The HF 24 airframe was a
masterpiece in aeronautical design .It is the finest platform the IAF has ever
had in this category of aircraft. It is even today more suited for actual
combat conditions. A resurrected, re-systemed Marut is a very low cost,
guaranteed platform that can supplement our efforts to increase our air
strength as a supplement to the LCA,MWF, and Jaguar aircraft.
The original aircraft was
produced with very limited resources and a capital outlay of only 16 crores in
less than five years 1956-1961. The revival of its proven airframe will take a
fraction of the time and resources of usual programmes.
Its aerodynamic performance is
acceptable even today and can be improved by small changes. The consequence is
that it will demand less from our engine development efforts.
Its strongest points were simplicity;
high performance on low power, very good handling but most of all was it was a
very balanced design giving versatility and very high levels of upgradability.
. The HF 24 design makes
eminent sense as a platform for meeting both the MWF requirement as well as a
supplement to the LCA programme as well as the Jaguar replacement need..
Its upgradability as regards additional future equipment will exceed both the LCA and the projected MWF.
The proposal deserves
consideration as a guaranteed economic and rapid solution with respect to
meeting the Air Force’s squadron strength needs.
Given the firm base and the
anticipated low development costs the project should be handled by the Private
sector particularly the Indian Automotive Industry which has the skills for
much of the detail engineering. It is a resource we are not utilizing at present.
INTRODUCTION
India is the only major economy which faces apart from
state sponsored terrorism the threat of armed attack by conventional forces
from powerful neighbours. These aggressions are a part of long term plans.
India thus has to maintain large and powerful conventional forces to deter the
adventurousness of its neighbours.
The Indian Air Force has a sanctioned strength of 42
squadrons. For reasons this needs to be reviewed and upgraded to 50 squadrons
(Appendix). This numerical strength can be achieved with an atmanirbhar Industry at a fraction of
the cost of imported solutions .
ATMANIRBHARATA
Atmanirbharata is not just self -reliance it is self -confident self–reliance. This means that we have the ability
to not only set up, tailor and manufacture to our own specifications but also
to modify our equipment to reflect the lessons learnt from active service.
AN ASSESMENT OF
THE TEJAS SITUATION
The following is an independent, open source assessment of the Tejas
situation. The self-contradictory information has been filtered by applying engineering common sense. The intent of the assessment is to highlight the risks with IAFs fulfillment plan and building an alternate option while keeping the focus on timely delivery of current indigenous fighter programmes.
1. The project was very badly begun and
it has continued to suffer from that bad start.
2. The standard of detail engineering
was very poor made worse by glacially slow rates of correcting them.
3.
It
appears that the first series aircraft have an empty weight approaching 8 tons
making them useless for any realistic purpose except trials and training.
4.
The
current utilization rate is around 50 hrs. / yr. per aircraft confirming pt.2
above.
5.
Low
production rates even after 2 IOCs / FOC indicate that the design is still not
satisfactory.
6. If
the above (2, 3) is true then any claim to speed rate of climb range etc. being
satisfactory is untrue.
7.
The
design lacks “balance”. In trying to make the smallest airframe the aircraft
has thrown away “upgradability”.
8. Even if successfully developed to meet FOC standard,
which is unlikely, this lack of upgradability will dog the design.
9. The
MWF configuration as projected is
extremely cluttered and almost certainly end up with a situation where the
additional power of the F 414 is frittered away by more weight and drag.
It
is quite possible that simple fixes and attention to detail may improve the
present performance of the LCA Mk,1 &1A by about 7 to 15 % but unfortunately that attitude of “Caritas” – a word
meaning care, love compassion and interest -is lacking in the concerned Organizations.
The aircraft does not need so much technology as “Caritas”.
Whatever the deeper reasons, the situation is that we
have a bad airframe with possibly good systems. Therefore combining the proven
excellence of the Marut airframe with what is usable of the developed systems
is worth a re- look.
