It has been consistently questioned by vikasrehman that if Gripen-C has a top speed of mach 2 using that F404 variant that has only 2 kN higher wet thrust than Tejas’ F2J3, then why does Tejas has a performance shortfall.

It must be clarified once again that Tejas’ non-peak performance at sea-level was found unsatisfactory; the dry thrust of the F2J3 engines is used for this purpose. As repeatedly mentioned earlier, the F2J3 has a dry thrust of only 48 kN, as compared to 54 kN of Gripen-C’s RM12 engine. This 12% lesser thrust is ‘solely’ responsible for the Tejas’ low non-peak performance at sea-level at Arakkonam.

The peak performance of other fighters of the same weight category i.e. T-50 and JF-17 are very similar to Tejas’ current performance, and hence, by other foreign examples as evidence, the Tejas’ design is not in doubt.

Yet, as per media reports, the IAF emphasizes on the wet thrust of the engine it is seeking and not the dry thrust. It is because it is a convention to refer to engine performances by max. wet thrusts only; this may not under emphasize the need for a higher dry thrust from the existing 48 kN.

However, the question may remain as to why Tejas is yet to match the Gripen-C in peak level performance i.e. mach >1.8 and 9Gs. The only viable explanation of the above is that Tejas’ envelop has not yet been expanded to these levels, and to accelerate the process, consultancy from Boeing is being sought. I may reiterate again, that if and only if Tejas fails to reach mach 1.8 on the current engines, then only “doubts may be cast” on Tejas’ design.

In my personal opinion only, the intakes of the J-10 may appear as aerodynamically “wayward”, and thus aesthetically “unappealing”, again in the aerodynamic sense.

The intakes of the J-10 may be compared with those of the F-16. The following are two photos of the said fighter planes taken from a similar angle and motion :

It may be subjectively observed that the intakes of J-10 appear to be “hanging” from “tethers”, and that the intake is “jabbed” into the fuselage at an angle. The latter may be more pronounced as seen in this photo .

In contrast, the F-16’s intake is a more “aesthetic” merger with the fuselage, and which also appears aerodynamically aesthetically “appealing”.

However, in my opinion the most aerodynamically “attractive” intakes may be those of the JF-17, when looked at frontally as seen in this photo.

I may also personally disagree with the opinion that Tejas’ wings are “wrong”. In fact, in flight, the Tejas’ wings may add significantly to it’s ‘allure’ as shown in the following photos :

Few well known ones is below of 3 Tejas units in formation :

It must be noted that only the empty-weight, top speed and g-limits of fighters having the same empty-weight as the Tejas are being presented, so as to establish that there are NO “thrust problems” with Tejas, as distortedly reported by the media.

It was deduced that there is no weight gain from 8,000 to 10,000 kgs, because other fighters having same empty-weight as Tejas like Gripen-C, T-50 and JF-17 also have a take-off weight of ~9000 kgs in the clean-config.

A simple comparison of Tejas’ peak performance of mach 1.6 and 6 Gs showed that it is again similar to that of the T-50 as well as the JF-17. It was observed that this performance of T-50 is acceptable as it’s only a trainer, whereas for the JF-17, a new engine will be required unless the PAF finds M 1.6 and 8.5 g acceptable.
Thus, it was noted that as fighter weights reached the limit of 6,400 kgs they all have such low peak-performance, and hence a change to a more powerful engine from older F404 types is needed at this stage. The Gripen’s case was a prime example, which was installed with a more powerful RM-12 engine since the design stage itself.

As regards the Gripen-C, though it’s top speed is of the order of mach 2, it is not comparable with Tejas yet, because Tejas’ flight-envelop has not yet been expanded to that level. However, discussed earlier, the IAF has objections over sea-level thrust performance, which is due to the 48 kN F2J3 engine. This may be compared with the 12% higher thrust of RM-12 engine of the Gripen-C (54 kN). Thus, leaving aside sea-level performance, the Tejas should be able to reach M 1.8 with the older F2J3 engines of 78 kN wet thrust itself, so as to match the Gripen-C’s performance with it’s RM-12 engine of 80.5 kN thrust. If it does not, then and only then it may be concluded that Tejas suffers from high drag or other design flaws.

Have a look at the detailed specs page ive listed above and do a comparison with the T-50 (if you must) taking the performance, range, weapons and avionics. And if you still believe JF-17 is equivalent to T-50, good luck to you and i have nothing more to add to this conversation.

The above is inaccurate. The differences in speed and g-limits respectively between the JF-17 and T-50 is 0.2 mach and 0.5 g only. The difference in max. external payload is 700 kgs only. However, difference in range is significant at 1,000 kms.

Both are ~80 kN in full AB, when the Gripen C has the better drag-thrust ratio compared to the Tejas. You compare dry with wet thrust and do use wrong values of both too.

Sens, I reiterate that the focus of IAF’s objections were due to the lack of dry thrust at sea-level trials at Arakkonam. The current F404-F2J3 has a dry installed thrust of 48 kN,a s compared to 54 kN of the RM12 engine of Gripen.

As per the official website of General Electric, the max. wet thrust of the F2J3 type is 78.8 kN, whereas that of the RM-12 is 80.5 kN, which is only 2 kN difference (other websites stated 81 kN for RM-12).

As mentioned earlier, the Tejas’ performance must have matched that of the Gripen-C at high altitudes as the empty-weights and wet thrusts respectively are almost equal.

