What happened
On March 14, 2014, a Tecnam P2002JF departed from Warsaw-Babice Airport (EPBC) with the intention of flying to Łódź-Lublinek (EPLL). During the initial climb phase, at approximately 250 feet AGL, the pilot observed a thin stream of blue fluid leaking from the left side of the cowling. Shortly after, the engine began to run unevenly. The pilot attempted to activate the electric fuel pump, but this did not resolve the engine's performance issues.
As the aircraft reached 300 feet AGL, the pilot noted a further drop in engine performance and a rise in cylinder head temperatures beyond permissible limits. The pilot declared intentions to return to the departure airfield and performed a precautionary landing. During the approach, steam was observed escaping from beneath the engine cowling. The aircraft landed safely without further incident.
The investigation
An investigation conducted by the user's commission revealed that the expansion tank cap had melted and significant traces of coolant were found within the engine compartment. The investigation established that the insufficient coolant level caused the temperature to rise, which subsequently melted the expansion tank cap.
Regarding pre-flight procedures, the aircraft's Flight Manual (AFM) specifies different inspection methods depending on whether the engine is cold or warm. For a warm engine, the pilot is only required to check the coolant level in the expansion tank. Because the aircraft had already completed one flight that day, the pilot performed the warm-engine check. However, the pilot had no way of verifying if the previous crew had correctly checked the main reservoir level, as opening the main reservoir on a warm engine poses a burn risk.
Furthermore, the aircraft was equipped with an older engine model featuring a main reservoir without a sight glass, necessitating the opening of the cap to verify levels. The expansion tank also lacked graduated markings. The investigation noted that a newer, optional expansion tank with MIN/MAX markings and a sight glass was available via Service Bulletin SB-089-CS, but had not been implemented on this aircraft.
Findings
- The primary cause of the engine malfunction was an insufficient coolant level.
- The low level was likely due to the previous crew failing to follow the correct inspection procedures.
- The use of an older engine model without a sight glass prevented the pilot from verifying the main reservoir level on a warm engine.
- The lack of implementation of the optional Service Bulletin SB-089-CS contributed to the difficulty in monitoring coolant levels.