Advanced Medium Combat Aircraft (AMCA) at Aero India: Single or Twin Seat?

[arp2041]

This is the second post of a series on the AMCA based on my discussion with a high ranking official of the Aeronautical Development Agency (ADA), which is developing the aircraft, at Aero India 2013.

The first post focused on the stealth characteristics of the aircraft that ADA is confident will fly before the end of this decade.

Despite a near frozen design, ADA isn't yet sure whether the fifth generation aircraft is going to be a single or twin seater!

The scale model displayed at Aero India 2013 was certainly a single seater, like the scale models displayed earlier at Aero India 2011 and Aero India 2009.

A pamphlet distributed by ADA at the 2013 show made no mention of the number of aircrew.

However, an animation video displayed during the show mentioned that the aircraft would accommodate a "pilot associate to reduce pilot work load."

The IAF's preference for twin seat fighters is well known. The service believes that the complexity of the sensors and weapons suites fitted on modern fighters can optimally be managed by a crew of two, not one. The Su-30MKIs seat a Weapon System Operator (WSO), as would the Rafale MMRCAs to be inducted into the IAF.

With aerial refueling, modern fighters can stay airborne for as long as 7-10 hours, a duration that is too taxing for a one man crew.

ADA is pitching the AMCA to the IAF as a single seater, but is prepared to redesign in case of the unlikely scenario that the IAF sticks to its twin seater preference.

Usually fitting a second seat in a fighter aircraft results in no penalty other than reduced range, since space for the second seat is made by reducing fuel capacity. Aircraft combat performance remains unaffected.

n the case of a stealth fighter, fitting a second seat is more complicated. Though performance still remains unaffected, there is inevitably a change in the aircraft's stealth characteristic because of a change in RCS.

The RCS can be optimized for either single or twin seat configuration, with a single seater likely to be the stealthier design.

With good reason, the Raptor, Lightening 2 and the PAK-FA are all single seaters.

ADA acknowledges that a pilot AMCA may not be able to fly to the limit of its endurance, but rightly points out that rarely does a wartime mission require a pilot to fly more than a couple of hours. This is especially true of India whose potential enemies are its neighbors.

Under the circumstances, it makes little sense to dilute the stealth characteristics of the AMCA to accommodate a second crew, says ADA.

Advanced Medium Combat Aircraft (AMCA) at Aero India 2013: Single or Twin Seat?

 

[Backbencher]

Two minds are better than one !!

 

[arp2041]

Just to add the First Post of Mr. VK Thakur.........

Advanced Medium Combat Aircraft (AMCA) at Aero India 2013: Stealth Characteristics

The Aeronautical Development Agency (ADA) hasn't completely frozen the design of the Advance Medium Combat Aircraft (AMCA), but the design has matured to a stage where ADA expects to make only small tweaks.

The current design, displayed as a scale model at Aero India 2013, has been validated for its reduced IR and Radar signature at a DRDO facility in Jodhpur. The aerodynamic characteristics of the design have been checked out in wind tunnel.

ADA is confident that the first prototype of the AMCA will be flying before the end of the decade and I believe their optimism is justified.

This is the first of a series of articles on the AMCA based on my discussion with a high ranking ADA official linked to the project during Aero India 2013. The article focuses on the stealth characteristics of the design.

Upcoming posts will focus on the AMCA engine and discuss whether the aircraft will be a single or twin seater.

The AMCA design is optimized for reduced signature, not maximized stealth.

The aircraft is not shaped for all aspect stealth, like the US Raptor (F-22) or the Chinese Chengdu J-20. Instead, shaping is optimized to minimize frontal Radar Cross Section (RCS).

The AMCA blends stealth with maneuverability, while keeping costs affordable. It represents an affirmation of the design philosophy that guided the development of the the Lightning 2 (F-35) and the PAK-FA.

ADA has done all that is theoretically possible to reduce the radar signature from the front, as is the case with the Raptor, Lightening 2, J-20 and the PAK-FA. A head on air-to-air missile threat is the most potent because of the limited reaction time available to a pilot for evasive measures (chaff, flares) and maneuvers, with the threat closure rate being a sum of the velocity vectors of the hostile missile and the defending aircraft.

Frontal Low Observability(LO) will give the IRST equipped AMCA the ability to close in to within lethal range of enemy aircraft while avoiding detection.

The AMCA is not heavily optimized to evade radar detection from the side. It will rely more on evading and spoofing ground radars to avoid tracking as is the case with other contemporary stealth aircraft.

ADA has made little attempt to reduce the radar signature of the aircraft from the rear, relying almost entirely on a reduced IR signature instead. A reduced RCS from the rear is difficult to achieve without very advanced engine technology represented by shaped exhaust nozzles as in the case of the Raptor, or a compromise on performance.

An air-to-air missile threat from the rear is comparatively less potent than a head on threat because the pilot has more time to react, with the threat closure determined by the differential in the velocity vectors of the aircraft and missile.

