A fighter is a flying machine designed to shoot
down enemy aircraft, besides performing many other ground attack roles. Depending on the threat to be countered, the
operating environment and the weapons available, capabilities of a fighter vary
widely. Trade-offs are made in several
areas, the more prominent ones being performance and manoeuvrability. Each fighter is, therefore, a compromise, but
with certain qualities emphasised in order to best fulfil the primary task for
which it has been designed.
Aircraft Performance includes
parameters like rate of climb, ceiling, acceleration and speed which play a
significant part in the interception of an adversary; the latter two parameters
can also help in rapidly extricating out of a thorny situation. As would be expected, unbeatable aircraft
performance is dependent on good design, and availability of excess
energy. Thrust produced by the engine can be a convenient
index of available energy; however, when an aircraft is considered as a mass
acting under the force of gravity, a simple reading of engine thrust values can
be misleading. ‘Thrust-to-Weight (T-W)
ratio’ is the factor that helps appraise aircraft performance in a correct
perspective. Besides enhancing basic performance
parameters, a high T-W ratio also helps sustain turn rates by countering the
effects of drag induced during manoeuvring flight.
Higher thrust is, of course,
produced by paying the penalty of higher fuel consumption. Sufficient on-board fuel quantity can thus be
seen as an important factor if aircraft performance is to be fully
exploited. ‘Fuel fraction’ is a term
used to denote the internal fuel as a fraction of aircraft weight in the clean
configuration. It gives an idea of the
staying power in a dogfight, assuming that fuel consumption rates of different turbojet
engines are largely similar. A fuel fraction of less than .25 for
afterburning turbojet fighters and .20 for non-afterburning ones is considered
inadequate.
Manoeuvrability, or the ability
to out-turn an opponent, is an important attribute of a fighter. Turning is measured both in terms of radius
of turn as well as rate of turn. A good
radius of turn is a ‘nice to have’ feature, but an attacker rarely needs to
turn as tightly as his adversary to maintain a favourable position in a stern
attack, unless at very close ranges. A defender, on the other hand, needs to
swing his tail away from an attacker’s flight path as fast as possible by
generating a high rate of turn. Thus in
a turning fight, rate of turn is of greater significance than radius of turn.
Turning ability is dependent on
wing design, and the easiest understood feature is ‘wing loading’ or the weight
of the aircraft per unit area of the wing (which is the source of most of the
aircraft lift). During a turn, when
banked flight tilts the lift vector away from the normal, and drag wrecks
whatever remains of the angled lift, a low wing loading comes in handy to help
balance the essential lift-weight equation.
Low wing loading is thus advantageous to an aircraft turning for a
smaller radius, as well as a higher rate of turn, at any given speed. At very low speeds, however, when an aircraft
is on the verge of stalling, devices like slats and flaps preserve/generate
much needed lift; in such speed regimes low wing loading does not help matters
much.
Creating lift in an aircraft incurs
an unavoidable penalty in the form of induced drag. Aerodynamic efficiency is achieved by
designing a wing that produces maximum lift for the least drag. This is done by having a high ‘aspect ratio,’
which is the ratio of the square of the wingspan to the wing area. Since
induced drag happens to be inversely proportional to the aspect ratio, greater
the wingspan, lower the induced drag. A
high aspect ratio is thus an important factor in combat, as it helps in
sustaining turn rates. A good combination
for manoeuvrability would, thus, be low wing loading for enhanced turning
ability, along with a high aspect ratio to help sustain it. (High aspect ratio also improves endurance
and ceiling, and shortens take-off/landing distances.)
As fighters become faster,
their aspect ratios have to be reduced to minimise supersonic wave drag. This is done by presenting a smaller frontal
area to the supersonic airflow with the help of a smaller wingspan, besides
other profile streamlining techniques.
It can thus be seen that the conflicting requirements of high-speed pursuit
flight and subsonic manoeuvring flight have a bearing on the aspect ratio, and
compromises invariably result.
Fighters of Indo-Pak Wars
include some of the classics of jet age. The Sabre, Starfighter, Gnat and Hunter had earned reknown in
the Indo-Pak sub-continent due to the 1965 War. The later MiGs and Mirages are
no less celebrated, if for no other reason than their large production numbers,
and service in numerous air forces. Fighter
pilots who have flown these aircraft would swear that theirs was the best
fighter ever, with facts and figures to back up their claims. With due regard to their opinions, here is a
brief description of these fighters on the basis of some well recognised
criteria.
