crease in nose up attitude without the appro- 
priate power change only controls the airplane 
to a lower speed. 
REGION 0~ REVERSED COMMAND 
The variation of power or thrust required 
with velocity defines the power settings neces- 
sary to maintain steady level flight at various 
airspeeds. To simplify the situation, a gener- 
ality could be,assumed that the airplane con- 
figuration and. altitude define a variation of 
power setting required (jet thrust required or 
prop power required) versus velocity. This 
general variation of required power setting 
versus velocity is illustrated by’the first graph 
of figure 6.2. This curve illustrates the fact 
that at low speeds near the stall or minimum 
control speed the power setting required for 
steady level flight is quite high. However, 
at low speeds, ant increase in speed reduces the 
required power setting until some minimum 
value is reached.at the conditions for maximum 
endurance. Increased speed beyond the con- 
ditions for maximum endurance will then 
in&ease the power setting required for steady 
level flight. 
REGIONS OF NORMAL AND REVERSED 
COMMAND. This .typical variation of re- 
quired power setting with speed allows a 
sort of terminology to be assigned to specific 
regimes of velocity. Speeds greater than the 
speed for maximum endurance require increas- 
ingly greater power settings to achieve steady, 
level flight. Since the normal command of 
flight assumes a higher power setting will 
achieve a greater speed, the regime of flight 
speeds greater than the speed for minimum 
required power setting is termed the “region 
of normal command.” Obviously, parasite 
drag or parasite power predominates in this 
regime to produce the increased power setting 
required with increased velocity. Of course, 
the major items of airplane flight performance 
take place in the region of normal command. 
Flight speeds below the sperd for maximum 
endurance produce required power settings 
NAVWEPS DCI-ROT-RD 
APPLICATION OF AERODYNAMICS 
TO SPECIFIC PROBLEMS OF FLYl,NG 
which increase with a decrease in speed. Since 
the increase in required power setting with 
decreased velocity is contrary to the normal 
command of flight, the regime of flight speeds 
between the speed for minimum required 
power setting and, the stall speed (or minimum 
control speed) is termed the “region of re- 
versed command. ” In this regime of flight, 
a decrease in airspeed ‘must be accompanied 
by an increased power setting in order to main- 
tain steady flight. Obviously, induced drag 
or induced power required predominates in 
this regime to produce the increased power 
setting required with decreased velocity. One 
fact should be made clear about the region of 
reversed command: flight in the “reversed” 
region of command does not imply that a 
decreased power setting will bring about a 
higher airspeed or an increased power setting 
will produce a lower airspeed. To be sure, 
the primary control of airspeed is not the 
power setting. Flight in the region of re- 
versed command only implies that a higher 
airspeed will repire a lower power setting and 
a lower airspeed will require a higher power 
setting to hold altitude. 
Because of the variation of required power 
setting throughout the range of flight speeds, 
it is possible that one particular power setting 
may be capable of achieving steady, level flight 
at two different, airspeeds. As shown on the 
first curve of figure 6.2, one given power setting 
would meet the power requirements and allow 
steady, level flight at both points 1 and 2. At 
speeds lower than point 2, a deficiency of power 1 
would exist and a rate of descent would be in- 
curred. Similarly, at speeds greater than point 
1, a deficiency of power would exist and the 1 
airplane would descend. The speed range be- 
tween points 1 and 2 would provide an excess 
of power and climbing flight would be pro- 
duccd 
FEATURES OF FLIGHT IN THE NOR- 
MAL AND REVERSED REGIONS OF COM-