What happened
On June 26, 2012, an ATR-72 was operating a flight from Gdańsk Lech Wałęsa Airport (EPGD) to Poznań-Ławica Airport (EPPO). After takeoff, once the aircraft had reached its target altitude and airspeed, the crew moved the power selector (PWR MTOG) to the cruise position. Immediately following this adjustment, the crew noticed unusual noises and unstable operation of engine number one.
Warnings for low oil pressure (OIL LOW PRESS) appeared on both the Crew Alerting Panel (CAP) and the local engine panel. In response to the instability, the crew shut down engine number one. Following the engine shutdown, an ELECTRICAL SMOKE warning appeared on the CAP. The crew reported a strong smell of burning oil and smoke entering the cockpit. The crew executed the appropriate checklists for low oil pressure and electrical smoke, declared an emergency, and proceeded to land safely at EPPO with all 37 passengers on board remaining uninjured.
The investigation
Following the landing, a technical inspection of the engine was conducted to investigate the cause of the low oil pressure warning. The inspection revealed a loss of oil from the reservoir. During the search for the source of the leak, investigators discovered that the oil filler cap had been incorrectly installed and was not properly secured.
To determine the origin of the error, the investigation reviewed maintenance activities performed in 2012 related to the oil system. It was established that an oil replenishment task had been performed the day before the incident. The investigation focused on whether this specific procedure led to the improper securing of the cap. No defects were found in the cap or the reservoir itself.
Findings
- The engine failure and subsequent smoke in the cockpit were caused by an improperly installed and secured oil filler cap on engine number one.
- The error likely occurred during oil replenishment activities performed on the day preceding the flight.
- The engine sustained damage due to the oil loss and could not be restarted, necessitating its removal and replacement with another unit.
Safety action
- The operator's technical maintenance manager was interviewed to identify any contributing circumstances that might lead to improper cap installation.
- A Quality Information Letter was issued to maintenance personnel providing updated guidelines for such tasks.