The Indonesian-led investigation into the December 1997 crash of a SilkAir Boeing 737-300 expects to produce a preliminary report by October, with the line of inquiries narrowed down to possible pilot suicide, or mechanical failure in the area of the vertical or horizontal stabiliser.
Indonesian Aircraft Accident Investigation Commission chairman Oetarjo Diran is reported to have said that a preliminary report is being prepared for the next scheduled meetings with the US National Transportation and Safety Board (NTSB). The US agency, along with Singaporean and Australian officials, is assisting with the investigation.
It is unclear, however, whether the report will be released to the public. In the nine months since the Sumatra crash, which killed all 104 people on board, the Indonesian authorities have consistently refused to release much information publicly, including transcripts and readouts from the cockpit voice and flight data recorders.
Diran has confirmed that both systems stopped working in quick succession minutes before the 737 departed controlled flight at its cruising altitude of 35,000ft (10,675m). This has led to suggestions that the recorders were deliberately deactivated by one of the pilots, who then put the aircraft into a terminal dive.
A human factors team is investigating the background of the crew, including reports that the pilot, Tsu Way Ming, had taken out a large life insurance policy just before the crash. While around 70-75% of the aircraft's wreckage by weight has been recovered, Diran told relatives during a recent briefing that little of the cockpit was found because of the speed of impact.
The other major area of focus is the horizontal stabiliser, rudder and tail components, elements of which were recovered outside the main impact area. Information obtained by Flight International shows that an inspection ordered by the US Federal Aviation Administration this year of 112 737-300/400/500s revealed 14 aircraft with horizontal stabiliser leading edge and elevator hinge attachment defects.
Source: Flight International
