airspeed will allow. If full flap deflection is 
utilized for takeoff it is important to recall that 
the last 50 percent of flap deflection creates 
more than half the total drag increase but less 
than half the total change in CL,-. Thus, for 
some configurations of airplanes, a greater re- 
duction in drag may be accomplished by partial 
retraction of the flaps rather than retraction of 
the landing gear. Also, it is important that no 
steep turns be attempted because of the unde- 
sirable increase in induced drag. 
During the landing with an engine inopera- 
tive, the same fundamental precautions must 
be observed as during takeoff, i.e., minimum 
directional control speed must be maintained 
(or exceeded), no steep turns should be at- 
tempted, and the extension of the flaps and 
landing gear must be well planned. In the case 
of’a critical power condition it may be neces- 
sary to delay the extension of the landing gear 
and full flaps until a successful landing is as- 
sured. If a waveoff is necessary, maximum per- 
formance will be obtained cleaning up the air- 
plane and accelerating to the best climb speed 
before attempting any gain in altitude. 
At all times during flight with an engine 
inoperative, the pilot must utilize the proper 
techniques for control of airspeed and altitude, 
e.g., for the conditions of steady flight, angle 
of attack is the primary control of airspeed 
and excess power is the primary control of 
rate of climb. For example, if during approach 
to landing the extension of full flaps and 
landing gear creates a deficiency of power at 
all speeds, the airplane will be committed to 
descend. If the approach is not properly 
planned and the airplane sinks below the 
desired glide path, an increase in angle of 
attack will only allow the airplane to fly more 
slowly and descend more rapidly. An attempt 
to hold altitude by increased angle of attack 
when a power deficiency exists only causes a 
continued loss of airspeed. Proper procedures 
and technique are an absolute necessity for 
safe flight when an engine failure occurs. 
NAVWEPS OO-BOT-80 
APPLICATION OF AERODYNAMICS 
TO SPECIFIC PROBLEMS OF FLYING 
GROUND EFFECT 
When an airplane in flight nears the ground 
(or water) surface, a change occurs in the 
three dimensional flow pattern because the 
local airflow cannot have a vertical component 
at the ground plane. Thus, the ground plane 
will furnish a restriction to the flow and alter 
the wing upwash, downwash, and tip vortices. 
These general effects due to the presence of 
the ground plane are referred to as “ground 
effect. ‘* 
AERODYNAMIC INFLUENCE OF 
GROUND EFFECT. While the aerodynamic 
characteristics of the tail and fuselage are 
altered by ground effects, the principal effects 
due to proximity of the ground plane are the 
changes in the aerodynamic characteristics 
of the wing. As the wing encounters ground 
effect and is maintained at a constant lift 
coefficient, there is a reduction in the upwash, 
downwash, and the tip vortices. These effects 
are illustrated by the sketches of figure 6.9. 
As a result of the reduced tip vortices, the wing 
in the presence of ground effect will behave as 
if it were of a greater aspect ratio. In other 
words, the induced velocities due to the tip 
(or trailing) vortices will be reduced and the 
wing will incur smaller values of induced 
drag coefficient, C,<, and induced angle of 
attack, OL;, for any specific lift coefhcient, C,. 
In order for ground effect to be of a signifi- 
cant magnitude, the wing must be quite close 
to the ground plane. Figure 6.9 illustrates 
one of the direct results of ground effect by 
the variation of induced drag coefficient with 
wing height above the ground plane for a 
representative unswept wing at constant lift 
coefficient. Notice that the wing must be 
quite close to the ground for a noticeable 
reduction in induced drag. When the wing 
is at a height equal to the span (h/b=l.O),