When that struck, the skid was thrust up into the belly of the airplane, and the magnesium ignited. It produced a fireball that enveloped the tail of the airplane, and ended up burning off the last 25' or so of the underside of the airplane...skin, stringers, etc.
Are you sure you were not hit by an
RPG?
I routinely machine magnesium components in my workshop... made various things for my TB20 out of it. Lightweight conrods really do up the power... Anyway, lots of "experts" told me that the stuff catches fire really easily when being machined.
Well, being really a big kid who loves setting things on fire, I tried to set fire to some magnesium.
It's amazingly hard to do, especially with a thick section. You have to get a blowlamp (an oxy-acetylene welding torch works better but I don't like wasting the gas) and you have to get at least a corner of the component bright red hot. With a hi-temp blowlamp (the one which uses a propane-acetylene mixture; yellow bottles rather than blue bottles) it takes about a minute to set fire to a piece of magnesium.
It's quite impressive after that, though...