Advanced Medium Combat Aircraft (AMCA) at Aero India 2013: Stealth Characteristics

 

[sancho]

IAF had preference for twin seaters only in the MKI, all other fighters come in the mix of more single seaters than twin seaters and that would be the same for AMCA.

 

[arp2041]

IAF had preference for twin seaters only in the MKI, all other fighters come in the mix of more single seaters than twin seaters and that would be the same for AMCA.

@sancho can you explain why IAF is not going for all twin seaters in case of say Rafale or FGFA or in future AMCA like they did in su-30mki, i though it was an IAF operational doctrine that preferred twin seaters over single seater?? Also you once said that air to ground operations in Libya were better performed by twin seaters Rafale & EF than single seater ones.

But in case of FGFA & AMCA, i think the reduction in stealth features with another pilot forced the IAF to go for single seaters.

 

[trident2010]

^^ Good to see that DRDO is not trying to make F-22 in one go. They are doing practical thing to go for reduced RCS rather than total stealth. It seems they have learned from the mistakes they made during LCA design phase. Bring the basic AMCA quickly and gradually introduce more advanced features with further upgrades.

 

[janon]

@sancho can you explain why IAF is not going for all twin seaters in case of say Rafale or FGFA or in future AMCA like they did in su-30mki, i though it was an IAF operational doctrine that preferred twin seaters over single seater?? Also you once said that air to ground operations in Libya were better performed by twin seaters Rafale & EF than single seater ones.

But in case of FGFA & AMCA, i think the reduction in stealth features with another pilot forced the IAF to go for single seaters.

Advances in electronics and sensor fusion will reduce the workload of pilots flying 5th gen fighters considerably. Hence it is not worth the compromise in stealth, and the cost of the additional pilots required.

 

[qwerrty]

Just to add the First Post of Mr. VK Thakur.........

Advanced Medium Combat Aircraft (AMCA) at Aero India 2013: Stealth Characteristics

The Aeronautical Development Agency (ADA) hasn't completely frozen the design of the Advance Medium Combat Aircraft (AMCA), but the design has matured to a stage where ADA expects to make only small tweaks...


Advanced Medium Combat Aircraft (AMCA) at Aero India 2013: Stealth Characteristics

good article without the usual hyper boasting..

 

[S-DUCT]

A conversation between BRFites & signature expert from ADE Sc 'D',near ADA stall.

On friday i visited the ADA stall. There was a youngish guy standing there by the model,I was clicking pictures and was discussing with my mates regarding the S duct and blocker and its differences etc he asked me if there was anything that i wanted to know. I was pleasantly surprised. He was the signature expert from ADE Sc 'D'. My first question was the target RCS for which he said "no numbers". I then asked him if he could tell me the umber of zeros before the decimal for which said "There are a few zeros and that's all i can say right now". I was almost jumping with joy. We then discussed about the RCS measurement tests the model went through at various places in the country. We both agreed that we definitely needed a closed full scale test chamber but he said the open field test was just as good with minor inaccuracies. He said the aerodynamic layout has more or less been frozen subject to minor changes. Then i asked him about the famous S duct, for which he said"we are not doing what the russians are doing" He also said the S duct in the AMCA would not just hide the compressor face but also have RAM coated interiors. At this point i asked him about the edge alignment and he said all that has been taken care of and he also said the vertical stab may see changes but not as dramatic as the PAK-FA stabs. Then asked him about the IR suppressors and as expected he agreed that the current plates are very heavy but very functional at the same time. He said work was on to reduce the weight and brig it to manageable limits. Then the most significant revelation in my opinion came when i asked him about the RAM. He said they have already got a few kinds of paints and have demonstrated it to the users on service aircrafts and he said the reduction was of the order of 15dB. When i pressed him further he said"no numbers, if you want something come meet me personally in my office". But the jingo in me was thoroughly satisfied with whatever i got and we exchanged cards. I'll probably meet him this week but may not be able to satisfy fellow rakshaks with the numbers. We had a discussion on the frequency bands but i don't think i can post it here. But from what i've got i believe this bird may be just as stealthy if not more than the T-50 and JSF. Regarding engines he said they are still finalizing and about the general avionics maybe we all know. Overall a very intellectually satisfying conversation.
Cheers!

Credit:raghuk BRF

 

[Abingdonboy]

I think single seat is all but assured on the AMCA.

 

[Backbencher]

I think single seat is all but assured on the AMCA.

Since you possess a lot of knowledge about aircrafts therefore i wanted to ask this question from quite a while now !!
What advantage and disadvantage does a single seater offers over a double one and vice versa .
@sancho :- Sir your views are also more than welcomed !!

 

[Abingdonboy]

Since you possess a lot of knowledge about aircrafts therefore i wanted to ask this question from quite a while now !!
What advantage and disadvantage does a single seater offers over a double one and vice versa .
@sancho :- Sir your views are also more than welcomed !!

