LOS ANGELES, FEB. 9 -- The crash of Pacific Southwest Airlines (PSA) commuter Flight 1771, which killed 43 last December, was not caused by problems with the plane's structure or engine, a National Transportation Safety Board report concluded today.

While the report does not make any conclusions about the cause of the crash, it supports the FBI investigators' theory that a fired airline employee shot both PSA pilots, causing the Dec. 7 crash into a California hillside.

The report is one of six that will be made public in the next several months as the board's investigation into the cause of the crash continues.

The report by Kenneth Ensslin, NTSB investigator in charge, said a review of the cockpit tape revealed no aircraft or engine problems in the 30 minutes prior to the crash and that there was no sign of fire as the plane crashed 25 seconds after air traffic controllers reported that the pilots radioed there was trouble and the sound of gunfire was heard.

Federal Bureau of Investigation agents have said they believe that David A. Burke, a former employee of USAir, which had merged with PSA, smuggled a loaded .44-cal. pistol on board using his company identification badge and shot both pilots.