In a podcast uploaded to YouTube in June, Mr Leeward said major changes were made to the plane before this year's race. He said his crew cut five feet off each wing and shortened the ailerons — the back edge of the main wings used to control balance — to 32 inches, down from about 60 inches.
I just heard about that, too. That changes everything about the crash scenario.
Cut 10 feet off a Mustang's wings and you've reduced wingspan by more than 25% and probably cut wing area by about the same amount. That means higher stall speed and more vulnerability to high speed stall. Cut back the ailerons and you've reduced maneuverability and ability to recover from a stall by a big chunk, too. Tune the engine up to the Nth degree, replace the standard cooling system with a bleed-off system where one of the fuel tanks used to be, and basically, you've got a plane that's really good at going around an oval at high speeds for 500-1000 feet for 20 minutes, but isn't much good for anything else. Take that plane out of the parameters it was designed for disaster is going to happen.
My new ignorant hypothesis: Leeward wasn't dead as he half looped, but he might has well have been. He was OK going into Turn 3, then something fixable but bad happened. Perhaps the elevator trim tab came loose, perhaps something in the coolant system blew up. That made it impossible for him to complete his turn, as his plane couldn't turn sharply enough.
He completes 45 degrees of a 90 degree turn, flies over the stands and begins to pitch up in a half roll (due to loss of elevator authority?). Then, perhaps he got disoriented at the top of the roll, underestimated his altitude or suffered the beginnings of GLOC. He then tries to roll out of the half loop to get back to the airport, forgetting that he's got limited elevator control and altitude and his speed is too high.
At that point, he might have gotten into a high speed stall and dived into the ground because he had too little altitude to recover. Given the speed and the g-forces involved, I don't think that there's much Leeward could have done to alter his path to avoid hitting the stands.
Normally, vapor coming off the wingtips would be telltale evidence of a stall, but given the low humidity in the desert there probably wasn't enough moisture in the air to condense.