PORTLAND, OR, USA
N42WC
ROBINSON R-22M
THE PILOT ATTEMPTED AN AUTOROTATION AFTER LOSS OF TAIL ROTOR EFFECTIVENESS. THE TAIL BOOM AND ROTOR STRUCK THE SURFACE WHEN THE FLOAT EQUIPPED HELICOPTER LANDED IN THE RIVER. INVESTIGATION REVEALED THAT THE TAIL ROTOR GEARBOX OUTPUT SHAFT PINION RETAINING KEY HAD NOT BEEN INSTALLED DURING ASSEMBLY. THE TAIL ROTOR HUB AND BLADE ASSEMBLY WERE FREE TO TURN ON THE SHAFT AT THE TIME OF INVESTIGATION.
On July 7, 1994, at 1125 Pacific daylight time, a Robinson R-22M, N42WC, sustained substantial damage during an autorotational forced landing to Ross Island beach, Portland, Oregon. The student pilot and certified flight instructor sustained minor injuries. No flight plan was filed for the instructional flight, which had departed Hillsboro, Oregon about 1105. The pilot stated that he had lost tail rotor effectivness and attempted an autorototation from about 75 feet AGL. The pilot stated that the aircraft continued turning through two or three rotations before toching down. The aircraft landed near shoreline, with the tail rotor and boom striking the water. Inspection revealed that the tail rotor gearbox (P/N A021-1) output shaft pinion (A545-1) retaining key (A114-2) was not installed at the time of factory assembly, allowing the tail rotor hub and blade to become disengaged.
TAIL ROTOR GEARBOX FAILURE DUE TO INADEQUATE ASSEMBLY AND INSPECTION PROCEDURES BY THE MANUFACTURER.
Source: NTSB Aviation Accident Database
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