Sukhoi-7 BMK - A whale of a fighter
- Category: Retired Aircraft Histories
- Last Updated: Sunday, 26 July 2015 05:08
- Written by R Chattopadhyay
- Hits: 18971
Adapted from Pushpindar Singh Chopra's "A Whale of a Fighter", 1983
The speed with which negotiations for the Su-7 were completed appear to have no precedent in the procurement policies of the IAF. Even former officers of the IAF are unable to explain the rationale for the purchase of this aircraft. While the Su-7 did enhance the Indian AF's strike capabilities, the selection of this aircraft despite its known shortcomings remains somewhat of a puzzle.
People within the IAF betray varying emotions towards the aircraft. In all fairness to the Su-7, the aircraft did serve the IAF with some distinction in the 1971 war. In the mid-60s, even as the MiG-21 was being received in increasing numbers, the IAF had sought a high performance offensive air support aircraft to replace the Mystere IVA and stiffen the strike force of Hunter F Mk.56s.
The HF-24 Marut status remained uncertain owing to the lack of a suitable power plant for this otherwise eminently suitable airframe. Delays in its production program led the Indian Government to evaluate the Sukhoi Su-7 tactical fighter in the summer of 1966.
Even as 36 Hunter F Mk.56A and 12 refurbished Hunter T Mk.66Ds were procured from Britain, an IAF test pilots team flew the Su-7 in the Soviet Union in mid-1967. This evaluation was followed rapidly by a contract for some 90 Su-7BM fighters and Su-7U two-seat conversion trainers at a reported cost of $100 million.
IAF pilots and maintenance personnel underwent conversion courses in the Soviet Union before the first aircraft arrived in crates by ship at Bombay. These were assembled at Santa Cruz and delivered to 26 Squadron which became the first squadron to operate the new type in March 1968.
Induction of the Su-7 by the IAF was extremely rapid. No.26 Sqn was followed by No.101 Sqn (ex-Vampire FR Mk 55) in July 1968, with No.221 Sqn (ex-Vampire FB Mk 52) converting to the Sukhoi in August. Two more batches of Su-7s were contracted for, taking total procurement to some 140 aircraft, and enabling formation of 3 more squadrons (No.32's Mysteres, No.108's Vampires, and the newly-raised No.222, the last-mentioned being formed in September 1969).
Thus, within 18 months, the IAF had raised six squadrons of supersonic attack aircraft which dramatically boosting its overall strike potential. The Su-7 force was earmarked the roles of offensive air support, counter-air, short term interdiction and tactical reconnaissance.
Although the Su-7 had an impressive performance, with a maximum speed of 1056 mph (1700 km/h) at 40,000 feet (12,190 m) and an initial climb rate of 29,900 ft/min (152 m/sec), its obvious handicaps were an overly modest radius of action and limited external stores carriage. The first Su-7s for the IAF, had two under-belly and two underwing hardpoints, but later deliveries consisted of aircraft incorporating two more stores stations underwing. The earlier aircraft were suitably retrofitted in India to include the additional stations.
For its warload-range capability, the Su-7 was considered an "oversize" aircraft by many in the IAF, the service having been used to more "compact" aircraft, the Gnat being of the other extreme! However, the Su-7 had two "firsts" to its credit, insofar as the IAF was concerned. It was the service's first combat aircraft with a full-fledged autopilot and also the first with a Jet Assisted Take Off ( JATO) facility.
Apart from the initial batch of pilots who underwent type conversion in the Soviet Union, all subsequent training was conducted in India, primarily by No.221 Sqn which was designated as type conversion squadron for some years until enough pilots were "fully ops" on the Su-7. Thereafter, conversion training was carried out by the individual squadrons, most of the younger pilots had a minimum of 260-300 hours on Hunters or Maruts.
After the mandatory MCF (Mobile Conversion Flight) attachment, pilots were given four dual-check flights in the Su-7U before their first solo. As the numbers of Su-7s declined, the diminishing numbers of pilots who were posted to the remaining Su-7 squadrons fresh from the Hunter OCU underwent about 12- 15 dual check flights before they went solo.
