20.  Power  -  As  required. 9-12. MAXIMUM GLIDE. In  the  event  of  failure  of  both  engines,  maximum gliding  distance  can  be  obtained  by  feathering  both propellers  to  reduce  propeller  drag  and  by  maintaining  the appropriate airspeed with the gear and flaps up. Figure 9-2 gives   the   approximated   gliding   distances   in   relation   to altitude. 9-13.   LANDING   WITH   TWO   ENGINES   IN- OPERATIVE. Maintain   best   glide   speed   (figure   9-2).   If   sufficient altitude  remains  after  reaching  a  suitable  landing  area,  a circular  pattern  will  provide  best  observation  of  surface conditions, wind  velocity  and  direction.  When  the condition of the terrain has been noted and the landing area selected, set   up   a   rectangular   pattern.   Extending APPROACH  flaps  and  landing  gear  early  in  the  pattern will  give  an  indication  of  glide  performance  sooner,  and will  allow  more  time  to  make  adjustments  for  the  added drag.   Fly   the   base   leg   as   necessary   to   control   Point   of touch-down.  Plan  to  overshoot  rather  than  undershoot, then use flaps as necessary to arrive at the selected landing point. Keep  in  mind  that,  with  both  propellers  feathered,  the normal  tendency  is  to  overshoot  due  to  less  drag.  In  the event   a   positive   gear-down   indication   cannot   be determined, prepare for a gear-up landing. Also, unless the surface of the landing area is hard and smooth, the landing should  be  made  with  the  landing  gear  up.  If  landing  on rough  terrain,  land  in  a  slightly  tail-low  attitude  to  keep nacelles  from  possibly  digging  in.  If  possible,  land  with flaps  fully  extended. 9-14.  LOW  OIL  PRESSURE. In the event of a low oil pressure indication, perform the procedures below, as applicable: 1. Oil pressure below 105 PSI below 21,000 feet or 85 PSI   at   21,000   feet   and   above,   torque   -   49% maximum. 2.  Oil  pressure  below  60  PSI  -  Perform  engine shutdown,  or  land  as  soon  as  practicable  using minimum power to ensure safe arrival. 9 - 1 5 .    C H I P    D E T E C T O R    W A R N I N G ANNUNCIATOR    ILLUMINATED. If  the  L  CHIP  DET  or  R  CHIP  DET  warning annunciator  illuminates,  and  safe  single-engine  flight  can be maintained, perform the following: 2.  Land  as  soon  as  practicable. 1.  Perform  engine  shutdown. 9-16.   DUCT   OVERTEMP   CAUTION   LIGHT ILLUMINATED. Insure  that  the  cabin  floor  outlets  are  open  and unobstructed,  then  perform  the  following  steps  in  sequence until  the  light  is  extinguished.  After  completion  of  steps  1. through   4.,   if   the   light   does   not   extinguish,   allow approximately   30   seconds   after   each   adjustment   for   the system   temperature   to   stabilize.   The   overtemperature condition  is  considered  corrected  at  any  point  during  the procedure that the light goes out. 1. Cabin air control - In. 2.  Cabin  temperature  mode  switch  -  AUTO. 3.  Cabin  temperature  rheostat  -  Full  decrease. 4.  Vent  blower  switch  -  HI. 5.  Cabin  temperature  mode  switch  -  MAN  HEAT. 6.  Manual  temperature  switch  -  DECREASE  (hold). 7. Left bleed air valve switch - ENVIRO OFF. 8.  Light  still  illuminated  (30  seconds)  -  Left  bleed  air valve switch - OPEN. 9. Right bleed air valve switch - ENVIRO OFF. 10.  Light  still  illuminated  (30  seconds)  -  Right  bleed  air valve switch - OPEN. N O T E If the overtemperature light has not extinguished after   completing   the   above   procedure,   the warning  system  has  malfunctioned. 9-17.  ICE  VANE  FAILURE. Ice  vane  failure  is  indicated  by  VANE  FAIL  caution light  illumination.  If  an  ice  vane  fails  to  operate electrically, perform the following: TM   55-1520-219-10 Change 3       9-5