TM  1-1520-240-10            2-5-3 Figure  2-5-2.  Cyclic Stick Grip 2-5-5.  AFCS Trim Switch. NOTE If the longitudinal CCDA fails, it can be recog- nized  by  loss  of  pitch  trim  or  failure  of  the centering   devise   to   release.   A   centering spring in the pitch axis allows these forces to be over-come. The AFCS trim switch (fig. 2-5-2) is used to make small changes in the pitch (airspeed) and roll attitude while the AFCS is operating. The switch is spring-loaded to center off position. Moving the switch forward or aft from center off  position  commands  an  increase  (forward)  or  de- crease (aft) in airspeed by driving a trim motor in the longitudinal CCDA. Moving the switch left or right commands the roll ILCA to bank the helicopter in the selected direction without mov- ing the stick. Power is supplied to drive the pitch trim motor from No. 1 AC bus through CLTV DRIVER ACTR circuit breaker on the No. 1 PDP. 2-5-6.  Directional Pedals. The directional pedals (7 and 24, fig. 2-1-3) are used for directional control of the helicopter during flight and while taxiing with the forward gear off the ground. When the right pedal is displaced forward, the forward rotor disk tilts to the right and the aft rotor disk tilts to the left. The opposite action occurs when the left pedal is displaced forward. An ILCA is installed to assist the pilot in moving the pedals. The  pedals  are  adjusted  individually  fore  and  aft  by pressing a lever mounted on the pedal support and mov- ing the pedal to a new position before repositioning the lever. Insure that both pedals are adjusted equally (left and right pedals in same respective hole position) and pedal   adjustment   lockpins   are   engaged.   A   balance spring is installed to reduce control sensitivity. 2-5-7.  Advanced Flight Control System. (AFCS) a. The Advanced Flight Control System (AFCS) sta- bilizes the helicopter about all axes and enhances control response. It automatically maintains desired airspeed, altitude, bank angle, and heading. An automatic turn fea- ture, coupled to the pilot or copilot HSI (horizontal situa- tion indicator) is also included in the AFCS. b. Built In Test Equipment (BITE) is installed in each AFCS computer. This equipment is intended for ground troubleshooting   purposes   only.   An   interlock   circuit through the engine condition control box prevents BITE use anytime either ECL is out of STOP. c. Power is supplied to the HDG ENGAGED, BARO ALT and RAD ALT ENGAGED lights from the DC essen- tial bus through the CAUTION PNL circuit breaker on the No. 1 PDP. The No. 1 AFCS receives AC and DC buses respectively through the AFCS NO. 1 circuit breakers on the No. 1 PDP. The No. 2 AFCS receives AC and DC power  from  the  No.  2  AC  and  DC  buses  respectively through the AFCS NO. 2 circuit breakers on the No. 2 PDP. d. The   AFCS   consists   of   the   following   compo- nents: (1) A cockpit control panel. (2) Two   AFCS   computers   in   the   avionics compartment. (3) Three ILCA’s in the flight control closet. (4) A differential airspeed hold (DASH) actuator in the flight control closet. (5) Two longitudinal cyclic trim (LCT) actuators are installed, one in the forward upper controls, the other in the aft upper controls. (6) Roll and yaw magnetic brakes, a longitudi- nal CCDA, and a thrust CCDA are all located in the flight controls closet.