text: NAVWEPS 00-801-80 
  AIRPLANE PERFORMANCE 
  
  have a fuel weight which is a large part of the 
  gross weight, cruise control procedures will be 
  necessary to account for the changes in opti- 
  mum airspeeds and power settings as fuel is 
  consumed. 
  
  The effect of altitude on the range of the 
  turbojet airplane is of great importance be- 
  cause no other single item can cause such large 
  variations of specific range. 
  If a given con- 
  figuration of airplane is operated at constant 
  gross weight and 
  coefficient for 
  the 
  (JCL/CDL, a change in altitude will produce 
  the following relationships: 
  
  vz 
  -= 
  VI  - 
  3 
  .Y* J 
  
  Tr=constant (neglecting compressibility 
  
  effects) 
  
  JR.2 
  -= 
  JR1  - 
  3 
  rJ*
  
  (neglecting factors affecting en- 
  
  gine performance)  J 
  
  where 