Paul Phelan/CAIRNS

Australian air accident investigators suspect that pilot incapacitation and loss of cabin pressurisation caused the crash of a Central Air Raytheon Beech Super King Air 200 at the end of a 4h 55min, apparently uncontrolled, flight. The aircraft crashed in Queensland on September 5, killing all eight occupants.

The accident mirrors the as yet unexplained 26 October, 1999, crash involving a Learjet 35 carrying US golf celebrity Payne Stewart on a flight across the USA.

The chartered aircraft VH-SKC was carrying mine workers from Perth, Western Australia, to Leonora, 614km (332nm) north east, when it failed to respond to air traffic control calls soon after the aircraft's departure.

The King Air overflew its destination and continued to climb through its initially cleared level of 24,000ft (7,320m). The pilot's last radio transmission, when controllers asked him to confirm he had climbed through his cleared level as he passed through 25,600ft, were the words "stand by" followed by heavy, irregular breathing into the microphone, which stayed open for several seconds. The aircraft eventually reached 34,000ft and followed a slightly erratic north easterly flight path. Two aircraft were sent up to intercept the flight as it passed Alice Springs, but they were unable to make contact.

The King Air 200 flew a total of 3,100km before beginning an apparently stable descent and then crashing near Burketown in the Gulf of Carpentaria.

The King Air has a warning light which flashes if the aircraft passes through 12,500ft unpressurised, and all Australian aircraft are required to carry automatically deploying oxygen masks if they fly above 24,000ft.

The accident appears to have similarities with two previous Australian King Air pressurisation incidents. In June last year, a passenger took over from an unconscious pilot at 25,000ft and descended to 6,000ft.

In another, a King Air on dry lease to the Royal Australian Air Force lost pressurisation. The test pilot became incapacitated and the co-pilot was partly disabled. A passenger drew the crew's attention to the flashing pressurisation light on the panel.

Source: Flight International