Airworthiness Directives; de Havilland Model DHC-8-102, -103, and -106 Series Airplanes

This amendment adopts a new airworthiness directive (AD) that is applicable to certain de Havilland Model DHC-8-102, -103, and -106 series airplanes. This action requires repetitive operational testing of the stall warning computers to ensure activation of the associated stick shakers, and replacement of non-operational stall warning computers with new or serviceable units. This action also provides an optional terminating action for the repetitive operational tests. This amendment is prompted by a report that, during a routine test, the stick shakers of the stall warning system did not activate, due to contamination of the weight-on-wheels contacts in the stall warning computer. The actions specified in this AD are intended to ensure that such contamination is detected. Contamination of the stall warning computers could lead to incorrect logic detection of the weight-on- wheels signal, and subsequent loss of the stick shaker function.