What happened
On July 30, 2017, a Bombardier Challenger 300 was performing a takeoff roll at Edinburgh Airport (EGPH) for a flight destined for Warsaw (EPWA). During the application of takeoff power, the left engine failed to reach the required thrust, triggering a "L ENG EXCEEDANCE" message on the cockpit displays. The crew initiated an aborted takeoff at a very low speed and vacated the runway.
Following the disappearance of the error message, the crew attempted a second takeoff. Although power was applied very gradually during this second attempt, the left engine again failed to reach takeoff power, with the N1 parameter increasing significantly slower than the right engine. This resulted in a second "L ENG EXCEEDANCE" alert, prompting the crew to vacate the runway again and return to the parking stand.
The investigation
An aircraft mechanic traveled to Edinburgh the following day to diagnose the malfunction. Initial engine data analysis revealed numerous errors. Following manufacturer recommendations from Honeywell, the crew adjusted the oil pressure, but the left engine N1 could not exceed 56% during testing. Subsequent data downloads identified a specific error code (MC-203) pointing toward the Compressor Variable Geometry (CGV) Actuator.
Upon inspecting the CGV Actuator on the left engine, investigators discovered that a bolt connecting the actuator to the connection rod was missing. The bolt was found at the bottom of the engine, though the associated nut could not be located. The engine was subsequently repaired with a new bolt and nut, and a successful test run allowed the aircraft to return to service.
An investigation by the operator's Safety Department revealed that one month prior to the incident, the left engine had been sent to an external maintenance facility in the Netherlands for servicing. During that service, components of the CGV Actuator mounting bracket were replaced. The investigation established that the bolt and nut had been incorrectly installed during that maintenance period. Because these components are located in an area of the engine that is not visible once installed, the error went undetected during the engine's reinstallation on the aircraft airframe.
Findings
- The direct cause of the incident was the missing bolt and nut at the connection between the CGV Actuator and the CGV Actuator Connection Rod due to improper installation.
- Contributing factors included inadequate staffing at the servicing organization, which led to personnel multitasking across various tasks.
- Maintenance documentation was found to be too vague, lacking specific details on task cards.
- Operational pressures, such as handovers between shifts and work interruptions caused by delays in receiving spare parts, contributed to the maintenance error.