India’s HAL HF-24 Marut confounded detractors with its respectable combat record.
The 1971 air war between India and Pakistan was of interest to foreign observers as a testing ground for such diverse Eastern and Western aircraft as the Mikoyan-Gurevich MiG-21, Sukhoi Su-7, Lockheed F-104, Mirage III, Folland Gnat and Hawker Hunter. For example, the two-week conflict marked the only occasion on which two much-vaunted Mach 2 fighters, the MiG-21 and F-104, engaged in one-on-one combat (the MiG won). The 1971 war also included another aeronautical event that was of great local significance: the combat debut of the Indian subcontinent’s first indigenous jet fighter, the Hindustan Aeronautics Limited (HAL) HF-24 Marut (Storm Spirit).
The Marut had been criticized in India because of its protracted development, and it had been derided by foreign observers for being outdated before it ever entered service. Without doubt there was some degree of validity to both charges. Nevertheless, the Indian fighter gave a good account of itself in both ground attack and air-to-air combat. Even the Pakistani Air Force (PAF), whose combat reports differed radically from those of the Indian Air Force (IAF), claimed that no Maruts had been shot down in aerial combat. The original requirement for which the Marut was developed dated from 1956, at which time HAL took on three major new projects on behalf of the IAF. One was the license production of the British Folland Gnat lightweight jet fighter, for which a new assembly line was to be set up in Bangalore. The second project was for a new basic trainer, which would eventually enter production as the HJT-16 Kiran (Ray of Light). The third and most ambitious project was for the development of a Mach 2 multirole fighter, which would eventually emerge as the HF-24.
The requirement for the Mach 2 fighter was extremely specific. The Indian Air Staff wanted a multirole fighter capable of operating both as a high-altitude interceptor and as a low-level ground attack aircraft. It was to have a speed of Mach 2, a ceiling of 60,000 feet and a 500-mile radius of action. The plane was expected to be adaptable for operation as an all-weather interceptor, as an advanced trainer and as a naval fighter for use aboard the aircraft carrier Vikrant. The Indian government also wanted the aircraft to be built in India, if possible.
The development of such an aircraft would have presented a considerable challenge in any of the major industrial nations during the mid-1950s, but in a Third World country like India it seemed almost beyond the realm of possibility. HAL, the sole aeronautical company in India at that time, had only existed since 1941.
HAL had originally been established for the assembly of foreign-built aircraft destined for India and nationalist China, and for the repair and overhaul of aircraft for the U.S. Army Air Forces. In 1942 the Indian government gained a controlling interest in the firm by purchasing three-quarters of the stock. Although India had built a few light aircraft of its own design since World War II, by the mid-1950s its only experience with modern, jet engine combat aircraft had been the construction of de Havilland Vampires under license. It was a big jump from building a first-generation jet fighter of mid-1940s vintage, based on somebody else’s design, to developing an indigenous Mach 2 fighter from scratch.
The development of such an aircraft admittedly was, to a certain degree, a matter of prestige. The production of a Mach 2 fighter plane would have enhanced the status of India and HAL in the eyes of the world. Yet the military requirement was equally real. India and Pakistan had been at odds ever since 1947, when the two independent countries were originally established. India’s military also had to be prepared to contend on the northern and eastern borders with the Chinese. Armed conflict had actually broken out in 1962.
The Indian government was willing to back the Mach 2 fighter project, and HAL’s small but enthusiastic staff was equally eager to go ahead with it. However, the staff was spread far too thin to handle the three new major projects at once. What the firm needed was an experienced aviation engineer to head the Mach 2 fighter project, someone familiar with the intricacies of developing advanced combat aircraft. Naturally enough, they looked to Europe for such an individual. Eleven years after the end of World War II, the aerospace industry was firmly under the domination of the two superpowers, the United States and the Soviet Union. Europe, still recovering from the ravages of war, was chock-full of unemployed aircraft engineers. HAL managed to engage the services of a German named Kurt Tank, whose qualifications for the job were impeccable. He had previously designed one of the finest fighter planes of WWII, the Focke Wulf Fw-190.