The F-6
was a Chinese copy of the MiG-19, the first supersonic fighter of the Soviet bloc.
It sported highly swept-back wings which, at 55 degrees, were considered
the right antidote to drag rise during transonic flight. Thick wings were the answer to the low lift generating ability of highly swept
wings, but drag rise due to the stubby profile did not help matters. Despite two powerful afterburning turbojet
engines which helped in initial acceleration, it could barely keep pace with subsonic
fighters at low altitude. Low wing loading coupled with a high aspect
ratio gave it excellent dogfighting abilities, though a poor fuel fraction limited its staying power in a dogfight. A pair of AIM-9B Sidewinder
missiles along with a set of three powerful 30-mm cannon were lethal weapons to
finish off an aerial target. The same cannon armed with armour-piercing
bullets, along with two rocket launchers having 8x57-mm rockets each, served a useful close air support
role.
Though of Korean War vintage, the F-86F Sabre continued
to soldier on in many air forces, due largely to laurels earned during that
conflict. It was a good fighter from the
point of view of manoeuvrability, as the low wing loading and high aspect ratio
would suggest. Its low T-W ratio however
was no help in preventing speed from bleeding off in sustained combat. Paradoxically, this was an advantage that
turned the tables on many an opponent because of the Sabre’s superb low speed
handling, thanks to a fine slatted wing.
An excellent all-round view from the bubble canopy was a delight for the
Sabre pilots. The Sabre’s six 0.5" guns with
a total of 1,800 rounds provided enough firing time to target several aircraft,
as was demonstrated twice in the 1965 War. The Canadair CL-13 Sabre
Mk-6 (designated F-86E in the PAF, not to be confused with the regular North American
Aviation ‘E’ model) was better endowed than the ‘F’ model in terms of
T-W ratio, due to a more powerful engine.
The F-6
was a Chinese copy of the MiG-19, the first supersonic fighter of the Soviet bloc.
It sported highly swept-back wings which, at 55 degrees, were considered
the right antidote to drag rise during transonic flight. Thick wings were the answer to the low lift generating ability of highly swept
wings, but drag rise due to the stubby profile did not help matters. Despite two powerful afterburning turbojet
engines which helped in initial acceleration, it could barely keep pace with subsonic
fighters at low altitude. Low wing loading coupled with a high aspect
ratio gave it excellent dogfighting abilities, though a poor fuel fraction limited its staying power in a dogfight. A pair of AIM-9B Sidewinder
missiles along with a set of three powerful 30-mm cannon were lethal weapons to
finish off an aerial target. The same cannon armed with armour-piercing
bullets, along with two rocket launchers having 8x57-mm rockets each, served a useful close air support
role. 
Though of Korean War vintage, the F-86F Sabre continued
to soldier on in many air forces, due largely to laurels earned during that
conflict. It was a good fighter from the
point of view of manoeuvrability, as the low wing loading and high aspect ratio
would suggest. Its low T-W ratio however
was no help in preventing speed from bleeding off in sustained combat. Paradoxically, this was an advantage that
turned the tables on many an opponent because of the Sabre’s superb low speed
handling, thanks to a fine slatted wing.
An excellent all-round view from the bubble canopy was a delight for the
Sabre pilots. The Sabre’s six 0.5" guns with
a total of 1,800 rounds provided enough firing time to target several aircraft,
as was demonstrated twice in the 1965 War. The Canadair CL-13 Sabre
Mk-6 (designated F-86E in the PAF, not to be confused with the regular North American
Aviation ‘E’ model) was better endowed than the ‘F’ model in terms of
T-W ratio, due to a more powerful engine. 
The F-104A Starfighter’s high T-W ratio coupled
with a streamlined supersonic design, positively impacted acceleration, maximum
speed and rate of climb. Due to its sleek profile and fantastic pursuit performance, it came to be known as a 'manned missile.' A good fuel
fraction ensured that it could maintain its high performance long enough. As far as manoeuvrability is concerned, the
Starfighter was an utter disappointment due to the very high wing loading and
low aspect ratio. Armed with a Gatling gun firing
66 rounds a second, along with AIM-9B Sidewinder missiles, the Starfighter generated
enough awe if not a high turn rate, to keep its adversaries at bay!
