That is way too big to be a trim tab. I have never worked on a P-51, but the size is right to be a servo tab. A trim tab would be about 1/10 the size of that tab if it were trim.
Servo tabs control the entire elevator, the idea is to keep stick forces manageable across a large speed range.
Agree. I’ve been reading across the web and have found “experts” who say the P-51 doesn’t use servo tabs and other that swear there are servo tabs on the P-51...
Sooo... it could be we see a broken servo tab - and so broken, would prevent elevator control... very likely why he could not pull the plane out of the dive.
“In the case of some aircraft the servo tab is the only control that is connected to the pilot’s stick or wheel”
Wonder if that was the case in this P-51. There are obviously significant modifications from the original design. If his was built that way,, he would have lost control when the tab separated.