The Su-7 at War: 1971
Although 15 air forces were operating the Su-7 as standard tactical fighter-bomber equipment by the early 1970s, it was to be the Indian Air Force that conducted this type's baptism in combat in December 1971. The sub-continent was plunged into armed conflict on December 3 with Pakistan's pre-emptive air strike that evening. Thereafter, from the fourth morning until the ceasefire on 17 December, the six Su-7 squadrons became responsible for the bulk of attacks by day, flying nearly 1500 offensive sorties, ranging from counter-air to short-term interdiction, close air support and tactical reconnaissance.
First counter-air missions at dawn on December 4th, were carried out by Su-7s with MiG-21s as top cover. No.26 Squadron struck at Chander, No.32 on Shorkot, No.101 on Pasrur and No.222 on Risalwala air bases. Loaded with two M-62 bombs each, the Su-7s swept in at extremely low lever and through intense anti-aircraft fire to deposit the bombs on the runways.
They satisfactorily achieved the immediate objective of neutralizing forward enemy airfields. Canberras by night, and Hunters by day concentrated on airfields further afield, including Sargodha, Murid, Chaklala, Kohat, Mianwali, Peshawar & Chakhamra and also bagged a number of aircraft on the ground. No.32's first action alone claimed two B-57s, one Mirage III and two Sabres at Shorkot. Just the time needed for the Su-7s to put in maximum effort against advancing enemy armour in the cauldron of the Chhamb.
The main task of the Western Army Command was to blunt the massive ground thrust against the Pakistan Army in the critical Poonch and Chhamb sectors, and the IAF concentrated on offensive air support (OAS) in this area of bitter contention. A Pakistani Corps, spearheaded by armoured brigades, advanced against Indian defences which had to be re-grouped behind the Mannawar Tawi river. As pressures increased, the number of close support sorties was stepped up and the Su-7 squadrons, having fulfilled their counter-air task, became the mainstay in this punishing role.
The OAS was mostly of a search & strike nature although, the battle area being on a narrow 10-mile (16 km) front, it was a short search & mostly strike. The limited airspace however meant only one mission could go in at a time: No 4 Tactical Air Centre (TAC), attached to the XV Corps, sent in four Su-7s every ½ hour, each mission spending about 10 minutes in the target area, bombing, rocketing, strafing troop concentrations and armour & artillery.
The rate of effort exceeded all plans. Sorties were being launched at the rate of six per pilot per day! In the words of the Adampur Base Cdr, "Instead of our efforts tapering off after the first few days, they continually increased as the war progressed. The ground support organization worked virtually around the-clock. Battle damage to aircraft was promptly patched and enthusiasm was magnificent."
No.101 Sqn, 'The Falcons', were at the Chamb forefront, relieving pressure on the embattled 10th Infantry Division, destroying enemy armour with 57mm rockets at the Munnawar Tawi crossing and following up with low-level attacks on troop & tank concentrations in both Chhamb and Sialkot.
The tally was 69 tanks, 25 field-guns and 57 "B" vehicles destroyed. Excerpts from the Squadron War Diary illustrate the intensity of operations: "On December 4th, 28 OAS sorties carried out against enemy tanks and gun positions. One train carrying tanks and fuel hit with rockets and left ablaze. On December 5th, 14 sorties flown against fuel dumps, gun positions. vehicle convoys and tanks in the Chhamb. On December 6-7th, 30 sorties launched in the Chamb area and Shakargarh bulge, against tanks, troop concentration, gun positions and vehicles." And so on till December 17th.
No.101 Sqn was involved in dramatic manner in the Army's capture of the Chicken's neck salient, essentially because of timely tactical reconnaissance effort and the subsequent close air support, which enabled the operation to be completed in the first 8 of an estimated 48 hours!
Other Su-7 squadrons played an equally important part. No.26 operated primarily over the Shakargarh bulge, controlled by No.8 TAC, attacking enemy defensive positions, tanks & troop concentrations at Zaffarwal and Shakargarh. No.32 Sqn (Thunderbirds) was engaged in OAS for the Army in the Sulemanki, Chhamb and Shakargarh areas and experienced two unusual situations.
