NAVWEPS OD-ROT-80 
APPLICATION OF AERODYNAMICS 
TO ‘SPECIFIC PROBLEMS OF FLYl,NG 
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 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),=, 
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. 
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