust control due to corruption of the signals to the FADEC caused by water freezing in the Ps3 sensing system. The actions specified in this AD are intended to prevent loss of thrust control due to corruption of the Ps3 and P3B signals to the FADEC which if it occurs in a critical phase of flight, could result in loss of aircraft control.

Interim Action

Both Ps3 and P3B pressure systems incorporate weep holes that allows drainage of water in the lines that may accumulate from condensation or ingested water; however, the field events and the investigation have determined that these design features may not always be effective in eliminating water from these systems. GE is assessing design changes that will prevent water from freezing in these systems and causing corruption of the signals to the FADEC. The requirements of this AD may change based on the ongoing investigation of the root cause and field inspection results, and future rulemaking may be necessary.

[sandbank]

LeftHandDownaBit
QUOTE
"...there is not necessarily any conflict between it and any statement the crew might make (though I'd rather they didn't talk to the media to be honest)."

Hmmm...Clearly journalists and the media at large seem to be held in pretty low regard by the professional pilots on this thread - but for the life of me I can't understand why.

There's nothing special or secret about the probable causes of an aircrash - such incidents are a matter of legitimate public concern. It's quite right that aircrew should be approached for interviews and that the public hears what they have to say.

After all, what is there to hide?

[DingerX]

Just a note, playing the logic referee:

There's plenty of stuff that's "out of bounds here"; plenty of folks saying things that betray outright ignorance, not only of how these things fly, but also of what those with evident knowledge and experience say about it.

On the other hand, there are plenty of arguments that deal merely in improbabilities. The poster child for this is fuel contamination. Chances are it wasn't. Hey, if there were a case of gross fuel contamination, we'd see a much worse situation (in turns of number of aircraft affected) that what we have here. To be honest, the system is set up to prevent any gross error that would have such a result. But, right at the borderline, where odds are it won't affect anyone, a subtle degradation could provide enough profit that the slight risk that only a morning long-haul flight through the Arctic would have to make it materialize. Was it the case? Doubtful, but what isn't doubtful at the moment?

In summary: while we need to consider every possibility with extreme skepticism, when something like this happens, by definition it is an extremely rare event. Therefore, while the argument "that would be extremely rare" provides a necessary skeptical perspective, it doesn't invalidate the claim (and, for those playing on conspiracy-theory "logic", actually validates it).

[barrymung]

I would agree; fuel icing is *very* unlikely in this case.

[barrymung]

In summary: while we need to consider every possibility with extreme skepticism, when something like this happens, by definition it is an extremely rare event. Therefore, while the argument "that would be extremely rare" provides a necessary skeptical perspective, it doesn't invalidate the claim (and, for those playing on conspiracy-theory "logic", actually validates it).

However, it is important to remember that *something* happened.

If we take the view that EVERY possibility is virtually impossible, then the only factor left would be pilot error!

From the accounts so far it appears as though the most likely reason for the problem was either engines, electronics or fuel.

[Contacttower]

After all, what is there to hide?

There's the possibility of 'tainting' witnesses of the crash, which could influence the investigation.

[HarryMann]

Fuel waxing or icing may be unlikely, but from Riverman's post, FADEC port or sensor icing may not be so unlikely...

Why wouldn't this AD cover Trent installations as well... ?

Simply, there hadn't been any (or not 7) instances of LOTC reported on Trents...

What is the ratio of RR 777's to GE 77's operating please?

[ManaAdaSystem]

Speaking in general, the only time I have seen a fuel temp of -42 degrees celsius was above Mongolia enroute to Bejing. OAT at that time, -72 degrees. We managed to stabilize the temp by increasing the cruise Mach. TOD came not so long after.

We would be subjected to those same temperatures on the way back, but normally we would be at a lower level and slightly higher OAT. The air would also get warmer as we progressed towards Europe. I have never seen an OAT of -71 degrees over Europe and UK. Until now.

As for Morphemes:

"Well sorry if I sound dismissive (which I am) but even several hours in very low temps won't send 30-odd tons of fuel below -47degC.

As well the obvious question - why didn't all the Far East-originating westbound traffic fall out of the sky together?"

A: You are wrong, and B: We take the neccessary steps to keep the fuel temp in check. It's part of the job and covered in the manuals.

I don't fly 777's so I cannot comment on how these aircraft cope with low OAT's, but I know one warning system on that BA 777 did not work (low thrust warning) and it's not impossible other warning systems were "out" too.

No, I don't think waxing was the cause, but it cannot be ruled out as a possible.

The same goes for ice ingestion. There was an Ice warning out for moderate icing around FL 90 (reported over BNN if I'm not mistaken). 9-10 degrees on ground. Possible, but not likely.

IMHO, Gentlemen!

BTW, that the engines failed to produce thrust doesn't neccessary mean they were turning at idle (or something like it).

And retracting flaps when you are in a no/low thust, low speed situation to begin with? Not something I would do, even if I managed to think about it.

They have the aircraft. They have the crew. They have the passengers. The facts will be on the table.

And I still take my hat off to the entire crew of BA 038.:D:D:D:D

[Dr Brian Evans]

Radio interference may have been part of the problem (laptops or cell phones turned on) - but it would be notoriously difficult to prove. Much lab time and effort is currently being spent in trying to correlate cell phones and lap top WiFi technology with brain cancers - but with no measurable success to date. The BioElectroMagnetics Society in the USA have yet to report any reproducable positive effects - though there have been a number of “one off” reports that defy duplication.

The sceptics bottom line is that if it can’t be reproduced then it didn’t happen. Or did it?

[Bronx]

sandbank
There's nothing special or secret about the probable causes of an aircrash - such incidents are a matter of legitimate public concern. It's quite right that aircrew should be approached for interviews and that the public hears what they have to say.

You're right, there is legitimate public concern. Thats why pilots involved in air accidents are interviewed by trained investigators that are qualified pilots or engineers (or both) whose job it is to produce an independent report for the public - not sell newspapers.

B.

[G-CPTN]

just tried it in the 777 sim...
... and we crashed exactly where they did...

sim visual data base has three low buildings at about 1 mile and we cleared those by maybe 10 feet ....don't know if those exist in the real world.
There's the Air Canada Cargo Facility dead on 1 mile from (normal) 'touch-down' . . .
Others further out are either not directly on flight-line or far enough away to be of no concern . . .
Check here (you can pan and zoom in/out):- http://wikimapia.org/#lat=51.464556&lon=-0.42851&z=16&l=0&m=a&v=2

[SaturnV]

The B777 FDR measures 700 parameters, the QAR measures 2000. Is fuel temp a parameter measured by either device? What about OAT?

Source:
http://www.asasi.org/papers/2003/Flight%20Data%20Analysis_Campbell.pdf

[hay diddle diddle]

Engines only stop in flight if they are manually shut down for any reason or they run out of gass!!

The aircraft would not have obtained its design approval if the engines failed through loss of electrical power!!. If any IRE/TRE's are reading this on any type, they should try turning off the electrical power in the sim and landing on the battery. Now, see if your engines respond with manual throttle input, if they don't re check your fuel load or give up flying!!.

I note the initial report said significant amounts, [how can they judge?? welly boots!!] of fuel drained from the number one tank after being ruptured by the left main gear. Well why no fire ?? strange.

The basic engine data on the dfdau or qar will provide the key information on fuel flow TGT and rotor speed plus other related sytem data such as full quantity. Why is it taking so long?? If this is all a bit much, then inspect the engine driven fuel pumps for cavitation [ remember they suck fuel into the engines ]

In low fuel senarios rapid pitch and roll inputs displace the remaining fuel away from the fuel feed path . On a final note why don't they make stack pipes anymore.?? 45 mins at MCT with the fuel low level lights ON!!!!!!!!!!!!! plenty of time.

I am off to have some chocolate licked off me , but it might taste a little different now!!

JNB tomorrow on 4, so Good night and I look forward to the official report in 12 or so months time [ hopfully retired]

[Hand Solo]

The QAR should cover it as in BA I am told they can reproduce every bit of information available to the pilot in the flight deck.

Edit to add in response to HDDs post, pleeaaase, drop the BS 'ran out of fuel' idea. Do you not think that the AAIB saying 'significant' amounts of fuel ran out of the tank is a clue? They are the experts in crawling over bust up aircraft remember including those that don't have any gas left. The crew did not declare any form of emergency related to fuel. The aircraft p****d fuel all over the crash site. The reasonably reliable rumours in BA are that the aircraft landed with over 10 tonnes of fuel on board. Are the AAIB, BA and the crew all in cahoots to conceal a mysterious low fuel state, or is it that something unknown caused this accident?

[parabellum]

I suspect no fire as the bulk of the spilt fuel fell onto the wet grass and mud and by the time the airframe came to a stop there was no ignition source. Pure conjecture on my part.

