LAS VEGAS — A plane that crashed into spectators at an air race in Reno, Nev., last year bore modifications that weakened its structure and showed evidence that it was flown beyond its limits, investigators said Monday.
The National Transportation Safety Board deemed the failure of a tail structure to be the probable cause of the crash of the souped-up World War II-era P-51 Mustang fighter that killed pilot Jimmy Leeward and 10 people on the ground at the National Championship Air Races in Reno and injured more than 70.
Leeward also was blamed for failing to fully document and test extensive modifications to the aircraft before the September 2011 crash.
Board member Robert Sumwalt said, "If you want to go out and fly fast and try to win, that's one thing. If you're modifying an aircraft without fully understanding how the modifications can affect the aerodynamics, you're playing Russian roulette."
Structural modifications of the aircraft dubbed the Galloping Ghost made it lighter and reduced drag, according to the NTSB report. But flight control modifications also made the aircraft less stable. The NTSB found that an elevator trim tab malfunction created aerodynamic instability that made Leeward's plane uncontrollable.
High-resolution photos show the skin wrinkling and the canopy separating on the plane seconds before the crash, and NTSB investigators later found loose screws in the crucial tail assembly.
At a board hearing in Washington, Chairwoman Deborah Hersman blamed the 74-year-old Leeward for "operating at the edge of the envelope" without fully reporting and testing modifications to his plane.
At the time of the crash, the propeller aircraft was flying faster than it ever had before, NTSB investigators found.
With the 2012 races set to start Sept. 12, the five-member panel has already issued several preliminary reports and recommendations for the Federal Aviation Administration and race organizers to improve safety.
The air race championship, entering its 49th year, is the only event of its kind. It draws thousands every year to Reno Stead Airport and features aircraft flying at speeds of more than 500 mph, sometimes wing tip to wing tip, around an oval pylon track.