The Mirage IIIE is a derivative of the earlier
‘C’ model, which was the first Mach 2 fighter from the Dassault stable. It came
to be the progenitor of a very successful series of multi-role fighters that
continue to operate well past their fifth decade since the prototype flight. The
Mirage IIIE has a very low wing loading that is helpful in instantaneous turns,
but an unimpressive T-W ratio robs it of the ability to keep up in a dogfight. A very poor aspect ratio (typical of delta
wing planforms) causes phenomenal drag rise in manoeuvring flight, which is
only worsened by the lack of a tailplane, since the upgoing elevons on the
wings deduct considerably from overall lift. Prolonging a dogfight is thus, sure to be
disastrous. Its Sidewinder missiles, hard
hitting 30-mm cannon, and an airframe customised for high speed are the saving
grace in a hit-and-run fight. The aptly named Mirage can easily go supersonic
at low altitude, and twice over at high altitude.
‘Jew’s Harp’ would not be a misplaced
moniker for the diminutive Gnat, which vied for a place amongst an ensemble of
more daunting fighters. A fine blend of performance and manoeuvrability, it had
a relatively high T-W ratio for a
subsonic fighter, giving it good acceleration, while its low wing loading and
relatively higher aspect ratio conferred it with an impressive turning
ability. Due to its small size, the Gnat
surprised its opponents on many an occasion when it was sighted too late. This
attribute especially, made it a formidable fighter in air combat. The Gnat’s size was, however, also a
liability in so far as it did not permit large external loads, and restricted
it to the role of a 'guns-only' point defence interceptor.
Propensity of its 30-mm cannon to jam was a sore point with pilots, as was claimed
to have happened in combat on more than one occasion. The Gnat had a reasonably good fuel fraction,
which at first sight would appear quite unlikely. 
India’s first indigenously built jet fighter, the
HF-24 Marut went through serious teething troubles which it failed to outgrow. What
might otherwise have been a first class fighter, it essentially failed to find
a potent powerplant. Poorly endowed with a pair of very low T-W ratio engines,
the HF-24 was useless as an air combat fighter. It was however put to limited
use for ground attack, in which role its four powerful 30-mm cannon packed a
powerful punch.
The Hunter F-56 was an outstanding fighter in
all respects. Though outdone by the Sabre in manoeuvrability by a slight margin, it made up with its higher speed and better
acceleration. Like the HF-24, its four 30-mm cannon
provided it with tremendous firepower against aerial, as well as ground targets.
The MiG-21FL had an uncomplicated 'tailed delta' design,
and was easy to fly even to the limits. It was more manoeuvrable than its
bisonic counterpart, the F-104A, but not in the class of its subsonic
contemporaries whose low wing loadings in particular, were unmatchable. The MiG’s low aspect ratio caused high drag
rise during turns, though a good T-W ratio offset this limitation to quite an
extent. Its K-13 missile, despite
employment restrictions, did instill caution in the minds of adversary pilots;
the 23-mm cannon, however, had low lethality as well as a very short
firing time.
The Mystère IVA was a reasonably good fighter,
though not as manoeuvrable as the Sabre. It lacked the latter's wing slats, and could not turn as well, especially at low speeds. Except for a few odd aerial engagements,
including a daring duel with an F-104 in the 1965 War, it did not figure
significantly in the fighter role.
With wings swept back at an audacious 62 degrees, the Su-7BMK looked every bit a high-speed fighter-interceptor. However,
its heavily loaded wings were no good for manoeuvrability. Due to a high T-W
ratio, it could rapidly accelerate away, provided it had not run out of three
afterburner light-up chances that were available, which was a serious handicap
in combat. With a poor fuel fraction, staying
in afterburner for long was not a viable prospect anyway. Though endowed with
two hard hitting 30-mm cannon, it could not carry IR missiles, and was best
employed as a ground attack fighter with up to four rocket launchers having 16x57-mm rockets each, as its primary ordnance. Its
robust structure earned it the reputation of being unbreakable, as was
demonstrated in several safe recoveries despite serious battle damage.
The aging Vampire FB-52 was not really a match
for the PAF fighters. Its aluminium and
balsa wood structure gave it a very light wing loading, but its poor T-W ratio
and unimpressive maximum speed were grave liabilities, due to which it was
relegated to a second-line role.Note: Aircraft profiles not to scale.
> Colour profiles of aircraft, courtesy Tom Cooper.
> PAF aircraft data obtained from respective Pilot's Flight Manual.
> IAF aircraft data obtained from Encyclopedia of World Air Power, edited by Bill Gunston; Hamlyn/Aerospace Publishing Ltd, London, 1981.
© KAISER TUFAIL
