What happened
On June 21, 2019, a Socata Rallye MS8LLB, registration G-AZKE, departed from the Szymanów airfield (EPWS) for a flight under VFR conditions. Shortly after takeoff, at an altitude of approximately 500 feet, the pilot noted increased engine noise and smoke entering the cockpit, though engine parameters initially remained normal. Because an immediate landing was not possible at that altitude, the pilot continued the climb.
At approximately 900 feet, the engine suddenly failed while the aircraft was over the residential area of Szymanów. The pilot executed a 180-degree turn to attempt a return to the airfield. However, the aircraft was unable to reach the runway and instead performed a forced landing in a recently reclaimed agricultural field, roughly 500 meters east of the runway 14 extension. There were no injuries to the crew or passengers, though the aircraft sustained severe damage.
The investigation
The PKBWL investigation focused on the mechanical state of the engine and exhaust system. Investigators examined the aircraft's maintenance records, which showed that all periodic inspections and maintenance tasks had been completed on schedule. The aircraft held a valid certificate of airworthiness.
Physical examination of the engine revealed a broken silencer end cap and a crack in the silencer wall. Investigators also found evidence of a fuel-air mixture fire within the carburetor and the air intake. The investigation determined that the high-temperature exhaust gases, reaching temperatures between 627°C and 827°C, had entered the carburetor through a faulty heat valve, which had developed excessive play due to bearing wear.
Findings
- The primary cause of the engine failure was a leak in the exhaust silencer.
- This leak allowed hot exhaust gases to escape into the carburetor heat system.
- The high temperature of the gases (exceeding the auto-ignition temperature of the fuel) caused a fire in the fuel-air mixture within the carburetor and air intake.
- This combustion process led to the sudden cessation of engine operation.
- The pilot's decision to continue climbing after noticing smoke was necessitated by the flight phase, as an immediate landing was not feasible at 500 feet.