What happened
On June 28, 2016, a SAAB 340 was performing a scheduled flight from Warsaw Chopin Airport (EPWA) to Krakow (UKKK). During the initial phases of the flight, including engine start, taxi, and takeoff, the aircraft operated normally without any noted irregularities.
While climbing to flight level 080, the crew received a Master Warning (MW) and a 'Tail Pipe Hot' alert specifically for the left engine. In response to the warning, the crew interrupted the climb and notified Air Traffic Control. Following the procedures outlined in the Quick Reference Handbook (QRH) Emergency Checklist for a 'Tail Pipe Hot light on' scenario, the crew proceeded to shut down the left engine. The aircraft then returned to the departure airport. The subsequent approach and landing on a single engine were completed without further complications. Meteorological conditions at the time of the event did not contribute to the incident.
The investigation
The investigation focused on determining the source of the engine warning light. The investigation established that the warning was triggered by an electrical issue rather than an actual thermal event within the engine exhaust.
Findings
The investigation determined that the primary cause of the warning on the central panel was the failure of the sealant used to insulate the electrical connections of the sensors. This leakage allowed external environmental conditions to affect the electrical connections, thereby triggering the false 'Tail Pipe Hot' indication.