The naming of the dog-an inquest into the HF 24 Marut :
Prof Prodyut Das
This has been published in The Vayu III/ 2021 as an inquest into the HF 24 Marut : Some tables are included in this piece.
The Aeronautical Press must not join in the general jollity triggered by the arrival of the Rafale which has been hailed as a game changer. The Rafale adds to the Air Forces capabilities but it is no game changer if only because game changers need to be both available and affordable. The Rafale is neither though we should be thankful that we have some!The Rafale has been a very excellent and welcome addition to the IAF fleet but to change the game we shall need a platform that has the following attributes. It should be available in numbers, it should be affordable in numbers and it should be aatmanirbhar. This word does not simply mean self-reliant; it means self-confident self-reliance. This translates into being master of the design its manufacture and our ability to continue to boldly tweak the design expeditiously to suit the ever changing needs of operations. In this context should we not re-look at the HF 24 which as a platform is the finest the Indian Air Force has ever had.
I mentioned the Rafale as an illustration. I put to you the case that we order the Rafale but do not buy the afterburner fuel pumps –to save foreign exchange- never mind the aircraft would never reach full potential. Then, say to save engine TBO or some such reason, the engine throttles were wire locked to give only 73% of the design’s cold thrust. Instead of working to get rid of the “wire locks” on priority, long term programmes are undertaken to design entirely new engines to replace what was available and ready to be modified. The benighted aircraft are sent war where they perform very reasonably suffering a lower actual loss rate than the SU-7. Subsequently the aircraft are often AOG éd for weeks for lack of tuppence worth of Bostik or a packet of AGS split pins. Finally the Rafales are deemed unsatisfactory and retired with alacrity after only fifteen years of colour service. Despite failing to improve the existing aircraft it is thought eminently sensible to launch an entirely new programme with all its brand new uncertainties! “Wait a minute! “ I can hear you remonstrate “No one sane will do a thing like that!”. Well that is actually what we did to the Marut. Should we not re-examine the brilliant airframe for fulfilling the MWF role as it would be a solution brilliant in its fasibility and simplicity.If you are ab initio on the Marut there is much material on the web. I would suggest that you look up www. Marutfans or go to Pushpindar Singh Chopra’s “The Spirit of the Wind” to hear all the anecdotes lovingly recounted. It was a wonderful aeroplane and to me if you tabulate the jaldi five (term in used in India for Bingo or Housie games for the quick five) of fighter evaluation –wing loading, T/W, Kg. of fuel per Kg. thrust, AR, Top speed at low level- you would probably conclude that the HF 24 if it was given its original engine the B.Or.12 of 6160/8160 lbs. st. thrust was the best of its distinguished contemporaries. The F 104 Starfighter was faster, the SAAB Draken was STOL, the Mirage III had outstanding high altitude performance and the MIG 21 was unbeatable if the task was to hunt down B 52s marauding over the Rodinya but for sheer heft and haft, blade and balance the HF 24 was the best of them all, a masterpiece by a master Swordsmith. The HF 24 showed all the attributes of its great predecessor the Focke Wulf FW 190- ease of manufacture, great visibility, pleasant handling and ease of piloting, strength of structure, devastating armament and outstanding performance from relatively modest engine power. Compared to its contemporaries the HF 24’s balance of the design and its upgradability are features that makes the aircraft relevant even today- sixty years after the first flight.
All fighters have faults and the HF 24 was no exception. The Marut’s faults, left uncured were used to “board out” the aircraft’s considerable capabilities. The following are based on notes made whilst I was a Trainee PGET in 1973.
Vibrations
The HF 24 suffered from severe to unacceptable cockpit vibrations and general vibrations during 4 gun firing which often led to aileron locking. These were both attributed to “’gun firing”. Actually the two vibrations had different root causes and needed two different solutions.
