NAWEPS OO-BOT-BO 
BASIC AERODYNAMICS 
takeoff distance may occur. Also, the initial 
climb performance may be marginal at an 
excessively low airspeed. There are modern 
configurations of airplanes of very low aspect 
ratio (plus sweepback) which-if over- 
rotated during a high altitude, high gross 
weight takeoff-cannot fly out of ground 
effect. With the more conventional airplane 
configuration, an excess angle of attack pro- 
duces a well defined stall. However, the 
modern airplane configuration at an excessive 
angle of attack has no sharply defined stall 
but developes an excessive amount of induced 
drag. To be sure that it will not go unsaid, 
an excessively low angle of attack on takeoff 
creates its own problems-excess takeoff 
speed and distance and critical tire loads. 
(2) During appra& where the pilot must 
exercise proper technique to control the 
flight path. “Attitude plus power equals 
performance.” The modern high speed con- 
figuration at low speeds will have low lift- 
drag ratios due to the high induced drag 1 
and can require relatively high power set- 
tings during the power approach. If the 
pilot interprets that his airplane is below 
the desired glide path, his first reaction rnu~t 
trot be to just ease the nose up. An increase 
in angle of attack without an increase in 
power will lower the airspeed and greatly 
increase the induced drag. Such a reaction 
could create a high rate of descent and lead 
to very undesirable consequences. The an- 
gle of attack indicator coupled with the 
mirror landing system provides reference to 
the pilot and emphasizes that during the 
steady approach “angle of attack is the 
primary control of airspeed and power is the 
primary control of rate of climb or descent.” 
Steep turns during approach at low airspeed 
are always undesirable in any type of air- 
plane because of the increased stall speed and 
induced drag. Steep turns at low airspeeds 
in a low aspect ratio airplane can create 
extremely high induced drag and can incur 
dangerous sink rates. 
very high speed flight does not favor the use of 
high aspect ratio planforms. Low aspect ratio 
planforms have structural advantages and 
allow the use of thin, low drag sections for high 
speed flight. The aerodynamics of transonic 
and supersonic flight also favor short span, low 
aspect ratio surfaces. Thus, the modern con- 
figuration of airplane designed for high speed 
flight will have a low aspect ratio planform 
with characteristic aspect ratios of two to four. 
The most important impression that should 
result is that the typical modern configuration 
will have high angles of attack for maximum 
lift and very prodigious drag due to lift at low 
flight speeds. This fact is of importance to 
theNaval Aviator because the majority of pilot- 
caused accidents occur during this regime of 
flight-during takeoff, approach, and landing. 
Induced drag predominates in these regimes of 
flight. 
The modern configuration of high speed air- 
plane usually has a low aspect ratio planform 
with high wing loading. When wing sweep- 
back is coupled with low aspect ratio, the wing 
lift curve has distinct curvature and is very flat 
at high angles of attack, i.e., at high CL, C, in- 
creases very slowly with an increase in 01. In 
addition, the drag curve shows extremely rapid 
rise at high lift coefficients since the drag due 
to lift is so very large. These effects produce 
flying qualities which are distinctly different 
from a more “conventional” high aspect ratio 
airplane configuration. 
Some of the most important ramifications of 
the modern high speed configuration are: 
(1) During takeoff where the airplane must 
not be over-rotated to an excessive angle of 
attack. Any given airplane will have some 
fixed angle of attack (and CJ which produces 
the best takeoff performance and this angle 
of attack will not vary with weight, density 
altitude, or temperature. An excessive angle