What happened
On 4 March 2004, a Short Brothers SD3-60 Variant 100, registration G-VBAC, was preparing for departure from London Stansted Airport. The aircraft was operating a public transport flight with 20 passengers and 3 crew members on board. After successfully starting the right engine, the crew attempted to start the left engine. During this process, the left propeller rotated slowly, but the gas generator (Ng) gauge failed to show the expected acceleration.
Following three unsuccessful start attempts, the crew noticed a mild electrical burning smell. In response, the commander shut down the right engine and requested the Airport Fire Service to attend as a precaution. The crew initiated a rapid disembarkation procedure, directing all passengers to exit the aircraft via the rear left door. While the aircraft was being evacuated, ground personnel observed a pool of fluid under the left engine and what appeared to be flames emerging from the top of the engine. The crew used an extinguisher to suppress the visible flame, and the fire service subsequently declared the aircraft safe.
The investigation
Technical examinations of the aircraft determined that the left engine's starter generator had experienced internal overheating. Investigators also identified a failure in the No 1 Ng transducer. Following the replacement of this transducer, the engine was able to start and function normally, suggesting the initial lack of gauge movement was an indication error rather than a mechanical failure of the engine to rotate.
Regarding the fluid found on the ground, a pool of oil measuring approximately two feet by nine inches was noted beneath the left engine. While the engine manufacturer suggested some oil could have been vented during the start attempts, the source of the remaining oil remained unconfirmed. Additionally, the commander suggested that the flames reported by the ground crew might have been reflected light, given that the sun had set 90 minutes prior to the incident.
Findings
- The primary cause of the incident was the internal overheating of the left engine starter generator.
- A failure of the No 1 Ng transducer prevented accurate engine start monitoring.
- There was no evidence of external burning caused by the overheating component.
- The origin of the oil pool beneath the engine could not be definitively established.