Incident Overview
On 14 January 2014, a SAAB-340A aircraft was preparing for a flight from Gdańsk Lech Wałęsa Airport (EPGD) to Warsaw Chopin Airport (EPWA). During the pre-flight inspection by the mechanic, no loose or open panels were found, and all latches were secured. The pilot also conducted a subsequent walk-around and confirmed that all panels and latches were properly closed.
Flight Details
During takeoff, after liftoff, the crew noticed pronounced vibrations. Engine parameters remained normal and consistent with the selected takeoff power. After reaching acceleration altitude and establishing climb parameters, the crew determined that the left engine cowling had opened during the takeoff roll, and the vibrations corresponded to the flapping of the open panel.
Immediately, the crew decided to abort the flight and return to EPGD. After leveling off at 3,000 feet and stabilizing at 160 knots, the open cowling closed on its own, which was accompanied by the cessation of the vibrations. The landing was normal.
Findings
Post-flight inspection of the cowling and engine bay revealed damage to the cowling's edge and surface indentations, but no serious damage to the cowling structure, hinges, or latches. The engine bay showed no damage. Examination of the cowling latch mechanism showed that the front latch lock was loose, allowing it to unlock under vibration. The direction of latch unlocking aligned with the airflow direction. It is possible that simultaneous vibrations from the engine and airflow pressure caused the loose lock to disengage, opening the front latch. The rear latch remained closed, but airflow deformed the cowling, causing it to open fully. The cowling was subsequently replaced.
Cause
The incident was attributed to the opening of the engine cowling in flight due to unlocking of the latch lock. The unlocking likely resulted from a combination of factors: vibrations, airflow, and wear from extended service.