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Last updated: 29 August 2016
Statuts:Enquête Officielle
Date:vendredi 10 septembre 1976
Type/Sous-type:Silhouette image of generic TRID model; specific model in this crash may look slightly different
Hawker Siddeley HS-121 Trident 3B
Compagnie:British Airways
Immatriculation: G-AWZT
Numéro de série: 2320
Année de Fabrication: 1972
Heures de vol:8627
Moteurs: 3 Rolls-Royce Spey 512-5W
Equipage:victimes: 9 / à bord: 9
Passagers:victimes: 54 / à bord: 54
Total:victimes: 63 / à bord: 63
Victime de la collision:victimes: 113
Dégats de l'appareil: Détruit
Conséquences: Written off (damaged beyond repair)
Lieu de l'accident:près de Vrbovec (   Croatie)
Phase de vol: En vol (ENR)
Nature:Transport de Passagers Intern.
Aéroport de départ:London-Heathrow Airport (LHR/EGLL), Royaume Uni
Aéroport de destination:Istanbul-Yesilköy Airport (IST/LTBA), Turquie
Numéro de vol: 475
Flight BA475 (a HS-121 Trident) took from London-Heathrow at 08:32 GMT for a flight to Istanbul. About 1½ hours later, the aircraft approached the ZAG VOR beacon on airway UB5 at FL330 (10000 m), heading 116° (speed 905 km/h).
At the same time the Inex Adria DC-9-31 also approached the ZAG VOR, but flew airway UB9, climbing from FL260 to FL350. The DC-9 had taken off from Split at 09:48 GMT for a flight to Köln.
At 10:14:14 the DC-9 captain radioed that they were climbing through FL325. According to ATC data the Flight BA475 was approaching ZAG VOR at FL335 (FL330 actually). Zagreb ATC asked (in Serbo-Croatian) the Inex flight to maintain their present altitude. At 10:14:38 the crew of flight JP550 replied (also in Serbo-Croatian) that they where maintaining FL330.
Three seconds afterwards the outer five meters of the DC-9's left wing cut through the Trident's cockpit.
Due to the sudden decompression, the forward part of the Trident's fuselage disintegrated. The remaining part of the fuselage struck the ground tail-first and slid some 4-5 m. to the left.
With it's left wing torn off, the DC-9 tumbled down and hit the ground right-wing first.
CAUSES OF THE ACCIDENT: "1) Direct cause of the accident was the struck of the DC-9 wing into the middle side of the TRIDENT THREE fuselage which occurred at the height of 33.000 feet above Zagreb VOR so that both aircraft became uncontrollable and fell on the ground.; 2) Improper ATC operation; 3) Non-compliance with regulations on continuous listening to the appropriate radio frequency of ATC and non-performance of look-out duty from the cockpits of either aircraft."

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Official accident investigation report
investigating agency: Air Accidents Investigation Branch (AAIB) - United Kingdom
report status: Final
report number: AAIB AAR 5/1977
report released:25 December 1976
duration of investigation: 106 days (4 months)
download report: Report on the collision to British Airways Trident, G-AWZT and Inex Adria DC9, YU-AJR, in the Zagreb area, Yugoslavia, 1 (AAIB AAR 5/1977)

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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 London-Heathrow Airport et Istanbul-Yesilköy Airport est de 2495 km (1560 miles).

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HS-121 Trident

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