Thunderbird Felled by Sticky Button

The Thunderbirds aerial demonstration team F-16 that crashed in Colorado on June 2—minutes after a flyby of the Air Force Academy graduation, attended by President Obama—was done in by a stuck button on the throttle, the service announced Wednesday. Normally the throttle won’t move all the way to cutoff unless the button is depressed, but the button had become stuck in the depressed position due to accumulated metallic debris, stray lubricant, a misaligned clevis pin, and wear on the spring mechanism, USAF’s official accident investigation found. The pilot, Maj. Alex Turner, inadvertently rotated the throttle to the engine cutoff position, and by the time he realized what had happened, was too low to restart the engine, though he attempted to do so. Turner delayed ejection for a few seconds to steer the jet away from a house. He ejected with only minor injury, was picked up, and was later introduced to Obama. Though the Air Force said it will not comment on disciplinary action, Turner apparently was considered blameless in the accident because he was promptly returned to flying duty. Though the jet, tail No. 92-3890, seemingly landed upright and largely intact, it was declared a total loss, at a value of $29.4 million. Technical orders have been changed to require a more thorough regular inspection of the mechanism and the proper alignment of the pin. The accident board wrote that “a significant number of sticky throttle triggers in F-16 history have led to hardware changes that have reduced but not eliminated the number of occurrences” of this problem. The throttle was recovered intact and the investigation team operated the button 50 times, finding that the button got stuck about 36 percent of the time. (Read the full report; Caution, large-sized file.)