limb wrote:But lmfs I think said something counts as supercruise only if its 1.8m+ like the F-22. Su-57 allegedly will only be able to achieve 1.6m with izd.30, and currently its below that.
When the 5th gen fighters (that is F-22) appeared, the term supercruise was coined, it referred to being capable of flying faster than 1.5 M on military thrust. There are and have been other planes capable of flying faster than 1 M on mil thrust, but what would be the use of doing that, unless the increase in speed is substantial? Using much more fuel and even AB to go through the transonic region to fly say 1.1 or 1.2 M instead of 0.9 does not make much sense. Both in US and USSR keeping high energy state on mil power was considered very
advantageous when 5th gen air superiority fighters were conceived and therefore corresponding engines and air vehicles were developed to allow for cruising speeds way higher than 1 M, not for a marginal "supercruise" capability as it has come to be used today as a catch word in order to make the own plane look like 5th gen. So in strict sense supercruising is > 1.5 M, in broad sense it is > 1 M but I consider this an improper use of the term.
IMO, for the Russians it would make sense for the Su-57 to fly as fast or faster than the F-22. Why?
> Because the importance of high and fast cruise flight is clear reading Russian experts, designers and military commanders for many years, as it is when analysing kinematics of launching and outrunning missiles.
> The intakes of the Su-57 are notably bigger than those of the F-22, and they are adjustable, needed for flight speeds between 2 < M < 3. Pressure recovery of fixed intakes is not really good approaching 2 M. That should mean more air should be available to the engine at high altitude and speed.
> Marchukov has repeatedly said the izd. 30 will have the highest specific thrust (or thrust per airflow unit) of any comparable engine, that means more than even the F119, which is the paradigm in that regard. The Su-57 has radar blockers, which detract from the intake performance, while F-22 has fixed intakes with S-duct and flat nozzle... my understanding is that F119 should lose more power due to all those factors than the izd. 30. Considering airframe / engine sizes and intake size and performance and therefore expected airflows it is logical to expect that izd. 30 will produce more thrust than F119 in mil settings on installed conditions. Considering similar size / cross sectional area of the planes and very apparent area ruling of the Sukhoi / explicit patent mentions to optimized supersonic performance, this should result in comparable cruising speeds, I actually think it will be faster than the F-22 but I cannot prove it.
Those figures about cruising speed 1.6 M with izd. 30 make no sense to me (why would it be slower than the F-22 if it has substantially more thrust?) and about the speed with current engine, I have seen no reliable source giving a figure.
What are the reasons that the Su-57 with the current engines can't supercruise when it has a higher T/W ratio than the F-22, due to it being lighter due to no S-Ducts?
Supercruising means that what counts is not maximum thrust but thrust in dry settings
at the operational conditions. We cannot exactly know the thrust reduction of US and Russian engines while cruising in altitude compared to spec values which are given in uninstalled conditions, but of course an engine like the F119 which is essentially a turbojet (bypass ratio is only 0.3:1) with very high dry thrust (ca. 11.7 tf from what we know) is head and shoulders above any AL-31F derived engine with way higher BPR (0.57:1 IIRC) and way lower dry thrust (9-9.5 for izd. 117). On top of that, it needs to be considered that the higher the BPR, the lesser the propulsive efficiency at thigh speeds. Supercruising engines are either turbojets or turbofans of low BPR or VCEs. In fact designing VCEs was at the core of designing the 5th gen planes, both US and USSR worked very hard on that and had their engines ready many years ago, but the fall of the USSR allowed US to go with a lower risk option, the F119.
miketheterrible wrote:It can super cruise. Su-35 can and uses same engines.
They don't use the same engines, the 117S has way worse parameters compared to 117. 8.8 tf dry / 14 tf wet (14.5 tf in special mode) vs 9-9.5 tf dry / 15 tf wet. Also the weight of the 117 is way lower
(>200 kg IIRC). Both Su-57 and Su-35 can marginally supercruise today, but that falls short from the intended goal and therefore Russian military decided to develop the izd. 30.
Isos wrote:I wonder what are the drawbacks of supercruising and if it's worth it.
Flying high and fast is equivalent to having high ground on a land battle, it allows you to hit the enemy while the enemy cannot hit back at you. It is the kind of unfair advantage everyone wants to count on when battling...