The cockpit vibration was caused by the Aden muzzle blast hitting the deflector baffle. The blast force was sufficient to shear off the blast tube attachment screws in the prototypes. The tube was slid into the fuselage and was secured to the structure by AGS (Aircraft General Standard) 8G screws which attached the flange to the cockpit frames 7, 8, 9. Unfortunately these were the very frames on which the cockpit dashboard and many of the flight and attack equipment were fitted. I do not recall any form of “staking” the flange to the fuselage frame so the vibration patterns would depend on which frame was taking the maximum brunt though I would not expect the shaken pilot to have noted the difference! The force twisted the three cockpit frames to varying degrees. In addition the blast tube acted as a “column in bending” and would buckle elastically under pressure and in between the rounds the tube would whip back into shape setting up lateral vibrations. The technically correct solution would be to anchor the blast tube “by the tail”. This would eliminate the buckling and keep the load under stable tension and the forces would not reach the cockpit area. Double walling the area of the mounting flanges inside the cockpit would be also another possibility. The Hunter has exactly the same arrangement in principle but because of the “subsonic contours of the fuselage nose the blast tube was less than a meter long and so the “whip” was about eight times less, In addition the forces were taken up by a very thick walled rigid “box” (Fig1) consisting of the 10swg cockpit floor and a 8 swg outer lower cockpit skin and it was enormously stiff with very strong diaphragm walls front and back. Rival aeronautical companies used to say that Sir Sydney Camm’s designs were fine examples of Victorian Railway Engineering but handsome is as handsome does! It is to be noted that solutions to the problems are both simple and often “lying around”. Most solutions do not need equipment or complex mathematical analysis.
The aileron locking during four gun firing full fire out was due to the Aden’s recoil – about 25kN after buffering-was taken by two very narrow based (about 30mm) brackets riveted on frame 19 of the gun bay ( fig.2). Each bracket would experience recoil of 1.3 tons to the rearward followed by a turning moment of 10,kN.M about ten microseconds later when the Aden’s revolver indexed-causing these brackets to twist and turn. Unfortunately the aileron jack was mounted opposite on the other side of the same structural panel and using, if I remember correctly, the same rivet holes! The claws of the aileron jack sometimes got stuck “half cock” causing a jammed aileron circuit. The solution would have been to simply extend the bases of the bracket or connect the two brackets to form a wider base to reduce the amplitude and the flexing of the bracket. The Hunter of course used a gun pack which though it weakened the structural rigidity of the fuselage at that point it also isolated the vibrations. I would note that the HF 24s gun layout was technically perfect in terms of maximizing the “area of lethal density”. If you still want four guns the HF 24s arrangement was mathematically the best and it can be made to work!
Why did the Germans not correct these simple things? I think they were packed off quite early –before the IOC flying trials began- no doubt to save precious foreign exchange required to import complete aircraft! The other possibility could be that the consultant would always leave some “bugs” in the design to extend their tenures. The Chinese of course routinely complain of getting doctored drawings from their collaborators and routinely tinker around with whatever they get. Sometimes they stir fried the prototypes and equipment they were tinkering with but usually tinkering led to happy results.
Judder during turns
All aircraft will judder during turns. The Boeing or Airbus turning into Finals for landing will tremble and judder during the turn. This is because the inner wing tip is flying at a much lower Reynolds number than at the roots-at least four times less in the case of the Marut. The Marut juddered in a 4G turn as the power available struggled with the power required. Kurt Tank used a laminar flow six percent NACA aerofoil which he modified with a cropped trailing edge and called it the Ta-006. The aerofoil had a sharp leading edge which is prone to flow separation. The usual corrections- many used by Free flight aero modellers -are a turbulator on the tip leading edge, in practice a 3mm dia. wick glued to the tip leading edge, “washout”, conical camber on the LE or as in the Gnat a combination of conical camber and a cambered “lifting” aerofoil towards the tip. The other possibility is that the span wise flow is separating. This happened on the early Vulcans and a kink on the leading edge cured it on the Vulcan B2. We could do the same or look at re-locating the “dog tooth”. With more power the judder would be at higher “g”s.
One interesting point is that the wing design of the HF 24 had a 20mm extruded alumimium LE- rather like a model aeroplane! This was an excellent feature because in case of a bird hit the stout LE extrusion would break up the bird and prevent damage or jamming of the aileron control rods as happened in the case of the loss of a SU7 to a bird strike at Hindon in the ‘80s. The extruded LE is mentioned because in the HF 24s personally examined fairly deep extrusion marks were noticed on the leading edge which would certainly unhelpful. I wonder if there is any connection to the problem.
