ASN Wikibase Occurrence # 368932
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| Date: | Thursday 13 April 1989 |
| Time: | 18:05 LT |
| Type: |  de Havilland Canada DHC-6 Twin Otter 100 |
| Owner/operator: | Cape Smythe Air Service |
| Registration: | N100AP |
| MSN: | 22 |
| Year of manufacture: | 1967 |
| Total airframe hrs: | 17780 hours |
| Engine model: | P&W PT6A-20 |
| Fatalities: | Fatalities: 0 / Occupants: 7 |
| Aircraft damage: | None |
| Category: | Serious incident |
| Location: | Barrow, AK -
 United States of America
|
| Phase: | Initial climb |
| Nature: | Unknown |
| Departure airport: | |
| Atqasuk, AK (ATK) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
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.
Probable Cause: THE PROPAGATION OF A FATIGUE CRACK FROM MULTIPLE ORIGINS DUE TO MANUFACTURING DEFECTS IN THE ELEVATOR BELLCRANK MOUNTING QUADRANT.
Accident investigation:
 |
|
Sources:
NTSB ANC89IA059
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 24-Mar-2024 09:02 | ASN Update Bot | Added |
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