What happened
On October 28, 2013, a British Aerospace Jetstream 31, registration SE-FVP, was preparing for departure from Kärdla airport in Estonia. The aircraft, operated by Avies AS, was carrying 17 passengers and 2 crew members. During the takeoff roll on runway 14, immediately after the application of takeoff power, the aircraft experienced a sharp rightward veer.
The sudden directional change was so severe that the crew could not maintain control using the rudder or nose wheel steering. The captain responded by reducing power to idle, but the aircraft continued its path until it exited the runway pavement. The aircraft eventually regained directional control on a grass strip located between the runway and the apron. The crew taxied the aircraft to the apron, where all passengers were safely disembarked. There were no injuries and no damage to the aircraft or surrounding property.
The investigation
The Estonian Safety Investigation Bureau (ESIB) examined the aircraft's technical logs, maintenance records, and cockpit voice recorder (CVR) to determine the cause of the excursion. The investigation focused on the crew's handling of the propeller starting lock system.
Technical analysis of the CVR revealed that during the after-start checklist, the co-pilot read the item regarding "Start Locks," but the captain did not provide a verbal response. While the engines were running, the investigators noted that the crew had attempted to disengage the locks, but the power levers were not moved far enough into the reverse position to ensure the right-hand propeller was released. Because the cockpit lacks a specific indicator to show the position of these starting latches, the crew was unaware that the right-hand propeller remained locked in the beta range while the left-hand engine had successfully unlocked into the alpha range.
Findings
- The primary cause of the incident was incorrect pilot action during the propeller lock disengagement procedure. The crew failed to pull the power levers fully to the reverse position and did not verify the torque increase necessary to confirm the locks were released.
- This resulted in asymmetrical thrust, as the left engine produced takeoff thrust while the right engine remained in a ground-mode thrust setting.
- A contributing factor was the lack of a cockpit indicator for the starting lock status, which led the crew to rely on unofficial methods for verification.
- The investigation also noted that the crew did not attempt to use the brakes to stop the aircraft once it began exiting the runway.