Kaduna2003, all fighter planes developed since 1970s till date (with either hydraulic or FBW controls) have a minimum requirement of 9 G, except the T-50 trainer and JF-17. Thus, the minimum global standard is missed in these 2 planes. Anyway, regardless of whether the JF-17 is restricted to not exceed 8.5 G, by the FBW or otherwise, it is due to a structural limitation only.

This limitation could be due to low powered engine thrust of the JF-17, which already does not exceed mach 1.6. It is close to T-50’s specification of mach 1.4 and 8G limit.

References :-

1) GE-F404 F2J3 (based on GE-F404 402)

2) RM-12

As per the following news report persons associated with the PAK-FA and former Air Chief S Krishnaswamy have questioned India’s role in the PAK-FA project.

India’s role in Sukhoi project questioned

Price, investment for fighter jet still being discussed; design specs have been decided, first flight slated for 2009
K. Raghu

Bangalore: India is yet to begin work on a futuristic technology demonstrator plane, a single-seat, fifth-generation fighter it is jointly developing with Russia’s Sukhoi Design Bureau, that will take to the skies for the first time in 2009.
Some analysts are questioning the contribution of Indian aerospace research and development (R&D) engineers to the programme, given that the aircraft’s design specifications have already been decided and the first flight is set for next year.

In October, India and Russia signed an agreement for the joint development and production of the fifth-generation fighter aircraft, or FGFA, making a commitment to sharing resources and work equally. A team of officials from Hindustan Aeronautics Ltd, or HAL, the country’s military plane maker, was in Moscow in late May for discussions on the estimated $4 billion, or Rs17,160 crore, project.
“We are (still) talking about the price and investment costs,” said one person familiar with the development who did not want to be named because of the sensitive nature of the project. “(Also) the more we delay, the less work we will get. That is a fact.”
The fighter plane will havea so-called swept-forward wing—which increases an aircraft’s agility and gives it the stealth feature to reduce risk of detection by radar. The (technology demonstrator) aircraft being built by Sukhoi will use the engines, systems and avionics of the previous generation Su-30 plane.
“If something is going to come in one year, where could we have participation?” asked former air chief marshal S. Krishnaswamy. “That actually has a negative impact onour own R&D people and laboratories.”
Another former Indian Air Force (IAF) official, air marshal B.K. Pandey, said, “If the prototype is already decided, there is nothing original that Indian aerospace industry can contribute to the programme.”
A person familiar with the programme’s development said India would bring in its expertise in carbon-composite technology used in HAL’s Dhruv advanced light helicopter and Tejas light combat aircraft, both of which are homegrown programmes.
Russian, Indian firms will make an equal number of planes during the development phase
Once the technology demonstrator flies next year, Russia will work on developing more than six two-seater prototypes of the stealth fighter. Indian engineers will contribute to the design of the front fuselage, build composites for better stealth features and work on avionics.
“Once the front fuselage undergoes a change (to accommodate two pilots instead of one as in the technology demonstrator), the aircraft lift conditions will change, wings will change. This is where our learning will become useful,” said the person familiar with the development.
The new aircraft would be nearly a third lighter than the Su-30 and be able to fly longer than conventional fighters, besides possessing the stealth features. The aircraft is expected to be ready for induction in the Indian and Russian air forces by 2018.
HAL has in the past produced, under licence, Russian aircraft such as the MiG 21, which forms the bulk of the IAF’s strike fighter fleet. IAF also has in its inventory the Su-30 MkI, the India variant of the fourth-generation Russian fighter with avionics built by an India-led team which HAL will make under licence in the country.
The new Indo-Russian fighter is being designed to carry weapons in its fuselage, making it similar to the Joint Strike Fighter of the US.
While the components and systems would be built equally at the Komsomolsk-na-Amure Aircraft Production Association in Russia and HAL facilities in India, the engines would be made at a factory of NPO Saturn, the Russian engine maker. Both plane makers would build an equal number of aircraft during the development phase.
[color=”red”]“Why did Russia want India to join (the programme)? Because they want money, they want (the) market,” said Pandey, a former head of IAF’s training command in Bangalore.“If we can get transfer of technology, HAL (will be) assembling the aircraft, then IAF has to buy the planes. So, they have an assured market”.[/color]
A majority of the planes in the IAF’s fleet are of Russian origin, with the rest from the UK and France. Although indigenous military plane programmes have been undertaken by the Defence Research and Development Organisation, or DRDO, and HAL, the Armed Forces remain dependent on imports.
India has floated a global tender to buy 126 multi-role combat aircraft that could cost a minimum of Rs42,000 crore, evoking the interest of aerospace companies such as Lockeed Martin Corp. and Boeing Co. of the US. It also plans to buy nearly 250 light- and medium-weight helicopters.
The Tejas fighter, conceived as a replacement for the ageing Russian-built MiG 21, is at least two years behind certification as it needs to achieve the so-called air staff requirements, or ASR, the standards set by IAF before induction. The military plane unit of Boeing has been asked to assist the Aeronautical Development Agency in certification of the LCA by 2010.
DRDO is now scouting for a foreign partner to build an engine for the Tejas fighter, after its unit Gas Turbine and Research Establishment failed to deliver the Kaveri engine even after nearly two decades of development.

Reference :-

http://www.livemint.com/2008/06/17233919/India8217s-role-in-Sukhoi-p.html