On September 10, 2002, a Hughes 500 (registration N9263F) operated by Charles F. Conner was involved in an aviation accident near Carnation, WA. Investigators recorded the probable cause as: The pilot's inadvertent delay in adding power during the flare, which resulted in a hard landing and subsequent contact between the main rotor blades and the tail boom. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A private pilot practicing power recovery autorotations delayed adding power during the flare, causing a hard landing that damaged the main rotor and tail boom.
What happened
The private pilot was conducting flight training exercises focused on power recovery autorotations. The intended destination for these maneuvers was an open field selected for its suitability as a safe landing zone. During the execution of the second practice autorotation, the pilot inadvertently delayed the application of engine power during the flare phase of the maneuver. This timing error resulted in the helicopter touching down with a nose-high attitude. The impact of this hard landing caused the main rotor blades to strike and contact the helicopter's tail boom.
The investigation
Examination of the aircraft revealed substantial damage resulting from the rotor-to-boom contact. The mechanical failure was directly linked to the high-energy impact during the uncommanded touchdown.
Probable cause
The pilot's inadvertent delay in adding power during the flare, which resulted in a hard landing and subsequent contact between the main rotor blades and the tail boom.