SilkAir Flight 185
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 Boeing 737-300, similar to Flight 185
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| Summary | |
|---|---|
| Date | December 19, 1997 |
| Type | NTSC: undetermined NTSB: suicide/homicide |
| Site | Palembang, Indonesia |
| Passengers | 97 |
| Crew | 7 |
| Injuries | 0 |
| Fatalities | 104 |
| Survivors | 0 |
| Aircraft type | Boeing 737-36N |
| Operator | SilkAir |
| Tail number | 9V-TRF |
| Flight origin | Soekarno-Hatta International Airport |
| Destination | Singapore Changi Airport |
SilkAir Flight 185, a Boeing 737-36N, registration 9V-TRF, was a scheduled passenger flight from Jakarta, Indonesia to Singapore, which crashed on December 19, 1997 after abruptly plunging into the Musi River from its 35,000 feet cruise altitude, killing all 104 people on board.[1]
Remarkably, the cockpit voice recorder and flight data recorder stopped recording, at different times and for no apparent reason, minutes before the aircraft departed level flight and entered a steep vertical dive.[2][3]
The crash was investigated by various groups, with different results. The Indonesian NTSC, who were lead investigators, were unable to determine the cause, while the U.S. NTSB concluded that the crash resulted from an intentional act by a pilot, most likely the captain.[1][3]
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[edit] Accident history
The Boeing 737-300 operating as Flight MI 185 was the newest in SilkAir's fleet, delivered to the airline on February 14, 1997, ten months prior to the crash.[4]
Carrying 97 passengers and a crew of seven, the Boeing departed Jakarta's Soekarno-Hatta International Airport's runway 25R at 15:37 local time (08:37 UTC) for a planned 80 minute flight to Singapore Changi Airport, with the captain at the controls.[3][1] Generally fair weather was expected for the route, except for some thunderstorms near Singkep Island, 120 nm south of Singapore.
The jetliner was cleared to climb to FL350 (approximately 35,000 feet above mean sea level), and to head directly to Palembang.[2] At 15:47 the aircraft climbed through FL245. The crew then requested a clearance to proceed directly to PARDI.[5] At 15:53 the crew reported reaching its cruise altitude of FL350 and was cleared to proceed directly to PARDI, and to report abeam Palembang. At 16:05 the CVR ceased recording. At 16:10 the controller informed the flight that it was abeam Palembang. The controller instructed the aircraft to maintain FL350 and to contact Singapore Control upon reaching PARDI. The crew acknowledged this call. At 16:11:27 the FDR ceased recording. Flight 185 remained level at FL350 until it started a rapid and nearly vertical dive, as shown on Jakarta radar, around 16:12:18. The aircraft broke up in flight, crashing into the Musi River, near Palembang, Sumatra.[3]
All 104 people on board, including the Singaporean captain, Tsu Way Ming and the co-pilot, New Zealander Duncan Ward, died in the crash.
The aircraft broke into pieces before impact, with the debris spread over several kilometres, though most of the wreckage was concentrated in a single 60x80 meter area at the river bottom.[2] There was not a complete body, body part or limb found, as the entire aircraft and passengers disintegrated upon impact. Only six positive identifications were later obtained from the few recovered human remains.[1][2]
Among those killed in the crash was Singaporean model and author Bonny Hicks.[6]
[edit] Passengers
The passengers included 40 Singaporeans, 23 Indonesians, 10 Malaysians, 5 Americans, 4 Germans, 3 British, 2 Japanese, and 1 each from Austria, Australia, Bosnia, India, and the Republic of China (Taiwan). [4]
[edit] Investigation and final report
The accident was investigated by the Indonesian National Transportation Safety Committee (NSTC), which was assisted by expert groups from the U.S., Singapore and Australia.
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.
On December 14, 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 cannot be determined:[2]
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, disagreed with the NTSC and concluded that the evidence was consistent with a deliberate manipulation of the flight controls, most likely by the captain, which put the aircraft into a vertical dive and caused it to crash.[1] In a letter to the NTSC dated December 11, 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.
[edit] Aftermath
[edit] Lawsuits
In 2001, six families who had sued SilkAir for damages based on the allegation that the crash was caused by the pilot, were turned down by a Singapore High Court judge, who ruled that "the onus of proving that flight MI185 was intentionally crashed has not been discharged."[3]
In 2004, a Los Angeles Superior Court jury in the United States, which was not allowed to hear or consider the NTSB's conclusions about the accident, decided that the crash was caused by a defective servo valve in the plane's rudder resulting in a rudder hard-over. The rudder manufacturer, Parker Hannifin, was ordered to pay the three families of victims involved in that case US$44 million. The company appealed the verdict, and the case was later settled out of court for an undisclosed amount.[7][3][8]
[edit] NTSB criticism
The Indonesian NTSC was highly criticised for failing to find and state any accident cause. The U.S. NTSB conducted extensive testing using simulators and computer modeling, which contradicted the Indonesian authority. There was unprecedented criticism from NTSB investigators, who were adamant the only way to achieve the flight profile that occurred immediately prior to impact, was "with sustained nose-down manual flight control input".[3]
[edit] Potential motives
In the aftermath of the crash, several potential motives for Tsu's alleged suicide/homicide were suggested, including recent financial losses (his securities trading privileges had been suspended ten days prior to the accident due to non-payment),[3] his obtaining an insurance policy on his life the previous week (the policy commenced on the day of the accident),[3] his receipt of several recent disciplinary actions on the part of the airline (including one that related to improper manipulation of the CVR circuit breaker),[3] and his possible grieving over the loss of four squadron mates during his military flight training, which occurred years earlier on the exact date of the crash.[2] He had also reportedly had several conflicts with Ward, and other co-pilots who had questioned his command suitability.[9] Investigations later revealed that his total assets were greater than his liabilities, although his liquid assets could not cover his immediate debts, his monthly income was less than his family's monthly expenditure, and he had some outstanding credit card debts.[3]
An official investigation by the Singapore Police Force into evidence of criminal offence leading to the crash found "no evidence that the pilot, co-pilot or any crew member had suicidal tendencies or a motive to deliberately cause the crash of [the aircraft]."[10]
Tsu was formerly a Republic of Singapore Air Force pilot and had over twenty years of flying experience in the A-4SU and TA-4SU Super SkyHawks. His last appointment was instructor pilot of a SkyHawk squadron. Due to his flying experience, it was considered highly unlikely that the aircraft lost control or fell into a stall or spin, as he would have had the experience to avoid or overcome such conditions. The U.S. NTSB investigators found no mechanical malfunctions, and they concluded the accident could only be explained by intentional pilot action.