Stall spin and roll coupling.
I have not heard if the HF 24 was spun but the design has the potential to be very spin resistant going by the similarities between the layout and that of the Northrop F5. With more power and L.E. flaps and small tweaks, the Marut can be made to sit and beg before stalling and snapping into a spin. Spin recovery should be crisp and certain given the low set tail plane but developing of a full spin may take time given the high fuselage inertia and damping. Considering the half a ton of Aden gunnery so far forward it is not surprising that there would be roll coupling. Using of the Russian GSh 6-30/ GSh2-30 underbelly on the centre line as in the MiG 27 or Su25 for example would reduce the magnitude of the problem. Judicious use of composites in items like the fin would help.
Internal fuel capacity
Specific fuel availability i.e. kg. fuel per 10 N/1Kg. cold of thrust is an indication of combat sustainability and an important factor in gauging the efficacy of a type. The HF 24 had an internal fuel capacity of 2067 kgs which was carried in the two wing tanks, a central collector tank and a saddle tank strapped over the c/s. The internal fuel capacity can be increased to 3300 kgs using integral tank technology (Fig 3) once the uprated engines are fitted.
I have written in some detail the past problems and their possible solutions/improvements to illustrate that our present problems are similar in nature and the cure to the problems is less of “technology“ and more of “caritas” an untranslatable word meaning love, care, compassion and interest.
The HF 24 Chronology
To understand the failure of the Marut programme to achieve its full potential one has to follow the historian’s method of noting down of the chronology of events and then to add, as Hercule Poirot would recommend, important contemporary events which may not seem to have a direct connection.
1) In 1955 Nikita Khrushchev and Bulganin arrive in India to tumultuous welcomes in a first outside visit of any Soviet Head of State.
2) In 1956 India adopts an Industrial Policy Resolution that gives “the commanding Heights of the Economy” to the Public Sector. Since the Armed Forces were supposed to be plotting coups when not on parade, the Industrialist were Capitalists, the businessmen were hoarders, the Politicians were impermanent and the general public the Great Unwashed the country slips into the hands of the Bureaucracy. The senior echelons of the Bureaucracy are packed with jumped up-due to the partition- young Cambridge Communists more inclined to prove Marxist Economic Theories are workable rather than achieve set targets. Industrially it is a disaster. Whether their political leanings had any proclivities towards bringing India into the world’s leftist bloc is not known.
3) Mahavir Prasad Tyagi one of the unsung Ministers of India is Defence Minister from 1952 to 1957. During his tenure the Indian Armed Forces are greatly expanded the Air Force is doubled in size and the twenty squadrons re equipped with the latest combat jets worth approximately GBP 120 million. More importantly he is in touch with three great Chief Designers- Messerschmitt, KW Tank and Petter. Petter is keen to settle in India which he feels is his spiritual home. Tank is recruited.
4) Tank arrives in India to lead the design of the HF 24 in September 1956.
5) Krishna Menon, a theosophist and a staunch leftist takes over the Ministry Defence in 1957. He is a keen advocate of the MiG 21.
6) The offer to develop the Orpheus 12 to suit the Marut for GBP 100,000 ( Rupees 11 lakh ) is turned down. A later offer to develop the required engine for GBP 1Million is also turned down. Even when the quote is reduced to GBP 300,000 it is still turned down. Foreign exchange however is sanctioned to set up a Shaktiman truck line which the Private Sector could have easily handled but it was a case of Marx Marx uber alles!. Men had lost their reason.
7) Petter is prevented from building a house in Poona where he had reportedly acquired a plot of land for the purpose and leaves India.
8) Air Chief Mukherjee dies suddenly in 1960 in Tokyo. Reportedly there is no autopsy or inquest.
