Trim tab.
Today the National Transportation Safety Board released its first report on the Reno Air Race crash that killed P-51 pilot Jimmy Leeward and 10 others. We did our own digging, talking to racers and crew members with years of experience at Reno about what went wrong. A small flap’s failure probably caused this deadly crash—but the accident could have been much worse.
via What Went Wrong at the Reno Air Races – P-51 Crash – Popular Mechanics.
Backgrounder on trim tabs here.
There is video of the crash — it’s a little disturbing.
http://www.youtube.com/watch?v=QWxM9H6DXck