L2021-04 Engine Malfunction on Airliner during Takeoff at Helsinki-Vantaa Airport on November 25, 2021

At 17:01 h on November 25, 2021, a Fokker 50 airplane operated by Amapola Flyg departed runway 22L at Helsinki-Vantaa airport, Finland, on a scheduled domestic service to Joensuu.

The airplane's warning system triggered a momentary alert during the initial phase of the takeoff run. The pilots heard the alert but did not have sufficient time to diagnose its origin. After liftoff, a failure occurred in the feathering system of the left propeller. As a result, the propeller feathered but the engine continued to operate at high power. The captain, who was at the controls, continued to fly the airplane while the first officer shut down the left engine in accordance with the engine-out procedure.

The flight crew declared mayday, and air traffic control began to vector the airplane to the departure airport as requested by the flight crew. The flight was following a procedure that could have led to the airplane exiting controlled airspace, bringing it into conflict with a tall transmission tower. The controller responded by providing headings that ensured adequate separation from the tower.

The flight crew made preparations for landing on runway 15. They conducted the applicable checklists. On final approach, when the captain asked the first officer to lower the landing gear, the flight crew noticed that the gear had remained extended during the entire flight. The airplane landed at 17:19 h and taxied to the apron. Rescue services were not required.

The Safety Investigation Authority Finland recommends that

* Fokker Services as the type certificate holder and Pratt & Whitney as the engine manufacturer co-operate and look at possibilities of building system redundancy to ensure that the failure of one torque sensor will not cause uncommanded feathering.

* Fokker Services as the type certificate holder and Pratt & Whitney as the engine manufacturer co-operate and look at the need for automatic engine shutdown upon uncommanded feathering.

* Fokker Services as the type certificate holder adds uncommanded feathering procedures in the pilot training syllabus.

* Fokker Services as the type certification holder adds to the abnormal and emergency checklists a separate item that instructs the flight crew to verify landing gear retraction.