9) The first prototype of the HF 24 is ready for first flight within 240 weeks of project start to an expenditure 14 crores which includes building up of facilities,
10) The first flight in May 1961 end in ignominy as the pilot retracts the undercarriage to abort the takeoff damaging the aircraft but it is a tribute to the aircraft’s sturdy construction that it is quickly repaired. Incidentally the same officer, when Base Commander Pathankot delayed apparently through indecision the launching of a Gnat CAP until too late and “Nosey” Hyder’s famous strike got off scot free.
11) Menon is retired after the 62 debacle and YB Chavan is the Defence Minister from December 1962. It was during his tenure that the offer for the Russian RD 9F is declined.
12) The HF 24 handling flight is raised in 1964 with four aircraft.
13) Thinning out of the German Consultants begins even before the flight trials are completed.
14) The first Marut squadron is raised on 1st April 1967 and based at. The first Night fighter variant with Ferranti Airpass III radar is lost within the month when both engines run dry due to faulty instrumentation or fuel pump failure. The wreckage-the aircraft “bellied in’ on its own near the airfield after the pilot ejected- shows about sixty gallons remain- about five –six minutes flying at low speeds for the Marut. I would have examined if the fuel pump quill shafts had been tampered with. It is very unusual to have both engines stop within a minute of each other.
15) A HF 24 is lost at Goa during a ferry flight in May 1970. The press described that the aircraft was engaged in four gun firing at that time the wreck of the aircraft and the pilot’s body is not recovered.
16) Three Squadrons of the aircraft are in service by 1971 being posted in the arduous Western Sector and often operate from austere newly established air force bases.
17) A word about people: Aircraft design requires high capability people. In 1971 an IIT B. Tech with a Postgraduate degree wishing to join HAL could expect a joining salary of around Rs.460 with two Increments. If he joined the State Trading Corporation with just a B. Tech his joining stipend was Rs. 950. EIL,BHEL all offer similar pay packets. Contemporary private sector jobs range from 1200 to 2200 per month. Nevertheless many IITians join but the marginal salary surplus meant few can continue. Things are not helped when many of the “next promotion” openings- 174 in Lucknow for example in the ‘seventies- goes to re-employ retired Wing Commanders which is a social obligation- but why HAL?
18) An attempt to clear the aircraft for four gun firing in late 1971 ends in the loss of the aircraft and the pilot. Again the aircraft is trialed over the sea and recovery is impossible. Our planning of development testing was bureaucratic rather than a technical exercise- it always left much to be desired. High altitude air to firing using auto destruct ammunition over the Thar would have given the pilot bigger margins for safety and assured recovery of the wreckage in case of accidents which is always a considerable possibility.
19) The aircraft performs creditably in the 1971 war suffering fewer losses/sortie than the Hunter or the Sukhoi but the evidence builds up against the aircraft which is often AOG-ed for lack of trivial spares and stores.
20) HAL proposals during 1973-1980 to upgrade the aircraft with the RB 199 or the R25 are turned down. The budget asked for was around 56 crores to be spent over 3 years.
21) The aircraft is retired from service in 1983 with some airframes having less than 100 hours. The Navy is reluctant to cast “cast offs”.
22) 22) In the same year 1983 the LCA project is sanctioned 560 crores with an all new organization de facto under the direct control of the South Bloc bureaucracy.
It is up to the reader to form his conclusions.
Noteworthy is that the project was sanctioned with Raj Mahindra the well known designer of the very successful HJT 16 Kiran jet trainer of which 250 were built. He was replaced shortly afterwards as the Chief by Dr. Kota Harinarayana who was less known. Dr. Kota was a graduate of engineering from BHU (Benares Hindu University) and joined HAL as a trainee in 1967; few details are known about this (1967-1985) phase the high points being that he then shifted from HAL to DRDO/Govt. of India working in Delhi and with Chief Resident Engineer office in Nashik MiG 21 factory where he would have worked on the validation documentation and certification of MiG 21 production. He also did his M.Tech and Ph.D (from IIT Bombay) during this period. Circa 1982 he reverted, from Head of CRE office, to HAL as Chief Designer Nashik for about two years before taking over the LCA programme.
