BA 777 landing accident at LHR

[Dmmoore]

The suggestion on FlightGlobal was contamination that froze solid at altitude, then thawed and remixed on descent, at which point it constituted a much higher percentage of the remaining contents.

Absolutely no idea if that's remotely plausible.

It is plausible, just but plausible.

[FlyingPhotog]

Autobrakes triggered before touchdown for some unknown reason?

Do you mean thrust reversers?

[Jorge]

It is plausible, just but plausible.

Hmm, your answer sounds like a Myth Busters episode.

[FlyingPhotog]

The YouTube crash video link no longer works, does anyone have a working one?

[aardvark2zz]

What's a power panel ?


......Inquiries by the Air Accidents Investigation Branch appear to rule out any form of pilot error in the approach for landing. One area of specific interest will be the electrical system after it emerged yesterday that there had been at least 12 serious incidents of overheating, causing "major damage" to power panels on at least four occasions.

The initial findings of investigators are based on interviews with the pilots and analysis of the black box flight recorder and cockpit voice recorder......

http://www.dailymail.co.uk/pages/live/articles/news/news.html?in_article_id=509163&in_page_id=1770&ct=5

[Dmmoore]

Hmm, your answer sounds like a Myth Busters episode.

Exactly. It only works when everything else is proven operational.

[AJ]

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.

http://www.aaib.dft.gov.uk/latest_news/accident__heathrow_17_january_2008___initial_report.cfm

This does not signify an autothrottle fault as all the system does is drive servos to drive up the thrust in lieu of the PF's hand!

There have been issues on our aircraft of lack of thrust response to more than one engine but fortunately it has always been in cruise flight and only in GE powered aircraft.

A double failure of RRs has me stumped.

[Cam]

^AJ, in those cases...what was determined to be the problem?

On a modern 777, how are the actually throttles connected to the engines? What is the "line of command" from where the crew puts their hands on the levers to the unit in the engine that adjusts the fuel and air mixture.

(Think about a throttle in a car, that's what I'm getting at)

[Gulfstream]

Few possibilities ...

After the first report, I was thinking it had to be windshear ...

Now, it seems like it is either a software issue, a massive bird strike, or fuel contamination.

Hopefully it's not a software issue ... unlikely given the 777's flawless record. Fuel contamination would be interesting.

[aardvark2zz]

After the first report, I was thinking it had to be windshear ...

Now, it seems like it is either a software issue, a massive bird strike, or fuel contamination.

Hopefully it's not a software issue ... unlikely given the 777's flawless record. Fuel contamination would be interesting.

Say what !? Read the following. Very interesting programming bug !

See Fig 1. and previous text.

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

excerpt

Testing, disassembly and examination of the ADIRU
--------------------------------------------------

........confirmed the presence of faults in two internal accelerometers8 and one ring-laser
gyroscope9 (gyro). It was determined that the ADIRU’s accelerometer number-6
failed at the time of the occurrence, and that accelerometer number-5 failed in June
2001, but was still capable of producing high acceleration values or voltages that
were erroneous

10. The component manufacturer reported that a search of all field
history records showed that there were a total of four other occasions when two
accelerometers had failed in other ADIRUs of the same type. None of these cases
resulted in reported erroneous output, indicating that the accelerometer hardware
failure modes in these cases had not produced similar high accelerometer
value/voltage.


Further investigation revealed that the conditions necessary for the occurrence were
(figure 1):
– an accelerometer failure producing high value/voltage output
– the ADIRU excluding that failed accelerometer from use in its acceleration
computations
– power to the ADIRU cycled (system reset)
– a second accelerometer then failing and the latent software anomaly allowing
the ADIRU to once more utilise the previously failed accelerometer
information with its high output values in its computations, resulting in
erroneous acceleration outputs into the flight control outputs but not the
navigation (ground speed, velocity, position, etc.) outputs.

Figure 1: Component event flow chart

June 2001, accelerometer
#5 fails with erroneous high
output values, ADIRU
disregards accelerometer
output values

Power Cycle on ADIRU
(occurs each occasion
aircraft electrical system is
shutdown and restarted)

August 2005, accelerometer
#6 fails, latent software
anomaly allows uses of
previously failed
accelerometer #5 output.

9M-MRG upset
event




.

[aardvark2zz]

Transcribed the following from Jay Leno's Friday night monologue and closed caption: Not my errors.

And yesterday they had a big crash landing in London with a 747, lucky nobody was killed but, you know I heard a guy from the FDA say that's not good enough for us, we're not gonna rest until we've reached our goal of 0 plane crashes, that's our goal 0 plane crashes, and everybody applauds......

well of course 0 is the goal.

What are you gonna say ?? We just want 1 big crash a year, that's all we want, give us 1 huge crash and were fine.

.

[Shorrick Mk2]

The problem is an engine at idle thrust (as these would be before the engines contacted any damage that stopped them) would not shop very much blade damage. The photo proves the engines were not operating at high power and that's about all.

True - however if APU autostart happened (which was a suggested possibility based on the APU intake being open) would that not indicate that the engines were not at merely idle thrust?

[turbotraker]

A double failure of RRs has me stumped.

Just out of interest AJ, if this was 747 or another 4 engined aircraft, how likely would it have been that all 4 engines lose power? Just wondering if there was any truth in Richard Bransons claim of 4 engines vs 2?

Murt

[L1011]

^AJ, in those cases...what was determined to be the problem?

On a modern 777, how are the actually throttles connected to the engines? What is the "line of command" from where the crew puts their hands on the levers to the unit in the engine that adjusts the fuel and air mixture.

(Think about a throttle in a car, that's what I'm getting at)

Electro-mechanical ( mechanical - electro ... ) link to a solenoid

[SammyG]

I'm gonna throw this out there, admittedly having no idea what I'm talking about, on the 1 in a million chance I turn out to be right.

They will determine that someones cell phone onboard somehow caused the engines fuel cutoff valves to be commanded closed.