Save the IAF-Revive the Marut                                                                               Prof. Prodyut Das

24/01/ 2025

There are now two distinct opinions about the Tejas programme.

The first is that the Tejas is brilliant aeroplane “a pearl” one worthy famously quoted about two decades ago (if nothing, shows how long we have waited for irresponsible promises to be fulfilled!), whose success now the perfidious Americans are trying to sabotage by delaying the supplies of engine, The second view is that the Mk1is a bit of a joke and all subsequent proposals, Mk1A, Mk2 TEBDF etc are clumsy attempts as the inept Design Agency stumbles from one half- baked solution to the next to correct the blunders of the Mk1.

No matter whosoever is right, the IAF cannot even begin to check the decline in its numbers, let alone rebuild its air strength. This is because:

If the first view is right then the US will continue playing games. Calling it “supply chain issues” won’t make the problem go away. If it is engines now it will be the Composites next. It is worth recounting what has happened before. The Viggen was offered for the NATO Starfighter replacement competition along with the Mirage FIE, and the F16. The problem was even though the Swedes had re-designed the civil JT8D engine- a larger fan, improved combustors, a thrust reverser and the after burner they still had no say over the engine. Note that the JT8D was a civil engine used on the B737 and being churned out like sausages. The point is if the Tejas is a threat to US products it will be tripped up. Unfair? Well, even if we get around to really making a wonderful aeroplane we won’t get to make the rules.

 I have put “civil” in italics to emphasize the need to think boldly and differently, starting from fundamentals and not parrot the strategies of others. So, even if the Tejas is good (which I most definitely do not think so) then we will be sanctioned and if it is even half as bad as I expect well then, the Tejas has scored a goal for the Import Lobby. As I said no aircraft either way.

Suppose we wanted a fighter that would, short of open warfare, be reasonably free of sanctions then below is an assessment of the workload.

The best engine option would have been the HTFE 25 but somehow the same set of people who stopped the Kaveri engine programme in 2008 seems to have stopped this important programme also. Presuming that the HTFE 25 and it’s afterburner is has been halted the next option would be revive the Orpheus B.Or.12 concept.

A tabulation of the work load remaining in developing a sanctions free fighter.

	Aircraft Project	Structural	Systems	Engine	Testing	Remarks
1	Tejas Mk1A/F404	Critical Weight improvement required	Presumed OK	Subject to sanction	Presumed OK	Poor producibility High- Cost design. Near useless for combat
2	Tejas Mk1A /Kaveri	Further critical weight improvement	As above	Engine requires further development and  a further 15,000 hrs of testing	As above	Better but Kaveri design requires urgent “different Thinking” attention
3	HF 42/Kaveri	About 50% of the airframe aft of front fuselage to be designed	Repackaging of Tejas systems. Only “trimming” tests required	Kaveri remarks apply	Further validation required	Cheaper and easier to build than Tejas
4	HF 24/ Orpheus based engine	No change in any prime structure	Tejas systems with interfacing to be worked out	Pl. see note below	Tested airframe	Sanctions proof. Lowest cost. Cheaper and easier to build.

Given the above situation i.e. that the “conventional thinking” set of solutions is liable to sanctions and the sanctions free solutions requires a start to be made, the surprise logical solution, is to focus on the 4^th option,

The 4^th option                        

The advantage of the fourth option- based on the HF 24 airframe and an engine based on the Orpheus and equaling the original B.Or.12- that our development load will be the least:

On the airframe: Only installation and repacking of systems. This task is made easy by the fact that the HF 24 has 40% more internal volume and much more real estate externally than the Tejas. Much of the certification testing has been already done and hence can be dispensed or boldly proceeded with.

On the engine: To frugally infuse a 1952 technology engine with some, but not all  of the 1980-1990s technology developed for the Kaveri so that the Orpheus 21 kN thrust is raised to 30kN. and an AB to increase the wet thrust of 43 kN. The Marut design does not need more. It will be more uncertain to develop the better Kaveri as compared to develop the simpler Orpheus. Pl. See the note on Orpheus development at the end.

