Silk Air Flight 185 - Investigation and Final Report

Investigation and Final Report

The accident was investigated by the Indonesian National Transportation Safety Committee (NTSC), which was assisted by expert groups from the U.S., Singapore and Australia, and the American National Transportation Safety Board (NTSB).

Approximately 73% of the wreckage (by weight) was recovered, partially reconstructed and examined. Both "black boxes" — the Cockpit voice recorder (CVR) and Flight data recorder (FDR) — were successfully retrieved from the wreckage, and their data was extracted and analyzed.

According to Mayday, At 16:00 Captain Tsu left the cockpit; 5 seconds later, the CVR stopped recording. It was believed that Captain Tsu tripped the CVR circuit breaker before leaving the cockpit. NTSC and NTSB investigators postulated that, if Captain Tsu was responsible for the crash, he returned and then concocted a pretense for First Officer Ward to leave the cockpit. Several minutes later, as recorded by Indonesian radar, the plane entered a rapid descent, broke up and crashed into the Musi River, disintegrating on impact.

On 14 December 2000, after three years of intensive investigation, the Indonesian NTSC issued its final report, in which it concluded that the evidence was inconclusive and that the cause of the accident could not be determined:

The NTSC has to conclude that the technical investigation has yielded no evidence as to the cause of the accident.

The U.S. National Transportation Safety Board (NTSB), which also participated in the investigation, concluded that the evidence was consistent with a deliberate manipulation of the flight controls, most likely by the captain.

In a letter to the NTSC dated 11 December 2000 the NTSB wrote:

The examination of all of the factual evidence is consistent with the conclusions that: 1) no airplane-related mechanical malfunctions or failures caused or contributed to the accident, and 2) the accident can be explained by intentional pilot action. Specifically, a) the accident airplane’s flight profile is consistent with sustained manual nose-down flight control inputs; b) the evidence suggests that the cockpit voice recorder (CVR) was intentionally disconnected; c) recovery of the airplane was possible but not attempted; and d) it is more likely that the nose-down flight control inputs were made by the captain than by the first officer.

Geoffrey Thomas of The Sydney Morning Herald said that "A secret report confirmed that the Indonesian authorities would not issue a public verdict because they feared it would make their own people too frightened to fly." Santoso Sayogo, an NTSC investigator who worked on the SilkAir 185 case, said in an episode of the Canadian television series Mayday (Air Crash Investigation, Air Emergency) that the NTSB opinion was in fact shared by some Indonesian investigators who were overruled by their boss.