NAVWEPS 00-801-80 
AIRPLANE PERFORMANCE 
define the maximum turning performance. 
The acrodynomic limir describes the minimum 
turn radius available to the airplane when 
operated at C,,,,. When the airplane is at the 
stall speed in level flight, all the lift is neces- 
sary to sustain the aircraft in flight and none 
is available to produce a steady turn. Hence, 
the turn radius at the stall speed is infinite. 
As speed is increased above the stall speed, the 
airplane at C,,, is able to develop lift greater 
than weight and produce a finite turn radius. 
For example, at a speed twice the stall speed, 
the airplane at CL,,,,= is able to develop a load 
factor of four and utilize a bank angle of 75.5’ 
(cos 75.~~ = 0.25). Continued increase in 
speed increases the load factor and bank angle 
which is available aerodynamically but, be- 
cause of the increase in velocity and the basic 
effect on turn radius, the turn radius approaches 
an absolute minimum value. When C,,, is 
unaffected by velocity, the aerodynamic mini- 
mum turn radius approaches this absolute 
value which is a function of C,,,,,,,, W/S, and 6. 
Actually, the one common denominator of 
aerodynamic turning performance is the wing 
level stall speed. 
The aerodynamic limit of turn radius requires 
that the increased velocity be utilized to pro- 
duce increasing load factors and greater angles 
of bank. Obviously, very high speeds will 
require very high load factors and the absolute 
aerodynamic minimum turn radius will require 
an infinite load factor. Increasing speed above 
the stall speed will eventually produce the 
limit load factor and continued increase in 
speed above this point will require that load 
factor and bank angle be limited to prevent 
structural damage. When the load factor and 
bank angle are held constant at the structural 
limit, the turn radius varies as the square of 
the velocity and increases rapidly above the 
aerodynamic limit. The intersection of ‘the 
aerodynamic limit and structural limit lines 
is the ‘*maneuver speed.” The maneuver 
speed is the minimum speed necessary to 
develop aerodynamically the limit load factor 
180 
and it produces the minimum turn radius 
within aerodynamic and structural limitations. 
At speeds less than the maneuver speed, the 
limit load factor is not available aerodynami- 
cally and turning performance is aerody- 
namically limited. At speeds greater than 
the maneuver speed, CL- and maximum 
aerodynamic load factor are not available and 
turning performance is structurally limited. 
When the stall speed and limit load factor 
are known for a particular configuration, the 
maneuver speed is related by the following 
expression: 
where 
V,=maneuver speed, knots 
V.=stall speed, knots 
n limit = limit load factor 
For example, an airplane with a limit load 
factor of 4.0 would have a maneuver speed 
which is twice the stall speed. 
The aerodynamic limit line of the first 
illustration of figure 2.30 is typical of an air- 
plane with a CL, which is invariant with 
speed. While this is applicable for the ma- 
jority of subsonic airplanes, considerable differ- 
ence would be typical of the transonic or 
supersonic airplane at altitude. Compressi- 
bility effects and changes in longitudinal 
control power may produce a maximum avail- 
able CL which varies with velocity and an 
aerodynamic turn radius which is not an 
absolute minimum at the maximum of velocity. 
The second illustration of figure 2.30 describes 
the constant altitude turning performance 
of an airplane. When an airplane is at high 
,altitude, the turning performance at the high 
speed end of the flight speed range is more 
usually thrust limited rather than structurally 
limited. In flight at constant altitude, the 
thrust must equal the drag to maintain equilib- 
rium and, thus, the constant altitude turn 
radius is infinite at the maximum level flight 
speed. Any bank or turn at maximum level