text: The propellers used on most large reciprocating 
  engines derive peak propeller efficiencies on the 
  order of s,=O.85 to 0.88. Of course, the peak 
  values are designed to occur at some specific 
  design condition. For example, the selection 
  of a propel!er for a !ong rasge transport wsuld 
  require matching of the engine-propeller com- 
  bination for peak efhciency at cruise condjtion. 
  On the other hand, selection of a propeller for 
  a utility or liaison type airplane would require 
  matching of the engine-propeller combination 
  to achieve high propulsive power at low speed 
  and high power for good takeoff and climb 
  performance. 
  
  The large drag which can be produced by 
  the rotating propeller can be utilized to im- 
  prove the stopping performance of the air- 
  plane. Rotation of the propekr blade to 
  small positive values or negative values with 
  applied power can produce large drag or re- 
  verse thrust. Since the thrust capability of the 
  propeller is quite high at low speeds, very 
  high deceleration can be provided by reverse 
  thrust alone, 
  The qs&zg 
  
  Several special considerations must be made 
  for the application of aircraft propellers. 
  In 
  the event of a powerplant malfunction or 
  failure, provision must be made to streamline 
  the propeller blades and reduce drag so that 
  flight may be continued on the remaining op- 
  is accomplished by 
  erating engines. This 
  feathering 
  the propeller blades which .stops 
  rotation and incurs a minimum of drag for the 
  inoperative engine. The necessity for feather- 
  ing is illustrated in figure 2.19 by the change 
  in equivalent parasite area, Af, with propeller 
  blade angle, 8, of a typical instaliation. When 
  the propeller blade angle is in the feathered 
  position, the change in parasite drag is at a 
  minimum and, in the case of a typical multi- 
  engine aircraft, the added parasite drag from 