Tank’s task went far beyond merely designing a jet fighter, however. Upon arrival in Bangalore in August 1956, Tank—along with a German assistant named Mittelhuber—found that HAL was woefully inadequate in both personnel and infrastructure to take on such a complex project. Among other deficiencies, the firm lacked a machine shop suitable for prototype engineering, adequate test equipment, static test rigs and a flight test laboratory. The firm’s entire design department consisted of only 54 Indian personnel, including three senior design engineers, two of whom were assigned to the jet trainer project. Tank found that he had not only to design an original jet aircraft but also help establish a modern industrial complex capable of developing one.
Unlike his Indian employers, Tank knew exactly what was involved in designing, building, testing, refining and mass-producing aircraft from his days at Focke Wulf. In addition to the Fw-190 fighter, he had designed the Fw-200 Condor four-engine commercial transport for Lufthansa. It first flew in 1937. When WWII began, the Condor design was modified into a highly successful maritime patrol bomber. Tank was also responsible for the Ta-154 Moskito, a high-performance, twin-engine, multirole combat aircraft built entirely of wood. Production of the Ta-154 was canceled when the factory that had been producing the special glue required for bonding the wooden airframe was bombed, cutting off the supply.
Despite the rudimentary nature of HAL’s facilities, work on the Mach 2 fighter—by then designated HF-24 and given the name Marut—went ahead at a relatively brisk pace. A full-scale wooden glider version of the HF-24 began aerodynamic flight trials, towed into the air by a Douglas DC-3, on April 1, 1959. Assembly of the first prototype commenced in April 1960. It was flown for the first time on June 17, 1961, by Wing Cmdr. Suranjan Das. A little more than a week later it was demonstrated for the minister of defense, V.K. Krishna Menon. A structural test airframe was completed in November, and a second flying prototype took to the air in October 1962.
The performance of the Marut did not live up to HAL’s ambitious promises, however. Its projected performance had been predicated upon the availability of the Rolls-Royce Bristol Orpheus BOr-12, a British-designed afterburning turbojet engine. The Marut was to have been powered by a pair of those engines, each delivering 8,170 pounds of thrust. The British government canceled its financial support for the development of the Orpheus BOr-12, however, and when the Indian government was not prepared to step in and foot the bills, the project was terminated.
Consequently, the Marut had to be fitted with a pair of nonafterburning Orpheus 703s, the engines that HAL was currently building under license for its Gnat lightweight fighters. However, the Orpheus 703 produced only 4,850 pounds of thrust, 44 percent less than the engine for which the Marut had been designed. As a result, the Marut was underpowered and was never able to fulfill its performance potential.
Throughout the 1960s, HAL directed a great deal of effort toward acquiring more powerful engines for the Marut from various foreign sources. However, the engines under consideration either could not provide a sufficient increase in performance, required too great a structural redesign of the airframe or became unavailable due to political or economic reasons. The most unusual and unlikely of those foreign sources was Egypt. For a while during the 1960s, India collaborated with Egypt’s efforts to develop its own turbojet engine, called the E-300. India even donated a preproduction Marut airframe to Egypt in which to flight-test the E-300. Egypt canceled the E-300 project in 1967, however, after the Six-Day War.
The IAF’s requirement for a Mach 2 interceptor was met when an agreement was struck with the Soviet Union in August 1962 for the acquisition of the MiG-21 interceptor. The availability of that formidable Soviet fighter, which HAL eventually produced under license, rendered the Marut’s lack of Mach 2 performance a moot point. The Indian jet’s development as an interceptor was no longer seriously pursued. Instead, HAL concentrated on developing the Marut as a low-level, single-seat strike fighter and a two-seat advanced trainer.
Two preproduction Marut strike fighters were handed over to the IAF for service trials on May 10, 1964. After three more years of development, the first Marut-equipped combat unit, No. 10 “Dagger” Squadron, was established on April 1, 1967. Kurt Tank was back in Germany by that time, working for the Messerschmitt-Bolkow-Blohm (MBB) aerospace consortium, although he continued to take an interest in the Marut and maintained close ties with his former employers.
