NAVWEPS OD-ROT-80  APPLICATION OF AERODYNAMICS  TO  ‘ SPECIFIC PROBLEMS  OF FLYl,NG  The eficct aj wind on gliding performance is  similar to the effect of wind on cruising range.  That is, a headwind will always reduce the  glide range and a tailwind will always increase  the glide range. The maximum glide range  of the airplane in still air will be obtained by  flight at (L/D),,,,.  However, when a wind is  present, the optimum gliding conditions may  not be accomplished by operation at (L/D)ma.  For example, when a headwind is present,  the optimum glide speed will be increased to  obtain a maximum proportion of ground dis-  tance to altitude.  In this sense,  the increased  glide speed helps to minimize the detrimental  effect of the headwind.  In the case of a tail-  wind, the optimum glide speed will be reduced  to maximize the benefit of the tailwind.  For  ordinary wind conditions, maintaining the  glide speed best for zero wind conditions will  suffice and the loss or gain in glide distance  must be accepted. However, when the wind  conditions are extreme and the wind velocity  is large in comparison with the glide speed,  e.g., wind velocity greater than 25 percent of  the glide speed, changes in the glide speed must  be made to obtain maximum possible ground  distance.  As a result of this relationship, a IO percent  increase  in gross weight would require a 5 per-  cent increase in glide  speed to  maintain  (L/D),,.  While  small. variations in gross  weight may produce a measurable change in  best glide speed, the airplane can tolerate small  deviations from the optimum C, without signif-  icant change in (L/D) and glide ratio.  For this  reason, a standard, single value of glide speed  may be specified for a small range of gross  weights at which glide performance  can be of  importance. A gross weight which is con-  siderably different from the normal range will  require a modification of best glide speed to  maintain the maximum glide ratio.  The effect  a! &it.&  on glide performance is  insignificant if there is no change in (L/D),.,.  Generally, the glide performance  of the major-  ity of airplanes is subsonic and there is no  noticeable variation of (L/D),,  with altitude.  Any specific airplane configuration at a partic-  ular gross weight will require a specific value  of dynamic pressure to sustain flight at the  C, for (L/D),,.  Thus, the airplane will have  a best glide speed which is a specific value of  equivalent airspeed (EAS) independent of  altitude.  For convenience  and simplicity, this  best glide speed is specified as a specific value  of indicated airspeed  (IAS) and compressibility  and position errors are neglected. The prin-  cipal effect of altitude is that at high altitude  the true airspeed (TAX) and rate of descent  along the optimum glide path are increased  above the low altitude conditions.  However,  if WD),.z  is maintained, the glide angle and  glide ratio are identical to the low altitllde  conditions.  THE FLAMEOUT PATTERN.  In the case  of failure of the powerplant, every effort  should be made to establish a well-planned,  stabilized approach if a suitable landing area  is available.  Generally a 360’ overhead ap-  proach is specified with the approach begin-  ning from the “high key” point of the flameout  pattern.  The function of a standardized  pattern is to provide a flight path well within  the capabilities of the airplane and the abilities  of the pilot to judge and control the flight  path.  The flight handbook will  generally  specify the particulars of the flameout pattern  such as the altitude at the high key, glide  speeds, use of flaps, etc. Of course, the par-  ticulars of the flameout pattern will  be de-  termined by the aerodynamic characteristics  of the airplane.  A principal factor is the  The effect  of configura+~n  has been noted pre-  viously in that the addition of parasite drag by  flaps, landing gear, speed brakes, external  stores, etc. will reduce the maximum lift-drag  ratio and cause a reduction of glide ratio.  In  the case where glide distance is of great im-  portance, the airplane must be maintained in  the clean configuration and flown at (L/D),=,  272 