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Inspector Sands13,820 posts since 25 Aug 2004
Jonathan H posted:

Forgive me. I know I'm being picky. Heathrow is the world's busiest international airport. There. I feel better now. Wink


It's a hotly contested title but can be interpreted in several ways: http://en.wikipedia.org/wiki/World's_busiest_airport
Atlanta is the busiest and the biggest - absolutely huge

Incidently in terms of flight technology and indider information, the forum to look at after such incidents is the Pilots Professional Rumour Network: http://www.pprune.org/forums/ unfortunately it's a little busy at the moment!
noggin14,535 posts since 26 Jun 2001
Jonathan H posted:
Markymark posted:
It was, but keep an open mind still. It may have simply just run out of fuel, in which case that puts a quite different perspective on the event.

It's extremely unlikely that it ran out of fuel. There would have been emergency services waiting, the runway would have been cleared for the inbound flight, ground controllers would have been alerted and much more of a sense of a 'managed' crisis, rather than the apparent bolt out of the blue that seems to have occurred yesterday.

There have been incidents in the past where pilots have been unaware of their low fuel status because of a fault in the indication syste, - or have been unable to believe their fuel indicators because they don't make sense. AIUI most modern airline control systems now compare fuel measurements with fuel estimates, as a discrepancy between the two can imply a fuel leak, but this isn't universally the case.
Jonathan H837 posts since 17 May 2004
noggin posted:
Jonathan H posted:
Markymark posted:
It was, but keep an open mind still. It may have simply just run out of fuel, in which case that puts a quite different perspective on the event.

It's extremely unlikely that it ran out of fuel. There would have been emergency services waiting, the runway would have been cleared for the inbound flight, ground controllers would have been alerted and much more of a sense of a 'managed' crisis, rather than the apparent bolt out of the blue that seems to have occurred yesterday.

There have been incidents in the past where pilots have been unaware of their low fuel status because of a fault in the indication syste, - or have been unable to believe their fuel indicators because they don't make sense. AIUI most modern airline control systems now compare fuel measurements with fuel estimates, as a discrepancy between the two can imply a fuel leak, but this isn't universally the case.

True enough, but the fact that a "considerable" amount of fuel was spilled from the fueslage and wings on impact would seem to largely discount that theory. It'll be fascinating to see what the problem turns out to be. I'm intrigued as to why, if the crew have been preliminarily cleared of fault, why all 777s haven't been grounded or at least checked over?

And if I understand the fuel tank configuration correctly, both fuel tanks running dry at exactly the same time? Weird.
Jonathan H837 posts since 17 May 2004
noggin posted:
There have been incidents in the past where pilots have been unaware of their low fuel status because of a fault in the indication syste, - or have been unable to believe their fuel indicators because they don't make sense. AIUI most modern airline control systems now compare fuel measurements with fuel estimates, as a discrepancy between the two can imply a fuel leak, but this isn't universally the case.

In fact, having just read the AAIB preliminary report, it makes no mention of either engine shutting down (as would be the case if the fuel had run out), but merely that

AAIB posted:
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.


It's not explicit, but it implies not that the engines shut down completely, but that they failed to provide an increase in thrust required to make the runway. Stranger and stranger!
Davidjb1,510 posts since 23 Mar 2001
Jonathan H posted:
noggin posted:
There have been incidents in the past where pilots have been unaware of their low fuel status because of a fault in the indication syste, - or have been unable to believe their fuel indicators because they don't make sense. AIUI most modern airline control systems now compare fuel measurements with fuel estimates, as a discrepancy between the two can imply a fuel leak, but this isn't universally the case.

In fact, having just read the AAIB preliminary report, it makes no mention of either engine shutting down (as would be the case if the fuel had run out), but merely that

AAIB posted:
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.


It's not explicit, but it implies not that the engines shut down completely, but that they failed to provide an increase in thrust required to make the runway. Stranger and stranger!


I would say engine failure is definately not to blame. Reason i say this is because if the two power turbines did shut down it would be very evident by reduced noise in the cabin areas (you would hear them whiring down). The chances of both turbines failing is almost un-heard of. Im guessing here that something went very wrong with the engine management software which instructs the turbine to spin faster etc. By the sounds of it the engines were in idle or very close to idle which is common for landings, but when a request for power was sent from the autothrottle system something didn't work. B-777's are completely fly-by-wire and maybe what we have just seen is the first B-777 f-b-w system fail at its most critical point!
Markymark7,063 posts since 13 Dec 2004
noggin posted:

There have been incidents in the past where pilots have been unaware of their low fuel status because of a fault in the indication syste, - or have been unable to believe their fuel indicators because they don't make sense. AIUI most modern airline control systems now compare fuel measurements with fuel estimates, as a discrepancy between the two can imply a fuel leak, but this isn't universally the case.


The most famous recent case is this:-

http://en.wikipedia.org/wiki/Air_Transat_Flight_236
noggin14,535 posts since 26 Jun 2001
Jonathan H posted:
noggin posted:
Jonathan H posted:
Markymark posted:
It was, but keep an open mind still. It may have simply just run out of fuel, in which case that puts a quite different perspective on the event.

It's extremely unlikely that it ran out of fuel. There would have been emergency services waiting, the runway would have been cleared for the inbound flight, ground controllers would have been alerted and much more of a sense of a 'managed' crisis, rather than the apparent bolt out of the blue that seems to have occurred yesterday.

There have been incidents in the past where pilots have been unaware of their low fuel status because of a fault in the indication syste, - or have been unable to believe their fuel indicators because they don't make sense. AIUI most modern airline control systems now compare fuel measurements with fuel estimates, as a discrepancy between the two can imply a fuel leak, but this isn't universally the case.

True enough, but the fact that a "considerable" amount of fuel was spilled from the fueslage and wings on impact would seem to largely discount that theory. It'll be fascinating to see what the problem turns out to be. I'm intrigued as to why, if the crew have been preliminarily cleared of fault, why all 777s haven't been grounded or at least checked over?

And if I understand the fuel tank configuration correctly, both fuel tanks running dry at exactly the same time? Weird.


I wasn't suggesting that running out of fuel was the cause - just that you can't always jump to conclusions that it wasn't. There have been cases where rebalancing fuel tanks have caused major leak issues - if one tank is suffering a leak, and you pump fuel from another to it to rebalance, then you can empty more than one tank. Not saying it was the cause in this incident - sounds very unlikely that it was.