Summary
This document proposes to adopt a new airworthiness directive (AD) that would apply to MAULE Models MX-7-240 and MST-7-420 airplanes, and Models M-7-235 and M-7-235A airplanes that are modified in accordance with Maule STC SA2661SO, which incorporates a certain gas turbine engine, certain amphibious floats, and certain propellers. The proposed AD would require amending the Limitations Section of the airplane flight manual (AFM) to prohibit the positioning of the power levers below the flight idle stop while the airplane is in flight. This amendment would include a statement of consequences if the limitation is not followed. The proposed AD is the result of numerous incidents and five documented accidents involving airplanes equipped with turboprop engines where the propeller beta was improperly utilized during flight. 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 below the flight idle stop while the airplane is in flight.