[WeekendFlyer]

In response to HDD's Post #149:

What are you on about? :ugh: FADEC controlled engines can fail in all manner of interesting ways if the FADECs do something odd. They are designed not to, but it seems likely to me, from the facts in the public domain to date (including the very carefully worded and excellent AAIB initial report), that something went wrong with the FADECs or another element in the control systems linking the cockpit to the engines. The AAIB report specifically states that the engines failed to respond, NOT that they flamed out, spooled down, went to idle, etc. I cannot believe the aircraft ran short of fuel, as the evidence in the report does not support such a conclusion.

Knowing that the AAIB are very careful with their choice of words in such circumstances, I believe we can take it as read that the engines did just that, i.e. failed to respond. As yet, we don't know what level of thrust they were producing, but by the grace of God it was enough to get the aircraft over the airfield boundary fence.

By the way - all those people who voted "Aliens" in the poll; thank you! It was the best laugh I have had all day :)

And also, to the chap who said this accident would put pilotless airliners back a few years, I heartily agree with you, and a good thing that is too.

[PJ2]

SaturnV;
The B777 FDR measures 700 parameters, the QAR measures 2000. Is fuel temp a parameter measured by either device? What about OAT?

The QAR (for SESMA/FDM/FOQA work) will record as many parameters as the installed data frame is designed for, (QAR software) and at sample rates that the frame is similarly designed for. The DFDR is capable of this as well but typically DFDR data frames are smaller and at less frequent sample rates for many parameters. Sample rates of 16 frames per second are possible but are expensive in terms of storage and recording capability. Sample rates from once every fourth second to eight times per second are common in both DFDR and QAR dataframes.

All this is by way of clarifying that "700 parameters" and "2000 parameters" is not a fixed, determined number. Our own 777 QARS are taking in more than 2600 parameters and our 320 dataframe provides us with over 1700 parameters, far more than the DFDR.

More difficult to program, are text-string based parameters to record EICAS/ECAM messages and FMGC entries and readings. Not all ECAM messages are recorded I know, and I suspect not all EICAS messages are recorded either.

Very good animations may be created from such rich data-sources - I suspect this was done within hours of retrieval of the recorders, including the QAR which I would expect to be in good shape.

[SaturnV]

Another question:

For those familiar with the usual practice of the AAIB, is it likely that an interim report with additional details from the FDR, e.g., a more detailed flight profile during the descent phase, will be issued before the 30 day report?

I presume if a likely cause is found near-term, and which necessitates an AD or a SB, that the AAIB would issue an interim report (with relevant flight data) that supports the issuance of an AD or SB.

And is it fair to assume that if the AAIB waits 30 days before its next report, that the incident will ultimately be seen as a one-off?

[KC135777]

I've been told- that much condensation was found to be in the E&E compartment... therefore, possible electrical shorting of the fuel control units- rendering autothrottle commands/throttle inputs useless.

Anyway, something to chew on...........

[Lemurian]

It is really amazing that the theory of a double flame-out, for fuel exhaustion / pollution /icing-waxing, keep turning up in spite of the information that has been given to us.
What we know, from the AAIB, is
The F/O was handling the approach (Question : A/P on or manual with FD ? )
Down to a height of 600 ft, the approach parameters were quite normal.
The engines were not responding to throttle demands (Question : One or both ? )
The aircraft was in a low energy state (Question : Due to the insufficient engine (s) output ?)

What we do know :
The aircrew has had a long 12-hour daylight flight before their approach to Heathrow and were probably past their peak of alertness.
The aircraft went below the ILS glideslope and touched-down 100 ft below said glide. That's not very much, if one puts the events into perspective.
The weather conditions were fair but there had been a forecast of instability and possible windshear over the British Isles on the zones ahead of a frontal occlusion and throughs.
There have been some instances of engines on the 777 not respoding to throttle commands. To the effect that there is a procedure to that effect. (granted, GE, not RR ).
My argument lies on the premise that a *hung thrust* is very hard to detect from a pilot's point of view. One would start to notice it, as the failure is in essence very subtle, only when the thrust demand becomes rather high, relatively to a normal required engine EPR.
As a matter of fact, if one omits the speed tape, all the approach parameters would seem normal : On the glide, FD bars crossed in the center of the PFD, EPRs coherent with the approach conditions. The only other visible clue that something is becoming quite wrong would also be the unusual pitch attitude, somewhat higher than normal, but the clue would be easily hidden by the *normallly*crossed command bars of the FD.
We now have the beginning of the ever worsening trap we all dread : A decaying airspeed, an increasing drag situation requiring more thrust that is not available any more which causes the speed to decay further while the AoA is increasing to achieve the "stay on glide" requirement...and so on....
At that point, the thrust required for exiting the situation would have been very important and from a piloting aspect we are probably close to a stall recovery-type of handling.
That close to the ground ? IMHO, some feat of reflex-flying !

Did I forget to say that as the F/O was handling the aircraft, that information taken in itself destroys the ideas of a double engine flame-out, as in this case, the only instruments available through the battery, would have been the captain's ? And neither the APU or the RAT would have enough time to come on-line.

[DingerX]

Yeah, double flame-out is not much of an option.

48-hour and 30-day reports are mandated. They could "find" something before after that necessitates immediate action; there's no reason it has to happen before or after either of these gates.

As for the "Dog and Pony Shows" of BA presenting some of the crew: there's no need to suggest that means they were or were not heroes (although the initial report makes it difficult to suspect they were at fault). But, in a moment when the press is desperate for something, sometimes chucking them the least bone possible helps. Situations like this are huge information vacuums, and the slightest whisper will be amplified to huge proportions. If you give the press access to authorities quoting non-controversial facts (Such as "It was a team effort"), you give them something to say without forcing them to probe the web forums (and come up with lines such as "unlike their commentary on any thread involving Iberia pilots, Ppruners were unequivocal in their praise for the pilots").

So, in short, don't read anything into the presentation or not of the crew to the press. It's not dictated by the facts, but by PR strategy.

[Hand Solo]

I have good reason to believe DingerX has hit the nail on the head PR-wise. The press in the UK are notoriously immoral and intrusive. If you give them nothing they'll take something. Best to be in control.

[huggychair]

I Think that Riverman (post #137) may be on the money here, icing may not have been an immediate issue here but a contributory one to the sensor points/connections (moisture).

The fact that it was picked up by the FAA on the G.E. powerplant rather than a Rolls-Royce one (on the same aircraft design) should make little difference to the underlying cause. Just because the FAA didn't put out an APB on the Trent engine doesn't mean they're infallible to the same control/FADEC issues!... it just meant they hadn't dealt with them at that time.

Operators with RR's would have looked away (understandably), but the FAA's remit was only to explore what was going on in ITS (much bigger) aviation industry, where G.E. engines dominate, and had lead to previous (unrelated) issues (IIRC)...

And if this BA workhorse 'was' doing the same route fequently, then it looks likely (reading some of the above route-based posts) that moisture could have been a <contributory> cause in losing control ...at that time of descent, whilst the fuel pressure/electricals were working overtime!

just my 2p's worth!

[d71146]

I don't think anyone can deny that for whatever the outcome of the AAIB report brings the flight crew did an outstanding job in landing the 777 and everyone getting out alive but what puzzles me is the press conference held by the airline persuading the flight crew to give a statement about the incident I just hope that it does not come back to bite them on the bottom.
I myself think that perhaps just naming the crew and showing their photos would have been quite sufficient and leave it at that but, perhaps I am a tad old fashioned in this respect.

[Norman Stanley Fletcher]

I would commend Dinger X and Hand Solo for their excellent analysis of the real driving force here - PR. We are faced with a press who know little about flying generally, and absolutely nothing about the B777 specifically. Couple this to an insatiable public appetite for tit-bits and news editorial pressure for programs to be filled and you have a bottomless pit of disinformation. The inevitable result is endless speculation and intrusion, coupled to the creation of heroes today who may become villains tomorrow. The AAIB initial report is the only true knowledge that anyone on this forum really has, myself included. I have no doubt that the likely causes of this accident have already been narrowed down to a very small range of possibilities indeed. Quite rightly the few people who really do know what is going on are acting as the cautious professionals they are, and have chosen to remain silent until all doubt is removed.

For what it is worth, my take on the BA handling of this accident is that they have been absolutely faultless. They have provided just enough entertainment to throw the numpties off the scent for a few days, whilst ensuring their brand exudes professionalism and skill in the face of an impossible emergency. From clapping employees to suave looking crew on display to the world who say everything but tell nothing, they have done it exactly right. I do not blame them one bit, as they have acted wisely to protect their company from a loss of consumer confidence and all that would mean for BA. They have simply avoided turning a 'drama into a crisis'

Whilst we all await any real information, I am reminded of the immortal words of the former US Defense Secretary, Donald Rumsfeld -

"Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns -- the ones we don't know we don't know."

