NTSB Identification: ANC89IA059.
The docket is stored on NTSB microfiche number 38593.
Scheduled 14 CFR
Incident occurred Thursday, April 13, 1989 in BARROW, AK
Probable Cause Approval Date: 08/26/1992
Aircraft: DE HAVILLAND DHC-6-100, registration: N100AP
Injuries: 7 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

THE AIRPLANE HAD JUST DEPARTED BARROW, AK, ON A SCHEDULED COMMUTER FLIGHT WITH FIVE PASSENGERS AND TWO CREW MEMBERS ON BOARD. UPON REACHING AN ALTITUDE OF 150 AGL, THE CONTROL YOKE WAS PULLED FORWARD OUT OF THE CAPTAIN'S HANDS AND PINNED AGAINST THE CONTROL PANEL. SIMULTANEOUSLY, THE NOSE OF THE AIRPLANE SUDDENLY PITCHED UP 60 DEGREES ABOVE THE HORIZON. THE CAPTAIN REDUCED POWER AND THE NOSE PITCHED 30 DEGREES BELOW THE HORIZON. THE FLIGHT CREW WAS EVENTUALLY ABLE TO MAINTAIN A LEVEL ATTITUDE BY POWER ADJUSTMENTS ALONE, AND RETURNED FOR A SAFE LANDING. INSPECTION REVEALED A FATIGUE FRACTURED ELEVATOR BELLCRANK MOUNTING QUADRANT, P/N C6CFM1142-1, RESULTING IN A COMPLETE LOSS OF ELEVATOR CONTROL. THE ELEVATOR BELLCRANK MOUNTING QUADRANT HAD BEEN IN SERVICE SINCE 1966 AND HAD BEEN OPERATING 17,826 HRS. THE FRACTURE OCCURRED BETWEEN THE VERTICAL STABILIZER STUB FIN ATTACHMENT BULKHEAD AND THE BELLCRANK. METALLURGICAL EXAM REVEALED MULTIPLE FATIGUE ORIGINS IN THE VICINITY OF SUPERFICIAL MACHINING ABRASIONS.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

THE PROPAGATION OF A FATIGUE CRACK FROM MULTIPLE ORIGINS DUE TO MANUFACTURING DEFECTS IN THE ELEVATOR BELLCRANK MOUNTING QUADRANT.

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