Operation Salvage                                                   

The US, whose budget allocations we cite and envy so persistently, would have closed down the Tejas programme long ago but we are Indians, The first step would be to continue to try and salvage the Tejas programme. We  cannot let defaulting organizations get off the hook with bragging rights intact by stopping this  programme.

1.       Have the Tejas design examined by a fresh set of people. No foreign consultants; they are not needed. As the HJT 36 has shown, it has been 11 years since foreigners were consulted and we still don’t have the product.  

2.       Crack the whip. Order the Tejas Mk1 empty weight to be reduced to below 5800 kgs i.e. the airframe weight is to be less than 1900 kgs and the U/c to be no more than 90% of the MiG 21bis undercarriage.  

3.       “Now it is ALL HAL’s problem” speaks of lack of professionalism, irresponsibility and a tacit admission that solving the created problems is beyond the capabilities of ADA. All agencies have to be equally responsible and have to work together.

4.       Give option 4 to a funded (at the same rate as DRDO development projects) with a Private sector Consortium working to re produce the Airframe and develop the engine (henceforth referred to as Engine R 19)

Conventional thinking would balk at yet another proposal but reality is that this proposal is most likely to succeed.

The Marut R 19 proposal is promising because the Tejas Mk1 is undevelopable which is why it has taken 24 years after first flight and we are still debugging it. The other possible  conclusion would be that ADA is in someway  either incompetent or unwilling to complete the job. The engine is trying to catch up with GE levels of performance. Given these, the Super Marut project uses existing experience to the maximum extent with careful usage of very discreet amounts of new technologies to give the customer full satisfaction and be politically “sanction” proof.

Note on developing Engine R19.

Kurt Tank developed the HF 24 around the Orpheus B. Or. 12 which was expected to give a dry thrust of 30,3 kN and a wet thrust of 39kN. Note two B,Or, 12 Orpheus would have slightly higher thrust as a GE F 404. The Orpheus B.Or.12.had developed its rated dry thrust of 30.3kN, passed it’s 150 hrs qualification tests and by 1956, the un-reheated engine had flown in a F 86 Sabre test bed. The after burning model developed 36 kN. It is to be noted that these thrust figures were achieved using early 1950s technologies. We in India must surely have crossed those levels handsomely bar engineering leadership which is conspicuous by its absence in some of the labs. The Dhruv ALH with 300 plus produced and with over 300,000 hours is proof that requisite Leadership was not lacking but is being kept out. The Orpheus engine was developed, within a span of twelve months April 1952 to May 1953 using earlier Bristol Orion’s Compressor as a base.

Using similar development strategies, it should be possible to develop the R 19 relying heavily on the existing engines – Orpheus and Pegasus cores- to achieve what is needed in terms of above thrust- not the world best or any particular T/W ratio or s.f.c.- but adequate to do the job.

The major design constraints would be what is the TET we can achieve. The Orpheus TET was for max. continuous cruise was 927 deg. K and I presume we are at present entirely comfortable about achieving 1300-1350 deg. K. Any proven increase above that would be welcome.  In terms of high temperature materials and production facilities no additions will be needed. We are basically gilding the lily of a 1950’s design. 

Starter generator: The existing bullet mounted starter generator is moved out by the overhung “zero stage” to the top or bottom of the engine casing. This will result in an increase of inlet area by almost 25% with consequent increase of mass flow, and inlet pressure drop improving thrust.

Compressor: The compressor is based on the Orpheus or Pegasus core compressor. In the case of the Orpheus a “zero” stage is added giving a total of 8 stages, the Pegasus core already having 8. The “zero stage” is overhung so that much of the de-icing equipment can be done away reducing weight and bleed related losses. The overhung zero stage will require relocation of the starter but as indicated above will increase compressor face area by 29% with consequent possibility of increasing mass flow and thus dry thrust.

