Incident Overview
On June 10, 2018, a Bombardier DHC-8-402 aircraft was conducting a scheduled flight from Warsaw (EPWA) to Budapest (LHBP). Shortly after takeoff, at approximately 14:10 UTC, the crew observed an increasing oil temperature on engine number 2. When the temperature reached 105°C (maximum allowable 107°C), the crew consulted the "HIGH OIL TEMPERATURE IN FLIGHT" checklist and reduced engine #2 power by 20%. This action lowered the oil temperature.
The aircraft's climb was stopped at flight level 100. The crew decided to return to EPWA and requested a holding pattern to burn off fuel and reduce landing weight. After consuming about 150 kg of fuel, the crew initiated an approach and landing, which was completed without further incident. The aircraft was then handed over to maintenance personnel. The crew submitted an Aircraft Safety Report (ASR).
Cause
The incident was caused by a malfunction of the engine #2 oil cooler flap actuator (ACOC FLAP ACTUATOR), part number 800600M03. Subsequent testing revealed that the actuator was stuck in the closed position, preventing proper oil cooling. The faulty actuator was replaced with a serviceable unit.
Safety Recommendations
No safety recommendations were issued by the investigation commission.