text: output power 
  mput power 
  ?%I= . 
  
  TV 
  
  ‘I’= T(V+a) 
  
  where 
  
  v,=propulsive efficiency 
  lbs. 
  T=thrust, 
  V=fligkt velocity, knots 
  IJ = velocity increment at the 
  
  propeller disc, knots 
  
  Since the final velocity, Vs, is the sum of total 
  velocity change 2a and the initial velocity, 
  V,, the propulsive efliciency rearranges to a 
  form identical to that for the turbojet. 
  
  2 
  VP’ 
  
  1+ k 
  0 
  
  The action of the propeller can be idealized 
  by the assumption that the rotating propeller 
  is simply an actuating disc. As shown in fig- 
  ure 2.18, the inflow approaching the propeller 
  disc indicates converging streamlines with an 
  increase in velocity and drop in pressure. The 
  converging streamlines leaving the propeller 
  disc indicate a drop in pressure and increase in 
  velocity behind the propeller. The pressure 
  change through the disc results from the distri- 
  bution of thrust over the area of the propeller 
  
  So, the same relationship exists as with 
  the 
  turbojet engine in that high efficiency is de- 
  the highest 
  veloped by producing thrust with 
  possible mass flow and smallest necessary 
  velocity change. 
  
  The actual propeller must be evaluated in a 
  more exact sense to appreciate the effect of 
  nonuniform disc loading, propeller blade drag 
  forces, interference flow between blades, etc. 
  With these differences from the ideal Propeller, 