TM 1-1510-225-10 3B-203 5.   GPWS    INOP     annunciator     light     – Extinguished. (2)   GCAS Self-Test. 1.   Pilot's  or  copilot's  PULL  UP  /  GPWS TEST  switch-indicator   (glareshield)  – Press    and    hold.        Check    for    the following indications: a.   Pilot's  and  copilot's    BELOW   G/S switch-indicators (glareshield) – Illuminated. b.   GPWS   INOP   annunciator  light    – Illuminated. c.   Warning voice (headsets/ speakers)     will     say     "Glideslope" once. d.   Pilot's     and     copilot's     PULL    UP  switch-indicators  will  start  flashing after approximately 1 second, then the    "Whoop,    Whoop,    Pull    Up"  warning voice will be heard. e.   After  several  repetitions  the  "Pull Up"  voice will stop. 2.   Pilot's and copilot's PULL UP / GPWS TEST  switch-indicator   (glareshield)  – Release.        Check    for    the    following indications: a.   "Pull Up" voice will stop, and  PULL UP light will extinguish. b.   Pilot's   and   copilot's   BELOW   G/S switch-indicators (glareshield) – Extinguished. c.   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    warnings    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   desensitize   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: (a)   Excessive     Sink     Rate     (Mode     1).   Mode   1,   Figure   3B-162,   provides   visual   and   aural warnings for excessive rate of descent with respect to terrain  when  below  2450  feet  AGL.   When  the  aircraft penetrates   the   outer   warning   boundary,   the   "Sink Rate"  aural  warning  will  be  given  and  repeated  every 0.75  seconds,  and   PULL  UP  indicator  lights  on  the glareshield will begin to flash.  If the rate of descent is not corrected and the second boundary is penetrated, the "Whoop, Whoop, Pull Up" aural warning will sound.   The  excessive  sink  rate  mode  is  independent  of  gear and flap configuration. (b)   Excessive Terrain Closure Rate (Mode 2).  Mode 2, Figure 3B -163, provides visual and aural warnings for excessive terrain closure rate.  The terrain  closure  rate  mode  is  a  function  of  inputs  of airspeed, radio altitude and rate of change, barometric altitude, and gear and flap position.  When the aircraft penetrates  the  outer  warning  area,  the  "Terrain"  aural warning will sound twice, and the  PULL UP  indicator lights will begin flashing.  If the excessive closure rate condition  remains  uncorrected  and  the  inner  warning boundary is  penetrated,  the  "Whoop,  Whoop  Pull  Up" aural  warning  will  sound  every  0.75  seconds.    Upon climbing    out    of    the    inner    warning    boundary,    the