What happened
During a final external walkaround, the first officer disconnected the strap extension from both the aircraft stairs and the propeller strap. However, the first officer inadvertently left the propeller strap itself attached to the left engine propeller and failed to rotate the propeller to the required orientation. After completing the walkaround, the first officer returned to the flight deck with the strap extension, which served as a misleading visual cue that all straps had been removed.
Following the closure of the aircraft door, the crew began the engine start checklist. The captain, operating under a high level of expectancy that the strap had been removed, did not identify the strap during the check. Simultaneously, a trainee airport services officer provided the signal to start the engine without detecting the remaining strap. The engine was subsequently started with the propeller strap still in place.
The investigation
The investigation examined the actions of the flight crew and ground staff, finding that the first officer's removal of the strap extension was an unintentional action slip. Because the extension was removed, the aircraft stairs could be retracted, further reducing the likelihood of detecting the remaining strap.
The captain's failure to detect the strap was attributed to inattentional blindness; the strap was thin and located in the shadow of the engine, making it difficult to see from the cockpit seat without leaning forward. Furthermore, the investigation found that the trainee airport services officer was not being closely supervised at the moment of engine start, as the supervising officer had departed the apron.
Findings
- The first officer's unintentional removal of the strap extension created a false perception that the task was complete.
- The captain's high expectancy that the propeller was clear prevented a thorough inspection of the left engine.
- The trainee airport services officer failed to detect the strap during the dispatch process.
- Regional Express dispatch procedures lacked sufficient detail regarding the function and importance of propeller straps and blade orientation.
- There was a lack of clarity regarding the specific roles and responsibilities of trainers and trainees during practical ground handling training.