Air Combat Maneuvering
Background
As you know, the available thrust of an aircraft varies with altitude and temperature but is independent of
airspeed in a jet aircraft. The thrust-to-weight ratio of an aircraft, computed by dividing thrust by combat
weight, commonly indicates an aircraft’s capability going into an ACM environment. Pilots flying aircraft
with thrust-to-weight ratios greater than one will use different tactics than pilots flying machines with
ratios less than one, as is the case of the T-45A.
You must consider wing loading, computed by dividing the combat weight by the wing area. For two
aircraft at co-airspeed, the aircraft with a higher wing loading will have a larger turn radius and a slower
turn rate. Conversely, aircraft with lower wing loading have a smaller turn radius and a faster turn rate.
Variable Factors
Other factors that will vary in the ACM arena include your altitude, airspeed, angle of attack (AOA), and
g—the “snapshot” that gives you the parameters to make the instantaneous decisions that will be
dependent on the above factors and will change over the course of the fight according to the type of
maneuver you choose. Although some of these decisions are limited by the aircraft characteristics, each
action you take during an engagement will affect aircraft performance.
Altitude provides potential energy (PE) for maneuvering. Airspeed is kinetic energy (KE). At a specific
AOA, the Cl and Cd for a given wing remain relatively constant regardless of airspeed, g, and altitude.
Depending upon the type of turn you choose, the optimum AOA reflects the lift-to-drag ratio for the
desired performance. In a given situation which dictates the type of turn you need to make, the optimum
AOAs will vary. Knowing and using the cornering speed and the appropriate AOAs give you the most
bang for the buck—the best turn performance for the minimum amount of energy loss. They are
delineated for you in the “energy management” section of the FTI.
The fixed and variable factors begin to interrelate. G is the ratio of lift to weight. As you know, in turns
or direction changes, lift must exceed weight, and you must apply g loads greater than 1. At a constant
TAS, to increase g, you must increase the AOA. Radial g will dictate the turn radius and rate. Maximum
instantaneous g is the maximum lift a wing may generate at a given airspeed. Maximum instantaneous g
is dependent upon the aircraft airframe capabilities. The max instantaneous g, displayed on the Vn
diagram, generates the maximum instantaneous rate of turn.
Total Energy (TE)
Total energy (TE) is the combination of the aircraft’s altitude (PE) and airspeed (KE). TE will be referred
to as your “energy package” and will vary according to your situation. Although determining the TE
advantage for a given aircraft is difficult because of the possible speed differences between fighters, TE
remains a vital factor for determining relative advantage.
In addition to the Vn diagram, specific excess power (PS) curves measure the capability of an aircraft to
increase its energy state by using excess thrust. Because you will be fighting a similar aircraft in
training, these curves are less important now than they will be in the fleet. When you superimpose your
PS curve over that of another type aircraft, you can compare where one aircraft may have capabilities
over another. Your comparison will directly influence the type of tactics and strategies you employ
against another aircraft.
For our purposes in the Training Command, cornering speed and the optimum AOAs are the most
important indicators of maximum performance. Cornering speed, introduced as “maneuvering speed” in
Aerodynamics, is indicated on the Vn diagram and is defined as the minimum airspeed at which you can
(10-98) Original
Page 7
Previous Page