The Commanding Officer, Wing Commander H.S. Mangat, was intercepted by PAF MiG-19s whilst on a photo-recce mission and his Su-7 hit by a Sidewinder missile. The explosion carried away half the rudder, the elevators, ailerons and flaps and were all heavily damaged. Wg. Cdr. Mangat disengaged successfully and then returned to his base despite the extensive damage to his aircraft, a tribute to his flying skill and to the toughness of the Su-7. The aft section of Mangat's Su-7 is, incidentally, now on display in the IAF Museum at Palam.
Not a single Su-7 was, in fact, lost to enemy air action, even though a number of aircraft were damaged in air combat. Flt. Lt. J.S. Ghuman's Su-7 was similarly hit by a Sidewinder. He later related, "The immediate symptoms were a shuddering of the aircraft followed by the fuel-warning light coming on. However, the aircraft continued to respond perfectly," and Ghuman flew back to base with pieces of the missile embedded in the tail and aft fuselage of the aircraft.
The Su-7 was not devoid of self-defence capability, as was evidenced when Flight Lieutenant S.S. Malhotra ("Mad Mally") of No.32 Squadron was engaged on a photo recce mission over Mianwali. Two MiG-19s on CAP reversed towards his Su-7. Instead of aborting his mission, however, and without jettisoning tanks, Malhotra turned into the MiG-19s and fired his cannon as the first aircraft slid into his gun sight. He then turned for home and returned to his base without officially claiming a "kill'', but the PAF were later to admit the loss of the MiG-19 over Mianwali.
No.222 Sqn, "Killers", concentrated on "round attack strikes with 1102 lbs. (500 kg) bombs against enemy armour, artillery & troops in the Dera Baba Nanak, Hussainwala and Ferozepore sectors. Short-term interdiction missions were directed against railway rolling stock, marshalling yards, bridges and convoys, and tactical-photo reconnaissance sorties were mounted to continuously monitor the battle front. To quote from the Squadron's War Diary: ''14 December: Rail traffic between Kasur to Pukhpattan and Montgomery attacked: goods trains, locomotives, railway junctions, bridges and marshalling yards hit. All rail traffic paralyzed."
The Su-7s were also employed in "rhubarb" type of targets of-opportunity raids, seeking out enemy armour around Fazilka-Ferozepore to disperse a major build-up. Enemy tanks concealed in haystacks and under groves of trees were attacked with rockets and bombs in Chitian Mandi and the Sejra Bulge, maximum effort being put in between 8-12 December.
On the Eastern front. Nos.108 and 221 squadrons supported the Army's blitzkrieg advance towards Dacca. No.221 Squadron was allocated the tasks of counter-air, offensive air support and photo recce, launching attacks against Kurmitola and Tezgaon air bases on December 4th and destroying three Sabres on the ground. 9 TAC directed the squadron against riverine traffic, railways and artillery positions. The Su-7s were operated in pairs and were called up by advancing army units to soften defence strong points by carrying out very accurate rocket attacks against bunkers.
In the war for bridges and ferry crossings, the Su-7s were particularly active and a large number of barges, steamers and gun boats were hit. Before No.221 Sqn was transferred to the Western Sector on 12 December, it was to play an important part in the capture of Kushtia. To quote the Squadron Diary: "On December 11th, one span of Hardinge Bridge was destroyed and constant bombardment of bunkers, troop positions and railway sidings near Kushtia was carried out.
This resulted in the fall of Kushtia the same evening, mostly because of the creditable performance of No.221 Sqn. On December 12th, to give this operation a final touch, bombs and rockets were delivered on withdrawing troops, ammunition depots, the main power house near Hardinge Bridge and on the ferry-craft carrying troops."
Opposition from enemy air was limited to fleeting gun or missile interception attempts by MiG-19s and Sabres, without any loss, but the Su-7s ran the full gauntlet of heavy ground fire. The Pakistani air defence system was based on the Chinese model, with multi-barrel 37mm cannon, plus concentrated machine gun and small arms fire.
Being a relatively large aircraft and continuously exposed, the Su-7 was certainly vulnerable to such concentrated air defence, and many aircraft were recovered to base "peppered", some having sustained extensive damage to wings and fuselage. But for its ruggedness, far more Su-7s would have been written off. Losses were commensurate with the scale of effort, if not below it.