AN
ASSESMENT OF THE MARUT AS A JAGUAR REPLACMENT
The Jaguar has been serving in the punishing low level
cross country role for over forty years and will need replacement as
serviceability and airframe life begins to reach their limits. Though the DARIN
III upgrades has been a matter of justifiable pride for the IAF the airframe is
old. More tellingly the Jaguar was designed for the low level attack role by
keeping the wing area as low as possible. This works fine in NATO because the
air temperature in North Europe ensures about 7 to 10 % more lift and thrust.
Under Indian conditions the combination of low wing area and lowered thrust
means the airframe is reaching the end of its potential. As the Table shows the
HF 24 airframe gives the same utiizable volume – possibly slightly more-and
being a low technology aircraft it is going to be substantially cheaper than
the Jaguar. Its performance as a platform will be superior to the Jaguar in
every way and we have in the IAF very highly developed upgrading skills.
The
HF 24 MARUT AIRFRAME
The Marut airframe has the following commendations:
1.
It
is totally Indian as regards intellectual property rights are concerned.
2.
The
design is all metal and the technology is sixty years old yet its performance
on even modest engine technology is completely relevant today and its
upgradability is high.
3.
It
was built at a project cost of Rs.15 crores and less than 5 years which
included capability to build at a modest rate of 16 aircraft per year.
4.
Its
re-creation will not need large sums of money or “sanctionable” resources.
5.
Over
100,000 hours was flown on the type. It has proved to be strong and reliable.
6.
It
is possible to manufacture single and two seat versions.
7.
Its
performance as a platform is up to current needs and there is scope for further
improvements by simple fixes.
8.
It
has proven super cruise abilities being known to do Mach1 at 5000 mts. on the limited
power of the B.Or.3. It should do Mach 1.2 - 1.3 with the simplest of the proposed
engines.
9.
The
aerodynamics of the aircraft made it a true “pilot’s aeroplane” - safe stable
pleasant to handle and easy to land.
10. For the same reason it requires less engine power to
meet a set of performance requirements. This puts less stress on our engine design
capability.
11. Like all great designs it is naturally upgradable.
12. It has almost double the “real estate” i.e. volume for
stowage of future equipment of the LCA Mk1A making future addition of equipment
quite easy to accommodate.
13. It can accommodate a larger radar dish about 10 cms
larger than the Tejas.
TWO
PROJECT STUDIES
There should be two different project studies:
1. To
make use of the systems developed centered around the F404/414 engine based
LCA. This will save a lot of the work. The flip side is that the rear fuselage
of the aircraft would have to be almost totally re-designed following the F
5E/F20 process to eliminate a lot of unnecessary flight testing w.r.t.
spinning.
2. The
second project study should aim at keeping the original airframe envelope as
intact as possible and modify the above systems/engine gearbox etc as required
as the engine outlet pressures and rpms would be different.
WEIGHT CONTROLAND
THE POSSIBILITY OF NEW EQUIPMENT
Weight estimate: The HF 24 with the Orpheus B.Or.3
weighed 6150kgs.
The following obsolete will be stripped from the old aircraft:
i)
ADF
11.44 Kgs
ii)
VHF
( 9XM2) 23.00
iii)
Radar
Ranging 45.46
iv)
IFF 22.00
v)
Gun
Top pair 174.00
vi)
Gun
Bottom pair 174.00
vii)
Gun
Camera 3.40
viii)
Gun
Sight ISIS 14.75
ix)
Ammo.Box
Top pair 16.30
x)
Ammo.Box
Bottom pair 16.30
xi)
Ejection
chute Top pr.
