The other compass would operate as a directional gyro which would have to be set manually periodically.

One directional gyro may be inoperative provided: a) flight is made in daylight VMC conditions...

The pilot's horizontal situation indicator (HSI) was removed on 21 September 1994 because of sluggishness and replaced with a directional gyro (DG).

During the flight, the directional gyro would have remained fixed on the last heading that was set, re-enforcing the pilots' belief that the aircraft was climbing straight ahead.

Four days before the accident, the pilot had experienced smoke in the cockpit resulting from an electrical short circuit in the directional gyro (DG).