Although the IAF admitted that its Su-7 force suffered attrition during the 14 Day War of 1971, this was by no means excessive given the scale of effort and exposure to enemy air defence. Most missions had to be flown by day and at low level, pilots making repeated attacks on well defended targets. Pakistani propaganda had claimed 34 Su-7s as destroyed in aerial combat or by ground fire, but in fact 14 were lost, including one in the East and most to ground fire. Not more than four were lost to aerial combat.
The somewhat derogatory opinion of the Su-7 apparently held by NATO was therefore entirely unfounded. Opposition had been different to that expected, the Su-7 units having anticipated more air interception and far less effective ground fire. New attack techniques were therefore worked out during the conflict with the result that loss rates were considerably reduced after the first days of action.
The Sukhoi Su-7 emerged from the 1971 operations with a mixed reputation. Propaganda against the type had led to superficial conclusions and exaggeration of its shortcomings. There was no doubt that the limitations of range and endurance, plus modest stores carriage vis-a-vis the aircraft's size, reduced operational flexibility.
But in the role to which it was assigned, the Su-7 more than earned its pay. It proved itself a steady weapons platform, enabling accurate pinpoint strikes to be carried out. It demonstrated the robustness of its airframe and its ability to absorb far greater punishment than other aircraft types, and it consistently achieved high serviceability rates, while the turn-around time between sorties proved satisfactorily short. The Su-7 was said to have spawned a special breed of pilot, combat-hardened and confident of both his and his aircraft's prowess.
The Aircraft in Detail
The Su-7 stands high off the ground and its highly swept wing (62º on the leading edge) endows it with a sleek appearance, despite its long, tube-like fuselage. The strong appearance of the aircraft is reinforced by the absence of "no step" signs, and there are no restricted areas for movement on the wing, which incorporates a very large flap over the entire trailing edge, from root to the inboard end of the aileron, and sports neither slats nor tabs. The tail unit is swept on all surfaces, the tail-plane being all moving, with anti-flutter `mass balance' bodies projecting forward at the tips.
A large fairing at the base of the conventional rudder houses twin brake- chutes. Cannon muzzles appear in each wing-root leading-edge with blast panels on the fuselage sides and there are six stores-attachment points, four underwing and two under the fuselage for a variety of weapons or fuel tanks. The pitot head is mounted above the air intake, offset to starboard, and adheres to the solid theme of the remainder of the aircraft unlike the pitot boom of the Mirage Fl which can be inadvertently bent by a careless ground handler.
AIR INTERNATIONAL incidentally, was invited to try a series of pull-ups on the Su-7's pitot boom which provided as solid a hoist as any gymnasium horizontal bar!
In the early years of its service with the IAF, the Su-7 became the object of irreverent, though good-humoured, asides. Some said it was initially designed as a tank, hence the solid structure! Others insisted it was meant to be a midget submarine, hence the periscope (in the rear cockpit of the trainer version!). A distinguished fighter pilot, then commanding a Gnat squadron, could only utter one word after his first flight in the Su-7. "Why?" Just a plain "Why?" and nothing else.
But banter aside, the Su-7 could really fly. Slowly but surely gained the profound respect of pilots flying other fighters. With reheat on, at low level, the Su-7 would leave all others standing, including the MiG-21. Simulated strikes on point-defended targets, with fighters on CAP, proved the point every time, and the Su-7 came to be considered in India as a "Whale of an Aircraft!"
The single key factor behind the Su-7's spirited performance is its Lyulka AL-7F-I turbojet whose sheer brute power 15,134 lbs. st/6865 kgp dry or 21,627 lbs. st/9810 kgp reheat thrust overcomes any shortcomings and disadvantages of design and thick-wing drag. The AL-7F-I is a single-shaft axial-flow turbojet with a nine-stage supersonic compressor.
The effective and rugged afterburning system has a variable area nozzle which is governed according to the turbine exit temperature and throttle-lever position. The AL-7F-I belongs to a basic family which has powered the Su-9, the Su-11 and a number of Soviet experimental bombers and reconnaissance aircraft, but being a product of mid-50s technology, has suffered inherent problems of maintenance and emergency procedures.
