What happened
On August 22, 2019, a Boeing 737-800, registration OK-TVO, operating flight TVS1125 from Thessaloniki (LGSM) to Prague (LKPR), experienced a significant engine failure. During the flight, one of the aircraft's two engines ceased functioning due to a fuel supply interruption. This failure was caused by a fuel pump operating without fuel to act as a lubricant, a condition stemming from a prior instance where the pump had run "dry."
Following the loss of thrust, the aircraft was unable to maintain its assigned altitude, necessitating a change in flight profile. Despite the emergency, the pilot in command (PIC) elected to continue the flight to the original destination in Prague rather than diverting to the nearest suitable airport. During the flight, the crew did not declare a PAN PAN emergency to air traffic control, and the cabin crew was instructed not to inform passengers of the specific nature of the technical failure to avoid panic.
The investigation
The ÚZPLN investigation examined the aircraft's technical history, cockpit voice recorder (CVR) transcripts, and the decision-making processes of the flight crew. The investigation established that the engine failure was a direct result of the fuel pump running without lubrication. Investigators also reviewed the airline's operations manual (OM) and found a "quasi" procedure intended for planning that was incorrectly applied during the emergency.
Technical analysis confirmed that the aircraft was airworthy and properly maintained, but a failure to address a previously recorded defect (an N1 speed discrepancy) contributed to the fuel system's failure. The investigation also looked into the crew resource management (CRM) dynamics, noting that the pilot in command performed the Non-Normal Checklist (NNC) at an unusually rapid pace, which hindered the first officer's ability to effectively participate in the decision-making process.
Findings
- The primary cause of the incident was the flawed decision-making process of the pilot in command following the loss of an engine, which failed to comply with the Quick Reference Handbook (QRH) and Flight Crew Training Manual (FCTM) procedures.
- The pilot failed to execute the mandatory instruction to "Plan to land at the nearest suitable airport."
- The engine failure was caused by a fuel pump running without lubrication, following a period of operation without fuel.
- The pilot in command did not follow CRM principles, effectively preventing the first officer from contributing to the emergency response.
- The crew failed to declare a PAN PAN emergency to air traffic services.
- There was a failure to properly manage the technical defect log, as a previous discrepancy regarding engine speed had been noted but not adequately addressed to prevent the subsequent failure.