HF-24 / HF-73 Heading - Redux

Aashish

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#1
Credit to @Tarun for finding matter on this topic

++++

The Other Side Of The Coin
Mr Pushpinder Singh sent an old article ” THE LOST DECADE”, of the 1970s, which appeared in the Nov – Dec 1990 issue of Vayu. The author, Mr Raj Mahindra, was former MD (Design and Development) at HAL. The article, written to mark the 50th year of Hindustan Aeronautics Limited, basically reviews the plans and projects that were considered and undertaken by HAL during the “lost decade and to speculate on what might have been had the powers-that-were persisted with the several opportunities that came up.”

We all hold opinions on HAL and its achievements, that is why this particular account, from within the establishment is of interest. One may agree or disagree with the contents, but there is no denying the fact that it makes for very interesting reading.

Without reproducing it in its entirety, I have paraphrased parts of it while resorting to direct quotes, wherever it was deemed appropriate. All italics and highlighting are mine.

The article begins with briefly recalling ASRs formulated at Air HQs in the 1970s, which discussed the gradual replacements for the MiG 21FL, Su-7, Hunter, HF 24, Canberra, the Vampire trainer and the aging transport fleet. These in turn were to be replaced by a single supersonic tactical airstrike aircraft (TASA), supersonic deep penetration aircraft, the AJT and versatile STOL transport aircraft respectively.

“In Hindustan Aeronautics Limited (HAL), the Indian Air Force, indeed the nation had an enormous reservoir of opportunity to meet the IAF’s requirements for most, if not all, its needs of the forthcoming generation from the mid-70s till the end of the century.” Till the 60s, HAL’s list of achievements boasted the HT-2, Pushpak, Krishak and Basant. The Kurt Tank led team also had the inducted into service HF 24 under its belt by the mid 60s. The search for a compatible engine, for the Marut, to match its superb design capabilities and which came to nought, was attributed to be “more due to lack of sustained Government/industry effort than technological reasons.” Once the Marut was consigned to history , the design and development team of the HAL were virtually jobless till the LCA project was launched in 1986. “Meanwhile, a great deal of experience, talent and time had been irretrievably lost.”

Aircraft design and development, according to the author, briefly comprises three distinct streams – where prototypes are built but not followed by series production, where prototype development is followed by production and operational deployment and thirdly where design studies, building of mock ups etc takes place without further follow up activity. “unfortunately, the last category was the fate of most of the efforts of HAL’s design teams in the lost decade of the seventies, a fact barely known to most and the real story, to just a few.”

During the period of the mid sixties an Advanced Projects Group, headed by the author, was assigned the task of focussing on and overseeing feasibility studies for likely military and civil aircraft.

This group initially conceived of the Ground Attack Fighter I (GAF I) powered by an M45 engine which was itself being developed as a joint venture between Bristol Siddeley and SNECMA and would have a radius of action of about 150 miles.

There was also a study made for a STOL transport cum freighter, as a civil airliner with a 100 seat capacity and also as a replacement for the Packet, Dakota and Caribou. The configuration was for using four Rolls Royce turbofan engines and another configuration powered by four turboprop engines.

“The design configuration was not only contemporary but had advanced features which were later seen to have been adopted by advanced aerospace companies in the West. Unfortunately, development work on this project was abandoned in favour of combat aircraft which had all the priorities. However, as later events unfolded, the tremendous efforts ………….did not succeed in persuading the Defence Ministry to launch full fledged design and development of even the combat aircraft …..”

In 1967, the Group took up studies for an interceptor – ground attack aircraft. The multi role F 4 Phantom was the role model of this study. The GAF II, as it was referred to, was put through wind tunnel tests and the “configuration presented a very good basis on which to launch a prototype development effort. It was, however, clear that a far more elaborate infrastructure would be required for HAL to develop and build a new generation fighter.”

In the event, an attempt was undertaken to fall back on the trusted Marut and a parallel design using the forward fuselage of the HF – 24 with some modification to its canopy contour was offered to the IAF. The aircraft would have a radius of action of 300 nm, maximum ordinance for a ground attack role with contemporary avionics. The study completed in 1970 envisaged induction into service by 1976. This did not apparently find favour and Air HQ issued a firm requirement for an Advanced Strike Aircraft (ASA). “The final configuration of the Advanced Strike Aircraft as proposed by HAL, met most of the essential requirements of the Indian Air Force. While evaluation continued for some time, approval for prototype development simply did not materialise.”

In 1973 there was an offer from Germany to jointly develop the HF 24 into the Hindustan Supersonic Strike Aircraft labelled the HSS 73 later to be known as the HF-73. This would retain the original mainframe, with radical changes to the fuselage, air intakes and the centre wing section. The cockpit was to be modified for better visibility, fuel capacity increased, and with a completely new avionics suite and powered by the Rolls Royce RB 199-34R engine would have a radius of action double that of the HF 24. “Eventually, this project had to be abandoned because, as some said, of non clearance of the RB 199 by the UK and Germany, the two partner governments involved in the engine development for the Tornado MRCA programme. Thus all efforts in developing an Indian combat aircraft had come to naught.”

Subsequently HAL took on a feasibility study for a small multi role passenger aircraft, the HAC 33. “A wind tunnel model was built but not tested as development funds, were once again, not approved.”

In the mid-70s, the IAF showed interest in development of an air superiority fighter. In 1974 HAL undertook designing and studying a configuration for the Air Superiority Fighter (ASF). The ASF 300 was considered with either an Indian GTX or a SNECMA engine. The configuration proposed by HAL, “even though it did not meet the ASR, could have provided a reasonable solution…..”

“At this stage the HAL design team, resilient as ever, projected a low cost HF-24-M53…….when compared with the ASF 300, was 2 tons lighter, and was comparable to the Jaguar for bomb carriage capability as well as penetration distance……….The combat capability offered through this configuration and the delivery schedules were not acceptable to the IAF, and therefore the work was discontinued.”

“How much disappointment does a man (or design team) need?”

There was yet another attempt made to redesign the dear old Marut and a detailed feasibility study was conducted for the next version, the HF 25. At an estimated cost of Rs 64 Crore at 1979 price levels, the HF 25 prototype was scheduled to be available in three years and induction into service was proposed seven years later, that is by 1986. “In spite of the low development cost of the project and low unit cost of the HF 25, the IAF showed preference for the Soviet MiG 23/27. The project was therefore discontinued.”

In 1980-82 design feasibility studies were undertaken for an Advanced Jet Trainer. The programme was disbanded as all available funds were diverted towards the Advanced Light Helicopter and the Light Combat Aircraft.

“It was not until 1986, thus, that the Ministry of Defence with its constituent departments encompassing the conceiver (Defence Research and Development Organisation) producer (Hindustan Aeronautics Limited) and operator (Indian Air Force) got its act together to clear the Light Combat Aircraft (LCA) project which has since been underway under the aegis of the Aeronautical Development Agency (ADA) which manages, funds and monitors the programme from its headquarters in Bangalore.”

The Other Side Of The Coin
 

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#2
Credit to @Tarun for finding matter on this topic

++++

The Other Side Of The Coin
Mr Pushpinder Singh sent an old article ” THE LOST DECADE”, of the 1970s, which appeared in the Nov – Dec 1990 issue of Vayu. The author, Mr Raj Mahindra, was former MD (Design and Development) at HAL. The article, written to mark the 50th year of Hindustan Aeronautics Limited, basically reviews the plans and projects that were considered and undertaken by HAL during the “lost decade and to speculate on what might have been had the powers-that-were persisted with the several opportunities that came up.”

We all hold opinions on HAL and its achievements, that is why this particular account, from within the establishment is of interest. One may agree or disagree with the contents, but there is no denying the fact that it makes for very interesting reading.

Without reproducing it in its entirety, I have paraphrased parts of it while resorting to direct quotes, wherever it was deemed appropriate. All italics and highlighting are mine.

The article begins with briefly recalling ASRs formulated at Air HQs in the 1970s, which discussed the gradual replacements for the MiG 21FL, Su-7, Hunter, HF 24, Canberra, the Vampire trainer and the aging transport fleet. These in turn were to be replaced by a single supersonic tactical airstrike aircraft (TASA), supersonic deep penetration aircraft, the AJT and versatile STOL transport aircraft respectively.

