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Aviation History
2001
2001 - 0026.PDF
NEWS ANALYSIS An unsatisfactory report Indonesia's conclusions on the SilkAir crash of December 1997 have done nothing to dispel the controversy over the incident ANDRZEJ JEZIORSKI/SINGAPORE npHEINDONESIANNation- J. al Transportation Safety Committee (NTSC) has produced an evasive and worthless report on die crash of a SilkAir Boeing 737- 300 on 19 December 1997, which killed 104 people. The investiga tion was always controversial, steeped in suggestions of pilot sui cide, obscured by lack of evidence from die cockpit voice recorder (CVR) and flight data recorder (FDR), and further shrouded by die Indonesian investigators' reluc tance to release data to die public. In an interview with Flight International'm 1999, NTSC chair man Oetarjo Diran said he was worried about making enemies for fear of undermining his plans to make die NTSC an international ly credible organisation to parallel the US National Transportation Safety Board (NTSB). In fact, Diran has achieved what he set out to avoid. The Committee has also plunged into direct conflict widi die NTSB, which took part in die investigation. Diran's summary of die report, issued on 14 December, says: "Due to die highly fragmented wreck age, and die nearly total lack of use ful data, information and evidence, die NTSC has to conclude diat die technical investigation has yielded no evidence to explain die cause of die accident." The NTSB disputes diis, citing "intentional pilot action" as die most probable cause, adding that the aircraft's descent profile was consistent widi manual nose-down control inputs. In a letter to Diran, NTSB chairman Jim Hall writes: "Please note diat our review of the draft final report revealed diat sev eral sections require correction, clarification, or the inclusion of additional information." He expresses "greatest concern" over die NTSC's inability to explain die aircraft's departure from level flight, and its recommendations "that are not supported by the fac tual evidence". Diran contends that die suicide dieory is a "plausible hypothesis", but "based on insufficient evi dence". He adds: "The object of diis investigation has to go beyond hypodiesising to establish conclu sions based on concrete evidence and proof." Diran appears to have made anodier mistake he set out to avoid: diat of treating this inquiry as if it were a court of law with die task of establishing guilt or inno cence, and the "prosecution" car rying the burden of proof. MOST PROBABLE CAUSE An accident inquiry is not con cerned with prosecution, guilt, innocence or with absolute proof in the legal sense. Its mandate is to establish a "most probable cause", recovery from high-speed flight upsets", the installation of flight envelope protection systems in all passenger aircraft, and the setting up of a regional framework for co operation in accident investigation "to support those states diat do not have die resources and facilities to do investigations on their own". There is no recommendation on monitoring flight crews' psycho logical condition, despite die fact diat die "plausible" suicide dieory remains the most likely explana tion. The investigators have suggested no coherent chain of events that could account for the "failure" of the CVR, then of the FDR six minutes later, the depar ture from level flight into a steep dive, die fact diat die engines ran at high power all the way to impact two minutes later, the fact diat no distress call was sent and diat radar offered any of diese for scrutiny. He does confirm, as was revealed in die mid-1999 interim report, that the aircraft's horizontal stabiliser trim at impact "corresponds widi an aircraft nose down attitude". The combination of systems and mechanical failures that might pro duce such a scenario by accident seems beyond reasonable proba bility. Add to this the pilot-in-com- mand's chequered professional history, three recent disciplinary actions, his debts and multiple life insurance policies. These were detailed internally by the NTSC's human performance group in mid- 1999, aldiough Diran has said new information has since shown the pilot had positive net worth at the time of die accident, despite S$2.2 5 million ($1.3 million) in share loss es. Diran has left out much of the new information, however, saying: The report into the 1997 crash of a SilkAir Boeing 731-300 leaves many questions unanswered and make recommendations to reduce die risk of a similar accident in the future. The report does not attempt to reduce diis risk. None of the report's six recom mendations addresses the suicide dieory. Diran proposes a review of FDR/CVR design to "identify and rectify latent factors associated widi stoppage...in flight", the fit ting of underwater locator beacons to recorders, the recording of flight instrument displays, a review of flight crew training "to include plots show no attempted recovery from the descent. Simulations based on the five radar plots available yielded only one combination of control inputs that would take the aircraft through that descent profile. Initially, investigators agreed diese inputs could only be explained by deliberate action, although Diran now says there is "no evidence", and diat diere could be "odier per mutations of inputs" that would produce the descent. He has not "Specific details, such [as] the pilot's personal details, etc, were not deemed appropriate for inclu sion in the final report." Diran, as an engineer, says he has carried out this investigation by scientific principles. Perhaps he is familiar with the principle of Occam's Razor, which states that once one has eliminated die impossible, "one should not increase, beyond what is necessary, the number of entities required to explain anything". J 24 FLIGHT INTERNATIONAL 2 - 8 January 2001
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