The engine problem
The problem of the Marut not having the selected Orpheus 12 engine is well known. It cut the tendons of the aircraft’s abilities. We turned down offers from Bristol Siddeley not once but twice in 1958 and in 1961. This was then compounded by refusing to accept in 1963 the Tyumanski RD 9F which was the power plant of the MiG 19 which was being phased out and we could have got it including the tooling for the proverbial song. The RD 9F was within 5% of the Orpheus 12 thrust and was a “drop fit”. It was our last chance with the original the excuse was that the RD 9F had a compressor stress limit of Mach 1.3 and we wanted Mach 2! Who wanted this.That makes three times we turned down feasible solutions –one is reminded of Goldfinger’s/ Felix Leiter “third time is enemy action” applicable?!
The Orpheus was numerically the most important engine for the Indian Air Force and the Industry of that time. Instead of beavering away trying to improve the Orpheus and having refused foreign help both GTRE and
Becoming SNECMA
France, under German occupation for most of the war, had no Jet engine technology. They took up the BMW 003 (apparently Brandenburgerische Motoren (“Bramo”) and not the more popular “Beymeywa” Bayerische!). The engine was a pretty crude device with a TBO of 10 hours and was so sensitive that in Luftwaffe service the German pilots were extremely cautious when handling the throttle for fear of flaming out the engine. It is not possible here to detail all the small but fascinating steps the French took to make the basic engine into a fully competitive product- these are available on the web and make fascinating reading but the summary below shows the extent of improvement in that is possible on axials given love and caritas.
The ATAR begins as a BMW 003 and gives 7.8kN -9.02 kN for 30secs.- on a 7 stage axial compressor and a single stage turbine at 8050 rpm. By 1948 it was giving 16.5kN on a piston engined flight test bed. By 1949 it was, as the ATAR 101B2, giving 24.5kN and by 1953 as the ATAR 101C it was delivering 28kN the rpm having gone up to 8500 rpm. The 101D finally got rid of the typically early German translating “onion” type nozzle area control and enlarged the turbine and by 1957 the ATAR 101E added a zero stage, increased the mass flow to 60kg./sec. Designed for 33.6kN it gave 36kN in production-lesson here!. By 1957 a totally redesigned ATAR but of same overall configuration had gone into production with increased mass flow and pressure ration giving about 42 kN. Differences between each step were small and easily implementable.
The hidden lesson is that SNECMA having got a fairly crude design as a base tackled the problem with caritas and managed to make a commercially viable jet engine. In achieving the above gains no major changes were made to the design. Most of it can be described as creative tinkering- fit finish tolerance polishing and changes to sub-assemblies at the most-perhaps just the blading at one of the stages-or some tinkering with the combustion chamber finish- small things like that.
The lessons for us are we do not need much. Whilst basic facilities are essential, imagination, interest and a willingness to think freely or in retrograde can be useful in problem solving of axials. One example of willing to be regressive, patient and flexible- to flow past the problem - will make the point: The BMW 003 used hollow turbine blades which were made by press working in fourteen stages a nickel alloy steel tube- rather like a “conformal transformation” of circle into a Joukowski aero foil if you know what I mean! Though a splendid idea- the process wasted no material, the resulting blade was air cooled and worked well at thrusts of 7.8kN of the original 003 engines. They began to create problems when thrusts rose to 30kN.The French engineers were able to detect the fact that the blades were buckling and fluttering using a mixture of quick calculations, and 1950s technology instrumentations. Having identified the problem they reverted to solid blades which were naturally stiffer though the weight must have gone up which was tackled separately. The point I want to make again is that what is needed at the last mile is not technology but a spirit of enquiry and initiative springing from caritas- a love for the engine or product. I don’t see how a consultant will give us that. I wonder, in mischief of course, whether the foreign interest in collaborating to get the Kaveri right is because they will have to do so little and earn so much!
