MARICOPA, AZ, USA
N8413Q
ROBINSON R22
THE WRECKAGE WAS LOCATED ON FLAT DESERT TERRAIN ALONG A DIRECT COURSE LINE BETWEEN THE DEPARTURE & DESTINATION AIRPORTS. THE TAIL BOOM HAD SEPARATED IN FLIGHT. DAMAGE WAS CONSISTENT WITH A LOW 'G' EVENT RESULTING IN A RAPID RIGHT ROLL & SUBSEQUENT MAIN ROTOR BLADE STRIKE ON THE LEFT SIDE OF THE CABIN. THE DESIGN STRENGTH OF THE TAIL CONE'S ATTACHMENT POINTS WAS EXCEEDED. ACCORDING TO THE MANUFACTURER'S PAPER ON LOW 'G' MAST BUMPING, BOTH LATERAL CONTROL AND DAMPING IN ROLL ARE PROPORTIONAL TO G-LOAD; IN A TWO G PULLUP THEY BOTH DOUBLE, AND IN A ZERO G PUSHOVER THEY BOTH GO TO ZERO. WHEN THEY ARE ZERO, THE PILOT HAS NO LATERAL CONTROL, AND THE HELICOPTER HAS NO DAMPING IN ROLL. THE PILOT WAS REPORTEDLY KEENLY AWARE THAT ONE SHOULD NOT PLACE THE R22 INTO A NEGATIVE 'G' SITUATION, OR EVEN A LOW 'G' SITUATION, AND WAS VERY KNOWLEDGEABLE OF THE R22'S STRUCTURE AND SYSTEMS.
DESTRUCTIVE MAST BUMPING FOR AN UNDETERMINED REASON(S).
Source: NTSB Aviation Accident Database
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