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Accident
Last updated: 13 December 2017
Statuts:Enquête Officielle
Date:dimanche 9 mai 1976
Heure:14:35 UTC
Type/Sous-type:Silhouette image of generic B741 model; specific model in this crash may look slightly different
Boeing 747-131F
Compagnie:Imperial Iranian Air Force - IIAF
Immatriculation: 5-8104
Numéro de série: 19677/73
Année de Fabrication: 1970-09-15 (5 years 8 months)
Moteurs: 4 Pratt & Whitney JT9D-7A
Equipage:victimes: 10 / à bord: 10
Passagers:victimes: 7 / à bord: 7
Total:victimes: 17 / à bord: 17
Dégats de l'appareil: Perte Totale
Conséquences: Written off (damaged beyond repair)
Lieu de l'accident:près de Madrid (   Espagne)
Phase de vol: En vol (ENR)
Nature:Cargo
Aéroport de départ:Tehran-Mehrabad Airport (THR/OIII), Iran
Aéroport de destination:Madrid-Torrejón AFB (TOJ/LETO), Espagne
Numéro de vol: 48
Détails:
The Boeing was operated on a military logistic flight from Tehran to McGuire AFB via Madrid. The flight took off from Tehran at 08:20 GMT and climbed to a cruising altitude of FL330. After establishing contact with Madrid control, clearance was received to CPL VOR via Castejon. At 14:25 the flight was cleared to FL100. At 14:30 the crew advised Madrid that they were diverting to the left because of thunderstorm activity, and at 14:32 Madrid cleared ULF48 to 5000 feet and directed him to contact Madrid approach control. At 14:33 the crew contacted approach control and advised them that there was too much weather activity ahead and requested to be vectored around it. Last radio contact was when ULF48 acknowledged the 260deg heading instructions and informed Madrid that they were descending to 5000 feet. The aircraft was later found to have crashed in farmland at 3000 feet msl following left wing separation.
It appeared that the aircraft had been struck by lightning, entering a forward part of the aircraft and exiting from a static discharger on the left wingtip. The lightning current's conductive path to the static discharger at the tip was through a bond strap along the trailing edge. Concentration of current at the riveted joint between this bond strap and a wing rib were sufficient conductive to cause the flash to reattach to this rivet and to leave the discharger. Fuel vapors in the no. 1 fuel tank then ignited. The explosion caused the upper wing skin panel to separate, causing a drastic altering of the aero elastic properties of the wing, and especially the outboard section of wing. The outer wing began to oscillate, developing loads which caused the high-frequency antenna and outer tip to separate. The whole wing failed a little later.

Accident investigation:
cover
Investigating agency: NTSB
Status: Investigation completed
Duration: 2 years and 5 months
Accident number: NTSB/AAR-78-12
Download report: Final report

Sources:
» Flight International 15.5.76(1283)
» ICAO Circular 146-AN/96 (116-140)
» NTSB-AAR-78-12


Photos

photo of Boeing 747-131F N53111
N53111 was sold to the Iranian Air Force in November 1975.
Add your photo of this accident or aircraft
 

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 Tehran-Mehrabad Airport et Madrid-Torrejón AFB est de 4713 km (2946 miles).
Accident location: Global; accuracy within tens or hundreds of kilometers.

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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