Isn't that the truth?

[huggychair]

In attempt to keep this thread how it started (RE:cause); two links:

http://www.pprune.org/forums/showpost.php?p=3850975&postcount=137

(A good FAA B777 Remit post)

...and my post about it here:

http://www.pprune.org/forums/showpost.php?p=3851337&postcount=160

:ugh: :)

[TheShadow]

Having taken the time and trouble to read all the BA 777 crash threads and analyze them (all) for their intrinsic worth, I've concluded the following about (by far) the most meritorious line of probable cause:


huggychair said (in post 160 (http://www.pprune.org/forums/showpost.php?p=3851337&postcount=160) of this thread)

I Think that Riverman (post #137 (http://www.pprune.org/forums/showpost.php?p=3850975&postcount=137)) may be on the money here, icing may not have been an immediate issue here but a contributory one to the sensor points/connections (moisture).

The fact that it was picked up by the FAA on the G.E. powerplant rather than a Rolls-Royce one (on the same aircraft design) should make little difference to the underlying cause. Just because the FAA didn't put out an APB on the Trent engine doesn't mean they're infallible to the same control/FADEC issues!... it just meant they hadn't dealt with them at that time....etc etc


He was picking up the theme originally started by Belgique in the previous thread at post 939 (http://www.pprune.org/forums/showpost.php?p=3849310&postcount=939)

and commented upon by UNCTUOUS in the previous thread at post 954 (http://www.pprune.org/forums/showpost.php?p=3849372&postcount=954) - but NOT later referred to by Riverman in this thread.


then interpreted further (in this thread) in that post (http://www.pprune.org/forums/showpost.php?p=3850975&postcount=137) (#137 of this thread) by Riverman (referred to by Huggychair)

Among all the 1000's of rabbiting Pprune posts about the accident (and a very few that have commented upon these four in particular) only those four posts seem to be quite "on the money" and inspirational as to a real possible and plausible cause.
.
Hats off to those gents (i.e. they like more than the sound of their own rants)

[Intruder]

The interesting thing is that you are required to achieve 2 gates on the CDA. 1000' should be fully configured in the landing configuration with the Vapp within 25 knots of landing speed and reducing. The engines do not need to be spooled up to approach power by this point but they need to be stable at approach power by 500'.
Unfortunately, that only applies to "you" -- not to me or MANY other Pilots who are not subject to BA SOP! CDA or otherwise, our "Stabilized Approach Policy" is:

A stabilized approach is when the airplane is in the landing configuration with the checklist complete, on airspeed, engines spooled up, and on the proper flight path. A stabilized approach must be established before descending below the following minimum stabilized approach heights, or a go-around is required:
• 500 feet above the TDZE during a VFR, visual, or straight-in instrument approach in VMC conditions.
• 1,000 feet above the TDZE during any straight-in instrument approach in IMC conditions.

So, the "160 to 4" (i.e., 160 knots to 1200', or 15 seconds prior to MY IMC "stabilized approach" gate) policy at LHR and other places makes it VERY difficult to adhere to MY airline's policy if I am flying a light airplane. Though we may make every attempt to comply, it will require a significant deviation from the policy and normal habit patterns when our target airspeed is in the 130 Kt range.

[HarryMann]

Whilst we all await any real information, I am reminded of the immortal words of the former US Defense Secretary, Donald Rumsfeld -

"Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns -- the ones we don't know we don't know."

Isn't that the truth?2 things..

I'm sure glad you didn't get the immortal and former words around the other way for Mr Rumsfeld.. an immortal Rumsfeld the world can do without!

A similar but shorter saying is...

Technicians know what they know, however, Engineers also know what they don't know...

[autoflight]

If A/T is operating and desired thrust is not achieved, how far do the thrust levers advance in an attempt to regain lost speed? It has been suggested that the engines did not respond to pilot action advancing of the thrust levers. It seems that the levers should already have been in an advanced position.

It is drawing a very long bow to think that the A/T was operating incorrectly AND that manually advancing the thrust levers was inneffective, as separate faults. If it was a single fault, would this point towards mechanical failure of the thrust levers? Logically this would tend to rule out fuel mishandling, fuel quality problems, fuel malfunction, engine failure etc.

[7times7]

CDA approach, thrust setting at flt idle almost till stabilized.

B777, with one Autothrottle Arm Switch off, there is an Eicas Msg.

Now get this, with both Switches off together, NO Eicas msg the last time I tried. Possibly modified by now.

Could both switches be accidently knocked off without anyone noticing until the autothrottle needed to maintain speed.

Then again fm idle to full power takes 8 secs if throttle was advanced manually.

[Selfloading]

That's the most relevant thing I've read yet. Well done. Probing, and thoughtful. And well worth discussion. There were only 135 people on that plane- less than half a load. Wonder what it would have been like with a full load, and FULL baggage.The question of what would have happened had the aeroplane been full has been asked before and answered, the result would probably have been the same.

[Binder]

Regarding post 170 and 'on the money posts'.

Weather was very cold at altitude during the time of the incident(SAT of -70to -72) which is right on the operating envelope for my A/C type.

Could this be of any relevance?

Binder

[pasoundman]

parabellum
I suspect no fire as the bulk of the spilt fuel fell onto the wet grass and mud and by the time the airframe came to a stop there was no ignition source. Pure conjecture on my part.


That helped no doubt, but additionally jet fuel doesn't ignite very readily unless in an aerosol form.

The lack of a single massive impact (it slowed down gradually) would have made the formation of an aerosol that much less likely.

[Wingswinger]

Ian W

Therefore I do not see that CDA per-se would have any bearing on this although it is possible that the BA or NATS procedures for flying them at LHR might have some impact.

That wasn't the point I was making. It was that a continuous descent at idle (if that is what occurred in this case) might have masked the problem whereas a step down to a platform altitude would have required a power-up and so revealed the problem at an earlier point in the approach. The crew would then have had the option of delaying gear/flap which might have enabled the aircraft to reach the runway.

[gatbusdriver]

Wingswinger

A CDA is not a descent in idle, it is a continuous descent (min I believe is 500fpm) with an allowable level segment (without checking think it is 2 mile i'm sure someone will correct me).

Therefore once you are established on the glide most people will only be at approach idle to get the speed back after 4 miles, where you have invariably been maintaining 160kts.

Ergo I think CDA's have little bearing on this incident.

[sandbank]

It's so long ago now -and so many posts back - it may be worth reminding ourselves that one of the flight crew - identified as "the captain" - told the driver of a tug immediately after the crash that he'd lost "all power and avionics". No nav lights or beacons can be discerned on the footage of the approach - despite the fact that it was such a gloomy day.

[ChippyChop]

Regarding the comments about no fire. I am no expert, but I surely hope the safety experts consider the positive implications of the plane landing on soft grass rather than the hard runway. There were two benefits that I can see, it arrested the planes speed very quickly and in my view avoided a major fire due to the lack of friction that would have resulted in the fuel vapourising and igniting. In these days where excess grassed areas are being sold off to line the coffers, I really think safety experts need to stipulate a minimum amount of grassed areas to give pilots the potential to land on grass. How many times have we seen the pilots do a fantastic job of getting the plane on the ground, albeit a hard landing, and then a fireball erupting which claims the lives of most of the passengers and crew.

[PAXboy]

mike bI too am also amazed that they havn't grounded 777's. This must mean that they do know what happened!It does not mean that they know what happened!

I am not amazed that they haven't grounded the type. Since this is the first hull loss of the type in ten years, whatever caused it is rare. Secondly, to ground the type would cause more loss of money than would be caused by a hull loss with all lives. That might be harsh but it is the kind of decision that insurers and public transport companies make every day.

[vapilot2004]

The idea that a computer or power failure could shutdown both engines
might be possible on some aircraft, but not this one.

Once lit, a normally operating Trent (or GE for that matter) will keep
running until fuel is stopped or a signal is sent to the
engine mounted FADEC box (EEC) on the 777.

Fuel:
Both the spar fuel cutoff and HMU main fuel valves are controlled in an
ELMS cabinet via relays which are hardwired to the Run/Cutoff switch.
The EEU (ELMS computer) does not command the relays nor does
any other digital devil.

EEC Shutdown signal:
The EEC can initiate a commanded shutdown only after both channels
A and B are given the reset signal, once again from
the relays controlled directly by the Run/Cutoff switches. The
channels are connected to separate relays.

Power loss will not affect the spar/HMU valve commanded positions
as these valves require power to both open and close. In addition,
the relays used for Run/Cutoff control are latching types, meaning that
a loss of power will not change relay state.

The autothrottles have been covered already. AT commands are right
in front of you - servos physically move the levers.
The 777 has no digital control link between the autothrust
computer and the engine control computers.

