text: As a result of this relationship, a IO percent 
  increase in gross weight would require a 5 per- 
  increase in glide speed to maintain 
  cent 
  (L/D),,. 
  in gross 
  While small. variations 
  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, 
  is maintained, the glide angle and 
  if WD),.z 
  glide ratio are identical to the low altitllde 
  conditions. 