The pilot of an Australian Metro III cargo plane had difficulty maintaining situational awareness when his horizon and attitude indicators didn’t display correct information during a night time departure, according to an ATSB investigation.
The Metro III aircraft, registered VH-UUO, took off from Brisbane Airport, Autralia for a domestic freight charter flight to Bankstown Airport, with one pilot on board. Following the take-off, when at about 200 feet above ground level, the pilot observed the horizontal situation indicator (HSI) indicating a right turn although the aircraft was still maintaining runway direction. The pilot reported that the attitude indicator (AI) displayed alternately a nose up and nose down attitude.
When at about 1600 feet above ground level, the pilot advised air traffic control of a ‘minor problem with heading’ and was directed to conduct a right turn onto an easterly heading to avoid noise sensitive areas. The pilot turned the aircraft to the right, towards the Pacific Ocean, while referring to the HSI on the co-pilot’s instrument panel, which was providing more accurate heading information. The pilot was aware that the captain’s AI and HSI instruments were providing erroneous indications, but became disoriented by continuing to scan those instruments. The pilot looked out of the window in an attempt to gain a visual reference but could see only blackness.
The pilot continued a shallow right turn until the lights of runway 19 became visible. The aircraft landed back at Brisbane, on runway 19 about 150 kg above the aircraft’s maximum landing weight.
The ATSB found that the cockpit was not configured correctly prior to taxi, nor was the incorrect heading reference detected or corrected during the taxi or line up. The left gyro slaving switch was selected to ‘free’ instead of ‘slave’ mode, resulting in the captain’s HSI indicating about 50° left of actual heading throughout the flight.
The AI probably intermittently malfunctioned after take-off, and the pilot became distracted by the two erroneous instrument indications. These, combined with the dark night and flight over water without visual reference, contributed to the pilot’s difficulty in maintaining orientation and achieving the planned departure track. The pilot therefore elected to return to land at Brisbane.