Throttle control inputs are powered by the EECs themselves and are
analog inputs. Each channel (A & B) has its own resolver.

So there you have it. Hardwired controls. Dual channel EECS with
dual power sources and inputs for each engine. It's a mystery.



It had been asked earlier:
An AA engineer tells me that the Trent 800 series
HMUs and EECs are manufactured by Goodrich.

[M.Mouse]

Mr. Mugabe

BA B777 landing flap is F25. F30 is used on limiting runways and on one or two other situations but F25 is the usual.

At risk of ruining the thread here are a few other realities. BA SOP into LHR on an ILS would be gear taken circa 2000', usually with F20. At 1500' landing flap and final speed reduction to comply with the ATC norm of 160kts to 4DME. The engines would be at idle thrust during that speed reduction and normally spooled up again by 1000'.

As we know in the case in question the aliens took over at 600' believing Gordon Brown was on board. They were in the employ of Al Queada.

[Taildragger67]

Mike B,

As Paxboy said, no, it doesn't.

I flew a 744 last night but would have been equally happy in aTripler.

Indeed I think Paxboy has it slightly wrong, IIRC this might end up being the first 777 hull loss since the type's introduction - so that's about 13-14 years.

Yes there might be a problem which will come out in the wash and which will make 777s and 787s even safer, but they've worked pretty darn well to date.

You seem to forget that the drivers and bikky-chuckers who work on them every day, also have families they want to see again and generally do not come to work with a death wish - if they are happy to climb aboard, so am I, and so should you be.

Please leave the scaremongering to the Daily Mail and its ilk. :*

[llanfairpg]

but I surely hope the safety experts consider the positive implications of the plane landing on soft grass rather than the hard runway.

Yes, lets have grass runways and wooden terminal buildings, much more fun.

[ILS27LEFT]

"From the accounts so far it appears as though the most likely reason for the problem was either engines, electronics or fuel" (quote)

I would eliminate the engines as an option. It is basically impossible the two totally independent engines failed to respond, at exactly the same time, after many hours of perfect functioning.:mad::eek:

It will be possibly a fuel related issue or an electronic/software glitch (which started earlier along the wires, not far from the cockpit) or a combination of these two factors. Software/Hardware within the engines cannot fail simultaneously instead (e.g FADEC).

This incident has sent a few strong messages out (in my modest opinion):

-Grass before/after/around the runway is essential, especially in RESA. The 27L RESA saved this 777 and we have had a few incidents in the last few years where RESA (combined to pilot's skills or errors) saved lives.
Modern aircrafts have very strong and flexible structures, they can definitely survive a crash-land on grass: RESA regulations/limitations should be possibly be reviewed on all runways and extended whenever possible. Some very profitable car parks will have to be moved (e.g. the one just in front of 27R! at EGLL).:mad:


On some aircraft types the windows on doors, where Cabin Crew sit (e.g. on Boeing 767, 777), are extremely small (it is impossible to see outside! Try it!) whilst CC should be able to see what is happening outside in emergencies,they can be in charge of an evacuation when pilots are unable to PA. On this 777 pax told CC what was going on outside. This is in my opinion unacceptable and you can waste valuable seconds.

Ground-Cameras should be installed on all approaches, capable of recording all final approaches and touch down: the cost of this is nowdays extremely low and they would really help an investigation.



:ok:The Pilots did an excellent job. Well done.:) Pilots skills, RESA and the 777 solid structure saved many lives at EGLL...:ok:

[N1 Vibes]

Here's a couple of rumours to mull over:

- The Times newspaper states that investigators focusing on avionics systems that control the engines. http://www.timesonline.co.uk/tol/news/uk/article3216042.ece

- Overheard very vague conversation that perhaps this a/c had a previous tech log write up for similar loss of power on both engines.

OK - go ahead shoot me down! This is after all a rumour network.

Bgrd's

N1 Vibes

[gregpend]

Questions for the pros:

I fly props only and I know that if I have an engine failure it's impossible to miss, but in a 777 how do you know if your engines have stopped working after a long descent at flight idle? Is it possible that the engines were completely dead but the pilots didn't notice? Would turbine temperature dropping cause an alarm? There's got to be something telling the pilots that the engines are no longer developing thrust...

If the reports that the RAT had deployed are true then it's most likely that both engines were no longer developing power, but could the RAT deployment instead be triggered by a software glitch if the computers thought the engines were out? This doesn't seem very likely to me: why would you design an emergency electricity generator to be triggered by software that needs electricity. I imagine that it's an independent system.

If the engines were dead the descent was likely keeping them spooling until the 3 degree glideslope was attained and when the descent was arrested and airspeed lowered the generated power from the engine spooling dropped below minimums which triggered the automatic RAT and APU deployment. Am I right about this or am I speculating?

[Rover90]

I am labouring under perhaps the misguided notion that the B777 was at 600ft in the normal landing configuration, gear down, flaps in the normal landing position, autopilot out with John Coward having his right hand on the control column and his left hand over the two thrust levers. (thrust levers...its a Boeing thing!).

If they were being good boys as I am sure they were, they should have been on a stabilised approach by then which means the engines should have been spooled up to a decent thrust level and very little adjustment would have been needed in the last 600 ft of the approach.

John would have sub-consciously seen a slight drop in airspeed or perhaps a slight dip below the glideslope or PAPI indicators at the threshold (two independent forms of glideslope angle).

As the thrust levers were squeezed forward John would have expected the thrust to increase slightly and the slight speed decay to stop and be back on the glide slope at the target speed.

When the slight squeeze forward did not rectify the problem the obvious action is push the thrust levers forward a little further until it dawned that the engines were not developing that little bit of extra thrust.

It is safe to assume that if the aircraft was stabilised down to 600ft with a normal approach power set then that power would take you to the runway albeit landing a little before the aiming point. I think I am with the team that suggests that the engines gently ran down, I know nothing about the B777 but the first real warning would probably be the generator dropping off line but it would have been supplying a common bus bar so probably no services would have been lost. There would have been a slight de-stabilisation of the approach due to the assymetric thrust and eye witnesses seem to suggest some bank greater than normal corrections being observed.

The second engine running down at some point later would similarly not manifest itself until its generator dropped off line but that would cause the bus bar to go dead and that would get your attention as you would now be supplied by the battery bus that powers essential instruments and services. I don't know the standard procedure for the APU, is it started in flight as a backup air and electrical supply or has fuel conservation knocked that one on the head? With no APU the windmilling engines and their respective hydraulic pumps would have been the sole source of hydraulic power for the control surfaces until the Ram Air Turbine had lowered and got up to speed.

My first thought is that the engines have been starved of fuel for whatever reason. Plenty of fuel on board apparently and the crew would have seen a gross figure that they were happy with or they would have declared an emergency or landed en route in Stansted/Amsterdam. I am absolutely convinced the crew believed that they had sufficient fuel plus an adequate margin.

So for all the people who know the B777 systems, How many fuel tanks does the aircraft have? What is the normal fuel config for landing? Is there any scope for a slip up when balancing the fuel? Are all fuel panel selections monitored?

I think there are many crew who must remember being in the hold waiting for an approach at LHR and after the third hold and getting a bit bored, a suggestion being made to tidy up the fuel ie balance it up across the four tanks. When you have 10,000kgs/20,000kgs or more in each tank a couple of hundred kilos difference is not significant, when you are down to a 2000kgs in each tank, 200kgs is now 10%.

So a decision is taken to balance the fuel, the crossfeed cock is opened and the respective pumps switched off but the fuel tank page is left displayed. As we all know we are human and only need something to distract us to wind up draining two tanks at an inappropriate time. You don't get a fuel assymetry warning as they drain down at approx the same rate.

As this is a forum for stupid questions and answers, a forum for off the wall ideas, I am curious that I have not seen any reference to fuel management. I can see how it could happen and I know for sure engines have been run down on multijets in the past due to finger trouble on the fuel panel.

[Hotel Mode]

So a decision is taken to balance the fuel, the crossfeed cock is opened and the respective pumps switched off but the fuel tank page is left displayed. As we all know we are human and only need something to distract us to wind up draining two tanks at an inappropriate time. You don't get a fuel assymetry warning as they drain down at approx the same rate.

I would be very surprised if that happened, fuel balancing is not encouraged at BA and i've never seen it done at that kind of stage in the approach. Turning main pumps off is more or less a no no. Also the Boeing would generate a fuel low tank x eicas long before it ran dry.

[pilotmike]

If the engines were dead the descent was likely keeping them spooling until the 3 degree glideslope was attained and when the descent was arrested and airspeed lowered the generated power from the engine spooling dropped below minimums which triggered ... blah... blah!
A fine theory if aircraft descended onto the glide slope, but as it happens, they don't. They tend to fly level, BELOW glide, WITH POWER, until intercepting it.

