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AAIB initial report out on BA B777 crash at LHR

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AAIB initial report out on BA B777 crash at LHR

Old 20th Jan 2008, 04:06
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AAIB initial report out on BA B777 crash at LHR

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.
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Old 20th Jan 2008, 06:52
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Thumbs up FDR

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.
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Old 20th Jan 2008, 07:00
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Auto throttle

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

OJJ
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Old 20th Jan 2008, 07:08
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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?
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Old 20th Jan 2008, 07:18
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So it's all about loss of throttle control at the moment.
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Old 20th Jan 2008, 07:27
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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
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Old 20th Jan 2008, 07:27
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-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.
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Old 20th Jan 2008, 07:30
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Thanks SuperRanger and ETOPS Jock

Clear and concise.
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Old 20th Jan 2008, 07:36
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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?
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Old 20th Jan 2008, 07:41
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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.
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Old 20th Jan 2008, 07:49
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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.
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Old 20th Jan 2008, 07:55
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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.
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Old 20th Jan 2008, 08:02
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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...
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Old 20th Jan 2008, 08:03
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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.
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Old 20th Jan 2008, 08:13
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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

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

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

NoD
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Old 20th Jan 2008, 08:20
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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

NoD
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Old 20th Jan 2008, 08:26
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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!

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
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Old 20th Jan 2008, 08:29
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Non Technical Issues

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 ďAny embarrassment at unnecessary brace position will be short lived, death is permanentĒ
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; letís not rely on luck for high survival rates.

Last edited by Giant Bird; 20th Jan 2008 at 08:37. Reason: Spelling
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Old 20th Jan 2008, 08:30
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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

J
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Old 20th Jan 2008, 08:42
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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
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