I am curious as to why Russian fifth gen and AMCA mk1 lack EOTS?
Is it so sophisticated to make or something else at play?
Wont the circular IRST return radar waves at all sides so why put IRST in a stealth fighter specially circular cause the turks are using hexagonal(? Don't know the shape exactly)
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Take each ray as a specific case so won't there be an angle at which there would be significant reflection?
About AMCA MK-1 lacking EOTs, my knowledge about that is limited but from what I have seen in the most recent wind tunnel model of AMCA, we definitely don't see any sort of EOTS like sensor like the one found on the F-35, rather we see a conventional design IRST style sensor on the wind tunnel model of AMCA like that found on planes like Su-57, Su-30, Su-35, Rafale, Eurofighter etc. Maybe in near future they might further increment the design so as to add something like a Stealthy EOTS found on the F-35, this is something I hope to see happen from the side of the AMCA design team. On the part about EOTS then I remember correctly that DRDO's IRDE was working on an EOTS type sensor. If timeline of the completion of development of this sensor and AMCA clash together than the chances are very high that we might finally see an EOTS on the final design of AMCA.
Here is a computer representation of DRDO's EOTS on AMCA, you can search up on google for the same, you will get a lot more useful information about the same.
Now I would want to speak about the Su-57 and why I think it's history with the IAF might answer whether AMCA MK-1 will have an EOTS sensor or not. I will be going really brief on this part cause this thread is about the Su-75 and not about AMCA or Su-57 but yeah I will start. One of the reasons that India had dropped out of the FGFA program in 2018 was because of the poor Stealth characteristics of T-50's design (FGFA was supposed to be an Indian modification of Su-57 tailored for Indian requirements like how was done with Su-30MKI), now we call it as Su-57 though. So Su-57 at the time had a conventional IRST sensor near the cockpit window on upper side of the aircraft's nose, it still has that till now as seen with Su-57 in service with RuAF. I think because of this design, Su-57's stealth characteristics had been worsened to the point that Indian Airforce didn't have any more interest in it anymore. I don't think the IAF wants to repeat that very same mistake with AMCA by letting it have that same less stealthy design of IRST, IAF would rather want the better and more Stealthly EOTS on AMCA. Also as we have seen with various new Stealth fighters in service already around the world, and ones which have recently rolled out (I speak of Turkish TAI FX in this regard) then we observe that all them have EOTS style design on them.
Take the example of TAI-FX, it itself has a EOTS sensor over its nose, in the same place where old conventional IRST sensors would be found, only a bit more centred as to allow better alignment with the aircraft's frame and better stealth characteristics as a whole. On the F-35 it is below the nose but the shape of the sensor as to my knowledge and observation is like the same as that of the F-35.
Now let us take another example, the J-20 in service with China's PLAAF. It too has the inclusion of the EOTS on it, similar to the one on the F-35. The design is almost identical in the case is J-20 and F-35 though with reference to EOTS.
So I think that we can safely assume that this type of EOTS design would be the standard ones on any upcoming stealth plane and therefore AMCA MK-1 or MK-2 will have it but I have listed my reasons as to why AMCA MK-1 would have the EOTS type of sensor on it, whether we go with the conventional IRST design or not, that is upto the designers provided they want to compromised Stealth characteristics for something, they know better than us.
Now ask why Russian fifth generation planes lack EOTS, I don't know if you are asking about Su-57, Su-75 or both but as far as Su-75 is concerned then it is having an EOTS on it's underside. I will attach a picture and show you. Look closely at the mockup, the EOTS has been marked.
Therefore Su-75 will have an EOTS sensor.
Now speaking about why Su-57 does not have EOTS, well I don't know, maybe the Russians thought that a conventional IRST was cheaper to develop, produce and maintain? That their air combat philosophy was such that they could do with a little compromise on stealth? I don't know the exact answer to this sorry.