Maybe the other thread called 'The thread for silly questions..' might have been the better place for gregpend to air this and all his other fanciful ideas.

PM

[Spooky 2]

Normal config for that stage of flight would be tank to engine, i.e, left tank to left engine, right tank to right engine and in all likelyhood the center tank would be empty. As soon as the 2nd engine failed, the APU would start up and the RAT would deploy for both hydraulics and electrical, with hyraulics having priority.

[woodpecker]

Rover90

So for all the people who know the B777 systems,

What is the normal fuel config for landing?

At this stage of the flight (as the centre tank is emptied first) the feed would have been tank to engine (L tank to L engine, R tank to R engine).

Is there any scope for a slip up when balancing the fuel? Are all fuel panel selections monitored?

First of all in in the six years that I flew the aircraft I never had to balance the fuel due to imbalance. However, should the need arise, the fuel panel (tanks, flow lines, valves, crossfeeds etc) display is selected on the lower EICAS, and pump/crossfeed selections made on the overhead panel, confirmed from switch lights and the display.

If the 11000 kgs which has been quoted as being in the tanks is correct I would be surprised if there was more than a 100kg difference between the two wing tanks.

Without suggesting what might have happened, if one engine had run down first then the associated warnings/cautions from elecs, fuel and hyd systems would have appeared on the upper EICAS (including "L/R Eng Fail") for the associated engine. However if the two engines (and hence their alternators) failed at the same time then the EICAS displays would have lost their power supply.

The Fly-by-wire "backup batteries" would have powered the relevant computers all be it is a very basic control mode. The APU automatically started to restore AC power to the aircraft (APU door can be seen open from photo's) Alas in the remaining time that the aircraft was airborne the APU would not have reached its governed speed and not be providing AC power.

The "gliding" exercises with two engines failed from height in the simulator were always conducted with the APU started prior to the failure. In the four attempts (approaches) we made (from between 10,000 and 20,000 feet) we were successful every time. The option if I remember was using the FMC to either arrive at the outer marker with an extra 60kts at the "normal" height or the "normal" speed at twice the height. Thereafter "suitable" gear and flap selections were made

gregpend

The fact that, with AC power still available, the command sector on the EPR gauge (difference between commanded and achieved) would be in view, and at some time the "L/R eng fail" message. However, as mentioned above, if both gens dropped off line at the same time there may well have been no messages/no EICAS, just the standby instruments powered.

[Wader2]

Radio interference may have been part of the problem (laptops or cell phones turned on) - but it would be notoriously difficult to prove. Much lab time and effort is currently being spent in trying to correlate cell phones and lap top WiFi technology with brain cancers - but with no measurable success to date. The BioElectroMagnetics Society in the USA have yet to report any reproducable positive effects - though there have been a number of “one off” reports that defy duplication.

Has anyone commented on this? I haven't noticed it. In today's Daily Telegraph there is a letter suggesting exactly this and that all cell phone logs and laptops should be recalled and checked to see if they were operating.

[Hotel Mode]

A fine theory if aircraft descended onto the glide slope, but as it happens, they don't. They tend to fly level, BELOW glide, WITH POWER, until intercepting it.


Not necessarily, Continuous descent approaches are the norm these days.

[Octane]

couple of points:
The flash point of JetA1 is above 30 degrees C, therefore unlikely an issue given ambient temp on the day that fire was a risk. Freeze point of JetA1 around -60C. unlikey an issue at low level flight. My guess is electronic failure, fuel contamination or fuel mismanagement. For what it's wortrh, my money is on options 1,3 and 2 in that order. The pictures give new meaning to the trrm 'engine braking'!

cheers

Octane

[boofhead]

It is great that nobody was seriously hurt. The B744 has a great record, perhaps statistically better than the 777, since there was only one accident causing fatalities (Taipei) and one hull loss (Hong Kong) and that one could have been saved until they blew the tail off with explosives.
So Boeing knows how to build great airplanes.
You guys have eliminated all causes, leaving only one: the engines were turned off manually. (this did happen on the 757).
I hope you are happy now.

[hetfield]

You guys have eliminated all causes, leaving only one: the engines were turned off manually.

Not true! Maybe there wasn't any credit of landing fee.

[Ivanbogus]

It is strange that the RAT was deployed if any of the engines were running.

[Hand Solo]

It's strange that the landing gear is sticking through the wing too. Perhaps the multi-G impact had something to do with it?

[happybiker]

Boofhead

and one hull loss (Hong Kong) and that one could have been saved until they blew the tail off with explosives.

The 744 hull loss at Kai Tak was inevitable after the 2 days it spent in the water of Victoria Harbour before they blew the tail off!!::ok:

[Emm4]

Haven't seen it mentioned but a vote of thanks must go to the Boeing designers responsible for crashworthiness and to the authorities who have been working over the years to establish standards that ensure that passengers actually do survive in survivable accidents.

For this accident, in spite of the impact forces, the door frames did not distort so allowing the doors to be opened, the slides deployed succesfully, the cabin overhead luggage compartments did not break free and collapse onto the pax, seats remained attached to the floor, and there was no fire when one might have been expected.

Well done!

[Double Zero]

Pardon me if this has already been stated, but it hasn't been in all the posts I've read;

Not even old hands or current 777 experts can say what happened; so why aren't Trent 777's grounded for now ?

Is the answer to the crash actually known already - a distinct possibility, but if not it must be down to £/$...

[Ivanbogus]

Because maybe it is not a powerplant failure.

[florida flamingo]

Ladies, Gentlemen & Officers!

The first thing we learn at IFALPA about Accident Investigation is to abstain from speculation. The investigators in this case have all the evidence and the recorders in good shape at their disposal. We will get a preliminary report quite soon. As profesionals we should keep our twitchy fingers off the keyboards.

Let us respect our colleagues who did a wonderful job. The MOST IMPORTANT fact is there was NO LOSS OF LIFE.

MORE THE MERRIER!

[Double Zero]

IvanBogus,

you are missing the point ( or a wind -up merchant ); plane fell out of sky, engines may well be spiffing, but this would seem to indicate there's a dodgy bit - or several - between them & cockpit.

As no answer publicly known - why allow similar a/c to fly ?

[Intruder]

Continuous descent approaches are the norm these days.
This is yet another example of tunnel vision -- 'That's the way WE do it, so that's the norm'...

While CDAs may be the norm at LHR and elsewhere in Europe, they are NOT the norm in the US and Asia.

[Zorst]

We will get a preliminary report quite soon


Mmmm, that assumes there's something to report - that something causal has been found...


As no answer publicly known - why allow similar a/c to fly ?


...errr, because it's unimaginable that anyone would take the decision to stop them flying, given that no problem has been identified, and while they're flying, they're making money.

[boofhead]

Happy Biker: You are probably right, but I was there when they pulled the airplane out of the water and they found that the only place that had water damage was the first class carpet. Even the electrical bay was dry and that had been underwater the entire time.
The salvage company bought the wreck from the insurers and made all their money back selling the landing gear alone. Everything else was jam.
The airplane was just weeks old and very tight.
The Air France 744 that stuck its nose in the drink in Papeete was saved, and it had more water damage than the CI one.

If the 777 is as tough as the 744 it can take anything you dish out.

Unless you work for CI or KE (or of course SQ).

I forgot that KE lost a 744 in a crosswind landing incident that stressed the hull so bad it could not be straightened out so they cut it up for scrap. Another almost-new airplane. That makes three hull losses, only one with fatalities.

[SaturnV]

A question:

If thrust was allowed to decay over a period of time to ~<30% N1, what might one expect to be the lag in time between an A/T or manual command for more thrust and the engines responding? Is this lag likely to be 5 seconds, 10 seconds, longer?

[skiesfull]

Afew thoughts on the speculation:-
Contaminated fuel - there was in incident of fuel contamination out of Lagos during the 90's. 4 aircraft were affected, 3 northbound and 1 southbound. The indications were of fuel filter blockage and not all the engines suffered at the same time, so I think it is an unlikely situation for the BA 038.
Fuel icing -as the fuel would be configured tank-to-engine, unlikely that both engines would suffer loss of thrust at the same time and surely the engines would 'cough and splutter' or surge?
Fuel starvation by configuring both engines to one tank -the AAIB has not indicated in it's interim report that a lack of fuel was found in either main tank, so again, and given BA's SOP'S, unlikely.
Pilot error in shutting off both fuel control levers during the approach - very, very unlikely.
Software glitch -perhaps due to condensation? Maybe not just due to condensation, but perhaps that one-in-a-billion statistic?
My money is on an electronic fault between throttle and engine.
Airframe by Boeing
Engines by Rolls-Royce
Micro-chips by Sum Ting Wong Electronics Ltd.

