In its final report, the NTSC found "no concrete evidence" to support the pilot suicide allegation, with the previously suspected Parker-Hannifin hydraulic power control unit (PCU) having already been determined by the manufacturer to be defect-free.

At the controls were Captain Tsu Way Ming (Chinese: 朱卫民; pinyin: Zhū Wèimín), 41, of Singapore, a former A-4 Skyhawk pilot, and First Officer Duncan Ward, 23, of New Zealand.

[note 1][1][2][3] Generally fair weather was expected for the route, except for some thunderstorms near Singkep Island, 120 km (75 mi; 65 nmi) south of Singapore.

[citation needed] At the time of the accident, it was the newest aircraft in SilkAir's fleet and had accumulated more than 2,200 flight hours in 1,300 cycles.

The NTSC and NTSB investigators thought that if Captain Tsu was responsible for the crash, he must have made up some excuse to get the first officer to leave the flight deck before disabling the FDR (which would have immediately triggered a Master Caution on both pilots' control panels), so that his actions would not be noticed.

[11] At 16:12, as recorded by Indonesian ground radar, the aircraft entered a rapid descent, disintegrated, and crashed into the Musi River.

[4][note 3] The American 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.

[12] Geoffrey Thomas of The Sydney Morning Herald said, "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.

[11] In the aftermath of the crash, several potential motives for the captain's alleged suicide and homicide were suggested, including recent financial losses of $1.2 million[6] (his share-trading showed trading of more than one million shares and his securities-trading privileges had been suspended 10 days before the accident due to nonpayment),[2] his obtaining a $600,000 life insurance policy the previous week, which was to have gone into effect on the day of the accident[6] (though it later emerged that this was a routine policy taken out as part of a mortgage requirement),[2][11] 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),[2] and the loss of four squadron mates during his military flight training, 18 years earlier on the exact date of the crash.

[18] During the investigation of Flight 427, the NTSB had discovered that the PCU's dual servo valve could jam, as well, and deflect the rudder in the opposite direction of the pilots' input, due to thermal shock, caused when cold PCUs are injected with hot hydraulic fluid.

As a result of this finding, the FAA ordered the servo valves to be replaced and new training protocol for pilots to handle unexpected movement of flight controls to be developed.

[21] In July 2001 six families began court proceedings against SilkAir for damages, based on the allegation that the crash was caused by the pilot, after each had rejected a compensation offer of $200,000 (£143,000).

[22] In October 2001 the claims 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.

"[2] Although the NTSB and Parker-Hannifin had already ruled out the possibility of mechanical failure as a cause to the crash of Flight 185 due to a defective PCU servo valve-unit (manufactured by Parker-Hannifin), an independent and private investigation refocused on and further examined the recovered PCU device whose malfunctioning has been pointed out in other sudden Boeing 737 crashes.

[23] After this investigation was complete, 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, found that the crash was caused by a defective servo valve in the plane's rudder.

[2][24] Parker-Hannifin spokesperson Lorrie Paul Crum stated that a federal law disallowed them from using the NTSB final report as evidence in the company's favor during the lawsuit.

The lawyer representing the plaintiffs, Walter Lack, stated that the law only disallowed using the NTSB report's conclusion and suggestions, while statements of fact are admissible.

[28][29] The documentary claimed that the accident aircraft's FDR had failed to record 60 out of the 296 parameters for periods lasting between 10 seconds and 10 minutes in the 25 hours preceding the crash.

[4][29] Singaporean singer JJ Lin's 2013 song "Practice Love" (Chinese: 修煉愛情) from the album Stories Untold (因你而在) is based on this incident,[30] as a close friend of the artist, Xu Chue Fern, was killed on the flight.