TM 1-1510-218-10 3B-29 (8)   Altitude  Preselect  Mode  (ALTSEL).  The altitude  preselect  mode  is  selected  by  pressing  the ALTSEL  button  on  the  mode  selector.    The  desired altitude is selected on the altitude preselect controller.   Pitch hold, VS or IAS may be selected as a mode to fly to  the  selected  altitude.    When  outside  the  altitude bracket   trip   point,   the    ALTSEL   ARM  annunciator, along with the selected pitch mode, are illuminated on the    mode    selector.        When    reaching    the    bracket altitude,   the   system   automatically   switches   to   the ALTSEL  CAP  mode  and  the  previously  selected  pitch mode is cancelled.  When the altitude is reached, the ALTSEL CAP mode is automatically cancelled and the flight director switches to the ALT hold mode.  If the air data computer is not valid, the altitude preselect mode cannot  be  selected.    The  ADI  command  cue  will  bias out of view if the VG is not valid. (9)   Altitude  Hold  Mode  (ALT).    The  altitude- hold mode is selected by pressing the   ALT  button  on the  mode  selector.    When    ALT  mode  is  selected,  it overrides  the  APR  CAP,  GA,  IAS,  VS,  and  ALTSEL CAP modes.  In the ALT mode the pitch command is proportional  to  the  altitude  error  provided  by  the  air data   computer.      The   altitude   error   signal   is   gain programmed  as  a  function  of  airspeed.  Pressing and holding the  TCS  button  allows  the  pilot  to  maneuver the  aircraft  to  a  new  altitude  hold  reference  without disengaging the mode.  Once engaged in the altitude hold   mode,   the   mode   will   be   reset   if   the   air   data computer  is  not  valid  and   the  ADI  command  cue  will bias out of view if the VG is not valid. NOTE If    the    baro    setting    on    the    altimeter    is changed,  a  command  is  generated  to  fly the   aircraft   back   to   the   original   altitude reference. (10)   Go-Around  Mode.    The  go-around mode is  selected  by  pressing  the  remote  go-around switch.   When  selected,  all  other  modes  are  reset,  and  the remote  Go-Around  (GA)  and  Yaw  Damp  (YD  ENG) annunciators  will  be  illuminated.    The  ADI  command cue receives a wings level command (zero command when  roll  is  zero).    The  command  cue  also  receives the go-around command, which is a 7° visual pitch up attitude   command.      Selecting   GA   disconnects   the autopilot, but the yaw damper remains on. Once  go-around  is  selected,  any  roll  mode  can be selected.  The wings level roll command will cancel.   The go-around mode is cancelled by selecting another pitch mode, or TCS. f. Autopilot Controller. The autopilot controller  engages  the  autopilot  and  yaw  damper,  as well  as  manually  controlling  the  autopilot  through  the turn knob and pitch wheel.  The autopilot system limits are listed in Table 3B -3. Table 3B-3.  Autopilot System Limits MODE CONTROL OF SENSOR PARAMETER VALUE Yaw Damper Yaw Control Engage Limit Unlimited Basic A/P Touch Control Roll Control Limit Up to ± 45° Roll Steering TCS Pitch Control Limit Up to ± 20° Pitch Turn Knob Roll Angle Limit ± 30° Roll Rate Limit ± 15°/sec Pitch Wheel Pitch Angle Limit ± 15° Pitch Heading Hold Roll Angle Limit Less than 6° and no roll mode selected Heading Select HSI Heading Roll Angle Limit ± 25° Select Knob Roll Rate Limit ± 3.5°/sec CAPTURE VOR Course Knob, NAV Receiver  and Beam Angle Intercept (HDG SEL) Up to ± 90° DME Receiver Roll Angle Limit ± 25° Course Cut Limit at Capture ± 45° Course