[FlightTester]

GB

Aviate, Navigate, Communicate!

Always in that order, faced with a potentially catastrophic situation as this the first rule of business is to fly the aeroplane.

[Milt]

Does anyone know the minimum IAS at which the RAT will do its thing? Does it produce DC and AC electrics and some hydraulics?

[BlooMoo]

The first thing we learn at IFALPA about Accident Investigation is to abstain from speculation. The investigators in this case have all the evidence and the recorders in good shape at their disposal. We will get a preliminary report quite soon. As profesionals we should keep our twitchy fingers off the keyboards.


Let us respect our colleagues who did a wonderful job. The MOST IMPORTANT fact is there was NO LOSS OF LIFE.

Might appear pedantic, I grant you but to me, the second quote (from the same post) contradicts the first.

Anyway, apart from a redirecting link to the forthcoming AAIB report, what is the purpose of any post on this thread/site if there is not an element of speculation involved?

[Milt]

777 RAT

Does the 777 RAT produce DC and AC electricals and hydraulics?
What is the minimum IAS for max outputs?

[Spooky 2]

The RAT will operate at all airspeeds and altitudes. If it can't maintain RPM it will load shed and the main battery will assume the load. The RAT produces AC which is then converted to DC through two seperate TRU's. It also produces Hyd. power to the Center system which has priority over the electrical. Doubt if any of this info has any bearing on the accident.

I'm clueless?

[bilderberger]

I have been informed by a source that the a/c did not run out of fuel. How much was in the tanks? I have not been able to find any official mention of this ..has anyone seen the figures or is this speculation.

Could a cup of coffee in the throttle area cause such a failure or would it at least leave the engines running but perhaps affect throttle response. The Fadecs are separate and would not in usch a circumstance shut the engines down...might alter power but surely not stop? I am always inistent that drinks go over my shoulder away from the panel just in case and in fact though that is the brief they often forget.

You would expect fuel contam to have affected more than one a/c as ha happened before and then earlier in the trip. The tanks usually mix the fuel well enough , so would the problem have occurred much earlier?

The temp on the day was plus 8...too high for icing ???especially at this stage of the flight. Would you say its still likely at that temp.

The engines seem to have stopped in a staggered fashion the left seems to have been rotating more than the right. what does this indicate?

what are your feelings

[Spooky 2]

Gents, please recall that when you select flaps 25 in the beast Approach Idle is automatically selected. There are several other parameters for this selection but none the less this should give you a fairly rapid spool up in the event of a rejected approach or landing. It is deselected after touchdown where it goes back into Minimum idle.

Still Clueless

[14SIX785]

If the fuel came from a contaminated source in Beijing I would have thought that it was likely that one or more aircraft could have used that same contaminated fuel source and sufferred engine malfunctions as a consequence?

[window-seat]

Having read the article in todays Flight International, it appears that:-

The Gear was deployed later than normal (according to a Tower Controller)!

Surely gear is usually taken by about 4 miles when slowing from 160 kts? If gear selection was left later than this, were the crew already experiencing problems well before 600 ft?

Anyway whatever the cause, a sterling job done by all involved! :D

WS

[blakkekatte]

Bilderberger says:

I have been informed by a source that the a/c did not run out of fuel. How much was in the tanks? I have not been able to find any official mention of this ..has anyone seen the figures or is this speculation.
The preliminary report, first post in this thread, says A significant amount of fuel leaked from the aircraft but there was no fire.

Then you say: Could a cup of coffee in the throttle area cause such a failure that sounds like the scenario in the film Fate is the Hunter" [/url]http://en.wikipedia.org/wiki/Fate_Is_the_Hunter_(film)[/url] which I understand was shown recently, with the plot line Eventually a test flight re-creating the actual flight shows that the the crash was caused by a cup of coffee spilling and shorting out critical wiring

[r011ingthunder]

I would respectfully ask that people read through both this and the previous (now closed) thread for answers to their questions before posting them. From watching this (originally very promising) thread develop it is apparent that people are sometimes not reading anything but the current page before posing an already answered question. Inevitably the thread will become an overly long rambling monster with little or no valuable input.
There seem to be some truly knowledgable people on here, and I for one, value their opinion, and enjoy reading their posts, but I'm sure they will eventually tire of answering the same old questions time and again.
Maybe a Mod might be able to modify the very first post with a short Q and A list to eliminate the need for people to read the whole 12 pages? Then if their question has already been answered they can be directed to the first page for info? (I realise this is cheeky coming from a newbie, sorry).

[parabellum]

In 1989/92 I was flying a CFM engined B767-300ER and that had, for a while, a disconcerting feature whereby when making an MCP or TOGA selection that required more thrust, sometime only one lever would move forward, sometimes neither and a quick handful was required. A bit hazy now but I believe it was due to the grease on the throttle cable near the hot part of the engine losing its viscosity, eventually the problem was cured by changing the grease, ISTR. We were all aware of the problem and guarded the throttles very carefully.

[Oldlae]

BB,
Have a look at the engineers site airmech there was apparently 8000 kgs of fuel. I doubt whether coffee could penetrate the conformal coating of pcb's and the like, unless they are overheated. Let's all accept the AAIB initial report, they are looking at the reasons for the apparent electronic control of both engines not increasing thrust when demanded. If that has been eliminated I am sure they would have made a statement by now. My concern is that whatever caused this incident may not have been recorded in the FDR because the relevant parameters have not been included.

[Alwaysairbus]

Having read all the posts again, the only one really is relevant in all the speculation... valipilot explains it very well....

Ignore the A/T.. 2 servos that drive the throttles. The throttles were pushed forward manually which overrides whatever a/t position was commanded. The TLA's (resolvers mechanically connected to the throttles and powered by the EEC's) send the EEC's commanded position.. forget autoflight/throttle the throttle position commands the relevant fuel flow/ EPR (it's not like Airbus).

No one knows (other than the AIB and the crew) whether the engines were running on touchdown, the only conceivable way if not is both master levers off (highly unlikely) or coffee spillage in the switches as a posibility (but again not very likely). If NAI had not been selected, again there would be handling problems and signs of surging/ EGT fluctuations when icing became apparent

If they were stuck in idle then it's EEC's controlling this.. rev unstowed would cause it but a dual failure again very unlikely so again it goes back to software.. an aircraft system input to the EEC's or EEC algorythem demanding min idle. Aircraft system interfaces generally demand more fuel, ie ECS demands, anti ice, flap position so unless there's been an electrical spike down a databus or dicrete line in then this can be ruled out.

Fuel contamination / icing could cause engine problems but you would expect somekind of surging or engine control problems earlier and most probably fuel filer bypass EICAS warning, not just not responding at idle. The heat management system (FCOC/ oil heat exchanger) preheats the fuel to prevent fuel waxing on the engine to prevent FMU torque motor problems.

EMI interference is another remote possibilty but then again i've used company mobiles during turnrounds and engine runs and they never even make the lcd's blink let alone interact with the current couplers!

Either way the flight crew had no time to troubleshoot or even work out whats going on so forget gliding angles, flap position and gear up/down and just commend them on bringing the airframe to a halt with no loss of life.

[Going Boeing]

A CFM powered B763 would struggle to get airborne - I believe that you mean a GE powered B763.

My understanding is that the B777 has an autothrottle for each engine which means that you have the assistance of an autothrottle during engine out manoeuves. It is considerably different to the B767 system.

[blakkekatte]

Double Zero, in post 201 asks As no answer publicly known - why allow similar a/c to fly ? A less cynical response than that of Zorst in post 203 is that, a risk management approach to the question would first consider the likelihood of a similar incident occurring again in the timeframe required to determine the root cause of the accident.

Given the safety history of the 777, the length of time in service and the number of flying hours accumulated (even with the same type of engine), and the fact that this is the first time this has ocurred, the likelihood of the accident recurring in the next few months has to be extremely small.

Once more is known about the specific cause, then the risk profile will be reassessed.

[Intruder]

please recall that when you select flaps 25 in the beast Approach Idle is automatically selected. There are several other parameters for this selection but none the less this should give you a fairly rapid spool up in the event of a rejected approach or landing.
However, we do not yet know his configuration at 600'. It it possible they were at or near idle and selected Flaps25 just prior to that, i.e., after the "160 at 4" gate, and the throttles "failed to respond" after configuring and decelerating? Indeed, if the Pilots were at flight idle instead of approach idle, the lack of response could be a bit alarming...

[NSEU]

"The engines seem to have stopped in a staggered fashion the left seems to have been rotating more than the right. what does this indicate?"

Maybe that one landing gear collapsed before the other one did?
:{

If the fuel came from a contaminated source in Beijing I would have thought that it was likely that one or more aircraft could have used that same contaminated fuel source and sufferred engine malfunctions as a consequence?

