text: TURBOPROP POWERED AIRPLANE. 
  The turbine engine has the preference for 
  relatively high power settings and high alti- 
  tudes to provide low specific fuel consumption. 
  Thus, the off-optimum conditions of range or 
  endurance can be concerned with altitudes 
  less than 
  less than the optimum. Altitudes 
  the optimum can reduce the range but the 
  loss can be minimized on the multiengine 
  airplane by shutting down some powerplants 
  and operating the remaining powerplants at a 
  higher, more efficient output. 
  this case 
  the change of range is confined to the variation 
  of specific fuel consumption with altitude. 
  
  In 
  
  Essentially the same situation exists in the 
  case of engine failure when cruising at optimum 
  If the propeller on the inoperative 
  altitude. 
  engine is feathered, the loss of range will be 
  confined to the change in specific fuel con- 
  sumption from the reduced cruise altitude. 
  If 
  a critical power situation exists due to engine 
  failure, a reduction in altitude provides im- 
  mediate benefit because of the reduction of 
  increase in power 
  power required and the 
  In addition, 
  available from the power plants. 
  the jettisoning of expendable weight 
  items 
  will 
  improve performance and, of course, the 
  clean configuration provides minimum parasite 
  drag. 