“In Hindustan Aeronautics Limited (HAL), the Indian Air Force, indeed the nation had an enormous reservoir of opportunity to meet the IAF’s requirements for most, if not all, its needs of the forthcoming generation from the mid-70s till the end of the century.” Till the 60s, HAL’s list of achievements boasted the HT-2, Pushpak, Krishak and Basant. The Kurt Tank led team also had the inducted into service HF 24 under its belt by the mid 60s. The search for a compatible engine, for the Marut, to match its superb design capabilities and which came to nought, was attributed to be “more due to lack of sustained Government/industry effort than technological reasons.” Once the Marut was consigned to history , the design and development team of the HAL were virtually jobless till the LCA project was launched in 1986. “Meanwhile, a great deal of experience, talent and time had been irretrievably lost.”

Aircraft design and development, according to the author, briefly comprises three distinct streams – where prototypes are built but not followed by series production, where prototype development is followed by production and operational deployment and thirdly where design studies, building of mock ups etc takes place without further follow up activity. “unfortunately, the last category was the fate of most of the efforts of HAL’s design teams in the lost decade of the seventies, a fact barely known to most and the real story, to just a few.”

During the period of the mid sixties an Advanced Projects Group, headed by the author, was assigned the task of focussing on and overseeing feasibility studies for likely military and civil aircraft.

This group initially conceived of the Ground Attack Fighter I (GAF I) powered by an M45 engine which was itself being developed as a joint venture between Bristol Siddeley and SNECMA and would have a radius of action of about 150 miles.

There was also a study made for a STOL transport cum freighter, as a civil airliner with a 100 seat capacity and also as a replacement for the Packet, Dakota and Caribou. The configuration was for using four Rolls Royce turbofan engines and another configuration powered by four turboprop engines.

“The design configuration was not only contemporary but had advanced features which were later seen to have been adopted by advanced aerospace companies in the West. Unfortunately, development work on this project was abandoned in favour of combat aircraft which had all the priorities. However, as later events unfolded, the tremendous efforts ………….did not succeed in persuading the Defence Ministry to launch full fledged design and development of even the combat aircraft …..”

In 1967, the Group took up studies for an interceptor – ground attack aircraft. The multi role F 4 Phantom was the role model of this study. The GAF II, as it was referred to, was put through wind tunnel tests and the “configuration presented a very good basis on which to launch a prototype development effort. It was, however, clear that a far more elaborate infrastructure would be required for HAL to develop and build a new generation fighter.”

In the event, an attempt was undertaken to fall back on the trusted Marut and a parallel design using the forward fuselage of the HF – 24 with some modification to its canopy contour was offered to the IAF. The aircraft would have a radius of action of 300 nm, maximum ordinance for a ground attack role with contemporary avionics. The study completed in 1970 envisaged induction into service by 1976. This did not apparently find favour and Air HQ issued a firm requirement for an Advanced Strike Aircraft (ASA). “The final configuration of the Advanced Strike Aircraft as proposed by HAL, met most of the essential requirements of the Indian Air Force. While evaluation continued for some time, approval for prototype development simply did not materialise.”

In 1973 there was an offer from Germany to jointly develop the HF 24 into the Hindustan Supersonic Strike Aircraft labelled the HSS 73 later to be known as the HF-73. This would retain the original mainframe, with radical changes to the fuselage, air intakes and the centre wing section. The cockpit was to be modified for better visibility, fuel capacity increased, and with a completely new avionics suite and powered by the Rolls Royce RB 199-34R engine would have a radius of action double that of the HF 24. “Eventually, this project had to be abandoned because, as some said, of non clearance of the RB 199 by the UK and Germany, the two partner governments involved in the engine development for the Tornado MRCA programme. Thus all efforts in developing an Indian combat aircraft had come to naught.”

Subsequently HAL took on a feasibility study for a small multi role passenger aircraft, the HAC 33. “A wind tunnel model was built but not tested as development funds, were once again, not approved.”

In the mid-70s, the IAF showed interest in development of an air superiority fighter. In 1974 HAL undertook designing and studying a configuration for the Air Superiority Fighter (ASF). The ASF 300 was considered with either an Indian GTX or a SNECMA engine. The configuration proposed by HAL, “even though it did not meet the ASR, could have provided a reasonable solution…..”

“At this stage the HAL design team, resilient as ever, projected a low cost HF-24-M53…….when compared with the ASF 300, was 2 tons lighter, and was comparable to the Jaguar for bomb carriage capability as well as penetration distance……….The combat capability offered through this configuration and the delivery schedules were not acceptable to the IAF, and therefore the work was discontinued.”

“How much disappointment does a man (or design team) need?”

There was yet another attempt made to redesign the dear old Marut and a detailed feasibility study was conducted for the next version, the HF 25. At an estimated cost of Rs 64 Crore at 1979 price levels, the HF 25 prototype was scheduled to be available in three years and induction into service was proposed seven years later, that is by 1986. “In spite of the low development cost of the project and low unit cost of the HF 25, the IAF showed preference for the Soviet MiG 23/27. The project was therefore discontinued.”

In 1980-82 design feasibility studies were undertaken for an Advanced Jet Trainer. The programme was disbanded as all available funds were diverted towards the Advanced Light Helicopter and the Light Combat Aircraft.

“It was not until 1986, thus, that the Ministry of Defence with its constituent departments encompassing the conceiver (Defence Research and Development Organisation) producer (Hindustan Aeronautics Limited) and operator (Indian Air Force) got its act together to clear the Light Combat Aircraft (LCA) project which has since been underway under the aegis of the Aeronautical Development Agency (ADA) which manages, funds and monitors the programme from its headquarters in Bangalore.”

The Other Side Of The Coin
A tragic tale of opportunities and talent squandered due to myopic strategic planning , creating exigencies to be fulfilled by imports thus sacrificing indigenization for expediency .
 
T

Tarun

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#3
HF-73 Hindustan

HF-73 was a joint India-West German project to develop , the then time (early 70s) an advanced DPSA (Deep Penetration Strike Aircraft ) . Initially known as Marut Mk. III , it was a twin engine jet variant of Marut fighter jet earlier developed by India.

Unfortunately, world politics intervened. Anglo-American pressure made West Germany to leave the project (as India was a Soviet ally country). Besides the engine by which the jet was going to be powered up , was a British one, which they denied to supply. At least one sources said India still made one prototype , but after it crashed killing pilot during flight test (very first flight?), the program was scrapped.

Surprisingly, HF-73 was very similar in appearance and performance with British Panavia Tornado which came to light in mid 70s. Most interesting thing is, MBB of West Germany , one of the partner in Tornado project was the very German company which helped to develop HF-73!
Many claims Tornado was actually based on HF-73 itself.

Later India went with Jaguar strike aircrafts.

No doubt India was made sacrifice by World Politics. If HF-73 would become a success, India would be in a much better position in avionics technology.

HAL HF-73 Design:
Capture.JPG




HF-73 model


Please share your thoughts about the choice of Sepecat Jaguar over own Development of HF-73..


@Hellfire @Abingdonboy @Ashwin @nair @Levina @Avi @Arvind @Shashank @Nilgiri @randomradio @Picdelamirand-oil @halloweene @smestarz @Aashish @tunguska @Himanshu @Himanshu Pandey @Ashutosh @Parthu @Nick @vstol Jockey @sunstersun @zebra7 @GuardianRED @bonobashi @Falcon @all
 
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#4
HF-73 Hindustan

HF-73 was a joint India-West German project to develop , the then time (early 70s) an advanced DPSA (Deep Penetration Strike Aircraft ) . Initially known as Marut Mk. III , it was a twin engine jet variant of Marut fighter jet earlier developed by India.

Unfortunately, world politics intervened. Anglo-American pressure made West Germany to leave the project (as India was a Soviet ally country). Besides the engine by which the jet was going to be powered up , was a British one, which they denied to supply. At least one sources said India still made one prototype , but after it crashed killing pilot during flight test (very first flight?), the program was scrapped.

Surprisingly, HF-73 was very similar in appearance and performance with British Panavia Tornado which came to light in mid 70s. Most interesting thing is, MBB of West Germany , one of the partner in Tornado project was the very German company which helped to develop HF-73!
Many claims Tornado was actually based on HF-73 itself.

Later India went with Jaguar strike aircrafts.

No doubt India was made sacrifice by World Politics. If HF-73 would become a success, India would be in a much better position in avionics technology.

HAL HF-73 Design:
View attachment 567



HF-73 model


Please share your thoughts about the choice of Sepecat Jaguar over own Development of HF-73..


