Fighter Combat - Tactics and Maneuvering

186 ONE-VERSUS-ONE MANEUVERING, DISSIMILAR AIRCRAFT
however, weight may exceed thrust; in this case the aircraft requires a
short horizontal run and assistance from the wings to get airborne or to
land safely. Also, since jet thrust is diminished by high altitude or hot
temperatures, horizontal takeoff and landing runs may be required under
some operating conditions, even at low weights. Still, the short-takeoff
and -landing capability allows operations to take place from short,
makeshift airfields in forward battle areas, from battle-damaged runways,
and from the decks of ships.
The second type of V/STOL fighter is the lift-fan design, such as the
Russian Yak-36 Forger. This type incorporates one or more (two in the
Forger) lift jets that exhaust only downward; these are used in conjunction
with the main engine(s). The primary engine of the Forger has two pivoting
exhausts located in the rear, much like the Harrier, to vector the thrust
downward or aft. The lift jets support the front of the aircraft and the main
engine supports the rear during a hover.
The added capabilities of V/STOL fighters are not achieved without
penalties. The primary limitations of these designs are short range and low
ordnance-carrying capability in comparison to conventional fighters of
similar technological level. The requirement for high thrust and low
weight leaves little margin for large structures, great amounts of fuel, or
large ordnance loads. Such fighters, therefore, are usually small, lightly
armed, and lightly armored, with limited radius of action and combat
endurance. Although T/W and wing loading must be compared to those of
an opposing aircraft for them to have much relevance to fighter performance,
some generalizations can be made. Since improved landing and
takeoff performance is provided by a vertical thrust component, large
wings are unnecessary. In addition, large wings reduce high-speed performance
and add weight, so V/STOL fighters tend to have relatively small
wings and high wing loading, which can degrade turn performance. Even
so, inherent high T/W generally keeps sustained turn performance rather
high. Instantaneous turn performance, however, is likely to suffer because
of high wing loading.
Some V/STOL fighters can improve their instantaneous turn performance
through a technique known as "VIFFing" (vectoring in forward
flight), in which thrust vectoring can be used to assist the wings. By
pointing the exhaust downward (relative to the aircraft), thrust vectoring
increases instantaneous load factor by about 1 G. Under slow-speed, low-G
conditions this feature might double instantaneous turn performance, but
at high speed and high G its effect would be minimal. This increased turn
performance also must be paid for, however. Since essentially all the thrust
is directed downward, there is no forward component to oppose drag, and
therefore the aircraft will decelerate even faster than a conventional
fighter performing a similar maneuver. The V/STOL fighter operating in
this way needs all that good T/W to accelerate out of its energy hole after
the turn.
Not all V/STOLs have the option of using thrust vectoring in this
manner. In particular, the lift-jet designs often have intake covers that
open outwardly to deflect air into the lift fans. These deflectors may have