The NTSB has determined that the probable cause of the Galloping Ghost’s crash at last year’s Reno Air Races was flutter. No surprise there -- I wrote about flutter within hours of the accident. At its presentation, the NTSB even showed the same NASA video demonstrating flutter that I had posted last year.
Flutter can occur whenever an aircraft is flown faster than it is designed to fly. As it turned out, Jimmy Leeward, the pilot of Galloping Ghost, exceeded by nearly 40 mph the aircraft’s previous top speed without any previous testing to determine if the aircraft would be able to resist flutter at the new speeds. As it turned out, it couldn’t. Board member (and pilot) Robert Sumwalt was highly critical of Leeward’s decision to fly the aircraft in competition without first testing it at race speeds:
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.”
A loose trim tab assembly contributed to the flutter’s onset. The assembly came apart because the lock nuts that held it in place had been reused multiple times. That’s a no-no. Each time locknuts are removed and then re-tightened, they lose a bit of their ability to grip. That’s why once removed, locknuts should always be replaced with new.
What was surprising was the NTSB’s sentiments concerning “assumption of risk”. According to the NTSB board chair Deborah Hersman:
At the heart of the tragedy was the fatal intersection in transference of risks from participant to observers. One moment, spectators were thrilled at the spectacle of speed only to have it followed by inescapable tragedy. The pilots understood the risks they assumed. The spectators assumed that their safety had been assessed.”
Those sentiments echoed what I wrote here. Judging from readers’ comments to that post, many disagree.
Transcript of the NTSB presentation here.
All this blog's Reno Air Crash posts here.