Here was me thinking the Telegraph was a respectable newspaper :yuk:

Reading the report, specially this part:
they owe a lot to keeping the autopilot on (and its design as well)!
That way all possible energy was used up to its full extend, bringing the aircraft within the airport perimeter.
I don't think a human could have done it better, probably not, as a pilot would have unconsciously lowered the nose.

Cavitation
 

Can someone explain how 'evidence of Cavitation' in the HP fuel pumps is being considered here?

Is it that the pump is trying to pump from an obstructed source causing bubbles (cavities) in the fuel or that there is evidence that the pumps are physically damaged?

What will be the evidence of cavitation? assuming THIS is a good explanation of such?

:confused:

As observed in an earlier post, all aboard were unbelievably lucky that BA038 ran out of lift where it did, landing on the only bit of waterlogged lawn within miles of their approach path.
I am sure that the 2 pros flying that sector were trying to get it onto 27L, which in the circumstances would have likely had a much more injurious outcome.

http://edition.cnn.com/2008/WORLD/eu...ef=mpstoryview


What was it then if not mechanical?

Evidence of cavitations would be small pits on the tips of the impeller blades of a certifugal pump, and in other key places of the pump (depending entirely on the design).

The pits are caused by the rapid collapse of bubbles.

Bubbles can be caused not only entrained air (such as a seal leak) but also when the fuel vapourises (ie. 'boils') at partial vacuums.

The report does not say that cavitation caused the problems, nor does it say when it occurred, It could have occurred at any time from new, up to the time of the crash.

Cavitation in itself does not cause a problem unless there is failure of the components themselves as a result of it, or unless the effects of cavittion causes a significant degradation of performance.

Cavitation however is a symptom of a choking of flow on the inlet of a pump, or the entrainment of air.

An example of cavitation could be the addition of a lighter solvent in the fuel which vaporises at a lower temperature than the bulk of the fuel. The suction pressure of the pump could cause the vaporisation of the additive and so cause vapourisation. The report does not report fuel contamination so this can be ruled out.

Another example of cavitation is when a restriction which is on the discharge side of the pump is suddenly taken away - the suction flow just cannot keep up, the pressure drops and cavitation occurs.

At this point I still go for: failed seals due to low temperature, then regaining flexibility on loss of altitude, then entraining air and causing foaming.

Cavitation..????
 

Mind the following information given in the report:

I sense Trolls in here.

I don't care whether the autopilot was left in deliberately or not, - it worked.

I do however know far too many professional pilots who believe they can do better than the automatics, usually wrongly!

I wasn't really getting at fuel waxing/freezing in my previous post......I was more thinking along the lines of water Hygroscopicly suspended in the fuel freezing somewhere in the system during the flight.

However all this is pure speculation at this stage.

At least all that garbage . . . . .
 

QUOTE: "BoeingMEL wrote: "............ at least all that garbage about EMI can be buried..... as can fuel exhaustion, windshear, finger trouble, Gordon Brown's heavies..."

To be fair, the report doesn't appear to rule any of that out...

Until the investigation is concluded anything is a possibility!" UNQUOTE

Exactly. Nothing can be ruled out at this time. Reading the report the investigators apparently are confronted with evidence of a normal functioning machine, which for a short period of time did not function normally. In other words, perhaps an intermittent failure of some kind, at this time not yet duplicated.

To quote the report: "The recorded data indicates that there were no anomalies in the major aircraft systems."

Question is then, what could have failed that is not recorded?

Regards,
Green-dot

i smell trouble ahead and no one rightly is going to stick their neck out and rightly till the final report is issued.:ouch:

No Fault Found.

Hmmmm.

The cavitation damage and some FOD in the tanks is not much to go on!!

So there was fuel in the tanks, the metering valve was fully open, and the pump was capable of supplying fuel.

:confused::confused::confused:

This would seem to suggest that the correct signals were getting through to both engines and the engines were trying to respond accordingly. Apparently no other as yet significant defects have been found.

Does this therefore narrow down the possible cause to a momentary absence of liquid Jet A1 under pressure at the burners?

I am totally speculating here, but given that air temperatures were lower than Jet A1 freeze temperature, and even though the tank temperature never got to critical levels according to instrumentation, would it be possible for a deposit (perhaps like cardiac plaque in arteries) of wax or frozen fuel to form somewhere in the fuel pipework?

As it warmed such a plaque could let go, blocking a filter and perhaps giving an engine the mechanical equivalent of a heart attack?

Of course that idea stretches credibility because it had to happen to both engines within seven seconds of each other, there was no EICAS message about clogged filters and it may be physically impossible to put a skin of frozen wax on the inside of a pipe thats carrying -34C jet A1.

No more speculation from me till the next official report.

Re: The Fire Swith does close the Spar Valve!
 

Perhaps worth noting that this was only the case on one wing, on the other side (as I read the report) both paths to the valve were cut by the damage, so no action would have closed it.

Sorry if this sounds oversimplified, but if the tanks had enough fuel, the EECs responded correctly to the request for more power, the fuel metering valves were wide open, and the HP fuel pumps were probably cavitating, then it seems reasonably clear to me that something was probably blocking the fuel flow.

Common mode failure.