Well like the article says, the IAF has a certain preference to twin seat fighter particularly for its air-dominance fighters and strike a/c. Advantages are that the pilot's workload on a 2 seater is inherently less- on a long flight the pilot and WSO can share flying whilst the other is resting. In combat the pilot can concentrate on positioning the fighter in the right place and the WSO can concentrate on weapon's firing (BVR) or targeting and striking ground targeting. Additionally a twin-seater can act as a command and control/mini-AWACS platform for other single seat fighters. The most prominet example of this is the USN and their F-18 SHs wherein a strike group will consist mostly of single seat "E" fighters but with 1-2 twin seat "F" fighters who will act as C&C platforms for the entire strike group and will assit the single seat fighters in correctly targeting their strikes. The IN has followed this model with their mix of MIG-29Ks (single seat) and KUBs (twin seats).


Disadvantages are as noted- less range as as a result of the additional seat there is less space for internal fuel storage on the fighter.

And for stealth fighters there is a certain RCS penalty for an additional seat it is said.


In 5th gen fighters these days it is said that the need for an additional fighter is crew-member as the on board mission computers are so advanced and the pilot interface so comprehensive. The computers are now said to be able to act as a "virtual-WSO" in 5th gen fighter. It is not for me to pass judgement on how correct this assessment is however given the F-35 and F-22 have no twin seat variants it seems the leading a/c Giants are very much of this theory.


It remains to be seen whether the IAF really will insist on a twin seat PAK-FA variant.

 

[arp2041]

Since you possess a lot of knowledge about aircrafts therefore i wanted to ask this question from quite a while now !!
What advantage and disadvantage does a single seater offers over a double one and vice versa .
@sancho :- Sir your views are also more than welcomed !!

Single seater fighters offers more stealth features than the twin seater ones as less surface is exposed than the twin seater one but the work of the only pilot becomes a tough job b'coz the same pilot is responsible for everything i.e. flying ac, launching air to air, air to ground missiles with accuracy, Air to air refuelling, etc. This pressure at the time of war becomes very intense for a single pilot.

whereas in twin seaters the work load gets equally divided b/w the two where one pilot flies the bird while another is responsible for launching missiles, but again this comes at a cost, & the cost is of reduction in stealth features with more expose of the surface.

IAF has an Operational doctrine which calls for a second pilot (like in case of sukhois) so that there is a better visibility of combat radius & better fighting capability, but i think not willing to compromise on stealth features, IAF is ready to go for single seaters in case of FGFA & AMCA.

 

[sancho]

@sancho can you explain why IAF is not going for all twin seaters in case of say Rafale or FGFA or in future AMCA like they did in su-30mki, i though it was an IAF operational doctrine that preferred twin seaters over single seater?? Also you once said that air to ground operations in Libya were better performed by twin seaters Rafale & EF than single seater ones.

But in case of FGFA & AMCA, i think the reduction in stealth features with another pilot forced the IAF to go for single seaters.

It was, but mainly because of the air superiority role of MKI. In long endurance CAP roles for example (reportedly up to 10hs), having 2 pilots is obviously better than having only one pilot, that needs to be concentrated for so long.
And as I told you, even most modern fighters with latest avionics and reduced workload, benefit from a WSO in the strike role. That's why the French have high twin seater numbers, that's why Israeli Sufas are completely twin seaters and why they even wanted a twin seat version of the F35 initially.
FGFA was meant for the same roles as MKI does today, therefor IAF initially had a twin seat version in mind as well, but that sadly seems to different now, imo possibly because of cost reasons.
Interceptors like Mig 21s, LCA, Mig 29s on the other hand, will not fly such long hour missions, are often even used to be scrambled only if needed, which makes twin seaters for the A2A roles less important and why these types have more single seaters too.
The difference from our doctrine to Russian forces for example is, that MKI and FGFA were meant to offer a balanced multi role performance, for A2A and A2G as well, while Russia aims on different version for different roles (single seat Su 35 for A2A and twin seat Su 34 for A2G, although both are multi role fighters too).

Since you possess a lot of knowledge about aircrafts therefore i wanted to ask this question from quite a while now !!
What advantage and disadvantage does a single seater offers over a double one and vice versa .
@sancho :- Sir your views are also more than welcomed !!

I guess I answered it with the post above.

 

[sancho]

Additionally a twin-seater can act as a command and control/mini-AWACS platform for other single seat fighters.

That actually has nothing to do with single or twin seaters, but with the capability of a fighter to gather long range radar data and divert them to other allied fighters via datalink. A single seat F22 flying in front of a batch of F15s for example could act as a mini awacs as well, by using it's radar and diverting the data to the F15s, which can remain passive then.

The most prominet example of this is the USN and their F-18 SHs wherein a strike group will consist mostly of single seat "E" fighters but with 1-2 twin seat "F" fighters who will act as C&C platforms for the entire strike group and will assit the single seat fighters in correctly targeting their strikes.

I don't think that's correct either, when you look at the mix of squads in the USN, you will see, that they have dedicated single seat and twin seat squadrons, almost in the same number:

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