With that as an introduction to the mental makeup if we re-examine the Marut’s engine problems this should have been the proposed route. The Orpheus though old is well known to us, cheap, simple, responsive (single shaft) and will do even today. We needed 27.4kN in dry and 36.5kN in afterburner and we had an engine that was giving us 21.6kNs. Simply by changing the fuel pump from “B” to “C” we would have picked up another 100N i.e. 21.7kN. Changing the fit finish and possibly the tip clearances- remember the Chinese and their worry of “doctored” drawings -we could have reached 25.36 kN. Even if this rating was not quite 27.4kN required by the design if held for three minutes/sortie it would have given the Marut a 17% decrease in its take off length which was always quite critical under certain conditions as well give it advantage in combat well beyond the percentage increase in thrust. ! It would have cost us nothing to try this out on the test bed. By 1967 this uprated engine would have been ready for the first production Maruts. By then the Tyumanski R 11 had brought air cooled turbine technology into Koraput. With a small increase in TET allowed by the R11’s technology we could have hit the 27.4 KN mark which was what was originally required and even without an afterburner the additional 20% power would have transformed the Marut with energy related performance such as climb and turn seeing a hundred percent improvement. With such a performance we would have a breathing space in which to continue production in volume whilst an afterburner was under development. There was no need for foreign collaboration, or high technology whatsoever at any time. What was lacking was a spirit of curiosity and probably an unwillingness to accept possible failure. Unless we can rectify this “spirit” further research funds will always be wasted and timely results improbable.
A future for the Marut?
Normally any design that first flew sixty years has no prospects but the aeronautical scene in India is not normal. Given the need for a fifty squadron Air force the HF 24 is a godsend. The LCA project is skating on thin ice- if two aircraft unpainted aircraft are flown in just a few days the financial year ending is the usual “nautanki”- more “bean counting” - a symptom of illness rather than of progress. It is likely that the LCA Mk2 or even the Mk1A etc will disappoint. Even if the LCA Mk IA /2 aircraft is ready on time ADA will turn up then i.e. in 2025 and ask for two more years to validate the FBW software. You read it here first!
We are in a situation where we have developed good systems have but the airframe is bad- made worse by being uncertain. In the HF 24 we have a proven airframe. A man from Mars would say that a combination of the two to produce alternative solutions is natural and logical. It therefore makes sense to look at the HF 24 Marut as it will meet all the Tejas /MWF requirements and on time. A technical note is under preparation but below is a summary:
The following about the Marut are undeniable:
1. The Marut airframe is proven aerodynamically and structurally and has over 100,000 hours of “un-mollycoddled” IAF service.
2. The prototype was built from scratch within five years for a sum of 15 crores using ‘sixties technology of drafting and prototyping.
3. Even with a B.Or.12 type engines the aircraft would behave like the “big wing” Jaguar proposed by BAC in the ‘80s.
4. The entire upper deck of the fuselage is free of spines and control runs making area ruled conformal packing very simple. Even without the above pack the Marut ,at present has, 91% and 62% more storage volume than the LCA Mk1 and the MWF.
5. The radome bulkhead (frame 5B) diameter will permit for radar antennae approximately 10 centimeter greater than the LCA’s.
6. The aircraft is available as both a two and single seater.
These are strong reasons for an independent, unbiased re-examination of reviving the Marut airframe to meet the MWF/LCA requirements.
Somewhat surprisingly the HF 24 was lighter than the Hunter though both had the same level of equipment and gunnery because the Hunter’s engine was about 400 kg heavier than the two Orpheus. The rest was I suppose Hawker engineering! With the obsolete 4x30 mm Adens and the 114 kg ballast weight removed and two B.Or12 equivalent engine we are looking at a flyable airframe weighing about 5350 kilos leaving a one ton and a half margin for upgrade equipment without using a gramme of composites. “New technology”- 115 v electricals or carbon brakes will give us another two hundred kilos and composites when introduced will save perhaps another 300 kilos so we have by and by a margin of about two tons of new equipment and systems whilst keeping the empty weight at around 6800 kilos. The ease of production and the use of conventional materials would result in rapid production and modifications for the initial batches as well as the ability to withstand sanctions on raw materials supply. The original aircraft cost little to produce from scratch in 1960. Even less will be needed to revive the HF 24 airframe and develop a NMG. Sufficient information exists in India to extract the DNA of the superb HF 24 airframe. We are rich in upgrade skills and this time we will do it on a bare airframe.
