Fighters of Indo-Pak Wars

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-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.

         

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> 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