TM 1-1510-223-10 Change 3          2-45 flap switch to the UP detent position. To return the flaps to APPROACH, move the flap switch to the UP position and then to the APPROACH detent position. For an inter- mediate flap position between APPROACH and DOWN, the APPROACH position acts as an OFF position. To return  to  any  position  between  full  DOWN  and  AP- PROACH, place flap switch to UP, and when the desired position is obtained, return the switch to the APPROACH detent. In the event that any two adjacent flap sections extend 3 to 5 degrees out of phase with the other, a safety mechanism is provided to discontinue power to the flap motor. b.   Wing Flap Position Indicator. Flap position in per- cent of travel from 0 percent (UP) to 100 percent (DOWN) is shown on an indicator, placarded FLAPS, located on the  center  subpanel  (fig.  2-6).  The  approach  and  full down flap positions are 14 and 35 degrees, respectively. The flap position indicator is protected by a 5-ampere circuit breaker, placarded FLAP CONTR, located on the overhead circuit breaker panel (fig. 2-7). Section  VI. PROPELLERS 2-41.   DESCRIPTION. A four-blade aluminum propeller is installed on each engine. The propeller is of the full feathering, constant speed, variable-pitch, counterweighted, reversible type; controlled by engine oil pressure through single action, engine   driven   propeller   governors.   The   propeller   is flange mounted to the engine shaft. Centrifugal counter- weights,   assisted   by   a   feathering   spring,   move   the blades toward the low RPM (high pitch) position and into the  feathered  position.  Governor  boosted  engine  oil pressure moves the propeller to the high RPM (low pitch) hydraulic stop and reverse position. The propellers have no low RPM (high pitch) stops; this allows the blades to feather after engine shutdown. Low pitch propeller posi- tion is determined by the low pitch stop which is a me- chanically  actuated,  hydraulic  stop.  Ground  fine  and reverse blade angles are controlled by the POWER lev- ers in the ground fine and reverse range. 2-42.   FEATHERING PROVISIONS. Both manual and automatic propeller feathering sys- tems are provided. Manual feathering is accomplished by pulling the corresponding PROP lever aft, past a fric- tion detent. To unfeather, the PROP lever is pushed for- ward into the governing range. The automatic feathering system will sense loss of torque and will feather an un- powered  propeller.  Feathering  springs  will  feather  the propeller when it is not turning. a.   Automatic  Feathering.  The  automatic  feathering system  provides  a  means  of  immediately  dumping  oil from the propeller servo to enable the feathering spring and  counterweights  to  start  feathering  action  of  the blades in the event of an engine failure. Although the system  is  armed  by  a  switch  on  the  overhead  control panel  (fig.  2-13),  placarded  AUTOFEATHER  TEST  - OFF - ARM, the completion of the arming phase occurs when both POWER levers are advanced above 89% N₁, at which time both annunciators on the caution/advisory annunciator  panel  indicate  a  fully  armed  system.  The annunciator  panel  annunciators  are  green  and  plac- arded #1 AUTOFEATHER (left engine) and #2 AUTO- FEATHER   (right   engine).   The   system   will   remain inoperative as long as either POWER lever is retarded below approximately the 89% N₁ position, unless TEST position of the autofeather switch is selected to disable the POWER lever limit switches. The system is designed for  use  only  during  takeoff  or  landing,  and  should  be turned off when establishing cruise climb. During takeoff or landing, should the torque for either engine drop to an indication between 19 - 13%, the autofeather system for the opposite engine will be disarmed. Disarming is con- firmed when the AUTOFEATHER annunciator of the op- posite  engine  becomes  extinguished.  If  torque  drops further, to a reading between 13 and 7%, oil is dumped from the servo of the affected propeller allowing a feath- ering spring to move the blades into the feathered spring to move the blades into the feathered position. Feather- ing also causes the AUTOFEATHER annunciator of the feathered propeller to extinguish. At this time, both the #1 AUTOFEATHER and #2 AUTOFEATHER annunciators are extinguished, the propeller of the defective engine has feathered, and the propeller of the operative engine has been disarmed from autofeathering capability. Only manual feathering control remains for the second propel- ler. b.   Propeller   Autofeather   Arm/Off/Test   Switch.   A switch placarded AUTOFEATHER TEST - OFF - ARM, located on the overhead control panel (fig. 2-13), is pro- vided for arming and disarming the system and for selec- tion  of  the  TEST  function.  The  TEST  position  of  the switch checks the readiness of the autofeather system below 89% N₁. c.   Autofeather Annunciators. Autofeather annuncia- tors consist of two green annunciators on the caution/ad- visory annunciator panel placarded #1 AUTOFEATHER and #2 AUTOFEATHER. When illuminated, the annun- ciators  indicate  that  the  autofeather  system  is  armed. Both annunciators will be extinguished if either propeller has been feathered or if the system is disarmed by re- tarding  a  POWER  lever.  Autofeather  circuits  are  pro- tected   by   one   5-ampere   circuit   breaker   placarded AUTOFEATHER, located on the overhead circuit break- er panel (fig. 2-7).