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Last updated: 24 January 2022
Statuts:Enquête Officielle
Date:mercredi 25 septembre 1985
Heure:13:33
Type/Sous-type:Silhouette image of generic B732 model; specific model in this crash may look slightly different
Boeing 737-2X6C
Compagnie:MarkAir
Immatriculation: N674MA
Numéro de série: 23292/1113
Année de Fabrication: 1985-05-06 (5 months)
Heures de vol:614
Moteurs: 2 Pratt & Whitney JT8D-17A
Equipage:victimes: 0 / à bord: 4
Passagers:victimes: 0 / à bord: 17
Total:victimes: 0 / à bord: 21
Dégats de l'appareil: Substantiels
Conséquences: Repaired
Lieu de l'accident:Unalaska Airport, AK (DUT) (   Etats-Unis d'Amérique)
Phase de vol: A l'atterrissage (LDG)
Nature:Transport de Passagers Nat.
Aéroport de départ:Anchorage-Ted Stevens International Airport, AK (ANC/PANC), Etats-Unis d'Amérique
Aéroport de destination:Unalaska Airport, AK (DUT/PADU), Etats-Unis d'Amérique
Numéro de vol:AS71
Détails:
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

Sources:
» NTSB


Opérations de secours

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Plan
Ce plan montre l'aéroport de départ ainsi que la supposée destination du vol. La ligne fixe reliant les deux aéroports n'est pas le plan de vol exact.
La distance entre Anchorage-Ted Stevens International Airport, AK et Unalaska Airport, AK est de 1261 km (788 miles).

Les informations ci-dessus ne représentent pas l'opinion de la 'Flight Safety Foundation' ou de 'Aviation Safety Network' sur les causes de l'accident. Ces informations prélimimaires sont basées sur les faits tel qu'ils sont connus à ce jour.
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