The vexed problem of the engine has to be tackled by a multi-pronged exploration for the best solutions. The aircraft should be re-examined for both single and twin engine configurations. Firstly the Marut, thanks to its aerodynamics, does not need 78/90kN currently being thought of for the MWF , the F 404 /Kaveri may just do what the more powerful F 414 needs to do for the “blunter draggier “LCA.. The Honeywell F 124, The Ukrainian AI 222-22As, the Adour are all contenders for the twin engine configuration. The HF 24s vertical sides at the center fuselage means that a small deepening of the fuselage (50-80 mm depending on the engine-(the Motor Sich Ivechenko AI222-22 will need no change) will cause minimum disturbance to the aerodynamics- talk about a brilliant airframe!
The second line of exploration will be a single engine to use the F414/ F 404 engines because it can then use directly most of the systems developed for the LCA. Though the HF 25 as proposed by SC Das in 1978 is aerodynamically superior in it would better to configure the HF 24/ F 404/414 in the style of the Northrop F 5E to F 20 transformation because a lot of the spinning and high AoA test flying will not be required. Incidentally the capture area of the intakes in the existing Marut is just about right for the F 404/414 needing only the usual “blow in” and dump doors.
For true Atmanirbharata (self- confident self- reliance) I would strongly pitch for developing the Orpheus B.Or.3 into the B.Or.12 equivalent. For our operational scenarios the Orpheus has a lot to recommend it. It is simple, it is cheap responsive and light and it will do. No major airframe changes are needed. The original Orpheus was designed and certificated within one year- that too on a 1955 base of knowledge and technology. Not only is such a development within our engineering and technology capabilities we have a secret engine candidate ready and waiting. This is the core of the Pegasus two- spool turbofan used on the Indian Navy’s Harriers. A quick bench check will confirm my guess that the core develops around 31.2 kN-33.7 kN (7000-7500 lbs.) which is more than enough to do the trick for the HF 24 .With that kind of power the Marut would be able to super cruise at Mach 1.2 at 10,000mts . With a smooth running basic engine developing the afterburner to get around 40 kN (9000lbs) will be easy. Even if my sanguine guess is wrong the engine has an additional stage with a higher compression ratio and being about a decade later it will have some interesting features useful to us. The HTFE 2500 and the Kaveri are also very suitable for consideration. We are spoilt for choice in terms of imported and local engines!
Going about it
The development of aircraft is a high attention task. Remaining in power in multi part democracy is another high attention task and the two do not co-exist. It is no coincidence that successful state run aeronautical industries exist only in “single party” democracies. When the State developed the HF 24 the polity was close to a single party democracy. The Government of India must put aside the infructuous and wasteful past and encourage the formation of a private sector consortium by providing equity and sharing of knowledge and facilities to develop an “upgraded” HF 24 along the line discussed.
We are no longer crippled by dogmas. Now waiting for the Government will be in vain. It is too busy to run an aerospace Industry. The private sector Automobile (sic) and Aerospace Industry must form a consortium to see how the Marut airframe with the two engine options- Kaveri and Orpheus- can be produced and how much it would cost. It should co-ordinate with the Government to see how much equity- in the form of capital, knowledge, facilities and legacy resources can be organized. The concept of the fighter is changing and the Marut Airframe is the best right thing in the right time. The Dog may yet be redeemed.
Table 1: Super Marut Engine options:
1. Twin engine (existing) aerodynamic configuration
Sl.No | Type | Thrust (kN) | Length (mm) | Dia. (mm.) | Weight (Kg.) | Mass flow (kg./sec) | PR.Ratio |
|
1 | Orpheus B.Or.3 |
| 1916 | 822 | 379 | 38.1 | 4.4 | For reference only |
2 | Orpheus B.Or.12 modified | 30.3/39.5 | 1916 | 822 | 460 | 43 | 6-10* |
|
3 | Honeywell F125 | 28/43.8 | 3150 | 914 | 521.6 |
| 25 |
|
4 | AI-222-22F | 25/42 | 3138 | 624 | 560 | 50 |
|
|
5 | Adour |
| 2971 | 762 | 809 | 50 |
|
|
6 | Pegasus Core | ? | ? | ? | ? | ? |
|
|
7 | Kabini | ? | ? | ? | ? | ? |
|
|
8 | HTFE 4000 | 25/40 | 1730/? |
| 350 | 43 |
|
|
· The small pressure rise results in a bigger engine but makes for very stable operations and fewer technical development challenges whilst providing an adequate engine.
