On Feb. 9, 1998, a pilot reported that the plane sometimes would not hold cabin pressure at low altitude, and in July 1999, mechanics again were asked to check the system, according to maintenance reports released Wednesday by the National Transportation Safety Board.
The logs also showed that a valve had to be replaced following inflight loss of cabin pressure on June 28, 1989.
The plane Stewart was on departed Orlando, Fla., on Oct. 25, for Dallas. Radio contact was lost with the plane as it passed north of Gainesville, Fla.
The flight continued on autopilot until it ran out of gas and crashed near Aberdeen, S.D. There has been speculation that the cabin pressure system failed, causing the crew and passengers to pass out from loss of oxygen.
The crash destroyed or damaged several parts of the oxygen and pressure systems; some remain missing.
The NTSB, which continues to investigate the accident, has released, without comment, a series of reports on the crash describing the findings of various teams of analysts.
The plane was operated by Sunjet Aviation Inc., which had done a repurchase inspection on the plane on Feb. 8, 1999. Since then, company records showed there had been a repair on a cabin door, some service was done on emergency air lines, an oxygen bottle line was replaced and a flow valve was cleaned.
On Oct. 12, two weeks before the crash, a bleed air leak was found in the plane's tail and was repaired by replacing a gasket. Bleed air is drawn from the plane's engines to increase the pressure inside the cabin.
The day before the accident, Sunjet maintenance workers fixed an engine power problem by replacing a fuel flow valve, the report showed. The morning of the crash the plane was flown to Orlando at altitudes of 12,000 feet to 13,000 feet with no pressure problems reported.
Airplanes are pressurized so that the atmosphere inside never feels higher than about 8,000 feet, even if the aircraft is flying much higher.
The FAA has reported that Stewart's plane climbed as high as 51,000 feet during its flight across the nation's heartland.
The jet flew four hours and 1,400 miles before it crashed in South Dakota.
The new report showed no conversation on the plane's cockpit voice recorder which, though heavily damaged in the crash, saved the final 30 minutes of sound.
That included an altitude warning alarm, which stopped just before the crash as the plane descended, and a high speed alarm which continued until the end of the tape. The cabin altitude warning alarm sounds when pressure drops below the 10,000 foot level.
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