Asymmetrical flaps bring down Lancair

This July 2010 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.

Aircraft: Lancair 320. Injuries: Minor Location: Spokane, Wash. Aircraft damage: Substantial.

What reportedly happened: The pilot initiated a go-around followed by a climbing left turn to re-enter the traffic pattern. He was unable to roll out of the turn. The bank angle continued to near 90° before he was able to maneuver the airplane close to the runway. The airplane ultimately stalled and crashed on the runway.

The post-accident examination revealed an asymmetric flap condition. Shortly after the accident, the airplane kit manufacturer issued a Service Bulletin that addressed the asymmetric flap problem. The bulletin advised operators to inspect for adequate clearance and ensure that sufficient stiffness is established so that when fully deployed, the flap’s leading edge will not have a tendency to flex upward and snag the trailing edge of the wing. The condition could jam the flap and subsequently preclude its retraction.

Probable cause: Loss of airplane control due to the asymmetric flap condition.

For more information: NTSB Identification: WPR10LA374


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