Combustion Chamber (CC) ; Pressure drop in CCs of this vintage were relatively high. It would nevertheless be wise to retain the existing system initially making only such common- sense changes as would be indicated by CFD studies. The Orpheus has a very simple but “bitty detailed” combustion chamber but one which makes production rejections easier to control. A parallel study could come later to have modern low loss annular CCs will decrease the energy loss due to combustion chamber resistance/

Turbine Inlet Guide Vanes (IGV). The existing IGVs are already air cooled but changes in material and internal contours will be required.

Turbine blades. Given the increase in TET it would be overloading the existing turbine resulting in unreliability and a two- stage turbine with a relatively lightly loaded first stage may be the trick given our anxiety about achievable TETs within metallurgical constraints. The two stage turbine would also  improve TBO and TTL.

Internal adjustable jet coneThe early German jets used a sliding “onion bulb” to coax the maximum performance from the BMW 003. That idea was used in the early ATARs but fell out of use with engine thrusts increasing rapidly. Pending development of a complex and heavy fully variable nozzle it would definitely be worthwhile to look at this simple solution for a simple low power jet like the R 19.

AFRC. For trials the present AFRCs are to be retained but if project appears promising work should start on a hybrid controller using at least electronic sensors for the usual control parameters. 

A table of Comparisons Dimensions in MKS unless stated otherwise 

Sl.No	Component	B. Or. Orpheus 3	R 19	Remarks
1	Length	1923	2023	Due to added “zero” stage
2	Dia inlet/Max	649	649	25% more inlet area
3	Dia Overall Max.	822	822
4	Weight	379 kg.	480 kg	Simple after burner
5	T/W	6:1	6.2:1
6	Compressor	7 stage single spool	8 stage single spool	Based on Orpheus or Pegasus compressors
7	Compression ratio	4.4 :1	6:1
8	Turbine	1 stage	2 stage	Improved TBO
9	Turbine/ TET	9270 K max. cont (3285)	13500 K	TET will be revised upwards with time if survey warrants
10	Thrust Dry/Wet	22kN/na	30.3 kN/40 kN	Simple after burner initially
11	AFRC	Mechanical	Hybrid/FADEC
12	Power take- off	4kW	20kW	PTO to be sized to KVA demands

Total test hours for all variants -about 5 - is 12,000 hrs on the bench and flight tests were 5600hrs

It is estimated that a Private sector consortium gathering a team of 50-60 people should be able to produce mass production worthy examples of the engine and a similar team the airframe in about two years and appropriate costs. The design team would do well to see if existing engines Orpheus or its components could be used to develop a few static non-flying test engines.

Project costs

Costs are highly subjective depending on the “indenting agency” of the funds and the degree of cost control. Our costs do not stand scrutiny and indeed on one very major project the accounts of the first ten years or so are reported to be missing. 

An approximation of what it should cost is given by History itself. Bristol originally asked for GBP 1 million to do the engine development and later lowered it GBP 300,000 which is equal to INR 1.2 Crores to INR 36 lakhs @ INR1958 respectively. The amounts would represent about Rs. 120 crores to 36 crores in Rs@ 2025 values all inclusive. That would give a starting figure. 

By the same token the HF 24 aircraft was developed for a cost of Rs14 crores which would be equal to Rs 1400 crores. These may seem incredible but are achievable with good teamwork and management. Most of our project costs- by my estimates much higher then US costs- are due to fundamental mistakes being made at the start of the design and then those mistake are inexpertly attempted to be corrected. 

Involving the Private sector 

One of the reasons one urges the handing over of some projects to the private sector is that the programme leaders and their monitors are people who have risen on their track record in achieving set targets. They pick up extraordinarily fast and can get into the details.

They also have continuity- the successful spend near 50 yrs. in the Company and the unsucessful are quietly weeded out.