Summary
This document proposes to adopt a new airworthiness directive (AD) that would apply to all de Havilland Inc. Models DHC-6-1, DHC-6- 100, DHC-6-200, and DHC-6-300 airplanes. The proposed AD would require amending the Limitations Section of the airplane flight manual (AFM) to prohibit the positioning of the power levers aft of the flight idle stop while the airplane is in flight. This AFM amendment would include a statement of consequences if the limitation is not followed. The proposed AD is a result of numerous incidents and five documented accidents involving airplanes equipped with turboprop engines where the propeller beta was improperly utilized during flight. None of the incidents or accidents involved de Havilland Inc. Models DHC-6-1, DHC- 6-100, DHC-6-200, and DHC-6-300 airplanes. The actions specified by the proposed AD are intended to prevent loss of airplane control or engine overspeed with consequent loss of engine power caused by the power levers being positioned aft of the flight idle stop while the airplane is in flight.