Date: September 10th, 1976
Type: HS-121 Trident
Registration: -
Operator: British Airlines
Where: Vrobec; nr ((former) Yugoslavia)
Report No.: Not Available
Report Date: -
Pages: -

This is not an accident investigation report.

Flight BA475 (a HS-121 Trident) took from London-Heathrow at 08.32h GMT for a flight to Istanbul. About 1 hours later, the aircraft approached the ZAG VOR beacon on airway UB5 at FL330 (10000m), heading 116 (speed 905km/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 09.48h GMT for a flight to Kln. 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 fligh 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 decrompression, the forward part of the Trident's fuselage desintegrated. The remaining paert of the fuselage struck the ground tail-first and slid some 4-5m. to the left. With it's left wong torn off, the DC-9 tumbled down and hit the ground right-wing first. CAUSE: Improper ATC operation at Zagreb ACC (a.o. use of Serbo-Croatian language in communications). Factors were a.o. the absence of an assistant for the Upper Sector controller and the fact that the Upper Sector controller didn't know that the Middle Sector controller had given permission of BA475 to climc to FL350.