Saturday, 26 July 2008

Qantas Boeing 747

Holy guacamole.

TimesOnline: The aviation experts say the terror could have been caused by a bomb.

Sure, baby. Could you please check if Osama's name shows up on the passenger list?

New York Times: Federal investigators say the accident was caused by metal fatigue, exacerbated by corrosion caused by salt water.

That's a weird location for fatigue to occur, though. It looks like the secondary structure is damaged, and not the primary.

A whole load of strain and pressure usually isn't likely to cause damage of that magnitude. However, corrosion has some nasty tricks up its sleeves.

I wouldn't want an insight into the thoughts of the Licensed Aircraft Maintenance Engineer who signed it off as airworthy before it took off. It's a very unpleasant position to be in.


walla said...

Any comments on the maintenance regime of AirAsia that's actually being followed? Anyone?

This question could be crucial.

Crankshaft said...

Hehe. You're fishing. I don't work for AirAsia, so I wouldn't know. Stuff like that is highly confidential.

But they have a fleet of A320s to replace the B737s.

jugular said...

More pics in today's SMH

and the article refers to an aviation blog talking about corrosion being found on that aircraft when it was in for a recent cabin fit out.

The Times say it could have been a bomb. That paper went downhill when the Dirty Digger took it over. Pretty lousy bomb to cause that sort of damage.

Corrosion or fatigue is more likely. The wing leading edge fillet fairing is missing but there's also a hole in the fuselage skin. Fairings tend to be composite (glass fibre) and are secondary structure. Also not susceptible to corrosion or fatigue, although I don't know the details of a 747. My guess is that the fuselage failed first and the depressurisation then blew off the fairing.

It'll be interesting to see what the investigators find.

Crankshaft said...

Well, I found the bomb reference hysterical. I could do better with nitro-fertiliser. But I guess 'bomb' sells the paper.

I was looking through my personal 747 libraries (sometimes, it pays to go to all those airshows on trade day and shamelessly ask for brochures) to find the components between the leading edge and fuselage.

Initially, from experience those parts are composites and not metallic. But then the B747 was designed really long ago, and it's possible that they're metallic after all. That would explain the fatigue.

We don't really check the composites for fatigue. But their very prone to corrosion, thermal expansion and whatnot.

Crankshaft said...

Oh great.

We get blamed for poor MRO services now?

Don't tell me the LAME is Malaysian?

missjolie said...

Did this Qantas 747 take-off from KLIA? Malaysian ground engineers at KLIA used staples to secure the gap earlier I believe. :P

Crankshaft said...

Nope, the B747 didn't come anywhere near Malaysia. Never been serviced here, even!

Bloomin' creeps, they were trying to shift the blame on us.

And it was most likely a can of aerosol - insect repellent or hairspray.

jugular said...

I wouldn't say that composites are prone to corrosion, quite the opposite (which is one of the reasons for the push on 787 for a composite fuselage (all that water vapour from passengers condensing on the cold fuselage skin and corroding it). Where it is in contact with some metals, particularly aluminium alloys, there can be corrosion due to the difference in dieletric constant but that happens to the metal not to the composite.

Oh and don't pay much attention to the Herald Sun. It's another one of the Dirty Digger's I believe. :)

Crankshaft said...

No, they're not corrosive - composites, that is. I don't know what I was smoking then. :) My sentence is broken. I can't remember what I was going to say after "their..."

My question: Are composites just as good without a primer? I remember huge discussions on weight-savings before overturning it and proceeding with primer on BOTH sides of the composite panel. You remember which project I was based on previously, don't you?

Remember how Airbus started using composites and then Boeing, which was initially skeptical, suddenly became more gung-ho about it with the 787? I just remembered it and found it amusing.

Crankshaft said...

I gotta ask. Who is dirty digger?

walla said...

it could have been an oxygen cylinder in the cargo hold...

jugular said...

The Dirty Digger is Rupert Murdoch, owner of some soft pr0n rags such as the Sun and News of the World.

Crankshaft said...

walla - so I hear. I wonder if it's standard procedure to keep one in the cargo hold or if some diver brought it in.

jugular - he of the dual citizenship. :)