August 27, 2012
WASHINGTON - The National
Transportation Safety Board determined today that deteriorated
locknut inserts found in the highly modified North American P-51D
airplane that crashed during the 2011 National Championship Air Races
in Reno, Nevada, allowed the trim tab attachment screws to become
loose, and even initiated fatigue cracking in one screw. This
condition, which resulted in reduced stiffness in the elevator trim
system, ultimately led to aerodynamic flutter at racing speed that
broke the trim tab linkages, resulting in a loss of controllability
and the eventual crash.
On September 16, 2011, as the
experimental single-seat P-51D airplane "The Galloping Ghost,"
traveling about 445 knots, or 512 mph, in the third lap of the
six-lap race, passed pylon 8, it experienced a left-roll upset and
high-G pitch up. During the upset sequence, the airplane's vertical
acceleration peaked at 17.3 G, causing incapacitation of the pilot.
Seconds later, a section of the left elevator trim tab separated in
flight. The airplane descended and impacted the ramp in the spectator
box seating area, killing the pilot and 10 spectators and injuring
more than 60 others.
"In Reno, the fine line between
observing risk and being impacted by the consequences when something
goes wrong was crossed," said NTSB Chairman Deborah A. P.
Hersman. "The pilots understood the risks they assumed; the
spectators assumed their safety had been assessed and addressed."
Contributing to the accident were the
undocumented and untested major modifications made to the airplane,
as well as the pilot's operation of the airplane in the unique air
racing environment without adequate flight testing.
The nearly 70-year-old airplane had
undergone numerous undocumented modifications. The modifications,
designed to increase speed, included shortening of the wings,
installation of a boil-off cooling system for the engine, increasing
the elevator counterweights, modification of the pitch trim system,
and changing the incidence of the horizontal and vertical
stabilizers.
Although the Federal Aviation
Administration required that a flight standards district office be
notified in writing of any major changes made to The Galloping Ghost
before it could be flown, investigators could find no records that
such notifications were made except for the installation of the
boil-off cooling system. The undocumented major modifications were
identified through wreckage examinations, photographic evidence, and
interviews with ground crewmembers.
In April, while the investigation was
ongoing and after the NTSB's investigative hearing in January on air
race and air show safety, the NTSB issued 10 safety recommendations
to the Reno Air Racing Association, the National Air racing Group
Unlimited Division, and the FAA.
A synopsis of the NTSB report,
including the probable cause and a complete list of the reclassified
safety recommendations, is available at:
http://www.ntsb.gov/news/events/2012/reno_nv/index.html.
Other information and previous press
releases related to the Reno Air Races investigation:
Reno Air Races Recommendations Issued
Earlier this Year: http://www.ntsb.gov/news/2012/120410.html
Air Race and Air Show Safety Hearing :
http://www.ntsb.gov/news/2012/120105.html
Investigation Update:
http://www.ntsb.gov/news/2011/111021.html
NTSB Opens Docket on Reno Air Races
Crash http://www.ntsb.gov/news/2012/120821b.html