3.09
xii)
Ejection
chute Bottom pair
5.09
xiii)
Feed
Chutes Top 2.88
xiv)
Feed
Chute Bottom
5.28
xv)
Link
Chute 2.144
xvi)
Link
Chute 2.144
xvii)
Pressure
Box 43.50
xviii)
Floor
16.50
xix)
Ballast 134
The total saved would be around 712 kilos and another
50 kilos can be saved by changing the design of the pylons which were
unnecessarily deep to accommodate the ML MK1A ejectors. This weight savings will bring the aircraft
empty weight 5430 kilos. Keeping a target empty weight of 6800 kilos for the Super
Marut there is thus a prospect of 1400 kilos to be used to upgrade the engines
and new NavAttack equipment on the first twenty aircraft. After fitting the
upgraded engines (Up rated Orpheus) there would still 1100 kilos for new
equipment. All this is without using a single gramme of composites whose
reliable Indian supply is uncertain. With weight saving using composites (250 kilos), FBW (100
kilos) Carbon brakes, new electrical harness, 115 v A.C. systems there would be
a further 500 kilos available for new equipment and 5thgeneration
systems. Beyond an empty weight of 6800 kilos recourse would have to be taken
in cutting the fuel load down from 3300 kilos. In sum allowing for even the
Modified Orpheus (aatmanirbhar,
developable without consultancy) engines there is about 1100 kilos
available to the designers to upgrade the aircraft nav. attack capabilities and
about 1500 kilos if the HTFE 4000 meets timelines.
ENGINES
The engine problem, self- created, killed the Marut
programme because the platform performance was then too indifferent to urge its
further development.
The engine therefore is going to be as important in
the remanufacture programme as with the original programme. As can be seen in
Tables 1 &2 there is a wide choice of engines that are commercially
available. These foreign engines must be seen as “back- up” or supplementary to
the several potential “atmanirbhar” engine possibilities, namely:
1.
The
Kaveri GTX
2.
The
Kabini core of the Kaveri.
3.
The
HTFE 4000
4.
The
Orpheus B. Or. 12 redux
5.
The
core of the Pegasus used by the Indian Navy. This is an “üp-to-date” (1970)
version of the Orpheus compared to the 1955 version of Orpheus that we have.
A
SHORT NOTE ON THE ORPHEUS AS THE PREFERRED ENGINE
There is a popular mis-conception that the fighter
engine has to be a turbofan to be fully efficient. In fact the bypass ratio is
way below anything to be effective and the two spool engines is chosen for
other reasons the “turbofan” thus being
only a by- product..
A developed
Orpheus engine is a strongly preferred option for the Super Marut second only
to the lighter and smaller HFTE 4000 when it gets ready. At the speeds that the
Marut operates there is little to choose between a “leaky” turbojet/turbofan
especially if one considers the factor of Atmanirbharata” and the simple single
shaft turbojet has much to commend it under combat conditions whilst the
simplicity of the design assures low costs and assures good response to
upgradations e.g. Electronic Fuel Control not necessarily FADEC. The following
engineering packages are anticipated.
1. Improvement
of fit finish tolerance, reduction of tip clearances, change to a bigger fuel
pump, and a “look” at the combustion chamber aerodynamics plus greater care and
documentation during assembly should push up the thrust to 5600-6000 lbs (25-27kn)
. Even without afterburner this will
allow the Marut to supercruise at Mach 1.1 at 5000mts. Since this engine
will only be Bench tested as a proof of concept engine and it may be possible
to rebuild an existing engine (s) to the new standard.
2. This
would be followed by a more comprehensive modification of the engine and would
include redesign of the turbine stage to take a higher TET so that a slightly higher
mass flow and Pr. Ratio can be achieved resulting in a cold Military thrust 6600
lb.st (30kN)
3.
Second
stage would be to develop an afterburner and to replace the mechanical AFRC
with an electronic fuel control system, particularly for the “root T” parameter
of the AFRC. Better control and less weight is expected. FADEC can wait at the
initial stage.
Notes on the Super Marut
specifications ( pl also see Table 1)
Dimensions: Both
aircraft have the identical dimensions in terms of span, length Height and wing
area. The following are the differences.
Engine Power :
Prototype and systems test Aircraft approx. twelve will be equipped with
Improved non after burning Orpheus of 6600 lbs thrust or 30kN. Production
aircraft will be equipped afterburning Orpheus of 39 kN. Final engine –which
can be fitted to earlier aircraft also will be the HTFE 4000.
Equipment fit:
The HF 24 has the advantage over the other designs in having one of the biggest
utilizable volumes. This is sufficient to incorporate all the Avionics and
systems planned for the MWF/ AMCA. viz :
