NAVWEPS 00-801-80  AIRPLANE PERFORMANCE  where  and  is at a minimum, (LID),.  Thus, for maxi-  mum steady-state  angle of climb, the turbojet  aircraft would be operated at the speed ,for  (L/D),.  This poses somewhat of a problem  in determining the proper procedure for ob-  stacle clearance after takeoff.  If the obstacle  is a considerable distance from the takeoff  point, the problem is essentially that of a long  term gain and steady state conditions will pre-  dominate. That is, acceleration  from the take-  off speed to (L/D),  speed will be favorable  because  the maximum steady climb angle can  be attained.  However, if the obstacle is a rela-  tively short distance from the takeoff point,  the additional distance required to accelerate  to (L/D),,  speed may be detrimental and the  resulting situation may prove to be a short  term gain problem. In this case, it may prove  necessary  to begin climb out at or near the take-  off speed or hold the aircraft on the runway  for extra speed and a subsequent zoom.  The  problem is su&ciently varied that no general  conclusion can be applied to all jer aircraft and  particular procedures  are specified for each air-  craft in the Flight Handbook.  101.3isthefactorconvertingknocstof.p.m.  The above relationship states that, for a given  weight airplane, the rate af climb (RC) depends  on the difference between the power available  and the power required (Pd- Pr), or excess  power. Of course, when the excess  power is  zero (Pa-Pr=O  or Pa==  PI), the rate of climb  is zero and the airplane is in steady level flight.  When the power available is greater than the  power required, the excess  power will, allow a  rate of climb specific  to the magnitude of excess  power. Also, when the power available is  less than the power required, the deficiency of  power produces a rate of descent.  This rela-  tionship provides the basis for an important  axiom of flight technique: “For the conditions  of steady flight, the power setting is the pri-  mary control of rate of climb or descent”.  One of the most important items of climb  performance is the maximum rate of climb.  By the previous equation for rate of climb,  maximum rate of climb would occur where  there exists the greatest difference between  power available and power required, i.e.,  maximum (Pa- Pr).  Figure 2.21 illustrates  the climb rate performance with the curves of  power available and power required versus  velocity.  The power required curve is again a  representative  airplane which could be powered  by either a turbojet or propeller type power-  plant.  The power available curves included  are for a characteristic propeller powerplant  and jet powerplant operating at maximum  output.  The power curves for the representative  pro-  peller aircraft show a variation of propulsive  power typical of a reciprocating engine-pro-  peller combination.  The maximum rate of  climb for this aircraft will occur at some speed  Of greater general interest in climb per-  formance are the factors which affect the rate of  climb. The vertical velocity of an airplane  depends on the flight speed and the inclination  of the flight path.  In fact, the rate of climb  is the vertical component of the flight path  velocity.  By the diagram of figure 2.21, the  following relationship is developed:  RC- 101.3 V sin y  since  then  a&  2-v  with Pa=%  and Pr=&  RC=101.3 V  154  RevId J4mwy 1ws  RC=rate of climb, f.p.-.  P11=power available, h.p.  Pr=power re  W=weight, 1  %  uired, h.p.  s  V=true airspeed, knots  33,000 is the factor converting horsepower  to ft-lbs/min 