TM 1-1510-224-10 pounds.        In    this    example    it    is    found    that    data    is presented for MAXIMUM RANGE POWER at 1500 RPM for ISA and ISA +10C at 24,000 feet and at 26,000 feet for     14,000     pounds,     but     not     for     16,000     pounds. Consequently, it is not possible to determine a maximum range   power   torque,   airspeed,   or   fuel   flow   for   15,000 pounds  at  25,000  feet,  since  chart  values  may  not  be extrapolated.      This   means   that   either   a   lower   altitude must be selected for the leg of the mission that would be using  reserve  fuel,  or  that  the  Normal  Cruise  Power  At 1500   RPM   values   must   be   used   to   determine   power setting  and  the  reserve  fuel  requirement.    If  no  values are   presented   for   the   given   conditions   in   the   Normal Cruise  Power  at  1500  RPM  tables,  either  select  a  lower altitude, or use the maximum cruise power at 1700 RPM table  values  to  determine  power  setting  and  the  reserve fuel requirement.  In this example it is found that data is presented   for   the   mission   conditions   in   the   Normal Cruise  Power  at  1500  RPM  tables,  so  that  data  can  be used.  Refer to table 7A-5 for an example of the reserve fuel determination procedure. (8) Total    fuel    requirement.        Expected    fuel usage  +  reserve  fuel  =  total  fuel  requirement.    (916  Ibs) + (537 Ibs) = 1453 lbs. (9) Zero-fuel     weight     limitation.          For     this example, the following conditions were assumed: Ramp Weight ...................................... 16,120 lbs Weight of Usable Fuel on Board............... 3631 lbs Zero Fuel Weight = (16,120 - 3631)....... 12,489 lbs Maximum Zero Fuel Weight (from Chapter 5) ..................................................... 13,100 lbs Maximum   zero   fuel   weight    limitation    will    not    be exceeded. Anytime  the  zero  fuel  weight  exceeds  the  maximum zero  fuel  weight  limit,  the  excess  weight  must  be  off- loaded from payload only (i.e., not from fuel).  If desired, additional    fuel    may    then    be    added.        However,    the foregoing  calculations  will  remain  unchanged  only  if  the fuel  added  is  equal  in  weight  to  the  payload  off-loaded, since  only  then  will  the  ramp  weight  and  takeoff  weight remain the same as before. n. Range and Endurance.    Estimates  of  the  effect of   fuel   load   and   power   setting   on   aircraft   range   and endurance   can   be   determined   from   the   Range   and Endurance  Profile  graphs.    The  range  of  a  mission  at normal  cruise  power  can  be  determined  by  entering  the Range  Profile  -  Normal  Cruise  Power  graph  at  25,000 feet,  reading  right  to  the  anticipated  fuel  load  and  down to  the  resulting  range.    This  chart  indicates  that  a  fuel load  as  low  as  1500  pounds  would  be  sufficient  for  the planned    217    nautical    mile    mission    from    Billings    to Casper.  The available range with full main and auxiliary tanks  (3631  pounds)  for  a  flight  at  25,000  feet  can  be determined to be 997 nautical miles.  If additional range is   required,   either   a   higher   altitude   or   a   lower   power setting could be selected.  To determine the range with a maximum  fuel  load,  enter  the  Range  Profile  -  Full  Main and  Aux  Tanks  graph  (fig.    7A-84)  at  25,000  feet,  read right   to   the   desired   power   setting   and   down   to   the resulting   range.      This   chart   depicts   that   for   a   full-fuel mission,   range   can   be   increased   from   997   to   1060 nautical   miles   by   reducing   power   to   maximum   range power. The  aircraft  endurance  can  be  determined  from  the various endurance profile graphs in a similar manner. It should be noted that all of these graphs are based on standard day temperatures, and the range graphs are also based on zero wind.  If forecast temperatures differ from  standard  values  or  if  headwinds  are  expected,  a more rigorous mission analysis should be accomplished. o. Landing Example. (1) Weight.    The  estimated  landing  weight  is determined  by  subtracting  the  fuel  usage  expected  for the trip from the ramp weight: Ramp Weight.............................................16,120 Fuel Usage Expected for Total Trip.........(-)916 lbs Landing Weight.................................... 15,204 lbs Maximum Landing Weight (Chapter 5)... 15,675 lbs Anytime    the    maximum    landing    weight    limitation would be exceeded, off-load the excess from useful load prior to Table 7A-4.  Example Time, Fuel, and Distance TIME FUEL DISTANCE ITEM MIN POUNDS NM Start, Runup, Taxi, and Takeoff Acceleration 0.0 120 0 Climb 21 343 49 Cruise 23.8 305 117 Descent 13.0 148 51 TOTAL 57.8 916 217 Block Speed: 217 NM Divided by 57.8 Minutes = 225 Knots. BT05884 7A-16