What happened
A Saab 340B operated by Link Airways was released for flight with a propeller strap still secured to the left propeller. During the engine start sequence, the rotational torque generated by the engine caused two pins holding the strap to the engine cowling to fail. This left fragments of the strap assembly and broken pins attached to the propeller blade. As the aircraft accelerated during takeoff, the partially detached strap assembly was flung from the propeller, striking the fuselage and resulting in one injury to a passenger.
The investigation
The investigation examined the pre-flight and engine start procedures, as well as ground handling and dispatching processes. It was determined that the first officer failed to identify and remove the strap during the final external walk-around. Several factors contributed to this oversight, including the absence of the strap extension, which might have otherwise served as a visual reminder. Additionally, the propeller strap was missing its high-visibility streamer, making it harder to detect.
During the engine start, the captain did not notice the strap, likely focusing on ensuring the area was clear of personnel. The investigation also noted that the window of time between the initial engine movement and the failure of the cowling pins was too brief for the flight crew to notice unusual instrument readings. Furthermore, the dispatch coordinator did not identify the strap during ground operations.
Findings
- The first officer did not remove the propeller strap during the pre-flight external check.
- The captain did not observe the strap or the incorrect propeller orientation prior to engine start.
- The propeller strap lacked a high-visibility streamer, reducing its visibility during ground operations.
- There was a lack of effective fleetwide management of propeller strap serviceability by the operator.
- Training for dispatch coordinators did not sufficiently cover the appearance or importance of the propeller straps.
- In many observed flights, the strap extension was not fitted between the strap and the airstairs; had it been correctly fitted, the cabin door could not have been closed, which would have prevented the flight from proceeding with the strap attached.