@Hellfire @Abingdonboy @Ashwin @nair @Levina @Avi @Arvind @Shashank @Nilgiri @randomradio @Picdelamirand-oil @halloweene @smestarz @Aashish @tunguska @Himanshu @Himanshu Pandey @Ashutosh @Parthu @Nick @vstol Jockey @sunstersun @zebra7 @GuardianRED @bonobashi @Falcon @all
I think that doing your own development is the best way to progress, having outside help can possibly accelerate a little learning, but we can not expect more.
The problem is that this route requires prolonged efforts and is very expensive. And in India you always think you can do everything quickly and cheaply. When that does not happen you think it's a failure when it's learning.
 

Shashank

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#5
I think that doing your own development is the best way to progress, having outside help can possibly accelerate a little learning, but we can not expect more.
The problem is that this route requires prolonged efforts and is very expensive. And in India you always think you can do everything quickly and cheaply. When that does not happen you think it's a failure when it's learning.
I feel slowly but steadily we are improving when it comes to putting money and efforts to develop indian systems. Unfortunately an economically powerful enemy next door is forcing us to look for short term and long term solutions at the same time. We cannot bridge gaps of decades of research by western countries in just few years years so we will have to wait for some time. Hope improved economy help us in putting in more money for research.
 
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T

Tarun

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HF-24 Marut, first Indian designed jet fighter



This is the story of India (and Asia's) first indigenously designed jet fighter the HF-24 Marut. It was a landmark achievement for the 1950s and 60s and I don’t wish to take anything away from that. Nevertheless this tale is narrated with what I hope is a balanced objectivity and not a nostalgic applaud. I have tried to balance between things we can be proud of, things we didn't do so well and lessons we ought to have learnt but may not have. Views expressed are my own and not intended to offend anyone. Reference sources at the end. Photo credits mentioned where known.



CONCEPTUALIZATION

India, in 1955, was a young nation full of enthusiasm for building the economy. A lot of projects were tried for the first time under the national objective of creating our own manufacturing and design capabilities. One such endeavour was to design and build in India, for the first time, our very own jet fighter. This was ambitious to say the least at a time when we had just started assembling diesel locomotives, had never built a major ship, had just started assembly of motor cars, possessed little aluminum smelting capacity etc etc. This was Pandit Nehru's vision and the IAF (Indian Air Force) enthusiastically went along. At the time of the Marut's conception, the domestic aviation industry's only design experience amounted to designing and manufacturing the HT-2, a piston engine propeller driven trainer. Whatever aircraft manufacturing capability existed resulted from the license assembly of the Vampire FighterBomber FBMk.52 and Trainer TMk.55. To have considered building a supersonic capable aircraft, given such limited capabilities, bordered on audacity. The only aircraft manufacturing capability lay in Hindustan Aircraft Ltd (HAL) set up by Walchand Hirachand in the 1930s and nationalized by the Government subsequently.




Pic: the HT-2 propeller driven primary trainer. This represented the only indigenous design capability in India at the time of the decision to design & build the Marut. The HT-2 was designed by Dr VM Ghatge and served the IAF and the Army Aviation Corps for 25 years. 172 were manufactured of which 12 were exported to Ghana.


The building of the Marut (Spirit of the Tempest), as this aircraft was to be called, was the first attempt of its kind anywhere outside the four major powers of USA, USSR, UK and France to build a supersonic jet fighter. Whatever else one might say the gumption deserves admiration. The political, bureaucratic and I dare say military hierarchies did not have a proper appreciation of the supply chain infrastructure and quality control challenges that would need to be overcome.




Pic: The end product, subject of our story, the Hindustan Fighter HF-24; this specimen preserved at the Kurt Tank Museum in Germany



AIR STAFF REQUIREMENT

The Marut was conceived to meet an Air Staff Requirement (ASR), that called for a multi-role aircraft suitable for both high-altitude interception and low-level ground attack. The specified performance attributes called for a speed of Mach 2.0 at altitude, a ceiling of 60,000 feet (18,290 m) and a combat radius of 500 miles (805 km). Furthermore, the Air Staff Requirement demanded that the basic design be suitable for adaptation as an advanced trainer, an all-weather fighter and for 'navalization' as a shipboard aircraft. It was directed that this aircraft be developed within the country. Nations with advanced military design and manufacturing capabilities rarely, if ever, put out specifications that are such all singing all dancing renditions. A military aircraft is designed to play one role well, a second role moderately well and sometimes , only sometimes, a third role in a limited form. Unfortunately out of lack of experience (and in my opinion a willingness to apply common sense) the Air Staff Requirement was too wide and reflected lack of clarity of aims and a complete lack of understanding of what it takes to design and build a fighter as opposed to flying one. It is like saying - I want a car that drives like a BMW 3 (Mach 2.0), suitable for both high and low altitudes (drive well on a race track as well on Delhi's rutted roads), can carry payload like a Isuzu D-Max pick-up (low level ground attack payload) and have the toughness of a 4-wheel drive cross country mud slogger (capable of all weather capabilities & navalization). The combat radius of ~800 kms was beyond the ken of the most efficient fighter turbojet even in the USA of the 1950s. These ranges were not achieved till military turbofan engines like the Rolls Royce Spey (on the Hawker Buccaneer, 1960s) or Rolls Royce Adour (Sepecat Jaguar, 1970s) amongst others came into play. All weather was at best in an experimental rudimentary stage even in USA and USSR in 1956 and no IAF aircraft of 1956 even carried a gun ranging radar let alone a search & track one. While I don’t wish to be too critical these were overly ambitious specifications for 1955 even for the UK, France or USSR. As an aside, it might be worth noting that the ASR for the current Light Combat Aircraft (LCA), Tejas, in mid-1980s, followed the same concept of all singing all dancing and (partly due to that) it is sadly still some way off from full operational service 30 years later. The only other aircraft of the 1950s and 1960s that was designed to similar specifications as the Marut and carried a requirement for navalization + all-weather was the legendary McDonnell Douglas F4 Phantom of the US Air Force and Navy. And let's remember the Americans were then and today the foremost in aviation R&D, design and production know-how. And even with the Phantom the Americans lost out on maneuverability.

Dr VM Ghatge, India's senior most aeronautical designer was the only voice against the Marut. He prescribed a more balanced step by step approach to building the nation's aviation industry by first designing & building propeller trainers, then basic jet trainers, then light attack fighter-bombers and then a more advanced light multi-role fighter and to do this in stages over 2 decades. In retrospect his was, in my opinion, the more sensible approach. But Ghatge's voice was drowned out.

Nehru tried to attract leading aeronautical designers from the west to work for India on this project. It was to his credit that he convinced Dr. Kurt Tank (of Focke Wulf fame) to take up this assignment along with his able deputy Engineer Mittelhuber. Both arrived in Bangalore in August 1956. As head of the design team it was Kurt Tank who would give the design shape and substance.

Dr Kurt Tank (1898 - 1983). Dr APJ Kalam was a student of his at Madras Institute of Technology where Tank taught while deputed to HAL





HAL in 1956, possessed only three senior Indian design engineers and the entire design department boasted only 54 personnel. It had no hangar space for construction of prototypes, no machine shop for prototype engineering, no suitable test equipment, structural test rigs or a flight test laboratory. In fact even the runway length was inadequate for a jet fighter prototype. It is to the credit of HAL team of that era that all this was created from scratch while Kurt Tank built up the design & prototype team of over 850 personnel including 18 German designers.


DESIGNING & BUILDING THE MARUT

A full scale representation (wooden glider) of the projected fighter was ready by early 1959. A test program was initiated with this glider on 1 April 1959. The new design was given the designation of Hindustan Fighter 24 or simply HF-24.




Pic: Wind tunnel testing of a scale model of the Marut, 1959. All this basic infrastructure was created from scratch by HAL. Photo credit: Marutfans.com




Pic: Wooden glider of Marut design in test flight towed behind a C-47 Dakota. Glider tests for aerodynamics started in April 1959. 78 test flights were conducted with the gliders which were released between 12,000 and 15,000 feet altitude. Use of wooden gliders was an integral part of Kurt Tank's style of design testing. Photo credit: Marutfans.com. Copyright Late Group Captain Kapil Bhargava

Assembly of the first HF-24 prototype (HF-001) began in April 1960 and after a comprehensive three month ground test programme, HF-001 (later re-numbered BR 462), with the late Wing Commander (later Group Captain) Suranjan Das at the controls, flew for the first time on 17 June 1961. In the circumstances this was a commendably short period of 15 months from starting to put together the prototype to first flight.


HF-001, the first prototype was first subjected to several days of ground run testing to check if at a basic level the controls, engines, fuel systems, hydraulics, electrics actually work in co-ordination.


Wing Commander (later group Captain) Suranjan Das, India's foremost test pilot, flew the HF-001 for the first time on 17th June, 1961. He led the test flying on the Marut as well as the later Kiran jet trainer. Earlier he had led the test flying for the Gnat. Tragically, he was killed in 1970 when testing a more advanced version of the Marut.