Maybe only one dead donkey fell into storage tank that day? Our Airbus fuel filters are frequently clogged up with Beijing's finest. A good point was raised about EICAS messages... On the 777, Cautions and Advisories are inhibited below 800' RA. A fuel fiter impending bypass appears as a Status Message (not something likely to cause concern....especially on finals). There are several stages of fuel filtering, by the way.

On the subject of those keen to ground the 777.... If it was deemed to be a pilot error.. do we ground all pilots? :E

Rgds
NSEU

P.S. I fly Flight Simulator on my days off :ok:

[denabol]

Has it been established beyond doubt that the auto throttles were armed or correctly set at the appropriate time?

[NSEU]

"I doubt whether coffee could penetrate the conformal coating of pcb's and the like, unless they are overheated."

Haven't looked at the wiring under the pedestal in a 777, but there are probably canon plug connections under the floor for the thrust lever position-sensing wiring (trying to keep it simple here for beginners). Oil and fuel get into them, so why not coffee?

However (and I'll say this again for those that weren't paying attention earlier)... there are independent circuits/wiring for each thrust lever. The chances of coffee getting into two different plugs at the same time and causing the same type of failure is rarer than...... 777 accidents.

...and hey, don't they have coffee cup holders on BA 777's??? (They do on their 747-400's). :ok:

(Edit) After further checking. The thrust lever position resolvers/wiring are mounted at opposite ends of the very wide assembly under the cockpit floor. The resolvers are not separated merely by the width of the thrust lever knobs. In each resolver, there are two channels (two sets of wiring) which feed the A & B channels in each EEC (fuel control computer on the engine)

[Yankee Whisky]

Someone pointed out the need for more detailed information and I totally agree.
Let us wait for the findings of blackbox and pilot information from an investigation team before starting to speculate the cause.
All options are open and that is some too many.:ok:

May I suggest that any technical information is always welcome, such as A/T use on approach, fuel control systems and computer/human decision making. Oh Man!, wasn't the DC3 "simple" in comparison? Maybe, this "simple" fact should be included in the KISS approach to design.

[SaturnV]

Intruder, if Flight International is correct in saying they were late with the gear, is it not then possible that they were late at the 1000ft gate (configuration wise) and matters got sticky from there.

You Gomboid (in the closed thread) stated that BA SOP (and I'm summarizing) is:
> have gear selected down by 2000ft RA (radio altitude=height above the ground)
> with concurrent selection of flap 20 and 55% N1 (offset 15 knot loss of speed)
> at 1500ft RA, select final flap setting of flap 25 (with small increase in thrust)
> by 1000ft RA, be configured in the final stabilised approach
> at 500ft RA, if not in correct configuration, profile, and speed fly a go-around.

The N1 number at 600ft may speak volumes.

[NSEU]

Let us wait for the findings of blackbox and pilot information from an investigation team before starting to speculate the cause.

Not sure that I agree... I know a lot more about 777's as a result of these PPRuNe threads than I did a few days ago because of the theories proposed here. Questions have been raised that I, personally, didn't immediately have an answer to... until I went back to my manuals (or until one of the more knowledgeable forum members responded).

Albeit maddening, it is a learning process.. Unfortunately, some of us don't take on information as easily as others ;)

Let's hope the FDR/CVR have the answers... but as someone already mentioned, it may not have what we are looking for. The FDR may tell us what was happening to the aircraft, but not necessarily why it was doing that. However, hopefully it should reduce the variables :ok:

Rgds.
NSEU

[Intruder]

Intruder, if Flight International is correct in saying they were late with the gear, is it not then possible that they were late at the 1000ft gate (configuration wise) and matters got sticky from there.
I haven't read FI. Is there a copy of the article on line somewhere that doesn't require a login?

That is, though, one plausible scenario...

[PAXboy]

KC13577I've been told- that much condensation was found to be in the E&E compartment...Would that be seconds after the a/c came to a halt or an hour later after all the good work by the fire crews? Ten hours later? After the local rain?

Serious questions (I hope) from a pax.
1) Based on a standard approach that follows expectations: from the moment that the engines where required to spool up for touch down - How much time elapses? So, for this crew, from the moment that they knew something was wrong, to hitting the deck - How many seconds?

2) Many have commented on the physical strength of the Triple and that this was a factor in ensuring no loss of life and that the hull could be picked up in one piece. Will the Dreamliner be made in the same way? Or are they moving more towards plastics and composites?

[grumpyoldgeek]

Speaking as an electronics engineer with a bit of aerospace experience, I would first suspect the physical components between the thrust levers backwards to the place the two signals fan out to the engines. From what I've read, if the EEC is disconnected from the thrust lever the engine will soldier on at it's current thrust level. In that case, one plausible scenario would be that the thrust lever assembly became either functionally or physically separated from the EEC's. This might happen if the thrust lever resolvers shared a common power supply or the box connected to the thrust lever resolvers had common power or clock circuitry. In the physical realm, I'd look for a broken cable or connector that carried the signals to both engines.

[realtime_it]

Thought I'd pitch in with some general observations concerning realtime software development in such systems such as boeing 777 avionics, honeywell aims, autothrottle and fadec (I've not worked on these systems but know of them).

Firstly all realtime software is based on modelling. Your software is only as good as the model you have developed.

Very simplistically the model need to do two things. It needs to simplify the complex outside world into an internal representation that is 100% predictive within the expected boundaries of the inputs AND the expected way that various input ranges should work together. i.e. As one set of inputs is moving up the model expects another set of inputs to be moving down, perhaps with a lag, because this is what is physically happening in reality.

The second part of modelling is making the model fault tolerant or fail safe. This is where you try to analyse all possible failure modes (of the inputs) to ensure that your output is still appropriate to the task in hand.

Simplistically this whole model is captured as a specification, testing is done against specification, in the 777, 99% of the code used ADA programming language. ADA's strength is that it you can enforce expected input and output boundaries on functions/procedures/methods and capture programming logic errors on this basis. In other words after completing testing and certification you can be sure your software is 99.9999% accurate to the specification, and adheres accurantely to your model.

The largest problem, by far, for realtime software, is where the inputs fail in such a way that they still provide data that is within the expected range for the model. The software's ability to control is now VERY dependant on whether this particular failure mode, has been anticipated, in the second part of the modelling process explaination above. If it has not been anticipated then this is where the software starts to make bizarre choices in terms of controlling the output.

I believe, IF it is a software problem, it will be due to inputs from measuring devices that have partially failed.

In basic terms my understanding of auto-throttle ->AIMS->fadec process is as follows.

Physical throttle settings in the cabin -> read by auto-throttle module in the honeywell AIMS system -> processing based on internal model -> specific thrust request command to the fadec -> fadec compares request to current measure/calculated thrust - > fadec adjust thrust accordingly.

Even where the auto-throttle is turned off, the auto-throttle module is still doing the interpretation of the manual throttle settings.

When autothrottle is turned on, the auto-throttle makes DIRECT request to be FADEC (via hardware buses) for appropriate thrust based on its calculations, and the auto-throttle THEN sends a signal to the physical throttle servos to move the physical throttles in the cabin for feedback to the pilots.

Each engine has its own FADEC. The auto-throttle would appear to be working within its model, as the pilots have reported that auto-throttle detected lower speed than set, and requested additional thrust, and communicated this to the pilots via the physical movement of the throttles in the cabin.

AIMS connection to each fadec is via dual bus channels. I find it hard to believe both channels to both engines failed simultaneously (that's four channels failing at once).

Reports from the captain said that half the displays blanked. This would be consistent with a loss of electrical generating power from the engines. On detecting a power loss, the system switches to battery, cuts all unessential systems (i.e. only one set of displays), and commands the APU to start. Once the APU starts and stabilises voltage (30sec- 1minute) the non-essential systems should restart.

IMO the blanking displays is part of the engines spooling down past idle, not the cause of the engines spooling down.

Loss of electrical generating power from both engines would only occur if the electrical power management unit completely failed - as per the qantas flight going into Bangkok earlier this month - or if both engines spooled down past idle.

Given what we know about the engines, it seems clear the engines spooled down past idle, causing the power failure and not the other way around.

Loss of communication between the AIMS and both FADECS, i.e. multiple bus failure, would not cause this. Loss of power to the AIMS system would not cause this. In simple terms the FADECS proceed with the last thrust command until commanded otherwise.

I do not know what unit commands the fadecs to turn-off the engines. But that request will be so tightly predicated, for that to happen, literally hundreds of inputs that confirm that the plane is on the ground would have to be met. I don't believe that this command could be sent accidently by the software or through a modelling error. (Reset, restart, dealing with flameouts, if not dealt automatically by the fadec, would be a different set of predicates, but the same meticulousness would still apply. Many conditions would have to be met to allow this command to go ahead.)