A problem encountered in earlier years was the tendency of the engine to surge in the event of compressor failure which could result from heavy turbulence or high-temperature overshoot, and this could lead to turbine blade failure. This problem is inherent in early state-of-the-art engine design and aircraft were retro-modified to incorporate "de-rumble" doors or valves in the forward fuselage which, in the high supersonic regime, would open automatically to bleed off air and thus reduce air intake surge. There were also bleed valves in the Vth and VIIth stages of the engine to bleed off excess air.
The engine oxygen is limited to provide a maximum of six engagements. The oxygen system was needed for the initial start. With some reserve required for relighting in case of a flameout, effectively only three afterburner engagements were permitted in a single sortie. Internal fuel capacity is limited to 647 Imp Gal (2940 L) housed by wing cells and saddle tanks, but the underbelly hardpoints carry two 132 Imp Gal (600 L) drop tanks. The inner wing stations can further carry 198 Imp Gal (900 L) drop tanks which allow a maximum of 1307 Imp Gal (5940 L) of fuel for ferry flights. Two JATO solid-propellant rocket units can be attached under the fuselage to assist in take-off, but the IAF has not adopted this procedure.
The cockpit, although spacious, is cluttered with a large number of instruments and switches, many of them redundant as the IAF did not adopt the JATO booster, Soviet-style air ventilated flying suit nor transponder. Instrumentation standard is good albeit of early 'sixties technology and the artificial horizon (attitude indicator) is possibly the best in the business. Interpretation is very good and reliable.
The Soviet approach to commonality with such equipment as clocks, radio compass, lighting indicator panels, circuit panels, etc, is apparent through various aircraft types, including the Su-7, MiG-21, MiG-23, MiG-25, An-12 and IL-76, and even extends to warships, tanks and missile carriers! A large range of radio frequencies can be tuned from a straight-select array in the switch box, but there is no direct digital tuning.
Some early Su-7s delivered to the IAF, had French or Arabic lettering on the instrumentation indicating their originally intended destination, but subsequent aircraft were lettered in English. Forward visibility from the cockpit is poor and height adjustment of the ejection seat and rudder adjustment are cumbersome, being fixed by the armament technician to suit the pilot's height. Even with the seat elevated to the highest position, shorter pilots still had problems with forward view. The rocket ejection seat has a 0/87 mph (0/140 km/h) capability, the Su-7 having been the first aircraft in IAF service to allow zero-level ejection.
The Su-7UM incorporates a second seat in place of the 441 lb. (200 kg) fuselage fuel tank, thereby reducing endurance, but is otherwise equipped to the same standards as the fighter, including armament. The instructor in the conversion trainer's rear cockpit has a failure simulation panel, with override facilities to simulate problems with the undercarriage, flaps and airbrakes.
View from the rear cockpit is, curiously, better than from the front, the instructor employing a periscope and mirror below 375 mph (600 km/h) speeds, particularly for circuits and landing approach. Both ejection seats have an interlock mechanism so that no inadvertent ejection can take place. The canopy slides forward and is securely locked on sliding-momentum. The air conditioning system, or lack of it, is a problem as the cockpit is essentially designed for cold weather heating, hardly necessary in Indian conditions, and during low level flight in summer the cockpit gets uncomfortably hot in consequence.
Steering is by differential braking, and take-off with full load on hot days is critical, the Su-7 requiring nearly 2625 yards, 2400 metres, of runway for lift off, the rotation speed being 224 mph (360 km/h). Once airborne, the Su-7 accelerates very quickly and, in clean condition, "climbs like a rocket", routine altitude for handling and instrument training flights being some 39,370 feet (12,000 metres), above which the Su-7 tends to become sluggish.
Even with two drop tanks underbelly, the aircraft turns well, although in hard turns speed washes off rapidly unless re-heat is employed. Flight controls have triple redundancy' the main hydraulics being backed by standby hydraulics and an emergency hydraulic pump, there being full freedom on standby control. No total failure has ever been reported in Indian service.
