text: specific fuel consumption is not adversely 
  affected as long as auto-lean or manual lean 
  power can be used at the cruise power setting. 
  One operating characteristic of the recipro- 
  cating engine is distinctly different from that 
  of the turbojet. Water vapor in the air will 
  cause a significant reduction in output power of 
  the reciprocating engine but a negligible loss 
  of thrust for the turbojet engine. This basic 
  reciprocating 
  difference exists because the 
  engine operates with a fixed displacement and 
  all air processed is directly associated with the 
  combustion process. If water vapor enters the 
  induction system of the reciprocating engine, 
  the amount of air available for combustion is 
  reduced and, since most carburetors do not 
  distinguish water vapor from air, an enrich- 
  takes place. The 
  ment of the fuel-air ratio 
  maximum power output at takeoff requires 
  fuel-air ratios richer than that for maximum 
  . . ..I1*-IF- 
  nnr:rLmm.c 
  -haezt re1m.e rn ,, C,I+P- 
  “W . A....A c. b.IIA.cIIIIICIIL “1111 La&C 
  place with subsequent loss of power. The 
  turbojet operates with such great excess of air 
  the combustion process essentially is 
  that 
  unaffected and the reduction of air mass flow 
  is the principal consideration. As an example, 
  extreme conditions which would produce high 
  specific humidity may cause a 3 percent thrust 
  loss for a turbojet but a 12 percent loss of BHP 
  for a reciprocating engine. Proper accounting 
  is essential in the 
  of the loss due to humidity 
  operation of the reciprocating engine. 