[edit] PA announcement
Captain Tsu made what appeared to be a routine PA announcement about the flight at 15:44:37, about seven minutes after takeoff, which was recorded by the CVR and transcribed by the NTSC:[2][11]
Good afternoon ladies and gentlemen, this is your Captain. My name is Tsu Wai Ming. On the flight deck this afternoon with me is first officer Duncan Ward. We'd like to welcome you aboard and ah we are now climbing through nineteen thousand feet. We'll be cruising today at thirty five thousand heading towards the north west tracking initially towards the eastern coast of Sumatra towards the town of Palembang before turning right towards Singapore. Flight time one hour twenty minutes. You can expect ah to arrive at Singapore at about six o'clock in the evening Singapore time which is one hour ahead of Jakarta time. Time in Singapore is now four forty five in the afternoon, this is about five minutes ahead of schedule. Weather conditions, clear skies out of Jakarta, very hot afternoon, and at the moment we are still in good weather, however toward Singapore we can expect a bit of showers, thunderstorm towards the southern part of Singapore. Arrival at Singapore should be fine with a temperature of about twenty eight degrees Celsius. The seatbelt sign is now off, feel free to move around the cabin, however while seated, for your own safety have your seatbelt fastened. Sit back and relax, enjoy the services provided today on SilkAir one eight five and I'll get back to you just before our descent into Singapore with an updated weather forecast. Thank you.
Tsu's announcement ended at 15:46. At 16:05, 19 minutes later, the CVR stopped recording. Six minutes later, at 16:11, the FDR stopped recording, and at 16:12 the aircraft plunged into its fatal dive.
[edit] CVR and FDR deactivation
The cockpit voice recorder and flight data recorder stopped recording minutes before the abrupt descent, but not at the same time.[2] A technical analysis of the sound signature of a CVR circuit breaker trip, as recorded by the CVR, was carried out by investigators and the evidence showed that the CVR stoppage was consistent with being manually initiated. The radio continued to work after the failure of the recorders, which indicates that power failure was not a cause, however there was no direct proof that the stoppage was the action of the pilot.[1][3] This lack of conclusive evidence, including the switched off data and voice recorders, made the case against Tsu impossible to prove.
[edit] Controversy
The Indonesian National Transportation Safety Committee, which led the investigation, was not able to find any conclusive cause and even several years after the fact, many conspiracy theories remain. Skeptics point to other difficult to explain accidents involving 737s which showed signs of quirky flight controls such as uncommanded rudder deflection, including USAir Flight 427 and United Airlines Flight 585.[citation needed] The pilot suicide theory and controversy is very similar to that of EgyptAir Flight 990.
[edit] B-737 rudder upgrade
The U.S. FAA has ordered an upgrade of all B-737 aircraft before November 12, 2008.[12] All airlines must install a new rudder control system that includes new components such as an aft torque tube, hydraulic actuators, and associated control rods, and additional wiring throughout the airplane to support failure annunciation of the rudder control system in the flight deck. The system also must incorporate two separate inputs, each with an override mechanism, to two separate servo valves on the main rudder power control unit (PCU) and an input to the standby PCU that also will include an override mechanism.
There was no conclusion by any of the investigative agencies that the Flight 185 crash was related to a rudder (or any other airplane-related) malfunction.
[edit] See also
- List of accidents and incidents on commercial airliners
- Air safety
- EgyptAir Flight 990
- Boeing 737 rudder issues
[edit] Notes
- ^ a b c d e f ASN Accident description of SilkAir Flight 185
- ^ a b c d e f g h NTSC report
- ^ a b c d e f g h i j k l SilkAir 185 - Flight Safety Australia Feb 2008
- ^ a b "Report No. 3, Friday 19 December 1997, 2145hrs (Singapore time)." SilkAir.
- ^ ATC reporting point north of Palembang.
- ^ Grieving relatives recall SilkAir crash victims, CNN, December 20, 1997
- ^ "SilkAir crash families finally receive answers with court verdict", Channel NewsAsia, July 15, 2004.
- ^ Jones Day Parker Hannifin settlement
- ^ Laurinda Keys, Suicide is possible cause of jet crash, officials say pilot had history of troublesome behavior. Associated Press, March 11, 1998.
- ^ Singapore Police Force, Investigation into the Police Report lodged on 25 Aug 99 by the Singapore-Accredited Representative to the National Transportation Safety Committee, December 14, 2000. (from archive.org)
- ^ Minor punctuation and typos have been fixed, refer to original transcript in Appendix A, p. A-12 of official NSTC report.[1]
- ^ B-737 rudder design defect upgrade, [2], November 12, 2002.
