WAIMEA, HI, USA
N9161F
HUGHES 369HS
THE CERTIFICATED AIR LINE TRANSPORT PILOT WAS CONDUCTING A HELICOPTER SIGHTSEEING FLIGHT WITH 4 PASSENGERS WHEN THE ENGINE SUDDENLY LOST POWER. THE PILOT MADE AN EMERGENCY AUTOROTATION TO THE BOTTOM OF A SMALL RIVER BOTTOM. WHILE LANDING, THE HELICOPTER ROLLED OVER. EXAMINATION OF THE ENGINE SHOWED THAT THE FUEL CONTROL PC TUBE TO THE POWER TURBINE GOVERNOR HAD FRACTURED, CAUSING THE ENGINE TO GO TO A FLIGHT IDLE CONDITION. THIS TUBE WAS FOUND TO EXCEED THE SPECIFIED REQUIRED LENGTH OF MANUFACTURE. DURING INSTALLATION, THE TUBE WAS BENT BY COMPANY MAINTENANCE PERSONNEL TO FIT. METALLURGICAL EXAM DISCLOSED A FRACTURE DUE TO FATIGUE NEAR THE FUEL CONTROL END. THIS FATIGUE WAS INTRODUCED BY BENDING STRESSES IN THE TUBE.
THE IMPROPER INSTALLATION OF THE PC TUBE BY COMPANY MAINTENANCE PERSONNEL, WHICH RESULTED IN FATIGUE FAILURE OF THE TUBE DUE TO INDUCED BENDING STRESSES.
Source: NTSB Aviation Accident Database
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