TM 1-1510-225-10 3C-60 (3)   GCAS  Flap  Override  Switch.  A guarded switch, placarded GPWS FLAP OVRD, located on the pedestal extension, provides a means of disabling the "Too  low  flap"  aural  warning  to  facilitate  landing  with the flaps in the  UP position.  The "GCAS too low flap," aural warning will not be activated if the flaps are in the APPROACH or LANDING positions (40° or greater). (4)   GCAS System Inoperative Caution Annunciator    Light.       Illumination    of    the    cautionary (yellow)   annunciator   light,   placarded    GPWS   INOP, located   on   the   caution/advisory   annunciator   panel, warns the flight crew that the GCAS is not functional. c.     Normal Operation. (1)   Startup     Procedure.      The GCAS is operable when the following conditions are met. 1.     Battery Switch – ON. 2.     Inverter Switch –  NO. 1 or  NO. 2. 3.     AVIONICS MASTER POWER Switch – On. 4.     GPWS POWER circuit breaker – In. 5.     GPWS    INOP    annunciator    light     – Extinguished. (2)   GCAS Self-Test. (a)  Pilot’s Or Copilot's  PULL UP / GPWS TEST Switch-Indicator (Glareshield)  – Press and hold.   Check for the following indications. 1.     Pilot's  and  copilot's   BELOW  GS switch-indicators   (glare-shield)   – Illuminated. 2.     GPWS  INOP  annunciator  light   – Illuminated. 3.     Warning voice (headsets/ speakers)    will    say    "Glideslope" once. 4.     Pilot's    and    copilot's    PULL    UP  switch-indicators will start flashing after  approximately  1 second,  the "Whoop,  whoop,  pull  up"  warning voice will be heard. 5.     After  several  repetitions  the  "Pull up" voice will stop. (b)  Pilot  Or  Copilot's   PULL  UP  /  GPWS TEST Switch-Indicator (Glareshield) – Release.   Check for the following indications. 1.     "Pull    up"    voice    will    stop,    and PULL UP light will extinguish. 2.     Pilot's  and  copilot's   BELOW  GS switch-indicators    (glareshield)     – Extinguished. 3.     GPWS  INOP  annunciator  light   – Extinguished. NOTE The  self-test  may  be  accomplished  while airborne if the radio altitude is above 1000 feet AGL and the landing gear is in the UP position. (3)   Response to Warnings. (a)  When   a   warning   occurs,   the   flight crew  should  initiate  corrective  action  to  remove  the cause of the warning. (b)  When   a   PULL   UP   warning   occurs, immediately  apply  engine  power,  establish  a  positive climb attitude, and climb at the maximum practical rate until the warning cease or terrain clearance is assured. NOTE Best   climb   angle   will   result   in   maximum ground clearance in the shortest horizontal distance. Increase pitch attitude smoothly.   Large   thrust   increases   may   result   in   a nose -up pitching tendency requiring forward column pressure and trim. When   flying   under   daylight   VFR   and   a warning threshold is deliberately exceeded or  encountered  due  to  specific  terrain  at certain    locations,    the    warning    may    be regarded  as  cautionary  and  the  approach may be continued. Where    operations    at    specific    locations must  be  conducted  in  close  proximity  to terrain, or a flaps up approach is flown, the GPWS  FLAP  OVRD  switch  may  be  set  to OVRD   to   de-sensitize  the  terrain  closure rate  warning  mode  (mode  2).    Reset  the GPWS  FLAP  OVRD  switch  after landing or immediately after making a go-around.   (4)   GCAS  Modes  of  Operation.     The  GCAS operates in the following six modes of operation.