Originally Posted by
infrequentflyer789
I think (if I understand tdracer right) this particular risk analysis is for debris from one engine impacting the other engine - if it has enough energy to go through the engine and take out the FADEC then both engines are toast anyway, but if it only has enough energy to get to the inboard side and do a little damage, it might be better if it didn't hit the FADEC. But not, in the end, better enough to justify building left and right engines.
Thank you infrequent - that's exactly what I meant. If debris from one engine had enough energy to penetrate
through the opposite engine to take out the FADEC or other engine critical system, it didn't matter because the opposite engine was already dead.
You can protect for low energy debris - blade fragments and the like. But when you start talking 1/3rd disc from an engine operating at high power, it's simply not feasible. You're talking
inches of armor plate to do any good (and you can't assume a perfect tangential trajectory - I think the range was 5 degrees for high energy debris - so you need to protect a rather large area). I used to work with a couple guys that had worked in the old Boeing turbine division (that's right, Boeing used to make small turbine engines back in the 1960s) that showed me pictures of the damage to their test cell due to a rotor burst - went through armor plate
and a brick wall - and that was just a little APU sized turbine.
I'm surprised the FAA allowed their personnel to be quoted in that NYT article (or even talk to the press - even off the record) - particularly during an active investigation. However I knew and worked with at least one of the quoted FAA engineers and I
wasn't impressed - classic paper pushing box checker who couldn't see the forest for the trees - couldn't judge if something was safe and compliant, only if they could check their box.