PPRuNe Forums - View Single Post - Qantas A380 uncontained #2 engine failure
Old 5th Nov 2010, 14:55
  #392 (permalink)  
WillDAQ
 
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There's a 747 thread for the 747 incident.

malcolmyoung a few posts back mentioned the risk of people on the ground in Bintan being hit. Bintan is 2,400 square km with a population of about 200,000. If one guesses the hazard zone for falling debris at an exceedingly conservative 1 square metre, the chance of death or injury from one compact piece would be less than 1:12,000. The risks of falling debris to people on the ground are negligible except near to major cities one would have thought, Lockerbie being a dreadful exception. I'll let others comment on the risks to folks on the plane, but thankfully looks like they were in the safest possible hands...
One of the of the key tenets of civil aviation safety is that you're not allowed to injure people on the ground. Passengers are to an extent expendable, they signed up to fly on the thing and there's an understanding in the public consciousness that sometimes things go wrong on aircraft. Yes the airlines have a liability, but it is to some extent reduced.

However, people on the ground getting hit by debris from above is essentially unlimited liability.

There a load of What If's...and unfortunately each of those What If's have a cost associated with them. I bet that if you were the bean counter on a plane in trouble, you would be having second guesses about what you didn't agree to as necessary to spend on a back up system if it would have helped you in the situation you are in.
It isn't simply a question of saving money, every extra system adds weight and complexity which simply leads to more stuff to go wrong. The cost of an airliner is a secondary effect of the technology it contains. But the technology is picked based on how effective it is rather than how much it costs.

If it were me on the plane I'd know that the fact the aircraft was still in the air after a disk failure meant that the worst of the risk was already passed.

I think as well, in this case, they had a part of the engine that they thought they would not need to contain, but it failed.
OK, lets try this again...

A TURBINE DISK FAILURE IS EFFECTIVELY UNCONTAINABLE

Which is why it's designed not to break in the first place. All of the discussion about the damage it caused to other systems is irrelevant. The reason the aircraft gets certified is on the basis that it won't fail in the first place!
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