Abnormal engine indications involving a Piper PA-31-350, VH-KGE, 45 km north-east of Wagga, New South Wales, on 16 May 1993

As the aircraft was climbing through 7,700 feet, 25 miles from Wagga, the pilot gave a Mayday call and reported returning to Wagga due to a fire in the left engine. Emergency services were alerted. Shortly after, the pilot reported the fire was extinguished and the engine had been shut down. The aircraft returned for a safe landing.

An investigation revealed indications of heavy detonation in No 1 cylinder. The side of the piston was burnt, which had allowed the sump to pressurise and dislodge the dipstick. Engine oil was then pumped out of the open dipstick hole and streamed back to the turbocharger, generating a large volume of smoke. There was no evidence of fire damage.

It was reported that the engine had suffered from an episode of rough running some 15 engine hours earlier. Rubber deposits had been found partially blocking the fuel injectors, but the source was not determined. The injectors were cleaned and the aircraft returned to service. It is likely that the partially blocked injectors resulted in a lean fuel mixture being supplied to the No 1 cylinder, resulting in detonation. The detonation created localised hot spots, causing pre-ignition and the burning of the piston.