The Marut Mk 1, as the production version was called, was a twin-engine, single-seat fighter with swept wings and tail surfaces. It was 52 feet long and had a wingspan of 29 feet 6 inches. The fighter weighed 13,658 pounds empty and had a maximum takeoff weight of 24,048 pounds.
The aircraft boasted many of the design features used on late 1950s aircraft to reduce supersonic drag, including an area-ruled fuselage and engine air intakes incorporating shock cones. Nevertheless, the lack of power available from the plane’s engines limited its top speed to Mach 1.02 at 40,000 feet.
The Marut’s principal armament consisted of four 30mm Aden cannons with 130 rounds per gun, the same armament used on the British Hawker Hunter, which the IAF was also operating at that time. The Aden cannon was a five-chambered revolving gun weighing 92 pounds that could fire 1,400 rounds per minute. The Marut was also armed with a retractable MATRA type 103 launching pack for 50 68mm unguided rockets, located in the fuselage just aft of the cannon bay. In addition, four underwing hardpoints could carry extra fuel tanks, air-to-ground rockets or up to 4,000 pounds of bombs.
Despite the Marut’s protracted development period of 11 years and its failure to achieve Mach 2 performance, the IAF was apparently satisfied with its new strike fighter. According to correspondent Pushpindar Chopra, IAF pilots affectionately described the Marut as a “Hunter Mk 2.” Although they criticized the Marut’s shortage of engine power, they praised the Indian jet’s control response and aerobatic ability. They also regarded it as a stable gun platform, possessing formidable firepower.
By the time hostilities broke out between India and Pakistan in December 1971, the IAF had two squadrons of Maruts in service, No. 10 Dagger Squadron and No. 220 “Tiger’s Head” Squadron. During that conflict, the Marut served with considerable success in the ground attack and interdiction role against targets in west Pakistan.
In combat the Indian fighter proved to be quite resilient. On at least three occasions, Maruts returned to base on one engine after the other had been damaged by groundfire. The jet’s flight controls were also designed to revert to manual control automatically if the hydraulic system failed, and at least one Indian pilot flew home on manual after his hydraulics were shot out.
Although no encounters ever took place between Maruts and the supersonic fighters then in service with the PAF—the MiG-19, Mirage III and F-104—they did occasionally engage in air combat with PAF Canadair Sabre VIs. No Maruts were lost to air combat, but on at least one occasion a Marut reportedly shot down a Sabre with cannon fire. Even the PAF, whose records are at variance with those of the IAF, claims that only five Maruts were destroyed during the course of the two-week war, three by small-arms fire and two strafed on the ground by PAF aircraft. That record stands in marked contrast to that of the foreign-built ground-attack fighters the IAF was using at that time. Pakistan claimed to have destroyed 31 Soviet-built Su-7 strike fighters and 17 British-built Hawker Hunters.
HAL continued producing the Marut Mk 1 for the IAF until 1974. Total production eventually reached 145 aircraft, including 16 two-seat Mk 1T conversion trainers. The trainers were similar to the standard Mk 1, with the addition of an instructor’s cockpit behind the pilot. Both aircraft types remained in IAF service until 1990, when the Maruts were replaced by MiG-23s.
Kurt Tank, the German aeronautical engineer who had designed the Marut, retained his close ties with HAL into the 1970s. He designed a successor to the Marut in 1973, designated the HF-73. The new fighter was to be powered by a pair of Rolls-Royce RB-199 turbofan engines and was intended to have true Mach 2 capability. It was also designed to carry twice the weapons load of the Marut. Negotiations with Rolls-Royce broke down, however. With the RB-199 engines no longer available, the HF-73 program was canceled.
The Marut was far from the best fighter in the world at the time it entered service. Both HAL and the IAF freely admitted that the aircraft was underpowered and never lived up to its full potential. It was certainly not in the same league as contemporary U.S., Soviet and Western European jets.
Yet the development of such an aircraft was a significant achievement for a Third World country that, at the time, possessed only an embryonic aerospace industry. Regardless of Tank’s contribution, it was a great tribute to the ambition and perseverance of the people at HAL that the aircraft was ever produced at all.
This feature first appeared in the May 2002 issue of Aviation History. Subscribe here!