Date: September 10th, 1976
Type: McDonnell Douglas DC- 9-31
Operator: THY (Turkish Air)
Where: Vrobec; nr ((former) Yugoslavia)
Report No.: Not Available
Report Date: -
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 116ø (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 K”ln.
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
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
didn't know that the Middle Sector controller had given permission of BA475
to climc to FL350.