Stick forces are heavy, and even with the spring-loaded powered-controls, the pilot must expend much muscle power. There is no rudder or aileron trim and the controls are heavier than those of most other aircraft of the Su-7's generation. A pilot's comment is that flying the Su-7 with its powered controls is akin to flying the Hunter on manual-control!
Without aileron trim, control gets tricky, particularly in the event of weapons hang-up, owing to asymmetric imbalance, and bombs from wing stations must be dropped simultaneously. Handling characteristics are good throughout the flight envelope, gust response is good and the aircraft's 8% thick wing allows stability at high speed and at low level, and is amenable to rapid manoeuvring.
In clean conditions, the Su-7 goes supersonic at any altitude and is also marginally supersonic at 40,000 feet (12,190 metres), in stores-configuration. The Su-7 goes supersonic at low level and remains steady, and the IAF has flown sonic salutes with Su-7 formations at special parades.
From M = 0.92 to M = 0.94 the Su-7's nose tends to drop and more backward pressure is applied on the stick till the aircraft steadies at M = 0.98, Mach unity being achieved without perceptible change. Maximum speed at low level, as recommended by the manufacturer, is 715 mph (1150 km/h), but the IAF has, with experience, been able to do far better, exploiting the Su-7's inherent potential achieving speeds up to 840 mph (1350 km/h) on the deck.
The Su-7's autopilot has a leveling mode. Up to +60º in pitch and bank, pressing of the levelling button on the control column would effect bringing the aircraft back to straight and level flight, and locking the control column so that a disoriented pilot can recover and regain manual control after tripping off the autopilot. There is no stall warning as such, the Su-7 just developing a rate of sink; at zero speed, provided there is no slip or skid, the aircraft recovers instantly with forward stick. Spinning is not undertaken intentionally, but in the event of an inadvertent spin correct use of control column enables the Su-7 to recover immediately.
After two turns, however, the AL-7 engine has a tendency to surge, in which case the pilot must close the throttle and attempt re-light. As per Soviet standard operating procedure, threshold speed on finals is 224 mph (360 km/h), but IAF pilots are quite comfortable at 211 mph (340 km/h). On touchdown it is mandatory to deploy the twin brake-chutes which are extremely effective and experienced pilots hardly use brakes except when turning off the runway. An average of 50-60 landings occur before a tire change is necessary.
The Su-7's underbelly is "soft" and emergency belly landings are dangerous, as, with its excessively long fuselage, the aircraft tends to porpoise and the forward fuselage can break up. In other respects, the Su-7 is an exceptionally robust aircraft and capable of absorbing a great deal of punishment.
Bird strikes have done little damage and the engine is tough enough to absorb all but the heaviest ingestion. On one aborted take-off, a Su-7 ploughed through the crash barrier, past the base perimeter fence and ended in a shallow ditch. The pilot got out, the aircraft was towed back, and after checks was ready to fly again the same day. The Su-7's ability to remain airborne and recover to base even after extensive battle damage is well recorded, bearing eloquent testimony to the sturdiness of its construction.
The Su-7 is a very stable weapons platform and a well harmonized guns-and-sight combination gives outstanding results. Armament is composed of two 30mm NR-30 cannon with 70 rounds per gun and a variety of stores distributed on four underwing and two underbelly hardpoints. Ordnance carried includes M-62 1102 lbs. (500 kg) bombs, 551 lbs. (250 kg) bombs, S-24 rocket- bombs or UB-I6-57U 57mm rocket pods. The wing outer-stations are stressed for 551 lbs. (250 kg) loads whilst the inner stations and under fuselage points are stressed for 1102 lbs. (500 kg) loads.
On counter-air or short-term interdiction missions, the Su-7s are normally fitted with M-62 bombs, and for offensive air support the 57mm rocket pods are particularly effective, the six pods containing a total of 96 rockets fired selectively or in salvo and resulting in a lethal spread 44 yards (40 m) wide and straddling 120 yards (110 metres) of frontal area.
The NR-30 cannon fires a heavy slug (1.98 lbs./O.9 kg) at the rate of 1200 rounds per minute and although firing at a relatively slow rate, this heavy caliber weapon's explosive force, has a great lethal impact and is effective against semi-armoured targets. The gyro gunsight, designated ASP-5PF, is of straightforward design and construction, and a well harmonized sight will give outstanding air-to-ground results.
