Fighter Combat - Tactics and Maneuvering

400 APPENDIX
veloped to lessen the effects of wave drag and increase MCR include
reducing aircraft cross-sectional area, sharpening leading edges, and
sweeping wings. The familiar "Coke-bottle" shape of many jet-fighter
fuselages also helps by smoothing out the changes in total aircraft crosssectional
area from nose to tail.
Figure A-10 shows how the various types of drag vary with airspeed and
combine to produce total aircraft drag (D). Note that parasite drag (Dp) is
insignificant at slow speeds but rises very rapidly as airspeed increases.
Conversely, induced drag (Dt) is greatest at very slow speeds and diminishes
quickly as the aircraft becomes faster. It should be understood,
however, that this plot is representative of an aircraft in straight and level
flight (i.e., load factor = 1). Since DI is proportional to the square of the load
factor, this drag component could still predominate in the total drag
picture of a high-G fighter even at high airspeeds. Trim drag is not shown
explicitly in this figure, but it can be considered as part of the induced-drag
component. Wave drag (DM) can be seen to begin at about MCR; it rises very
rapidly in the transonic regime and increases at a slower rate thereafter.
The effects of altitude on drag can be quite complex. Both parasite drag
and wave drag usually decrease with higher altitude, but induced drag
normally increases. Whether this results in more total drag or less generally
depends on aircraft speed and load factor. At low speeds or high G,
total drag tends to increase with altitude, but under high-speed, low-G
conditions, drag often decreases with increasing altitude.
H-M Diagrams
It should be obvious, considering all the variations in thrust and drag with
speed, altitude, etc., that the Ps capabilities of a fighter can be complex.
These capabilities are usually determined by flight tests and displayed in
graphical formats for pilot study. One such common format is called the
H-M (altitude-Mach) diagram. Figure A-ll is an example of this plot for a
typical supersonic jet fighter.
Figure A-10. Drag Variation with Airspeed