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Accident
Last updated: 18 October 2017
Status:Definitief
Datum:vrijdag 10 september 1976
Tijd:10:14
Type:Silhouette image of generic TRID model; specific model in this crash may look slightly different
Hawker Siddeley HS-121 Trident 3B
Luchtvaartmaatschappij:British Airways
Registratie: G-AWZT
Constructienummer: 2320
Bouwjaar: 1972
Aantal vlieguren:8627
Aantal vluchten:6952
Motoren: 3 Rolls-Royce Spey 512-5W
Bemanning:slachtoffers: 9 / inzittenden: 9
Passagiers:slachtoffers: 54 / inzittenden: 54
Totaal:slachtoffers: 63 / inzittenden: 63
Botsingsslachtoffers:slachtoffers: 113
Schade: Vernield
Gevolgen: Written off (damaged beyond repair)
Plaats:nabij Vrbovec (   Kroatië)
Fase: Kruisvlucht (ENR)
Soort vlucht:Internationale lijnvlucht
Vliegveld van vertrek:London-Heathrow Airport (LHR/EGLL), Verenigd Koninkrijk
Vliegveld van aankomst:Istanbul-Yesilköy Airport (IST/LTBA), Turkije
Vluchtnummer:BE475
Beschrijving:
Hawker Siddeley HS-121 Trident 3B operated by British Airways as flight BE476 and a McDonnell Douglas DC-9-31, operated by Inex-Adria Aviopromet, were destroyed when both aircraft crashed near Vrobec following a mid-air collision. All 176 on board both aircraft were killed.
The Trident was on a scheduled flight from London-Heathrow Airport in England to Istanbul-Yesilköy Airport in Turkey, carrying 54 passengers and a crew of 9. The aircraft took off at 08:32 GMT and the flight proceeded normally. First contact with the Zagreb Area Control Centre was established on the Upper Sector frequency 134,45 MHz at 10:04 GMT. The flight was requested to report passing the Zagreb VOR at flight level 330.
The aircraft flew along the centreline of airway UB5 with slight side deviation 1-2 km to the right due to wind. At 2 minutes and 50 seconds before the collision, the aircraft changed heading to 115° to head back towards the airway centreline. Airspeed was 295 Kts.
The DC-9 departed Split Airport at 09:48 GMT to fly 108 West German tourists back to Cologne. Flight JP550 was issued instructions to climb to FL180.
At 09:54 the flight, on passing flight level 130, switched to the Zagreb Area Control Centre lower sector east frequency of 124.6 MHz, receiving clearance to climb to FL240 and later to FL260.
At 10:03 the crew switched to the frequency of the middle sector controller, responsible for safety and regulation of traffic between flight levels 250 and 310. This controller cleared to flight to FL350.
The aircraft assumed a heading of 353° and a speed of 273 Kts as it passed a beam and to the west of the KOS NDB, approximately 2-3 km from the airway centreline. While heading towards the Zagreb VOR, the flight crew radioed the Upper Sector controller on frequency 134,45 MHz at 10:14:04 GMT and reported that they were climbing through FL325. The controller then requested, in Serbo-Croatian, flight JP550 to maintain their present altitude and report passing the Zagreb VOR. The controller stated that an aircraft was in front passing from left to right at FL335, while in fact BE476 was at FL330. At 10:14:38 the crew replied, also in Serbo-Croatian, that they where maintaining FL330.
Three seconds later both aircraft collided. 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. With it's left wing torn off, the DC-9 tumbled down and hit the ground right-wing first.

Probable Cause:

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."

Accident investigation:
cover
Investigating agency: AIB
Status: Investigation completed
Duration: 106 days (4 months)
Accident number: AAR 5/1977
Download report: Final report

Bronnen:
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» Collision course / by Tony Brkic


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photo of Hawker Siddeley HS-121 Trident 3B / DC-9-31
photo of Hawker Siddeley HS-121 Trident 3B / DC-9-31
photo of Hawker Siddeley HS-121 Trident 3B G-AWZT
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Kaart
Deze kaart geeft het vliegveld van vetrek weer en de geplande bestemming van de vlucht. De lijn tussen de vliegvelden geeft niet de exacte vliegroute weer.
De afstand tussen London-Heathrow Airport en Istanbul-Yesilköy Airport bedraagt 2495 km (1560 miles).
Accident location: Exact; as reported in the official accident report.

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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HS-121 Trident

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