Airworthiness Directives; MAULE Models MX-7-420 and MXT-7-420 Airplanes and Models M-7-235 and M-7-235A Airplanes Modified in Accordance With Maule Supplemental Type Certificate (STC) SA2661SO

This amendment adopts a new airworthiness directive (AD) that applies to all MAULE Models MX-7-420 and MXT-7-420 airplanes, and all 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. This AD requires 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 AFM amendment will include a statement of consequences if the limitation is not followed. This AD results from 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 this 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.