PROPELLER LEVERS.

TM 1-1510-223-10 Change 3 2-47 NOTE If the synchrophaser is ON but does not adjust properly, the synchrophaser has reached the limit of its range. Turn the system OFF, manually adjust the propeller RPM into synchronization, then turn the synchrophaser ON. The propeller synchrophaser may be used on takeoff at the pilot’s option. b. Synchrophaser Control Box. The control box, lo- cated forward of the pedestal, converts pulse rate differ- ences into correction commands. Differences in pulse rate, and/or propeller position, cause the control box to vary the voltage in the primary governor coil, which in turn increases propeller speed until the correct speed and phasing are obtained. The system is protected by a 5-ampere circuit breaker placarded PROP SYNC, lo- cated on the overhead circuit breaker panel (fig. 2-7). c. Synchroscope. The propeller synchroscope indi- cator, located on the pilot’s instrument panel, provides an indication of synchronization of the propellers. If the right propeller is operating at a higher RPM than the left, a black and white cross pattern spins in a clockwise direc- tion. Left, or counterclockwise, rotation indicates a higher RPM of the left propeller. This instrument aids the pilot in obtaining complete synchronization of the propellers. 2-47. PROPELLER LEVERS. Two PROP levers on the control pedestal (fig. 2-12), placarded PROP, are used to regulate propeller speeds. Each lever controls a primary governor, which acts to regulate propeller speeds within the normal operational range. The full forward position of the levers is placarded TAKE-OFF, LANDING, AND REVERSE - HIGH RPM. The full aft position of the levers is placarded FEATHER. When a lever is placed at HIGH RPM, the propeller may attain a static RPM of 1700 depending upon POWER le- ver position. As a lever is moved aft, passing through the propeller governing range, but stopping at the feathering detent, the propeller RPM will correspondingly decrease to the lowest limit (approximately 1200 RPM). Moving a PROP lever aft past the detent into FEATHER will feather the propeller. 2-48. PROPELLER REVERSING. CAUTION Do not move the POWER levers below the flight idle gate unless the engine is running. Damage to the reverse linkage mechanisms will occur. Propeller reversing on deteriorating surfaces may cause engine FOD and propeller erosion from reversed airflow. Consideration should be given to not reversing propellers when operating in snow or dusty conditions, to prevent obscuring the pilot’s vision. The engine POWER levers actuate an engine mounted cambox which is connected to the engine FCU (fuel control unit) and the propeller reversing cable. The cambox is arranged so that the reversing cable is not af- fected by POWER lever movement forward of the idle stop. When the POWER levers are lifted over the revers- ing detent and moved rearward, the reversing cable is pulled aft. This action resets the beta valve rearward, al- lowing the governor to pump more oil into the propeller, thus moving the blades through the ground fine range to- ward reverse pitch. As the blades move the mechanical feedback collar is moved forward. This movement is transmitted by a carbon block on the end of the reversing lever to the beta valve, causing it to move forward. As the POWER levers are moved further rearward (into the striped area), the propeller blades are moved further to- ward the reverse pitch stop, and the FCU is reset to in- crease engine speed. 2-49. PROPELLER TACHOMETERS. Two tachometers on the instrument panel register pro- pellerspeedinhundredsofRPM(fig.2-16).Eachindicator is slaved to a tachometer-generator unit attached to the correspondingengine,installedonthereductiongearbox.