The Tejas effort to create an indigenous fighter for India took a dramatic turn with last week’s reveal of a plan for a twin-engined variant with twice the thrust and almost doubled weight. The new aircraft is a close-coupled canard delta in the same class as the Rafale. Jim Smith gives his analysis. 

Update here. 

“At the turn of the year, Harsh Vardhan Thakur, a test pilot with Hindustan Aerospace, released an image of a twin-engine version of Tejas, identified as ORCA – an acronym for Omni-Role Combat aircraft. Subsequently, comments on the ORCA rendering were made by defenceupdate.in, and by ndtv.com. Having provided a couple of quick comments to @Hush_Kit on the ORCA image, I have been asked to provide an item for the blog.

Firstly, it is apparent that, as is normal with Tejas, the story is not as simple as at appears at first sight. In addition to ORCA, a concept for a twin-engine deck-based fighter (TEDBF) also exists, and if such a project were to proceed, ORCA would essentially be an air force variant, with lower weight, as, among other changes, the deck-landing capable undercarriage could be replaced with lighter landing gear. Neither of these variants relate to the existing air force or navy procurement plans, or directly to the development of the Advanced Medium Combat Aircraft (AMCA), a future Indian-developed stealthy fighter, although some technology developments for ORCA and TEDBF might provide risk reduction for AMCA.

Configuration Design

 The ORCA rendering shows a close-coupled canard using the Tejas wing planform with twin-engines. Dimensions, weights, engine-specifics are unstated, but the render shows a significant external weapons payload, and what appear to be conformal fuel tanks located on the upper shoulder of the fuselage, as in late-model F-16s.

Initial commentary by defenceupdate.in appears to assume the use of two GE F404 engines, rather than the more powerful F414 engines, and draws attention to the significant design changes that would be required to develop this configuration from the existing Tejas.

Subsequent commentary by ndtv.com provides significantly more detail, focussed primarily on the TEDBF variant. This indicates that TEDBF would be a significantly larger aircraft than Tejas, would feature wing fold and would use two GE F414 engines. These engines are stated (Janes All the Worlds Aircraft) to have a maximum take-off thrust of 22,000 lb (97.9 kN), compared to 18,000 lb (80 kN) for the GE F404 variant fitted to Tejas. The GE F414 is the engine for the F/A-18E/F Super Hornet, while the GE F404 is the powerplant of the F/A-18 ‘Classic’ Hornet.

The most startling aspect of the TEDBF discussion is the stated weight of the aircraft, which is quoted as 23 tonnes, compared to 13.5 tonnes for Tejas Mk1. As an indication, 23 tonnes is close to the max overload weight of the Typhoon, and similar to quoted maximum take-off weights for Rafale. So TEDBF is in no way the cheap and cheerful solution that might originally have been considered as an outcome of Tejas.

In addition, the TEDBF is expected to carry a significantly greater weapons payload than Tejas, stated to be 9 tonnes, and to have an integrated sensor and avionics suite including AESA radar, IRST, datalinks and sensor fusion.

Configuration comments

 On the whole, the illustrations available of TEDBF and ORCA appear credible as twin-engine evolutions of Tejas. However, there are some interesting differences between the designs, and some questionable features. Firstly, the ORCA rendering does not seem to allow sufficient fuselage width to accommodate two engines, noting that there will need to be a strong firewall between the two engines. For TEDBF, it would appear logical to use such a structure as the anchor point for the arrestor hook, but no hook is apparent in the illustrations.

The fuselage of TEDBF appears slightly longer than shown in the ORCA illustration, resulting in a slightly further forward position of the canard relative to the wing. Of course, this might result from the concept drawings representing as-yet unrefined designs, or perhaps related designs at different stages of concept definition. In my view, both ORCA and TEDBF would benefit from a fuselage plug to lengthen the aircraft and position the canards slightly further forward, so that they do not overlap the wing leading edge. I would expect this to improve the canard-wing aerodynamics and lift-dependent drag, as well as increasing fuselage fineness ratio, which should improve wave drag slightly, and provide additional volume for fuel or avionics.

Of course, the big unanswered question is whether the aircraft has GE F404 or F414 engines. I would assume the latter, given the quoted weights, and if so, the larger fan diameter, and airflow requirements for the engine are likely to require larger intake ducts than in the original Tejas.

Tejas: thoughts on an unusual wing here

Development Issues

 The ndtv.com commentary on the TEDBF quotes project sources as indicating a cheap and rapid development path exists, building on Tejas experience, and further suggests a development timescale of 6 years from go-ahead.

Let’s consider what would need to be done. Firstly, the propulsion system change will require substantial redesign of the fuselage, together with revision of the structure to accommodate the additional weight and size of the airframe. While some aspects (such as the wing) appear to re-use Tejas components, I suggest this is a superficial resemblance, since the use of a canard, rather than Leading-Edge Vortex Controllers (LEVCONs), will change the aircraft aerodynamics, stability and control and control laws. The significantly higher weight will result in increased loads and require redesign of the structure. Additionally, the landing gear will need to accommodate higher weights, and, presumably will be rearranged for the TEDBF so that the arrestor hook can take advantage of the engine-bay firewall as an attachment point.

To deliver the required operational flexibility and capability, a substantial weapons, sensors and avionics integration programme will be required. Much of this might piggyback on existing or planned integration work for Tejas and other platforms, but type-specific weapons integration, carriage and release programmes will also be required.

Should all this development work succeed, the operational TEDBF will emerge as an aircraft with the same size, weight, configuration and, perhaps, capability as the Rafale aircraft currently just being delivered to India. They would supplement the capability of that aircraft, and would have the imprimatur of being Indian designed and built. Could the ORCA variant then replace the SU-30 MKI? Perhaps, but this seems to be the intent for the Advanced Medium Combat Aircraft (AMCA) programme.

Where would ORCA sit compared to the AMCA? If that aircraft is to be stealthy, a further increment of technical difficulty is added in configuration design, manufacturing and propulsion and sensor integration. If the ultimate aim is for India to be able to design its own 5^th or even 6^th generation stealthy fighter, then the necessary confidence in aerodynamics, control system design, propulsion and system integration gained in a ORCA/TEDBF programme would de-risk at least some platform and system elements. But ORCA/TEDBF could at best be a reduced signature aircraft – more significant configuration changes would be needed to achieve a low signature outcome.

Notwithstanding some risk reduction for AMCA from ORCA/TEDBF, the challenges of materials, build standard, internal weapon and, integrated sensors, stealth system maintenance and operations planning of a 5^th or 6^th generation system would still remain as the step up to AMCA.”

Update here. 

We spoke to Tejas test pilot Harsh Vardhan Thakur who noted – ” These are (one of) many concept drawings. There are many more. Canards will not overlap with the main planes.” So perhaps caution should be exercised in reading too much into the artwork.

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