ATC Miscommunication Precedes Fatal Controlled Flight Into Terrain

At 1411 hours, on 04 September 1991, a Gulfstream II, registered as N204C belonging to Dupont De Memours crashed on a ridge while executing an intermediate approach to land on runway 02 Kota Kinabalu Airport, Sabah, Malaysia. The aircraft collided with the top of a mountain in the Crocker Range, at a spot height of 4,180 feet, 31 Nautical Miles South of the airfield. The aircraft disintegrated on impact and fatally injured 3 crew and 9 passengers.

The Area Control Centre (ACC) Kota Kinabalu notified the accident to the Chief Inspector of Aircraft Accidents, Department Civil Aviation (DCA) Malaysia on the same day and the investigation began on the following day. The investigation team comprised of an Inspector Incharge and 3 members from the same Department. In addition, a representative each from the National Transport Safety Board, USA and Federal Aviation Authority (FAA), USA, participated as Ac Representatives in the early stages of the investigation.

The most probable causes of the accident were: the approach controller's decision to descend the aircraft below the minimum sector altitude of 9,500 ft. and the flight crew's failure to examine discover and object the Air Traffic Controller's cleared altitudes that were below minimum safe sector altitude. Immediately after establishing radio contact on Approach Control frequency of 118.3 Mhz, the Controller instructed the aircraft to maintain FL 150.

At about this time, the flight crew asked the Approach Controller whether the Controller wanted them to track outbound on 258 degrees radial or hold over the VJN VOR. The Approach Controller replied and instructed the crew to maintain radial 025 degrees. From the Cockpit Voice Recorder (CVR), both flight crew mentioned to each other "I didn't hear what he said on it" and "I didn't either".

At 1402 hours and on passing the JN VOR, the flight crew again asked the Approach Controller whether they were to go outbound on radial 258 degrees VJN. Since there were other traffics within Kota Kinabalu area, the Controller told the crew to descend over the VJN VOR to Nine Thousand Five Hundred feet. The crew immediately acknowledged that they understood they were to descend to 9,500 ft'.

The commander remarked " I still did not understand, did he say we could outbound on the VJN VOR or did we have to hold". By then the aircraft had departed the VJN VOR and was already to the South of the airfield. partially missed the instruction by the approach controller to descend over the VJN VOR.

At 1404 hours, the flight crew again seek clarification and asked the air traffic controller "We are still uncertain you want us to go outbound on the 258 degrees radial or you want us to hold". The approach controller responded "N204C descend South of the airfield to 9500 now". The crew acknowledged the instruction and made no other remarks regarding the clearance.

At 1406:47 hours, the aircraft descended through 10,000 feet and was further cleared to descend to 6000 feet. At 1408:16 hours, the Approach Controller asked the crew to report its distance from the field. The Approach Controller after having verified that the aircraft was 21 NM from the field, instructed it to turn inbound after passing four thousands feet.

From the Voice Recorder, the First Officer remarked "We are coming close to the hills". At 1410:20 hours the aircraft was passing 4,000 feet, and was at approximately 29 NM from the field. At this calculated point, the aircraft was only 44 seconds or 3 NM from point of impact.

The Approach Controller cleared the aircraft to join Final Runway Zero Two and to descend to 2,500 feet At 1410:46 hours or 15 seconds before impact the first officer remarked "God' I tell you' and this was followed by the commander's comment "I don't like what we got here I'm climbing this socket out of here". There was an increase in the engine noise in the Cockpit Voice Recorder (CVR). At 1411:01 hours the sound of impact was recorded.

The accident occurred at about 1411.01 hours, on a mountain, 4,180 feet above sea level, about 31 NM from Kota Kinabalu airport. It was also determined that the impact speed was around 221 Nautical Miles per hour