What happened
On June 6, 2017, a Bombardier DHC-8-400 operated by PLL LOT SA was at Hamburg Airport (EDDH) when the crew attempted to start engine number 1. The initial start attempt failed, as there was no observed increase in Interstage Turbine Temperature (ITT). Following the failure, the crew performed the prescribed aborted engine start checklist procedures. A second attempt was made without ignition to clear excess fuel from the engine, but this also failed, with the engine showing no temperature rise despite fuel flow and rotation.
During the process, a puddle of fuel had accumulated on the ground, which was subsequently cleared by airport services. As a result of the failed start attempts, the passengers were disembarked and returned to the terminal.
The investigation
The investigation, conducted by the operator, focused on the mechanical failure of the engine start sequence. Technical personnel sent from Warsaw arrived to inspect the aircraft. Upon analyzing the symptoms, the maintenance team replaced the Fuel Metering Unit (FMU) in accordance with the Aircraft Maintenance Manual (AMM). Following the component replacement, a successful idle run test was performed, and all engine parameters were found to be within normal operating limits, allowing the aircraft to return to service.
Findings
- The primary cause of the incident was an internal failure of the Fuel Metering Unit (FMU).
- This malfunction caused the unit to deliver an excessive amount of fuel, leading to the engine being flooded during the start sequence.