On December 2, 1988, a Bell 47D1 (registration N163B) was involved in an aviation accident near Russell, MA. Investigators recorded the probable cause as: A PILOT INDUCED LOW ROTOR RPM CONDITION, FOLLOWED BY BLADE FLAPPING AS THE MAIN ROTOR BLADE CONTACTED THE TAIL OF THE HELICOPTER. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A Bell 47D1 helicopter crashed in a wooded area during a solo cross-country flight. Investigation revealed a missing stabilizer bar that had failed opposite the direction of rotation, along with evidence of blade flapping and low rotor RPM.
Accident Details
A Bell 47D1 helicopter, operated by a commercial-rated pilot working on a rotorcraft rating, was on a solo cross-country flight when it crashed in a wooded area. Debris was spread along the flight path for over a quarter mile.
Post-Crash Examination
Examination of the wreckage showed that one stabilizer bar was missing from the rotor head. The stabilizer bar had failed opposite the direction of rotation and was not recovered. Evidence of blade flapping and low rotor RPM conditions was present.
Flight Control and Engine Systems
No evidence of a failure in the flight control system was found, other than the missing stabilizer bar. Similarly, no evidence of an engine failure was noted, although conditions were present for the formation of carburetor ice.