What happened
On July 12, 2023, an instructor and a student pilot were preparing for a solo training flight involving a cross-country route and a landing at a different aerodrome. Due to the student's concerns regarding engine starting reliability, the instructor assisted with the startup procedure at EPNT (Nowy Targ).
During the initial attempts, the engine failed to start. The instructor directed the student to follow a specific procedure that deviated from the aircraft's official Flight Manual. During the second attempt, smoke became visible in the engine compartment; however, the instructor dismissed the smoke as a normal occurrence and continued the startup process. The subsequent attempts involved priming the engine with four fuel injections each time, followed by extensive throttle movements between 75% and 100% open after the starter had been engaged.
On the fourth attempt, fuel vapors ignited within the engine compartment, resulting in flames and smoke. The crew quickly evacuated the cabin and extinguished the fire using onboard fire extinguishers. There were no injuries, though the Cessna 152, registration SP-KER, sustained damage.
The investigation
The PKBWL investigation focused on the engine starting sequence and the deviation from established operating procedures. The investigation established that the instructor utilized an unauthorized technique involving an excessive amount of fuel priming and aggressive throttle-pumping that was not supported by the aircraft's documentation.
Findings
- The primary cause of the ignition of fuel vapors was performing the engine start in a manner inconsistent with the aircraft's Flight Manual.
- The instructor ignored the presence of smoke during the second attempt, continuing the startup despite clear indicators of a potential fire.
- The instructor applied a non-standard, personal technique for starting this specific aircraft, which included excessive fuel priming and improper throttle manipulation during the cranking process.
Safety action
- The aircraft operator committed to discussing the incident within the aero club's airplane pilot community before resuming flights in Cessna 152/172 aircraft.
- The incident will be reviewed during a safety conference prior to the 2024 season, specifically focusing on the dangers of disregarding established procedures and safety principles.