On 27th June 1961 they built up enough confidence and test hours to show case the prototype to Prime Minister Nehru. The prototype was re-numbered BR462. By November 1961, a structural test airframe had been completed and was subjected to extensive structural and functional tests in rigs designed and fabricated at Bangalore. On 4 October 1962, a second prototype (BR 463) joined the flight development programme and the two prototypes were extensively tested by Das and a team of three Air Force test pilots for aerodynamics & stability, engine protocol, armament, instrumentation, emergency procedures etc. It was a remarkable achievement for its era. India became only the 6th country to design and fly its own supersonic jet combat aircraft after USA, UK, USSR, France and Sweden.




Pic: BR462 towed out for its first flight in presence of Prime Minister Nehru 27th June 1961. C-119G Packet medium transport in background. This is the HAL airstrip. Note the open expanse now packed with buildings on two sides. Photo Copyright: HAL




Pic: Prototype now numbered BR462 on a flight after 27th June 1961. Unfortunately I have located no photograph of the first flights of either 17th June or 27th June 1961 Photo Copyright Group Captain Polly Singh


SEARCH FOR A SUITABLE POWER PLANT

The design of the HF-24 had been based around the expected availability of the 3700 kgf (kilogram force) afterburning Bristol Siddeley (later Rolls Royce) Orpheus engine which the British planned to develop. An after burning turbo jet is one in which fuel is injected and exploded in the hot exhaust of the jet (behind the turbines) which still has some oxygen in it. The resultant combustion of pure vaporized fuel into a red hot efflux blasting rearwards at hundreds of metres per second results in a rocket like acceleration and very high power to weight ratios. Afterburners consume prodigious volumes of fuels and are usually used when high thrust is needed for a few minutes. Unfortunately, the British requirement for this power plant was discarded and the IndianGovernment in a short sighted decision declined to underwrite its continued development (to Rolls Royce) even though the budget was only £13 million not a large sum even by the standards of 1961. This decision was to bedevil the Marut programme permanently. The design team was forced to adopt the non-afterburning 2200 kgf Orpheus 703 which powered the Gnat as an interim solution. It was an utterly reliable engine but with inadequate power for the Marut. We evaluated the Soviet Tumansky RD-9F that powered the contemporary Mig-19. The Tumansky powerplant had a full thrust of 3750 kgf with afterburners and put it just right for the Marut. But for reasons I don’t fully understand the Tumansky engine was rejected on grounds of surging and limited MTBO (Mean Time Between Overhauls). Speaking in favour of the Tumansky RD9F it was a rugged engine, had great acceleration, was resistant to ingestion of dust, mud and ice and went on to power the Soviet Mig-19, Yak-25, the Chinese ShenyangJ-6 & Nanchang Q-5. It is popular in Western literature to decry the old Soviet engines as having a lower MTBO. What is less understood is that between the two MTBO points this Soviet engine needed little care & maintenance. However, I don’t want to be harsh in judging those who took these decisions as I have not stood in their shoes.





Pic: Rolls Royce Orpheus. HF-24's powerplant - light & reliable




Pic: Tumansky RD9. Over 23,000 were built making it the one of the two most produced jet engines ever


The lack of an appropriate power plant meant the Marut could not fulfill its role as an interceptor though the scope of being a reasonable ground attack fighter-bomber was very possible. A lot of hard work by Kurt Tank and team, by HAL and by Suranjan Das who led the team of test pilots did help mature the Marut into a flyable aircraft. Despite IAF reluctance and unwillingness to understand that it was in its own interests to support a fledgling home industry the Government sensibly ordered 18 pre-production aircraft and 62 operational ones to arm 2 or 3 squadrons. In fairness to the IAF there is a long journey from an aircraft that flies to an aircraft that fights and does so consistently in adverse conditions. In 1963 the Marut development efforts had not traveled that distance and the IAF was justified in not being keen to take an immature product into operational squadrons. In fact it would be 1971 by the time most defects were ironed out.


AIRCRAFT DESIGN & FEATURES

It is said that a picture is worth of thousand words. The design of the Marut is explained below with help of photos rather than lengthy aeronautical verbiage.


Overall Design




Pic: This photo, one of my favourites from the Kurt Tank museum, shows - (i) Marut's streamlined, aerodynamically clean pencil fuselage with its side air in-takes for the twin power plants; (ii) thin wing designed for supersonic flight; (iii) Under the wings we see the 2 weapon pylons of the port (left) wing; (iv) wide track under carriage to support landings on rough airfields; (v) the bubble canopy for good visibility; and (vi) the fairings, under the nose for the four 30 mm Aden cannons each firing 10 rounds per second Photo Copyright: Kurt Tank Museum, Germany


Fuselage




Pic: Photo taken from one of my early aircraft books, 'The World Guide to Combat Planes by William Green, 1966 edition'. The side view shows the fuselage design layout of one-behind-the-other - right to left, marked with blue arrows, are - (i)the avionics bay in the pencil nose cone, (ii) the cockpit, (iii) the gun bay beneath & behind the cockpit, (iv) the internal rocket pack (for ground attack), (v) the central main fuselage fuel tank, (vi) landing gear and (vii) the twin engines. The pilot sat high in a canopy that afforded a very useful view through a 300 degree arc and down wards too. Also shows the highly swept supersonic wing - more on it in the next section. This was my first big book on aircraft gifted in 1967 and as a child I gawked endlessly at the photos (reading came a little later and understanding the contents a lot later!)


Wings




Pic: Line drawing depicting clearly - (i) the high sweep back of the wing. Sweep back reduces drag significantly and aids high speed flight (ii) blue- leading edge with dog tooth. The dog tooth creates a vortex of high speed spinning air that flows back horizontally over the wing (or scrubs tightly over the wing surfaces) and helps maintain better aerodynamic control especially at high angles of attack (iii) orange - the ailerons for turns (iv) pink - the flaps to increase the wing area and lift for aiding lower landing and take-off speeds (v) green - the cover of the retracted undercarriage; and (vi) purple - the streamlined internal launcher for the 50 internally loaded 68mm SNEB rockets (vii) grey circle on nose - 30mm twin cannons on starboard side (ie right side) and grey oval marking the under wing for weapons/fuel pylon each rated at 454 kgs carrying capacity.

Marut's wing was highly swept and thin and large - all three characteristics for an interceptor. The sweep and thickness together determine the planes ability to fly across the speed of sound - greater the sweep and thinner the wing the lower is the thrust to weight ratio needed to get the aircraft supersonic. However, on the flip side, the greater the sweep and thinner the wing the higher becomes the landing speed and the less stable and maneuverable is the aircraft at low speeds below 250 knots (450 kmph). The Marut wing is a well balanced compromise of adequate sweep to get supersonic (provided the engines develop the thrust) and the thickness was enough to maintain moderate landing speeds and low speed stability. The wing bestowed on the HF-24 an acceleration and low altitude speed that the Pakistani Sabres and Indian Hawker Hunters could not match. In fact the Marut was one of the few, if not the only, frontline aircraft that could cross Mach 1.0 without afterburners - albeit just about at high altitudes.




Pic: Detailed cut away drawing with table. Note twin engine bay (89); long narrow air intakes (44, 45); centre body with fuel tanks (49); integral fuel in the wings (57); airbrakes (94); brake parachute (78); rear view vision mirror (19) ORVM!; Matra SNEB 68mm rocket pack (116); 454 litre drop tank (114); Copyright: Pilot Press

The wings were designed to carry 4 pylons (or hardpoints) rated at 454 kgs each (1000 lbs). In addition each wing carried about 700 litres of fuel in the integral tanks. An integral tank means the internal space within the wing is sealed up and filled with fuel floating between the structural members. This means each wing carried a payload of about 1425 kgs of fuel and weapons. Think of it as carrying four Maruti Alto 800s, two under each wing and clipping away at 550 knots (~1000 kmph).


Cockpit




Pic: Cockpit of HF-24. Classic layout, uncluttered, clear view. Source: Bharat Rakshak



TECHNICAL DETAILS


General

Crew: 1 in the fighter-bomber; 2 in the conversion trainer

Length: 52' 1"

Wingspan: 29' 6"

Height: 11' 10"

Wing Area: 301 square feet (~28 sq metres)

Wing Sweep: Approximately 52 degrees
[PS: I have not located definitive data on the Marut's sweep angle. This is my educated guess. BHPians from the IAF or HAL could throw more light on this.]



