On 15 December 2009, a De Havilland Canada DHC-8-102 aircraft,
registered VH-XFU, departed Perth, Western Australia (WA) on a
charter passenger service to Darlot, WA. While cruising at flight
level (FL) 230, the aircraft sustained multiple system failures,
followed by a depressurisation. The crew actioned the aircraft
depressurisation checklist and commenced an emergency descent.
During the descent, a number of system cautions and warnings
illuminated. The crew elected to return to Perth and a descent to
8,000 ft was made. Shortly after, the majority of the aircraft's
systems returned to normal.
A subsequent engineering investigation was unable to replicate
the system faults. However, it appeared that the number-1 direct
current (DC) generator output was spiking, causing power to the
left DC buses to be repeatedly switched between the number-1
transformer rectifier unit and the left DC generator. This repeated
power switching resulted in some of the aircraft's systems behaving
erratically.
As a precaution, the number-1 generator control unit, number-1 DC
generator and left bus tie relay were replaced.