Loss of separation involving a Boeing 767-300, OE-LAU and McDonnell Douglas DC-10, HS-TMB, SABEX, Western Australia, on 19 March 1995

OE-LAV, a Boeing B767 aircraft (flight number LDA2) enroute from Melbourne to Singapore at Flight Level 350 (FL350) suffered a reduction of oil pressure in one engine. The problem could not be rectified in flight and the engine was shut down.

The crew notified Perth ATC of the problem, advising that they were commencing an emergency descent to FL240 and required a diversion to Darwin. They were advised of opposite direction traffic, HS-TMB, a DC10 aircraft (flight number THA991), at FL330 which should be passing their present position at that time.

They were initially cleared to FL340, but the crew advised that their TCAS equipment had shown they had passed THA991 and were now diverting right of track and requiring an immediate descent to FL240.

THA 991 was instructed to descend to FL290, but as ATC could not provide a positive separation standard between the two aircraft instructed LDA2 to maintain its own separation while descending to FL240 and track direct to Darwin.