Ground resonance fails AS350 tail boom
Just seen this (abbreviated) report on the NTSB accident site. Unusual, to say the least. Anyone come across this sort of thing before?
"On November 18, 2006, a Eurocopter AS 350 BA separated its tail boom during a ground resonance occurrence at the Buckingham Field Airport, Fort Myers, Florida.
The pilot started the aircraft without any discrepancies. After about one minute, he began to slowly advance the fuel control to flight gate. During this process, he monitored the torque gage not to exceed 40%. He continued to advance the throttle, and observed a sudden spike in the torque that exceed 40% then went below 40%, at the same time he heard the engine begin to rev rapidly. He stopped the advancement of the throttle and again the torque gage indicated a spike that exceeded 40% as the engine rev extremely fast and noted a spike in the RPM as the helicopter started to shake violently. He retarded the throttle to the closed position; however, he still heard the engine revving high. The helicopter began to bounce on the ground. He applied downward pressure on the collective as the helicopter rocked back and forth extremely violently. He attempted to close the fuel shutoff valve; however, the collective rose when he released it and elected to keep his left hand on the collective to ensure the throttle was closed. The helicopter continued to shake and bounce violently on the ground for sometime prior to coming to a rest upright, 90 degrees from its original startup position.
A witness stated he observed the helicopter at flight idle. When the engine was advanced, it seemed like it advanced very quickly. He immediately thought that it was an overspeed, just by the way the blades sounded. The helicopter then started with a slight lateral bounce, which progressed into severe bouncing back and forth from skid to skid. The helicopter then rotated 90 degrees to the right and the tail boom separated, falling to the ground."