55-18-01: Solenoid Operated Throttle Locks

55-18-01 CONVAIR: Applies to All Models 240 and 340 Aircraft. Compliance required as soon as practicable but not later than January 1, 1957. 1. Because of instances of inadvertent propeller reversing due to malfunctioning of the solenoid operated throttle locks and improper operation of throttles at time of touchdown on landing, a more positive means of preventing inadvertent movement of the throttles into the reverse segment of the throttle quadrant must be installed. 2. This modification consists of the installation of a protective device which will require a separate and distinct motion by the flight crew member accomplishing the reversing, in order to place the throttles in the reverse pitch range. It must also provide safeguards against disarming or unlocking of this protective device when the throttle levers are further forward than idle setting or, if it is possible to unlock at a forward power setting; movement of the throttles toward idle from slow cruise orlanding gear warning positions shall reengage the lock prior to reaching the idle position. 3. Convair Bulletins Numbers 240-460A and 340-141A covering this modification are an acceptable method of compliance. Alternate designs may be acceptable if the objectives of this directive, as expressed in paragraph 2 have been met. However, because of the many technical considerations involved, all alternate methods of accomplishing this modification should be referred to FAA for engineering evaluation and approval.