One of the main features of the fifth generation aircraft is the "stealth" technology (from the English. Stealth - secretly, stealthily), i.e. property to go unnoticed for enemy aircraft radars, as well as ground installations. At least, this is claimed in the United States, which has two such fighters in service - Lockheed / Boeing F-22 Raptor and Lockheed Martin F-35 Lightning II. Also, the countries that have developed fifth-generation aircraft today include Russia with the Su-57 being tested and China with the J-20 Chengdu.
Two other signs of the fifth generation are called super-maneuverability and cruising supersonic, but the Americans on their F-35 fighters refused super-maneuverability, replacing it with “stealth”, and there is no cruising supersonic on the F-35, which turned out to be very harmful for expensive coverage. In the absence of these two important criteria, the Americans still call their fighter a new generation. In turn, the F-22, which is the most expensive fighter in the world, has supersonic sound without afterburner, powerful avionics, low visibility, but inferior in maneuverability to many Russian fighters of even the fourth generation.
Bet on stealth is like a mistake
Note that stealth technology is based on reducing visibility in the radar and infrared ranges, which are achieved due to the special coating, the specific shape and materials of the manufacture of the aircraft body.
The stealth technology itself is super expensive. In 2019, the U.S. Government Accountability Office issued a report that said the cost of repairing F-35 fighters was significantly exceeded due to peeling of expensive coating. The same problem was identified with the F-22 fighter.
Another problem, in addition to coverage, is that fighters built using stealth technology are designed to solve a very narrow range of tasks, i.e. their use is possible only in a very narrow combat range. Such a fighter can carry weapons only in the internal compartments, since placing it on an external sling immediately removes it from the "invisible" category. The fighter is limited in speed (peeling off the coating at supersonic sound) and must use its radar with caution, since its radiation is easily detected by the radars of enemy aircraft or ground-based air defense systems. You cannot make serious changes to the design of the aircraft, this will also disrupt its disguise.
On the other hand, the rapid development of air defense systems, and in particular radars, led to the fact that the so-called "stealth fighters" are clearly visible, whatever the US military would say. This is especially true for the F-35, which in terms of the effective scattering area (EPR) is much worse than the F-22. The American fighter can see radar S-400, and, accordingly, the promising S-500.
The same can be said about the onboard radar of Russian aircraft. For example, in 2018, Su-30MKI fighters with a Bars phased array antenna H011 radar, which are armed with the Indian Air Force, discovered the so-called Chinese Air Force Chehgdu J-20 invisibles. In the same 2018, the Russian Su-35S fighter photographed an American F-22 in the sky of Syria. Then the American media said that the Raptor is invisible in the infrared "only at a considerable distance", and it is clearly visible near it.
What is the result?
The question arises: is it really necessary to invest huge amounts of money in the development of a fighter called "invisible", but perfectly visible, despite the fact that its combat range is limited by this stealth. Or it’s better to invest in fighters of the previous, fourth generation, which have powerful weapons, over-maneuverability, over-sound, even elements of stealth, but which are not “stealth aircraft”. The use of modern electronic warfare systems with radar suppression on such fighters makes these vehicles as inconspicuous as fifth-generation fighters, without losing other qualities.
As for the fifth-generation Russian fighter Su-57, created using the stealth technology, it will fully comply with the new generation after receiving the engines of the second stage, allowing it to develop after-supersonic speed. At the same time, the fighter already has excellent maneuverability both vertically and horizontally at all speeds. The aircraft is spacious weapons a compartment that allows you to carry a much more "heavy" weapon than the F-35.
However, we can fully judge the Su-57 only after it has been put into service and all the characteristics of the aircraft have been published.