SilkAir Flight 185

SilkAir Flight 185 was a scheduled passenger flight operated by a Boeing 737-300 from Soekarno–Hatta International Airport in Jakarta, Indonesia to Changi Airport in Singapore that crashed into the Musi River near Palembang, Sumatra on 19 December 1997, killing all 97 passengers and seven crew on board.

The cause of the crash was independently investigated by two agencies in two countries: the U.S. National Transportation Safety Board (NTSB) and the Indonesian National Transportation Safety Committee (NTSC). The NTSB, which had jurisdiction based on Boeing's manufacture of the aircraft in the U.S., investigated the crash under lead investigator Greg Feith. Its investigation concluded that the crash was the result of deliberate flight-control inputs "most likely by the captain". While the Indonesian NTSC investigators found "no concrete evidence" to support the pilot suicide allegation, and the previously suspected Parker-Hannifin hydraulic power control unit (PCU) had already been determined by the manufacturer to be defect-free, the final statement from the NTSC was that they were unable to determine a cause of the crash and thus inconclusive.

Regardless of the findings, or lack thereof, the potential factor of a defective Parker-Hannifin-made PCU that controlled the aircraft's rudder is still believed to have possibly led to the crash of the aircraft. The cause of some previous 737 crashes, such as United Airlines Flight 585 and USAir Flight 427, had been attributed to the 737's rudder issues. Although the NTSB and PCU manufacturer Parker-Hannifin had already determined that the PCU was properly working, and thus not the cause of the crash, a private and independent investigation into the crash for a civil lawsuit tried by jury in Los Angeles County Superior Court, which was not allowed to hear or consider the NTSB's and Parker-Hannifin's conclusions, decided that the crash was caused by a defective servo valve inside the PCU based on forensic findings from an electron microscope, which determined that minute defects within the PCU had caused the rudder hard-over and a subsequent uncontrollable flight and crash. The manufacturer of the aircraft's rudder controls and the families later reached an out-of-court settlement.

Aircraft
The aircraft operating flight 185 was a Boeing 737-300 with manufacturer serial number 28556, registered as 9V-TRF and was powered by two CFM56-3B2 engines. Having completed its maiden flight on January 27, 1997, the aircraft was delivered to SilkAir on February 14, 1997, 10 months before the crash. At the time of the accident, it was the newest aircraft in SilkAir's fleet and had accumulated 2,238 flight hours in 1,306 cycles. This is the first and only fatal hull loss for SilkAir.

Accident
Carrying 97 passengers and a crew of seven, the Boeing 737 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's Changi Airport, with captain Tsu Way Ming (Chinese: 朱卫民; pinyin: Zhū Wèimín), 41, of Singapore, a former A-4 Skyhawk pilot, at the controls, along with first officer Duncan Ward, 23, of New Zealand.Generally fair weather was expected for the route, except for some thunderstorms near Singkep Island, 120 km (75 mi; 65 nmi) south of Singapore.

The aircraft was cleared to climb to flight level 350 (FL350), about 35,000 ft (11,000 m), and to head directly to Palembang. At 15:47:06, while climbing through 24,500 ft (7,468 m), the crew requested clearance to proceed directly to waypoint PARDI (0°34′S 104°13′E). At 15:53, the crew reported reaching the cruise altitude of FL350 and was cleared to proceed directly to PARDI, and to report abeam Palembang. The cockpit voice recorder (CVR) ceased recording at 16:05. The documentary television series Mayday agrues Captain Tsu may have taken the opportunity of leaving the cockpit for tripping the CVR circuit breaker to turn off the CVR. At 16:10, the air traffic controller informed the flight that it was abeam Palembang and instructed the aircraft to maintain FL350 and to contact Singapore Control upon reaching PARDI. First Officer Ward acknowledged this call. At 16:11, nearly 6 minutes after the CVR ceased recording, the flight data recorder (FDR) also stopped recording. Mayday shows that Tsu is thought to have come up with an excuse to get Ward out of the cockpit. Having done so, the pilot then proceeded to lock his co-pilot out of the flight deck before disabling the FDR: Tsu is presumed to have done this to ensure that no record would be made of what he was going to do next.

Flight 185 remained level at FL350 until it started a rapid and nearly vertical dive around 16:12. While descending through 12,000 ft (3,700 m), parts of the aircraft, including a great extent of the tail section, started to separate from the aircraft's fuselage due to high forces arising from the nearly supersonic dive. Seconds later, the aircraft hit the Musi River, near Palembang, Sumatra, killing all 104 people on board. The time it took the aircraft to dive from cruise altitude into the river was less than one minute. The plane was travelling faster than the speed of sound for a few seconds before impact. Parts of the wreckage were embedded 15 ft (4.6 m) into the riverbed.

The aircraft broke into pieces before impact, with the debris spread over a wide area, though most of the wreckage was concentrated in a single 60-metre (200 ft) by 80-metre (260 ft) area at the river bottom. No complete body, body part, or limb was found, as the entire aircraft and passengers disintegrated upon impact. Only six positive identifications were later obtained from the few recovered human remains.

Passengers and crew
SilkAir issued a press release on December 19, 1997 with a passenger count by nationality, and another the following day with crew details and a complete passenger manifest. Among those killed in the crash was Singaporean model and author Bonny Hicks.