# NTSB ANC89IA059: De Havilland DHC-6-100, N100AP, Barrow, AK, April 14, 1989

- Type: NTSB incident investigation
- Classification: Incident · No injuries · Incident investigation · Final report
- Date: April 13, 1989, 17:05 local (Apr 14, 1989, 01:05 UTC)
- Place: Barrow, AK
- Coordinates: 71.280563, -156.779006 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=71.2806&lon=-156.7790&mi=10
- Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 7 uninjured
- Status: Completed, report August 26, 1992
- Report: Approved by Office Director
- NTSB office: Alaska Regional Office
- NTSB case key (mKey): 5128
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC89IA059
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/5128/pdf
- Page: https://openairdocs.org/ntsb/ANC89IA059

## Probable cause

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

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, takeoff - initial climb
  - flt control syst,elevator control - fatigue (cause)
  - flt control syst,elevator control - failure,total (cause)
  - inadequate quality control, manufacturer (cause)

## Analysis

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.

## Aircraft

- Registration: [N100AP](https://openairdocs.org/aircraft/N100AP), registered now, S/N 22, built 1967 (OpenAirDocs)
- Reported make and model: DE HAVILLAND DHC-6-100
- Registry model: [Dehavilland DHC-6 TWIN OTTER](https://openairdocs.org/model/dehavilland-dhc-6-twin-otter) (registry code 2802606) (OpenAirDocs)
- Registry engine: [Pratt & Whitney Canada PT6A-60A](https://openairdocs.org/engine/pratt-whitney-canada-pt6a-60a) (registry code 52043, turbo-prop) (OpenAirDocs)
- Category: Airplane
- Serial number: 22
- Airframe hours: 17780
- Engines: P&W PT6A-20 550 horsepower turbo prop
- Damage: No damage
- Flight: Part 135
- Registered owner: Cape Smythe Air Service
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, March 14, 1989, 57 hours before
- Destination: ATK, ATQASUK, AK
- Flight plan: VFR
- Airport: BRW, Wiley Post, runway 24, 6,500 × 150 ft, asphalt

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 31; flight instructor, airline transport; airplane ratings: multi-engine land, single-engine land, single-engine sea; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: left; flight hours: 5,666 total, 2,014 in this make and model, 5,261 as pilot in command, 213 in the last 90 days, 133 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 150° at 18 knots
- Visibility: 7 statute miles
- Lowest ceiling: 6,000 ft overcast
- Temperature: 36 °F, dew point 30 °F
- Altimeter: 29.00 inHg
- Observed at: BRW

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Incident 19890413010119I](https://openairdocs.org/incident/19890413010119I), Apr 13, 1989: Dhav DHC6TWNOTTER, Barrow, AK. Lost elevator control after takeoff. Returned. Landed safely. Elevator control quadrant mount broke.

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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