Narrative:
The Boeing 737-200 aircraft was dispatched to a restricted airport with a 3900 ft runway and notamed: 3 inch standing water on north end of runway. A sigmet was in effect for moderate to severe turbulence below 10,000 feet due to strong low level wind and associated windshear. The captain made a shallow overwater approach to runway 12, which had a near vertical 70 ft bluff skirting its left edge, approx 106 feet from the runway centerline. On final approach, the captain noted variable wind conditions and a sudden 15 kt increase in IAS due to windshear. He continued the approach, but the aircraft settled and touched down 72 feet short of the runway. The left hand main gear hit a log that was washed onto shore and a large rock, then collapsed after the aircraft bounced and landed on the runway. Unpredictable winds and downdrafts were reportedly prevalent at this airport.
Official 13:49 ADT wind was from 160 degrees at 8 kts, but at the approach end of runway, wind was reported coming over the bluff and was gusty. The FAA had granted MarkAir exemption to operate at Unalaska without overrun/safety areas. There was also no VASI at the approach end of runway 12. The owner (State of Alaska) delayed improvements due to funding problems. This was the captain's 10th landing at Unalaska. The required dry landing field length was computed to be 3700 feet.
PROBABLE CAUSE(S):
planning/decision..improper..company/operator management
compensation for wind conditions..inadequate..pilot in command
proper touchdown point..not attained..pilot in command
CONTRIBUTING FACTORS:
insuff standards/requirements,operation/operator..FAA(organization)
airport/facilities..inadequate
other airport/runway maintenance..inadequate
inadequate surveillance of operation..FAA(organization)
inadequate surveillance of operation..other govt organization
light condition..sunglare
visual/aural perception..pilot in command
airport facilities,visual apch slope ind(vasi)..unavailable
weather condition..unfavorable wind
weather condition..windshear
lack of familiarity with geographic area..pilot in command
terrain condition..rough/uneven
terrain condition..loose objects
Undershoot/overshoot
| Status: | Accident investigation report completed and information captured |
| Date: | Wednesday 25 September 1985 |
| Time: | 13:33 |
| Type: |  Boeing 737-2X6C |
| Operator: | MarkAir |
| Registration: | N674MA |
| MSN: | 23292/1113 |
| First flight: | 1985-05-06 (5 months) |
| Total airframe hrs: | 614 |
| Engines: | 2 Pratt & Whitney JT8D-17A |
| Crew: | Fatalities: 0 / Occupants: 4 |
| Passengers: | Fatalities: 0 / Occupants: 17 |
| Total: | Fatalities: 0 / Occupants: 21 |
| Aircraft damage: | Substantial |
| Aircraft fate: | Repaired |
| Location: | Unalaska Airport, AK (DUT) ( United States of America)
|
| Phase: | Landing (LDG) |
| Nature: | Domestic Scheduled Passenger |
| Departure airport: | Anchorage-Ted Stevens International Airport, AK (ANC/PANC), United States of America |
| Unalaska Airport, AK (DUT/PADU), United States of America | |
| Flightnumber: | BF71 |
The Boeing 737-200 aircraft was dispatched to a restricted airport with a 3900 ft runway and notamed: 3 inch standing water on north end of runway. A sigmet was in effect for moderate to severe turbulence below 10,000 feet due to strong low level wind and associated windshear. The captain made a shallow overwater approach to runway 12, which had a near vertical 70 ft bluff skirting its left edge, approx 106 feet from the runway centerline. On final approach, the captain noted variable wind conditions and a sudden 15 kt increase in IAS due to windshear. He continued the approach, but the aircraft settled and touched down 72 feet short of the runway. The left hand main gear hit a log that was washed onto shore and a large rock, then collapsed after the aircraft bounced and landed on the runway. Unpredictable winds and downdrafts were reportedly prevalent at this airport.
Official 13:49 ADT wind was from 160 degrees at 8 kts, but at the approach end of runway, wind was reported coming over the bluff and was gusty. The FAA had granted MarkAir exemption to operate at Unalaska without overrun/safety areas. There was also no VASI at the approach end of runway 12. The owner (State of Alaska) delayed improvements due to funding problems. This was the captain's 10th landing at Unalaska. The required dry landing field length was computed to be 3700 feet.
Probable Cause:
PROBABLE CAUSE(S):
planning/decision..improper..company/operator management
compensation for wind conditions..inadequate..pilot in command
proper touchdown point..not attained..pilot in command
CONTRIBUTING FACTORS:
insuff standards/requirements,operation/operator..FAA(organization)
airport/facilities..inadequate
other airport/runway maintenance..inadequate
inadequate surveillance of operation..FAA(organization)
inadequate surveillance of operation..other govt organization
light condition..sunglare
visual/aural perception..pilot in command
airport facilities,visual apch slope ind(vasi)..unavailable
weather condition..unfavorable wind
weather condition..windshear
lack of familiarity with geographic area..pilot in command
terrain condition..rough/uneven
terrain condition..loose objects
Accident investigation:
|
Classification:
Windshear/downdraftUndershoot/overshoot
Sources:
» NTSBFollow-up / safety actions
NTSB issued 2 Safety Recommendations
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Photos
Map
This map shows the airport of departure and the intended destination of the flight. The line between the airports does not display the exact flight path.
Distance from Anchorage-Ted Stevens International Airport, AK to Unalaska Airport, AK as the crow flies is 1261 km (788 miles).
Distance from Anchorage-Ted Stevens International Airport, AK to Unalaska Airport, AK as the crow flies is 1261 km (788 miles).
This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.
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