text: The effect of density altitude on powerplant 
  thrust depends much on the type of power- 
  plant. An increase in altitude above standard 
  sea level will bring an 
  immediate decrease in 
  power output for the unsupercharged or ground 
  boosted reciprocating engine or the turbojet 
  and turboprop engines. However, an 
  increase 
  in altitude above standard sea level will not 
  cause a decrease in power output for the super- 
  charged reciprocating engine until the altitude 
  exceeds the critical altitude. For those power- 
  plants which experience a decay in thrust with 
  the effect on the net 
  an increase in altitude, 
  accelerating force and acceleration can be ap- 
  proximated by assuming a direct variation 
  with density. Actually, 
  this assumed vari- 
  ation would closely approximate the effect on 
  airplanes with high 
  ratios. 
  thrust-to-weight 
  This relationship would be as follows: 
  a2 Fm 
  P 
  -=-=-En 
  al Frill PO 
  
  As a result of these relationships, it should. 
  be appreciated that density altitude will affect 
  takeoff performance in a fashion depending 
  much on the powerplant type. The effect of 
  density altitude on takeoff distance can be 
  appreciated by the following comparison: 
  where 