Weights

Empty equipped: 6195 kgs/13,658 lbs

Loaded Clean: 8951 kgs/19,734 lbs

Fully Loaded: 10925 kgs/ 24,085 lbs


Power Plant

Type: Two 2200 kgp (4850 lbs) Rolls Royce Orpheus 703 turbojets

Size & Weight: These were a variant of the Gnat powerplant. Small & compact at 75" length and 32" diameter. Weight = 379 kgs Power to Weight ratio of 5.9 kgp/kg of weight.

Fuel Consumption: Specific fuel consumption for the Orpheus is 1080 grammes/kgp/hour. At full thrust for the Marut this translates to 106 litres per minute flying at 600 knots in clean condition … 175 metres per litre … this is just a rough calculation to tickle the petrohead in all of us.


Performance

Maximum Speed: 1112 kmph / 600 knots* or Mach 0.91** at sea level; 1086 kmph/ 586knots or Mach 1.02 at altitude

* a knot = 1 nautical mile per hour i.e. 1.852 kmph; a nautical mile equals 1 minute of arc of any meridian of the earth
** Mach 1.0 is the speed of sound at a given altitude; Mach 2.0 by inference is twice the speed of sound. At sea level Mach 1.0 = ~1225 kmph; at 36,000 feet altitude it is ~ 1054 kmph.


Stall Speed: 248 kmph / 133 knots

Initial climb rate: 6000 feet/min or 30 metres/second at sea level

Range/Radius: 396 kms / 214 nm lo-lo-lo with a 1800 kgs warload

lo-lo-lo is the typical fighter-bomber flight configuration it means ingress, attack and egress are all at low altitudes typically below 500 feet or 1000 feet, depending on terrain, to avoid radar detection; similarly you can have configurations such as lo-lo-hi or hi-lo-hi. Ferry flights by nature will be hi-hi-hi to get the best fuel economy


Wing Loading: ~66 lbs/ square foot in clean loaded condition; 80 lbs/ square foot at maximum weight.

The first figure is one factor on its ability to dog fight out of enemy territory after releasing its warload on target. 66 is a lightly loaded wing supporting maneuverability. Corresponding figures for the Gnat are 57 lbs/ square foot and that for the very capable modern F-16 is 88.
The latter figure of 80 indicates how well the wing will take to heavily loaded low level attack. Here we need a highly loaded wing to reduce the gust response (or bone jarring bumps) the aircraft encounters when flying at 550 knots below 1000'. Here The HF-24 doesn't do so well. Classic lo-lo-lo attack aircraft like the Sepecat Jaguar have wing loadings as high as 130 lbs/square foot


You can design a wing for interception - large, triangular, low loading, highly swept, thin or for low level attack - small, long chord (length at the root), high wing loading, moderate sweep to enhance lift and low speed control and thicker for aerodynamics and greater fuel.

Power Loading: 0.50 at clean weights; 0.41 at full weight

These were moderate power loadings even for the 1960s. It reflected the unsuccessful hunt for the right engine or given the engine you had asking too much in the Air Staff Requirement. Normally for the 1960s the desired power loading in clean condition, for an interceptor, would have been 0.60 to 0.70 compared to Marut's much weaker 0.50. On the other hand in that era a dedicated ground attack aircraft (such as the McDonnell Douglas A4 Skyhawk) would have a maximum power to weight loading of 0.33 to 0.45. Here Marut's 0.41 ratio was in the right spot.

Service Ceiling: ~ 45,000'; as it was primarily used as a ground attack aircraft in combat it would usually fly at low altitudes below 1000' to avoid detection by radar


Armament

Four 30mm Aden cannons with 130 rounds per gun; combined rate of fire 2400 rounds per minute ie 40 rounds per second. Some reports talk of blanking out two guns to reduce vibrations while firing. This was an issue in the 1960s and even cost the life of one test pilot. I don’t know if this was a temporary problem or a permanent issue.

4 underwing pylons rated for 1000 lbs /454 kgs each; typical loads were bombs of 1000lbs, 500 lbs & 250 lbs, 68mm SNEB rocket packs typically of 18 or 36 rockets per pack & napalm bombs. Not known if the HF-24 was configured for cluster munitions such as Hunting BL755 which was (and is) in common use by the IAF

50 French SNEB 68mm ground attack rockets in internal pack behind pilot; The French rocket is used even today and is the world's most widely produced unguided rocket armament. The rockets can be fired in ripples with a spacing of 0.33 milliseconds. Typical warheads, amongst several variants, were high explosive, fragmentation & anti-tank. By possessing an internal weapons bay the HF-24 could carry these 50 SNEB rockets without their carriage inducing drag. This gave it greater flexibility in how the 4 pylons would be used to carry fuel or weapons for greater payload on target or a greater range for a given payload.




Pic: SNEB rocket pod with red tipped rocket shown as if in flight. Photo Source - Wikipedia




Pic: SNEB rocket pack slung below this display HF-24 the way it would look when loading it up. Once loaded the pack would sit flush with the under surface of the air frame. Original Photo - HAL; Current Source - Bharat Rakshak.com


SQUADRON SERVICE

HAL & IAF conducted 1800 test flights, between 1962 and 1967, to iron out the defects of the Marut. In April 1967 No.10 Flying Daggers Squadron became the first unit to be equipped with India's first indigenous combat aircraft. Close liaison between the IAF and the Hindustan Aircraft (as HAL was then named as) continued to progressively modify the Marut for the lo-lo-lo attack role.

During the early years Maruts with the IAF suffered from the non-availability of spares which in turn adversely affected serviceability. These chronic shortages affected the Marut fleet between 1965 and 1968, however as production picked up the situation improved markedly. But the aircraft had teething troubles that were not solved until 1970, and only a very meticulous reporting of problems and the professionalism of the pilots and engineers, prevented any fatalities from occurring.




Pic: HF-24, line maintenance and sortie preparation, circa 1980

There is wide consensus about excellent handling characteristics of the aircraft. Most pilots who have flown the aircraft describe it as pleasant to fly and excellent for aerobatics with fine control responses. And its ability to out-accelerate the Sabre jet, especially at low levels, was a useful asset in 1971. The Marut offered a stable weapon delivery platform and packed a formidable punch. While the Marut's pilots expressed an understandable desire for more thrust than the Orpheus 703 offered, they were unanimous in their view that the aircraft proved itself a thoroughly competent vehicle for the low-level ground attack profile. One defect which, I believe, remained was malfunction of roll control aerodynamic surfaces and the canopy flying off when all four 30mm cannons were fired simultaneously and the impact the recoil had on the electrics of the aircraft. HAL, I believe, claimed to have cured the problem but the IAF decided to be safe and blanked off the two upper cannons and operating only with the lower two in squadron service. The Marut was a robust aircraft with extremely good visibility for the pilot, and was aerodynamically one of the cleanest fighters of its time.

The Marut eventually equipped three IAF Squadrons. No.10 Squadron was the first to convert in April 1967, the No.220 the Desert Tigers converted in May 1969 and the No.31 The Lions in March 1974. Of the 145 Maruts produced, 130+ entered squadron service the rest were used for testing & development




Pic: Formation Flying: The HF-24 in the middle and in the background are twin seat conversion trainers. The second seat (rear one) was for the instructor and was fitted at the expense of the SNEB rocket pack and 3 of the 30mm cannons. Photo Source %% (see reference section)


PERFORMANCE IN COMBAT

Both Squadrons mounted on the HF-24 operated from Jodhpur in December 1971 and served exclusively in attacking enemy ground targets such as fuel dumps, lines of supply, communication nodes, Pakistani airfields, railway junctions, armoured vehicles and troop concentrations. The HF-24 also took part in the battle of Longewala providing support to the 4 Hunters from Jaisalmer, that led the Indian offensive, by attacking the supply lines to the Pakistani tank brigade. About 100 enemy tanks were destroyed or damaged and their bid to attack Jaisalmer was subverted.

The Marut's flew approximately 200 combat sorties during the two week war. On one strike mission they flew 200 nautical miles (~370 kms) into enemy territory to deliver their goods. The Marut also demonstrated that when flown clean it could tackle a Sabre jet. A Marut flown by Squadron Leader KK Bakshi of 220 Squadron also shot down a PAF F-86 Sabre on 7th December 1971 (Flying Officer Hamid Khwaja of 15 Squadron PAF). No aircraft were lost to air action although by the end of the war three Maruts had been lost to ground fire and one lost on the ground.

