Fighter Combat - Tactics and Maneuvering

406 APPENDIX
Figure A-15. Sample Climb Profile
Unloading to a. full zero-G condition may be limited in some fighters
because of engine design. Piston engines with float-type carburetors are
notorious for "cutting out" under zero G, which, although usually a
temporary condition, obviously would not help acceleration. During
World War II fuel-injected German aircraft often used steep unloaded
climbs and dives to escape from carbureted Allied fighters. The fuel and oil
systems of many other power plants, including quite a few jets, are also
restricted or time limited in this maneuver. In such cases unloading may
have to be performed at a slightly positive G or be limited in its duration. It
is also possible that minimum induced drag will be achieved with some
fighters at other than zero G. The fighter pilot should be aware of the
characteristics of his particular aircraft and operate accordingly. Figure
A-16 illustrates the effects of unloading from 1 G to zero G on the acceleration
performance of a typical jet fighter.
This figure is a plot of percentage improvement in acceleration
(A Acceleration) versus Mach number at various altitudes from sea level to
30 KFT. Note the very large improvement in acceleration at slower speeds,
particularly at high altitudes, which can be attributed to the fact that
induced drag is the major contributor to total aircraft drag under these
conditions. At medium speeds, where induced drag is not as great, its
elimination by unloading is seen to have less effect.
Acceleration is of key impoitance and often overlooked.
Lt. General Adolph Galland, Luftwaffe
Aside from induced-drag reduction, unloading may have other benefits.
Parasite drag also may be lowered because of the reduction in frontal area
presented to the airstream and a lessening of airflow turbulence over the