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.
Prof Prodyut Das
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.
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