Maruts constantly found themselves under heavy and concentrated fire from the ground during their low-level attack missions. On at least three occasions, Maruts regained their base after one engine had been lost to ground fire. On one of these, a Marut returned to base without escort on one engine, from about 240 kms inside hostile territory. Another safety factor was the automatic reversion to manual control in the event of a failure in the hydraulic flying control system, and there were several instances of Maruts being flown back from a sortie manually. Throughout the December 1971 hostilities, the Marutsquadrons enjoyed extremely high serviceability rates (in contrast to the late 1960s), this undoubtedly owed much to an improved spares situation and the original design's emphasis on ease of maintenance.


CONTINUED DEVELOPMENT

Dr. Kurt Tank and his team returned back to Germany in 1967 and the leadership for developing the Marut further passed onto Group Captain Suranjan Das who also served as the Chief Test Pilot. The Indian team at HAL successfully developed a two seat conversion trainer which moved into squadron service as the HF-24 T Mark 1. A prototype with an Indian developed experimental after burning Orpheus engine designated Mark 1R was lost while being test flown by Group Captain Suranjan Das. His death and challenges with the afterburner led to the demise of this line of development.


A PRE-MATURE END

The Marut served on in the IAF through the 1970s. The IAF developed two Air Staff Requirements namely the Deep Strike Penetration Aircraft (DPSA) and the shorter range Tactical Attack & Strike Aircraft (TASA). The IAF was not interested in waiting for HAL or DRDO to develop the Marut further to meet either of these requirements although with the right effort and sans the bureaucracy the TASA requirement could have been met by a Marut powered by the Rolls Royce Adour that powered the Sepecat Jaguar. The IAF went on to select two very fine aircraft to meet these requirements - the Sepecat Jaguar for the DPSA and the Mig-23BN followed by the Mig-27M for the TASA. Unlike the Indian Navy and the Chinese Air Force who both supported their home industry with orders for step by step improvements the IAF chose not to do this. Speaking in favour of the IAF - those days the Indo-Soviet friendship was at its peak and the Soviets were offering license production for the Mig-27M, a superb tactical attack aircraft, with Rupee trade payments and the IAF must have felt this was a better alternative than to spend yet several more years dealing with HAL's development journey. Maybe HAL was not to blame. Maybe the early demise of the Marut was sown in the overly ambitious specifications laid out in 1956-57. The last Marut was withdrawn in 1990. Today one can only wonder what could have been possible if HAL and other development agencies like DRDO had the focus and competence of ISRO and the IAF had a long term view like the Indian Navy which working with Mazagon Docks & Cochin Shipyard has built up some meaningful indigenous capability in design and construction after having started in the early 1960s same as the HF-24. To develop a nations aviation industry you have to think in terms of a 50 year horizon and go step by step.




Pic: Sepecat Jaguar, Deep Penetration Strike Aircraft with the IAF today. It carries a 4.5 tonne warload and can fly a lo-lo-lo strike mission with a radius of ~800 kms with a meaningful payload of guided weapons.





Pic: Mig -27 fulfilled the Tactical Attack & Strike Aircraft TASA role. Its variable geometry wings swing forward on take off to increase lift and swing back to a high sweep angle for high speed flight


In mid-1980s the ASR was laid out for the Tejas Light Combat Aircraft. Once again it was an ambitious set of specifications calling for capabilities and technology such as fly by wire flight control systems, multi-mode pulse doppler radar and an afterburning turbofan engine in the 10,000 kgf class. These were technological assets which only the Americans (F-16 & F-15) had successfully put into service at that time, the French were about to (Mirage 2000) and the Soviets were still developing. Partly due to, once again, putting out highly stretched specifications and partly the bureaucratic approach of the agencies involved the Tejas took three decades to develop, has just been inducted into the IAF for operational breaking-in and is still maybe a year short of full scale operational service. The more things change the more they stay the same.

The current generation of engineers & designers working on the Tejas cannot be blamed for woolly headed thinking of 33 years ago. We should cheer them and support them as they work to put the country's second indigenous fast combat aircraft into full operational service this year. Aerodynamically speaking the Tejas is a superb design and this time around with the adoption of the General Electric F404 afterburning turbofan we also have a winner of an engine. Jai Hind.




Pic: HF-24 scale model at home. You can't take the boy out of a man

REFERENCES:
World Guide to Combat Planes by William Green, 1966; Macdonald Publishers

Observers Book of Aircraft by William Green, 1965; Fredrick Warne & Co

Articles by K.Chatterjee in Bharat-Rakshak.com

Combat Aircraft by Bill Gunston, 1976; Salamander Books

Green, William, Chopra, Pushpindar Singh and Swanborough, Gordon. Editors - 'The Indian Air Force and its Aircraft. IAF Golden Jubilee. 1932-82' Ducimus Books, UK.


@Hellfire @Abingdonboy @Ashwin @nair @Levina @Avi @Arvind @Shashank @Nilgiri @randomradio @Picdelamirand-oil @halloweene @smestarz @Aashish @tunguska @Himanshu @Himanshu Pandey @Ashutosh @Parthu @Nick @vstol Jockey @sunstersun @zebra7 @GuardianRED@bonobashi @Falcon @all
 

smestarz

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#7
With HF 73, we could have been in the world aerospace map but we got sacrificed. Externally the HF-73 does look similar to Panvaia Tornado, externally, but also it can be claimed to be derived from design of F-15. Dont you see that similarity? Also an important difference between HF-73 and Panavia Tornado, is that Panavia Tornado catered to the then need of variable geometry plane that would allow the plane to take off from short run way with wings spread out.,and then cruise or with swept back wings can be inside enemy territory in a flash. Su-24, F-111, Tornado and even F-14 are of this era.. And planes of those particular era were sort of designed after one another. With the fixed wing design it can be compared to F-15 and MiG-25 roughly..

HF-73 Hindustan

HF-73 was a joint India-West German project to develop , the then time (early 70s) an advanced DPSA (Deep Penetration Strike Aircraft ) . Initially known as Marut Mk. III , it was a twin engine jet variant of Marut fighter jet earlier developed by India.

Unfortunately, world politics intervened. Anglo-American pressure made West Germany to leave the project (as India was a Soviet ally country). Besides the engine by which the jet was going to be powered up , was a British one, which they denied to supply. At least one sources said India still made one prototype , but after it crashed killing pilot during flight test (very first flight?), the program was scrapped.

Surprisingly, HF-73 was very similar in appearance and performance with British Panavia Tornado which came to light in mid 70s. Most interesting thing is, MBB of West Germany , one of the partner in Tornado project was the very German company which helped to develop HF-73!
Many claims Tornado was actually based on HF-73 itself.

Later India went with Jaguar strike aircrafts.

No doubt India was made sacrifice by World Politics. If HF-73 would become a success, India would be in a much better position in avionics technology.

HAL HF-73 Design:
View attachment 567



HF-73 model


Please share your thoughts about the choice of Sepecat Jaguar over own Development of HF-73..


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Gautam

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#8
Flying & fighting in the HAL HF-24 Marut: Interview with IAF pilot Vijainder K Thakur

October 30, 2019.


Following the defeat of nazi Germany, the aircraft designer Kurt Tank — creator of the world-beating Focke-Wulf Fw 190 — went to Argentina. Here he worked on jet fighters, before heading to India with a great deal of research material. Hindustan Aircraft Limited (HAL) worked with Tank on an exceptionally sleek new fighter, the Marut. Seldom remembered, and when recalled often written off as a failure, the Marut actually had the potential – but not the requisite good fortune – to have become an exceptional machine. We spoke to former IAF pilot Vijainder K Thakur about flying and fighting in Kurt Tank’s final fighter.


Vijainder K Thakur.

Which three words best describe the Marut?

“Pretty, Promising, Played.”

What were your first impressions?

“Having already flown the Hunter, a similar class aircraft, at Operation Conversion Unit (OCU) the move to Maruts wasn’t daunting. The Hunter had a better thrust-to-weight ratio than the Marut. However, the Marut’s supersonic design, spacious cockpit and pleasant cockpit interiors looked inviting. There was also the hope that the aircraft would get a better engine gaining speed and punch.”



What was the best thing about it?

“Good low-level handling – fast and responsive. We could clock 620 kts at 500 ft in the late production (extended chord) D series and around 650 kts in earlier BD series. Twin engines ensured safety from bird hits at low levels and a spacious cockpit facilitated map storage and reading. “

And the worst thing?

“The large number of technical issues that plagued the aircraft. The Marut’s high pressure (4000 psi) hydraulic system was prone to failures. Backup manual controls mitigated the impact of such failures but there was always the fear of the leaking hydraulic fluid catching fire. There were several cases of compressor blades rubbing against engine casing leading to catastrophic failures. Poor HAL workmanship caused fatal accidents such as canopy jettisoning failure!”

