NAVWEPS 00-8OT-80  AIRPLANE PERFORffANCE  “feel”  of the airplane but will produce an un-  desirable increase in takeoff distance.  Assum-  ing that the acceleration is essentially un-  affected, the takeoff distance varies as the  square of the takeoff velocity,  The cffcct  of nrnzuay  slope on takeoff distance  is due to the component of weight along the  inclined path of the airplane.  A runway  slope of 1 percent would provide a force com-  ponent along the path of the airplane which is  1 percent of the gross weight.  Of course, an  upslope would contribute a retarding force  component while a downslope would contri-  bute an accelerating force component. For  the case of the upslope, the retarding force  component adds to drag and rolling friction to  reduce the net accelerating force.  Ordinarily,  a 1 percent runway slope can cause a 2 ’ tO 4  percent change in takeoff distance depending  on rhe airplane characrerisrics. The airplane  with the high thrust-to-weight ratio is least  affected  while the airplane with the low thrust-  to-weight ratio is most affected because the  slope force component causes a relatively  greater change in the net accelerating force.  Thus, 10 percent excess  airspeed would increase  the takeoff distance 21 percent.  In most criti-  cal takeoff conditions, such an increase in  takeoff distance would be prohibitive and the  pilot must adhere to the recommended  takeoff  speeds.  The effect of prcs~wc  altitude and ambient  rcmpcraturc  is to define primarily the density  altitude and its effect on takeoff performance.  While subsequent corrections are appropriate  for the effect of temperature on certain items  of powerplant performance, density altitude  defines certain effects on takeoff performance.  An increase in density altitude can produce a  two-fold effect on takeoff performance: (I) in-  creased takeoff velocity and (2) decreased  thrust and reduced net accelerating force. If  a given weight and configuration of airplane is  taken to altitude above standard sea level, the  airplane will  still require the same dynamic  pressure  to become airborne at the takeoff lift  coefficient.  Thus, the airplane at altitude will  take 05 at the same equivalent airspeed (EAS)  as at sea level, but because of the reduced  density, the true airspeed (TAS) will  be  greater.  From basic aerodynamics, the rela-  tionship between true airspeed and equivalent  airspeed is as follows:  The effect of runway slope must be consid-  ered when predicting the takeoff distance but  the effect is usually minor for the ordinary run-  way slopes and airplanes with  moderate  thrust-to-weight ratios.  In fact, runway slope  considerations are of great significance only  when the runway slope is large and the airplane  has an intrinsic low acceleration, i.e., low  thrust-to-weight ratio.  In the ordinary case,  the selection of the takeoff runway will favor  the direction with an upslope and headwind  rather than the direction with a downslope  and tailwind.  The effect of proper  takeoff  t&city is important  when runway lengths and takeoff distances are  critical.  The takeoff speeds specified in the  flight handbook are generally the minimum  safe speeds at which the airplane can become  airborne.  Any attempt to take 05 below the  recommended speed may mean that the air-  craft may stall, be difficult to control, or have  very low initial rate of climb.  In some cases,  an excessive angle of attack may not allow  the airplane to climb out of ground effect.  On  the other hand, an excessive  airspeed at takeoff  may improve the initial  rare of climb and  where  TAS= true airspeed  EAS= equivalent airspeed  n=altitude density ratio  0 = Plpo  TAS  1  EAS=F  190  s*  vz.2  -=  -  0  J-1  v, 