Airworthiness Directives; Saab Model SAAB SF340A and SAAB 340B Series Airplanes

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Saab Model SAAB SF340A and SAAB 340B series airplanes. This action requires the installation of a mechanical flight idle stop on the control quadrant of the flight compartment. This action also requires a revision of the Airplane Flight Manual to ensure the use of certain operating procedures after the mechanical flight idle stop is installed. Additionally, this action provides an optional terminating action for the requirements of this AD. This amendment is prompted by a report indicating that the means of protection against the selection of the ``beta'' range of propeller operation during flight has been reduced on certain modified control quadrants. Additionally, there have been reports indicating that power levers on the control quadrant have been moved aft of the flight idle position during flight due to improper usage of the mechanical beta stop. The actions specified in this AD are intended to prevent such movement of the power lever(s) during flight, which could result in propeller overspeed, engine damage, and loss of power to one or both engines.