How do you rate the Marut in the following categories?

A. Instantaneous turn

Good at low levels, with turn rate limited by G limit.

B. Sustained turn

Reasonably good at low levels as long as you didn’t excessively bleed your speed below 420 kts.

C. High alpha

Sluggish but safe.

D. Acceleration

Good at low levels up to speeds of around 580 kts. Poor at higher altitudes.

E. Climb rate

Good at low levels.

When did India procure the Marut and where were you trained?

“The Marut was operationally inducted into the IAF on April 1, 1967 at Armament Training Wing (ATW), Jamnagar with the standing up of No. 10 Squadron (Daggers), which had been number-plated since April 1964. The squadron was raised with 12 prototype and pre-production Maruts and two Hunter T 66 trainer aircraft. Prior to their operational induction, these Maruts had been test flown and evaluated by the IAF’s Aircraft and Armament Testing Unit (A&ATU), the predecessor to the present day Aircraft and Systems Testing Establishment (ASTE). The initial batch of Marut pilots underwent pre-solo conversion on the Hunter T 66 trainer aircraft practicing take-offs, circuits and landings flying at speeds and using patterns and glide slopes identical to the Marut. Within two months of operational induction, there were two major Marut accidents – a fatal crash and an ejection.

After requipping and becoming operational with Maruts, No 10 sqn took on the role of Marut training squadrons and helped raise two additional Marut squadrons – 220 (Desert Tigers) and 31 (Lions).

Around May 1969, 10 squadron moved from Jamnagar to Pune; shortly thereafter, 220 sqn was raised from pilots and aircraft that had accreted to 10 sqn since its raising. The two Marut squadrons moved to Jodhpur in December 1970.


“The Marut was built tough. Dr Kurt Tank designed the Marut to be tough enough to slice a tree in half with its wing… its fin could cut through high tension cables with just a gash to show for it. A gash that could be easily repaired to preclude raising even an incident report or linking it to a massive power failure south of Jodhpur!”


What was its combat record?

“During the 1971 ops, 10 and 220 squadrons operated from Jodhpur and proved their mettle flying Close Air Support and Interdiction missions. Three Maruts were lost to enemy ground-fire.

The Maruts reportedly flew around 300 sorties during the 1970 Ops. Those who participated in the ops feel that the aircraft was grossly under-utilised. For example, its very potent 30-mm Aden cannon and T-10 / Matra rockets, and the safety accruing from two engines, could have been used to augment the firepower of the Hunters at Longowal. The reason why Op planners overlooked the Marut was probably lack of knowledge about the aircraft’s performance and capability!



Besides ground attack, Marut scored one air combat kill without any air-to-air losses. The air combat kill was claimed by Sqn Ldr KK (Joe) Bakshi when his strike mission was bounced by four PAF Sabres resulting in a melee.

Joe was pulling out of a strafing run when he saw a Sabre flying across his bow at close quarters. His finger on the trigger already, Joe reacted instantly and fired his twin 30-mm Aden cannons at close quarters as the Sabre disappeared in his hind quarters. Flt Lt KP Sreekant (later Air Vice Marshal) was part of the same formation. He was trying to gain positional advantage on a Sabre ahead when he saw another Sabre criss-crossing trailing black smoke. Joe was awarded the kill based on an R/T call made by KPS about the Sabre trailing black smoke, since there was no way of physically confirming the kill.

The 3rd and final squadron of Maruts was raised in 1973 with 31 sqn (Lions) converting from Mystères to Maruts.

I was posted to 10 Sqn in end 1975 for my type conversion, after I completed my training at Operational Conversion Unit (OCU) in Kalaikunda, West Bengal. Post conversion, I moved to the Lions where I remained until 1981 logging around 650 hrs. During my tenure, the Maruts were grounded over safety issues for long spells on two occasions and for short spells on several occasions. The total grounding period was around 1 yr 6 months.”

What was your most memorable mission?

I readily recall three missions – two of them out of a sense of accomplishment and the third out of a sense of the bizarre.

In March and April 1979, while preparing for a forthcoming DASI (Directorate of Air Staff Inspection) visit, our CO, Wing Commander SK Sonpar (Stona), put the squadron through the hoops with DACT. We worked meticulously – planning and sketching coordinated manoeuvres to ward off Type 77 (MiG-21) aircraft attacks, practiced the manoeuvres, and spent hours debriefing. In April 1979, I flew several DACT 2 vs 1 combat sorties with Type 77 aircraft which felt so much more real than practice with a Marut as attacker. Our ability to hold our own through early spotting and teamwork gave me a lot of satisfaction and confidence.

Flt Lt VS Kochar (Koch) and I volunteered to take on the DACT exercise with the two of us executing a coordinated strike and a DASI inspector in a Type 77 bouncing us.

A fatal accident on range cut short the DASI visit and we never got a chance to shake down a DASI inspector in a T-77. Word about our squadron’s intensive DACT preparations must have reached the ears of DASI inspectors because they assessed the squadron as Average plus based purely on the squadron’s performance on the range. The DASI could have opted to withhold a rating and make another visit.

In October and November 1979, ahead of South Western Air Command (SWAC) inter squadron steep glide bombing competition, our squadron started working on the theory and practice of steep glide bombing, determined to win the trophy.

The key to accurate steep glide bombing is getting the 45-deg dive right and the Lion bombing team comprising Stona, Sqn Ldr SK Sanadi (Sandy), Sqn Ldr KR Singh (Keru), Flt Lt James Sebastian (Jimmy) and self initially perfected our dive angles by doing bombing runs over the Jodhpur runway, using the R/W markers as accurate cues.

Later, we practiced on Pokhran range. Eventually, it was time to practice with live bombs. The effectiveness of our mathematics based training surprised us. Hitherto, steep glide bombing had been notorious for large errors upto 100 yards. When we started dropping bombs, we didn’t drop one more than 20 yards off. Typically, the bombs dropped on the Bulls eye or within 10 yards. No other SWAC squadron stood a chance. We won the trophy easily.

The bizarre mission that I referred to wasn’t planned. In March 1979, I had just completed a front gun firing dive at Pokharan when I got a R/T call* from Jodhpur ATC.

“83, Jodhpur”

“Jodhpur, Go ahead”

“83, Have you finished your ammo”

“Negative”

“Roger, make your guns safe. Wait for 33 SU instructions.”

“Roger”

“83, this is 33 Su.”

“Go head”

“Climb to 10G and steer course 270 for interception. Check your fuel state.”

“Good for 20 mins loiter”

I don’t remember the fuel that I had. I was flying in clean configuration and Jaisalmer wasn’t far. So I told the radar I was good.

Having settled on an interception course that was very obviously taking me towards the Pakistan border, my heart started to beat a little faster.


Lions Steep Glide Bombing Team
L to R : Self, Sandy, Stona, Keru, Jimmy

The excitement was short lived. Within a minute 33 SU instructed me to return to base.

The incident happened after a day or two after Pakistan’s supreme court turned down former Pakistan Prime Minister ZA Bhotto’s appeal against his death penalty. Indian intelligence had indicated that Bhutto might try and escape by air to India and apparently 33 SU had picked up a track.

Think about it! With a little bit of luck, I would have made one line nondescript entry into history books!”

Which aircraft have you flown DACT against and which was the most challenging?

“During my Marut tenure, the MiG-21 (Type 77) and MiG-21M (Type 96) were the most advanced fighters in the IAF inventory. Those were the days when the IAF had 30 squadrons of MiG-21s!

Most DACT involved MiG-21s intercepting low-level Marut strikes.

Despite its significantly lower thrust-to-weight ratio, the Marut was no walkover. I will explain why. MiG-21s of yore had intercept radars with no ‘look down’ capability. For intercepting Marut strikes, the MiGs relied heavily on voice vectoring by controllers of ground based radars such as the mobile P-18 VHF early warning radars of 254 SU deployed near Jodhpur. At 500-ft, the preferred cruising height of Marut strikes, detection range was severely limited by radar horizon, while detection quality was constrained by the two dimensional tracking by the radar. Following the operationalisation of 33 SU equipped with the French THD-1955 high power three dimensional radar near Jodhpur the vectoring became more effective.