The gun-sight is cleared up to 45º dive angles, though normal attack angles are 20-25 deg. Radar ranging is provided for both air-to-air and air-to-ground estimations, and the Serena tail warning detector radar is a passive device which provides a panel blinker and audio warning. An unusual arrangement is the Su-7's ability to fire Very cartridges from an orifice under the starboard wing leading edge root which can also be employed for dispensing chaff.
One in every four Su-7s delivered to the IAF was fitted with a simple vertical camera aft of the nosewheel, the camera hatch being actuated by the pilot when on a photo recce run. The fixed camera covers an area directly proportionate to the height above ground and has been a very useful tactical asset.
For over a decade since that war, the Su-7 has remained in the front-line OAS force, although war losses and normal attrition over the years meant steady depletion of the inventory. As the IAF did not obtain replacement Su-7s, a number of squadrons were re-equipped with the MiG-21 and MiG-23, and the last Su-7 formations (Nos.32 and 222 Sqns) converted to MiG-27s towards 1984 - 85. As pilots gained familiarity with the type, the Su-7's full potential was realized and exploited. In one-to-one dissimilar type combat, the Su-7 could outfight the MiG-21 under exercise conditions.
In the IAF's annual competition for ground attack air defence squadrons, No.221 Sqn won the trophy for highest-proficiency rating in 1973 and 1974, whilst No.222 continued the Su-7's success story by winning the prestigious "Arjuna" gunnery trophy and overall championship in 1978 and 1980, recording an average of 97% hits on target and edging out competing aircraft types of far classier lineage. Yet of all modern combat aircraft inducted into IAF service, the Su-7 had one of the shortest service histories, just under two decades. By contrast the Hunter has notched up well over forty years of service.
As part of the Indian Air Force's Golden Jubilee celebrations in February 1983, the Service displayed a range of its combat aircraft and live weaponry in an impressive spectacle of firepower and aerobatics at the Tilpat range, south of Delhi.
Amongst the many events were two involving the Sukhoi Su-7, an aircraft type which by then was regarded as "a diminishing asset", yet, here, in the presence of distinguished invitees including foreign air attaches, effectively demonstrating continuing capability.
In the first event, a Su-7 and a MiG-21 conducted simulated air combat, an exhilarating display of tight maneuvering in which the Su-7, given the limitations of the airspace, obviously more than held its own. Commencing combat at about 560 mph (900 km/h) at low lever, with pre-set call conditions primarily because the MiG-21 has an instant re-light on reheat whilst the Su-7 needs 6-7 seconds for afterburner light up), the "clean" Su-7 out-turned, out-climbed and out accelerated the MiG-21, the critical factor of power reserve standing out in the Sukhoi's favour.
In the close-in turning fight, the MiG-21 had to repeatedly converts its turn into the vertical plane in order to keep the Su-7 within range. Dropping speed, in low-speed maneuvers, the MiG-21 eventually gained the advantage owing to the better aileron control offered by its delta wing by comparison with the highly swept wings of the Su-7, aileron control of which starts to fade and necessitates excess rudder being employed. Of course, owing to the Su-7's high fuel consumption in the full re-heat regime (794 lbs./360 kg per min) engagement time was short, but the Su-7 could disengage at will.
This factor has proved critical in actual combat as, in such circumstances as those simulated, all external stores, including fuel drop tanks, are jettisoned, leaving only internal fuel and therefore strictly limiting time on task. The second event involved cannon and rocket attacks by Su-7s against ground targets.
At a dive-angle of 25º, the lead Su-7 fired a short burst from its NR-30 cannon, pulverizing the aircraft target on the ground, and a defence complex was straddled by S-24 rocket bombs fired by a section of Su-7s. It was self-evident why Sukhoi squadrons have been notching the highest points in IAF gunnery meets over the past few years and why the Su-7 has gained sober respect for its capability as a steady and sturdy weapons platform. Yet even after it has passed from service the Su-7 saga continues to remain controversial.