[427TJ]

This is only speculation based on watching a video of the mishap.

The lead Mustang, a heavier D-model, landed on-speed and began to decelerate immediately. The wingman, a lighter A-model, was high on the approach and at the last few seconds lowered the nose to land in formation. In lowering the nose, the wingman P-51A accelerated and began to overtake the leader. The leader, with a larger four-blade prop that makes more drag in idle than the A's smaller 3-blade prop, was already decelerating at a faster rate and the A rapidly overtook the D. The A pilot may have kept his power in a split-second longer and that would have exacerbated his developing overtake problem. By the time the wingman A-model realized his overtake problem, as well as an overlap problem between his right wing and the tail of lead, it was too late to avoid collision. Note also that it appears that the wingman may have never actually touched-down fully--his airplane was flying, or at least very light on the wheels, throughout the mishap and thus the wings were still making lift, allowing the rolling of the wings during impact. The wingman's right wing impacted lead's tail, forcing the wingman's left (opposite) wing to move forward and therefore accelerate and therefore make more lift and fly upward. Up flew the A's left wing, inducing a right-roll. As the A rolled its wings toward vertical, the pilot did not input full left rudder. Note: An airplane's rudder is the last control surface to be effective in a stall or as speed decreases. The ailerons (on the wings) lose effectiveness first, then the elevators (horizontal across the tail), then the rudder is last to lose effectiveness. Full left rudder might have kept the tail down as the wings went vertical and the A-model might have stayed right-side up and merely cartwheeled and/or spun on its belly shearing-off the landing gear, etc. Unfortunately, the situation developed so fast that the pilot in the A seems to not have been able to jam in full left rudder to keep the A right-side up. The rest is obvious from the photos and from video.

Again, my friend, an experienced military and WWII fighter operator, shuddered as he watched the video of this accident. Warbird fighter pilots RARELY perform formation landings, especially in dissimilar types such as a P-51D/P-51A pairing with differing weights, differing prop drag, and thus differing rates of deceleration. Another mistake was that lead touched-down first. He thus immediately decelerated as the wingman, still airborne, dove to land and thus accelerated. Watch the Blue Angels or Snowbirds perform their formation landings and you will see that the following aircraft always lands first and the leader is the last to touch down. That way, the formation decelerates from the rear and not from the front, as we see in the Oshkosh mishap.

This is not intended to unfairly criticize a dead pilot. Such accidents can happen to anyone and they often do. Any smart pilot who hears about a crash shudders and realizes but for the grace of God...