When MiG-21 vectoring did succeed, Marut pilots were instinctively inclined to stay in their comfort zone – low levels where the aircraft was fleet footed and very responsive. Visually sighting Maruts flying nap-of-the-earth was challenging. It became even more challenging when in the late 70’s HAL decided to desert camouflage the aircraft

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Based on the IAF’s air combat experience in the 1971 war, Tactics Development Establishment (TACDE) at Jamnager developed air combat tactics that focused on positional manoeuvring and the Marut squadrons were quick to embrace these tactics. Wing Commander SK Sonpar (Stona), a Fighter Combat Leader (FCL) who commanded 31 sqn from Nov 1977 to September 1980, pioneered the switch to positional air combat from the traditional energy and manoeuvre focused air combat.

No more would you see two Maruts on a strike mission in the same glance. They would be 2-3 kms apart and abreast of each other, ready to quickly sandwich any hostile that came astern of either or both through a simple hard turn. The sandwich would force the attacker to break and give a chance for the Maruts to hit the deck and escape. A four aircraft strike would be spread over 9 sq. kms and a six aircraft strike over 12 sq. kms!

“The Marut was a sweet lady, not a bitch!”

Under Stona we developed and practiced tactics that would allow us to attack enemy ground targets while providing mutual cover and retaining full positional and energy advantage. The effectiveness of our tactics gave us complete confidence in our ability to strike targets despite the threat of superior enemy fighters. The key to the success of our tactics was spotting the MiGs before they closed in to missile / gun kill ranges.

Our confidence levels rose to an extent where we started playing with the MiGs. I remember one exercise; I was part of a formation led by Stona that bamboozled the MiGs by zooming up after striking the target and cruising back to base at 15,000 ft! The hot in-pursuit MiGs missed us completely… they kept looking down while being vectored. The radar controllers at 33 SU, despite the height readouts on their scopes, never realised what was going on! So confident were we of our positional manoeuvring, we didn’t think we were taking a risk by cruising at 15,000ft!

TACDE developed positional manoeuvring notwithstanding, many Marut stalwarts remained convinced that your best bet against Type-77 was to hit the deck and get the hell out of there. It’s indeed moot how accurately a Type-77 would be able to engage a Marut flying at 200-ft and 620 kts.”



How good were the sensors?

“Other than its gunsight, the only sensors in the aircraft were our eyeballs and trust me they were very good because our lives depended on them. We maintained them in perfect order through exercises! To begin with, the Marut had a gunsight similar to the Hunter. The D variants, that I flew, had an ISIS gunsight that was very stable and accurate.”

How easy is to fly? What is the hardest thing about flying it?

“The Marut was easy to fly with reasonably good cockpit visibility. The controls were responsive during the entire flight envelope. Departure of any sort was unheard of.

As per the SOPs, you were required to enter a looping manoeuvre at around 460 kts, an embarrassingly high speed for a fighter aircraft. To increase pride and confidence in newcomers, Marut stalwarts like Sqn Ldr SK Singh experimented and progressively reduced entry speed. Eventually, Marut pilots started entering a loop at 350kts. On top of the loop, the speed would drop to around 60kts but the aircraft would go around with ease, sluggish controls notwithstanding.

Pilot error accidents in Maruts were rare and always on account of misjudgement, not failure to extricate the aircraft from a departure. The Marut was a sweet lady, not a bitch!”



Is the cockpit tiny?

“The cockpit is spacious and well laid out.”

How would you rate the cockpit?

“Excellent. Perhaps roomier than required! Each and every switch or circuit breaker is easily accessible.”

Have you fired live weapons – if so, what was it like?

“Besides its twin 30-mm Aden cannons, the Marut could carry T-10 rockets and 1000-lb bombs. Dr. Kurt Tank designed the Marut as a twin seater. In the fighter variant the rear seat was replaced by retractable stack that could hold around 50 Matra rockets! Yes, it had an internal weapons bay! Later, before I joined the Maruts, carriage of Matra rockets was discontinued and the rear cockpit space was utilised to carry extra fuel.

Post 1971, HAL attempted to fit 4 Aden cannons on the Marut. The attempt was abandoned following a fatal accident during trials over the sea, when excessive vibrations caused the aileron lugs to get detached causing the aircraft to roll into the sea.

ASTE tested the Marut with S-24 stand off rocket bombs but by the time I left the fleet the weapon had not been inducted into squadron service.

Gun and rocket attacks involved shallow 12-15 deg dives, but bombs had to be released in a 45-deg steep glide because they were not retarded. The attack profile involved zooming up to 15,000 ft and bleeding speed to around 250 kts, throttling back and then rolling into a kamikaze like dive hanging by your straps under zero g, and positioning the gun sight on the target catering to calculated wind induced drift. Once settled in the dive, the heavily laden aircraft would accelerate rapidly, the altimeter would start to spin down crazily and tracking with the gunsight would become challenging. Releasing the bombs at the right height, irrespective of the state of your target tracking, was critical because in case of release failure you would be pulling out of the 45-deg dive with 2000 lbs more than you planned!

After 1971 ops, HAL attempted to arm the aircraft with four 30-mm Aden cannons instead of two. During the gun trials we lost a test pilot when because of excessive vibrations aileron lugs got detached and the aircraft rolled into the sea. This issue was never fixed and the aircraft was limited to firing two guns at a time and later the two outer guns were removed.”

What is the greatest myth about the Marut?



“That the aircraft didn’t meet expectations. The aircraft met expectations, the project didn’t! Because MoD never put into the aircraft the engines that the aircraft was built for.

When I was posted from Maruts to Jaguars in 1981 it dawned on me how hopelessly doomed the Marut had become. Aviation technology had moved so far ahead while HAL had struggled to fix Marut manufacturing shortcomings.

The future doesn’t depend on what you do today. It depends on what you did yesterday. What you do today depends on the follow-up required on what you did yesterday. How long could the aircraft remain relevant with the 1952 vintage Orpheus 703 interim engine?”

How combat effective was the Marut?

“The Marut’s limited range and weapon load didn’t make it a very effective combat platform. I don’t believe the three Marut squadrons were ever a great worry for the PAF. The aircraft had the potential to become a great worry for the PAF. That potential was never realised.”

How reliable and easy to maintain is it?

“In the 650 hrs that I flew the Marut, I didn’t encounter a single technical failure. During the 425 hrs that I flew the Jaguar I had an engine fire that mandated a single engine landing. Going by my own experience, the Marut was as reliable as any contemporary fighter. But there is no denying that Maruts were plagued by technical problems that led to frequent loss of life and write-offs.

There were no serious maintenance issues. The Lions operated with 100% serviceability on many occasions during my tenure, even when we had more aircraft on strength than the establishment. The fact that HAL technicians were always on hand to help fix issues was a factor.”

Tell me something I don’t know about the Marut

“The Marut was built tough. Dr Kurt Tank designed the Marut to be tough enough to slice a tree in half with its wing! I don’t believe that capability ever came to be tested, but Marut pilots know for a fact that its fin could cut through high tension cables with just a gash to show for it. A gash that could be easily repaired to preclude raising even an incident report or linking it to a massive power failure south of Jodhpur!

What tips would you give new pilots coming onto the Marut?

“Watch your G when pulling out of dives on range or when turning at high speeds because she will do as you bid!”

What is the hardest manoeuvre to pull off in a Marut?

“Flying at the 300-ft AGL over the Rajasthan desert! Believe me it’s difficult! Stona grounded me for 2 full days while we were on detachment to Uttarlai. He spotted me at a much lower height and I had no choice but to tell him tongue-in-cheek that I found it too hard to maintain level flight at 300-ft. Many years later, when Stona visited our house in Austin, Texas, he recited the incident to my highschool-going daughters with mock indignation and feigned hurt.”

What should I have asked you?

“What was your biggest takeaway from the Marut flying experience? My answer would have been: God loves me! Flying Maruts, I realised low level strikes are a lot more fun than air combat. I just came to believe, hitting the adversary with bombs and rockets was a lot more fun than running around in circles with the adversary! I believe providence had a hand in my subsequent posting to Jaguars.”

Acknowledgements

I would like to thank Marut stalwarts Wg Cdr DK Cooper, Air Vice Marshal KP Sreekant, Wg Cdr KR Singh and Wg Cdr VS Kochar for their suggestions and review of my responses.

I served in the IAF for 20 years (1974 – 1994) flying the HF-24 Marut and the Jaguar. After taking premature retirement, I learnt software programming. In 1998 I took up a job in the US and stayed there till 2006 after which I resigned and returned to India.

I am a military technology enthusiast, particularly military aviation technology. I blog on Indian weapon system procurement and defence posture. I write for print and online publications. I am frequently quoted by the online and print media.

I have authored a fictional romance thriller set in the IAF.

Flying & fighting in the HAL HF-24 Marut: Interview with IAF pilot Vijainder K Thakur