Flight History
The aircraft, registered VH-CCW, departed Jandakot for Perth at approximately 08:00 on 3 May 1981. The pilot had arranged to meet an engineer, but the engineer could not attend. During the morning, the aircraft was seen parked with engine cowls removed, and the pilot worked near the propeller governors. At about 11:00, the pilot started the engines, taxied, and conducted high-power checks. At 11:09, he contacted Perth Surface Movement Control, requesting clearance for an air test at Flight Level 200. Clearance was granted, and the aircraft was instructed to taxi to Runway 20.
After takeoff, the aircraft turned right and tracked west on the 270 radial of the VOR, as instructed. The pilot advised he wished to continue west until further notice. Weather in the Perth area was fine with no cloud and a light southwesterly surface wind. The aircraft appeared to operate normally except for a thin smoke trail from the right engine.
Accident Sequence
At 11:19, the pilot reported his test completed, stating he was at 7,000 feet and 10 miles DME from the airport. Over the next five minutes, routine radio exchanges occurred, and the pilot did not indicate any abnormality. At 11:24, he reported at right base for Runway 20 and was cleared to land, which he acknowledged.
The right base position is over the suburb of Bassendean. Witnesses noted the aircraft was lower than normal, with louder engine noise and smoke trailing from the right engine. Both propellers were rotating, and landing gear was retracted. As the aircraft commenced an apparently normal right base turn, it suddenly rolled inverted. The nose may have pitched up just before the roll. The aircraft then rotated and descended rapidly, later rolling back to upright. After about two turns, rotation stopped, and the aircraft dropped vertically to the ground in a backyard. The left wing and tailplane struck a house roof just before impact. An intense fire immediately broke out and consumed most of the wreckage.
Examination Findings
Wreckage examination found no pre-existing defects or malfunctions apart from loose attachment nuts on the left side of the propeller governor on the right engine. Oil had leaked from this position, covering the engine and causing the observed smoke. Internal inspection of the right engine showed all bearing surfaces were oil-wetted, but the remaining oil quantity at impact could not be determined due to leakage and fire.
Both engines were operating at impact. The right engine was at a low power setting, probably idle; the left engine was at a higher power (exact setting undetermined). The left propeller blade angle was consistent with higher power output. The right propeller blade angle was outside the normal operating range, consistent with movement toward the feather position, either from pilot selection or oil supply exhaustion. It was not determined whether the pilot initiated feathering.
The stability augmentation system servo was at maximum elevator-down spring tension, a position automatically driven by low airspeed. Elevator trim was set 10 degrees nose-up, also consistent with low-speed flight. Rudder trim was at full-left rudder, indicating prolonged operation with high power on the left engine and low power on the right. Flaps were half extended, and landing gear was down at impact.
Post-mortem examination found the pilot had extensive coronary artery disease. This condition could have caused sudden incapacitation or death, or severe chest pain leading to unintentional coarse control inputs. The pilot had completed regular medical examinations for license renewal, but his condition was not detected.