On July 31, 2008 The GCA Skymaster N538JP crashed in the mountains near the city of Coban due to a mechanical flap failure. Miraculously, there were no injuries.
Many pilots keep their hands on the gear switch until receiving a positive gear-down indication. This helps to prevent gear up landings by keeping the landing gear at the forefront of the pilot’s attention and helping him recognize failures earlier.
The same procedure should be used when extending or retracting the flaps, to help recognize a split flap condition. By keeping your hand on the flap lever, you can more easily diagnose and correct a split flap condition before it becomes unrecoverable.
Like engine failures, a split flap condition causes a sudden uncommanded roll, which may trick the pilot into using the wrong recovery procedure, with disastrous consequences. To help, here are two rules of the thumb:
An uncommanded roll on takeoff is most likely caused by an engine failure. An engine failure on takeoff will produce a large amount of roll and yaw. Split flaps rarely cause an uncommanded roll on takeoff since most piston twins are not approved for takeoff with flaps.
An uncommanded roll on landing is most likely caused by a split flap since an engine failure on landing produces little roll or yaw.
Submitted by Kyle Lyons, Training Center Manager