To me the areas of interest are the fadecs on each engine, the inputs to the fadec that give feedback for actual measured thrust, the fuel management system, the fuel level sensors, and the fuel.

I can't see that both fadecs would fail simultaneously. Even if physical conditions outside the plane caused, say, engine thrust inputs to falsely give a high reading, the fadec would not spool the engines down past idle, based on this.

My best guess is that it is something to do with the fuel level sensors - which I believe are ultrasonic - and would go for the subtle, swopped inputs problem, as this by definition means the model is working in the fault-tolerant area of its model.

a. Swopped inputs.

For example, Sensor for Tank A is plugged into input for Tank B. Sensor for Tank B is plugged into input for Tank A. This would cause the system to swop from a full tank to an empty tank. Obviously with more sensors and more possible combinations of swopping you can see how you could have fuel on board, yet not get fuel to the engines. Obviously the swapping could be more subtle, even a digital swopping. i.e. If a sensor unit connects to the data-bus, and the unit malfunctions and starts sending out levels under multiple valid sensor ids, you can see how this would confuse the fuel management system. Don't know if this is possible in exactly this fashion, but you can see how swopped inputs, digital or physical, can cause havoc.

[parabellum]

Thanks Going Boeing, stupid me!!!:ugh: The engines were GE??B2.

[NSEU]

This might happen if the thrust lever resolvers shared a common power supply or the box connected to the thrust lever resolvers had common power or clock circuitry. In the physical realm, I'd look for a broken cable or connector that carried the signals to both engines.

Let's put this one to bed....

#Each dual-redundant channel (A & B) of each engine EEC can supply the individual left/right thrust lever position resolvers with power (excitation).
Each EEC channel is powered by individual windings in a permanent magnet dedicated engine-driven alternator (which can function at a mere 5% N3... although some sources quote 8%). There are also independent sources of power from the main AC busses (Left Bus feeds Left engine EEC, etc) should the dedicated generators fail.

#Separate wiring with large gap between (see a few messages above) the position resolvers.

A picture is worth a thousand words... but all the pics I have are protected by copyright.

Rgds.
NSEU

(Edited for clarity)

[RatherBeFlying]

Investigations of approach accidents often include review of FDR (and QAR if available) data from the last few a/c that did the approach for comparison pupposes. If a 777 did an approach shortly before at about the same weight, contrasting the two sets of data may help identify where it started to go wrong.

[scrubbs]

have these pictures from the landing been posted yet?

a member if Anet took them and had to wait until they got them back from the authorities...

http://www.dailymail.co.uk/pages/live/articles/news/news.html?in_article_id=509646&in_page_id=1770

http://img.dailymail.co.uk/i/pix/2008/01_04/p31plane2DM_800x492.jpg

[Wingswinger]

Gatbusdriver,

A CDA is not a descent in idle, it is a continuous descent (min I believe is 500fpm) with an allowable level segment (without checking think it is 2 mile i'm sure someone will correct me).

Therefore once you are established on the glide most people will only be at approach idle to get the speed back after 4 miles, where you have invariably been maintaining 160kts.

Ergo I think CDA's have little bearing on this incident.

Thanks, but I know that. I have seen plenty CDAs which do result in a descent at idle to inside four miles, especially at LHR where the controllers will cut you in short if there is an opportunity for them to do so - just as they do at LGW. That's why I posed the original question.

[ACMS]

Well if that is a photo of YMMM on the day then 2 observations:

1/ Nose Gear Landing Lights are on
2/ No Rat deployed.

Indicates they had plenty of AC power running.


mmmmmmmmmmmm

Plot thickens..................I think it's time we called in Inspector Morse.

[ACMS]

Mate it doesn't matter, if both transfer busses were unpowered, as some suggested from a dual engine failure, then high Powered AC Landing Lights would NOT be running AND you'd see the RAT.

So they had at least one Eng AC Gen online.

Either the crew attempted to start the APU or it Auto started after the impact knocked off the Transfer Busses?

Who knows.

[squeaker]

The RAT is clearly visible (under R2) in many post accident pics, and the APU inlet door is open too.

[ACMS]

Mate have you seen what the IMPACT with the ground did to the Wheels?
It was a big impact to drive the Oleos up through the wing. The Rat is just behind the right wing and it probably "fell out" during the sudden impact Jolt.
Also the RAT's blades dont look very damageded.


As for the APU door open? Who knows? if one Engine had failed the crew may have had time to get it up and running ( it takes about 60 seconds to come up running ) If both failed at once at 600' then it would have Auto started and been "running" just as they hit the ground and no use at all.
But the photo shows Landing Lights "on" and NO RAT at 150', this means that one or both Transfer busses were powered at that time.

maybe the loss of power to the transfer busses as it hit the ground Auto started the APU and unlocked the RAT?

Basically with the Lts on and no RAT there had to be at least one of the three Jet Engines running ( Left Eng, Right Eng or APU )

[Pinkman]

When you look at all the speculation as to the cause, you need to evaluate each hypothesis by first looking for one of two things:

1. Common Mode issues (multiple systems capable of being affected by a single event) - examples are catastrophic power failure, fuel (waxing, freezing or lack of), or a commanded / not commanded event)

2. Multiple single mode (coincidental) issues where two or more unrelated and unforseen events happen, neither in and of themselves capable of causing the failure but together they can.

I suppose there are even some root causes that belong to both categories. There was a software bug in the UK ATC system (the old one) that remained dormant for years until a particular set of circumstances on a particular day bought it to the surface.

Given the redundancy in the systems some of the postulated events just dont add up. Put this post in 'silly' if you like, but if everyone used the above as a reality check before sounding off it might help.

[r011ingthunder]

I presume it is possible that something similar to the incident in Aug 05 near Malaysia involving accelerometer failure on a B777 may have happened insofar as if there were "hidden" failures already present in the aircraft, then the redundant systems or failsafes or whatever were the last line of defence and all it would take is one failure to cause a catastrophic incident?

http://www.atsb.gov.au/publications/investigation_reports/2005/AAIR/pdf/aair200503722_001.pdf

Go easy on my theory, I'm NOT an expert, just an interested enthusiast.

[alistairbailes]

From these photos the left hand engine has fan damage and the right hand has not.

http://www.militaryphotos.net/forums/showthread.php?t=127323

[alistairbailes]

LH Engine with fan damage:

http://www.flightglobal.com/assets/getAsset.aspx?ItemID=21166

RH engine without fan damage:


http://www.flightglobal.com/assets/getAsset.aspx?ItemID=21167

[Morpheme]

Would a 777 endorsed pilot be able to advise if it is possible to confuse a double electrical failure with a double engine failure. If so I see this as a possible scenario that could end up creating what we saw with this aircraft.

No, unless he can't read.

The EICAS and intuitive electronic checklist will prioritise any faults, and helpfully name the fault and direct you to the appropriate checklist.

Comparing the 737 diagnostic process with the 777 is pointless - the 777 tells you what is wrong with it, in order of priority.

The initial AAIB report also says something interesting - THE ENGINES DID NOT FAIL!

Perhaps this is the moment for all those hundreds of people on here who claim to fly triplers (I just wonder how many of them are genuine?) - and those who profess to disliking journalists - and consider the Daily Mail to be the work of the devil - to avert their eyes.

Sandbank - anything that shows BA in a bad light will be faithfully printed by the Daily Mail, regardless of its source or veracity. That might help your desire for objectivity.

[sky9]

For the problem to affect both engines it has to be either
1 Fuel
2 Ambient conditions - icing etc.
3 Software.

My guess is poor quality fuel out of Beijing, add cold soak during cruise and descent with blocked fuel filters restricting the amount of fuel to the engine. Now someone will tell me that they have fuel filter bypasses.

[alistairbailes]

For the problem to affect both engines it has to be either
1 Fuel
2 Ambient conditions - icing etc.
3 Software.

See post 267. Only ONE engine was affected. This perhaps explains the eye witness accounts of excess roll that corresponds to when power was commanded.

[Morpheme]

For the problem to affect both engines it has to be either
1 Fuel
2 Ambient conditions - icing etc.
3 Software.

My guess is poor quality fuel out of Beijing, add cold soak during cruise and descent with blocked fuel filters restricting the amount of fuel to the engine. Now someone will tell me that they have fuel filter bypasses.

:{:{:{:{:{:{:{:{:{:{:{:{:{:{:{

sky mate - read the rest of the thread(s) it might save you the trouble of "guessing".

Better still, wait for the full AAIB report and you won't have to guess at all!

[Flight Safety]

Just to sum up items noticed from the Daily Mail photgraphs, including a couple of items not mentioned yet.

1. Nose gear landing lights are on (from the approach photo)
2. Wing root landing lights are on (from the approach photo)
3. The RAT is not deployed (from the approach photo)
4. The APU inlet door is not open (from the ground impact photo)