Table 2: Engine Options
2. Single engine configuration
Sl.No. | Type | Thrust (kN) | Length (mm) | Dia. (mm) | Weight (kgs) | Mass flow (kg/sec) | Remarks |
1 | Kaveri | 52 / 72 | 3490 | 986 | 1235 | 78 |
|
2 | F404 |
| 3912 | 889 | 1036 | 70 |
|
3 | F414 | 58 / 98 | 3910 | 890ivses | 1110 | 77.1 |
|
4 | M 88 | 50 /75 | 3538 | 696 | 897 | 65 |
|
The Orpheus max. diameter is 835 mm and the two engines together weigh about the above table is an indication of the amount of “deepening” the Marut airframe will require to accommodate the single engine in the F5/F20 resurgey style. Reductions of weight and drag are expected even with the heavier Kaveri.
Table 1: Marut permutations and comparisons
Sl. | Type | We.(Kg) | Thrust (kN) | Disp. Load (kg) | T/W (Clean) | Fuel Fraction | Fixed Guns | A.R. | W.L. (kg/M2) | VMax.SL(kts) | GIUV M3 | Remarks |
1 | HF 24.Mk.1 | 6150 | 2x21.6 | 4713 | 0.492 | 0.539 | 4x30 | 2.9 | 387 | 600 | 15.8 |
|
2 | MiG 21 FL | 5100 | 39.5/61.20 | 3450 | 0.57/0.85 | 0.574 | Nil | 2.22 | 370 | 610 | 8.3 | a) |
3 | HF 24 Mk.2 | 6450 | 2x27.4/36.3 | 8400 | 0.57/0.755 | 0.6 | 4x30 | 2.9 | 530 | 610 | 15.8 |
|
4 | Jaguar | 7000 | 2x 24.56/37.3 | 8400 | 0.678/ | 0.7 | 2x30 | 3.12 | 637 | 713 | 16.3 | b) |
5 | Kaveri Marut | 6800 | 49.84/79 | 8600 |
|
| GSh2-30 | 2.9 | 550 |
| 16.3 |
|
6 | Marut F 124 | 6500 | /40.5 | 8600 | 0.85 |
| GSh2-30 | 2.9 | 546 |
| 16.3 |
|
7 | Tejas Mk1A | 7040 | 50/78 | 6400 |
| 0.46 | GSh 23 | 1.7 | 370 | n.a. | 8.25 | c) |
8 | MWF | 7700 | 58/98 | 9800 | 0.9 | 0.56 | GSh 23 | 1.7 | 426 |
| 9.8 |
|
Notes:
a) The development of the HF 24 Mk.2 would have made the import/production of the MiG 21, Jaguar and the Hunter F56A – about a thousand aircraft unnecessary. Compared to the Marut Mk2 the MiG’21 FLs load- range was pathetic.
b) GIUV is the volume of the airframe available for storage of fuel and equipment after subtracting the volume required for the cockpit and the propulsion system i.e. engine inlet, engine and jet pipe. It is an index of upgradability. The Marut’s “balance” of design is reflected in the figures. The Jaguar is videshi. The MWF has a lower wing loading but the amount of space is much lower and it is not confidence inspiring. The Marut is a happy balance.
Remarkably both the Marut and the Jaguar have approximately the same GIUV. The Jaguar, optimized for the low level DPSA role is on its last legs because of its high wing loading. This may have been a factor in non-selection of the Honeywell F124 upgrade because the “small wing” as with the Northrop F20, would have not been able handle to the full the improvement offered. In the 1980s BAC had proposed a big wing Jaguar! The HF 24 of course could increase its MTOW by at least another ton.
7c
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