agree with you
but i'm talking about 3D TVC with rectangular nozzle,,i think it's impossible..!
It is certainly not easy, but I wouldn't say impossible. A round nozzle is made up of petals that intermesh so there are no gaps when it opens out wide or closes in to a small tight hole (called convergent/divergent nozzle). There is no reason why a rectangular nozzle could not be made the same way so that the nozzle remains a four sided shape but that the sides of the nozzle can change size.
If you think about a rectangle and you shorten it on one side and extend it on the other opposite side you are basically moving the nozzle to one side from where it was. Doing it back the other way and you have 2D thrust vectoring. Being able to adjust it vertically at the same time is mechanically tricky but I wouldn't say impossible.
You could take it a step further and start from a round nozzle and say that it really isn't actually round because each of the petals are flat so instead of aligning the petals to form a round nozzle you could alter their angle and make the nozzle a geometric shape like a 10 sided shape, or an octagon (8 sided), or a Hexagon (6 sided) or a pentagon (5 sides). With the flat sides you might be able to get the RCS reduction and IR reduction without having to go to rectangular nozzles. You might actually find that triangular nozzles (3 sides) is actually even better than 4 for RCS and IR reduction and 3D vectoring might be easier with three sides.
so why russians leave RCS benefits??
i think russians alredy reduce RCS by making astealthy shape and composite materials to the pak fa,but round nozzle still increase RCS...
i think it's not necessary,,f35(5th gen.) althogh has round nozzle and low maneuverity than pak fa !!
I don't think they will spend billions of dollars on it, but if they can solve the problems having 3D TVC that is stealthy in radar and IR wavebands is something they want.
Think of a sniper in a ghillie suit with a bright shiny stainless steel rifle and scope. All the effort and disguising the shape and signature of the sniper is ruined because the same effort applied to the man wasn't applied to his kit.
There are shortcuts... weapons are carried internally because it is cheaper and simpler than making all the weapons stealthy.
The exposed area of the engines that make them look like the engine installation on the Flanker series suggests there is work left to be done at the rear of the aircraft. The fact that the engines are widely separated and angled outwards suggests first they wanted large internal weapon bays, but also that they wanted increased angle of momentum for TVC engines. By putting the engines further apart they increase the separation of the nozzles so when one nozzle is deflected up and one is deflected down it generates more rotational force on the aircraft. It is like a corkscrew. The wider the handle the less force you have to apply to the ends of the handle to turn it. If the handle was 1mm long the leverage would be tiny and it would be easier to twist the cork off with your bare hands. If the handle was 5-10cm it is easier to grip but the leverage means even the toughest cork can be defeated.
so,you mean russian will produce rec. nozzles in the first patch of pak fa??
I don't know. I would expect they would find 2D rectangular nozzles fairly straight forward because the issue of materials for diverting exhaust flow even in AB have been mastered in the Yak-41 and also in the engines for the Mig-29OVT and Su-30MKI and Su-30MKM and the Su-35 and Su-37.
Remember the main engine of the Yak-41 is in the 18-20 ton thrust class so it is a very powerful engine.
at your view: what are yoiu prefer:
# 2D TVC thrust with rec.nozzles(benefits here low RCS and low IR signature)...
#3D TVC thrust with round nozzles(benefits here high maneuver against enemy missiles plus more speed)..
It doesn't matter what sort of TVC you have... dodging missiles requires excellent awareness of the incoming missile and really doesn't rely on a high g turn... when you turn 120 degrees in a cobra you basically stop in mid air, you don't suddenly start heading backwards at the same speed you were moving forwards at. You basically stall.
That was bad without TVC because you have no control till you get your aircraft flying nose forward and have air flowing over the wings and tail control surfaces so you can manoeuvre your aircraft.
With TVC you can use engine thrust to continue to point your nose where you want and continue fighting so to speak and you can manouver your nose down... accelerate and then fly away from the area whereas without TVC you have to just wait till your nose falls and you can accelerate and regain control.
Most of the weapons of an aircraft are still optimised to face forward. If you can't turn your nose at a target and fire your missiles then you are a spectator not a fighter.
Without TVC when you stall you are useless.
With TVC you might choose to enter a stall to suddenly change direction or to directly fire at a newly appeared target... it becomes just another tactic option.
Regarding your question ideally as a pilot you want to see them and have them not see you so giving up some manoeuvre capability for Stealth actually makes sense. 2D TVC is still TVC so you can do all those fancy post stall manoeuvres. Whether you have 3D or 2D is really only important to your flight control system which is doing all the work. For the pilot it makes some manoeuvres harder... you might need to roll the aircraft a bit before you can turn a particular way, but remember at normal speed you have all the flight control surfaces plus thrust vector control and also engine differential control as well to manoeuvre the aircraft.
At the end of the day if you see him and can shoot first you have an enormous advantage and the best chance of a kill, so I would take 2D thrust vectoring nozzles of lower RCS and IR signature over 2D thrust vectoring nozzles of higher RCS and IR signature.
is there any other techniqes to reduce ir signature of the engine ..instead of using rectangular nozzles????
sorry for language..
There are some exotic technologies I have seen mentioned where chemicals are sprayed into the engine exhausts... most of them refer to the B-2 bomber... being a large aircraft with room for that sort of thing.
In practical terms I know of two options... the obvious is to use a higher bypass turbofan. A turbojet engine is basically a tube with a shaft or several shafts down the centre linked together with fans on them... a big fan at the front to suck in cold air and in the middle where the tube narrows there are smaller higher temperature fans (where it narrows it compresses the air which heats it up... this is the high pressure or hot section... also known as the combustion chamber... where fuel is added and burned to heat it further) Then at the rear the tube widens to allow the hot air to expand and sometimes more fuel is sprayed here where it is called an Afterburner or reheat. A turbofan is like a big tube around this turbojet and the shaft from the hot section is connected to a bigger front fan that sucks air into the turbojet engine but also through the outer tube the air going through the outer tube is cold but also very dense so you get more thrust from it than from the thinner faster air through the turbojet. The air going through the outer tube is bypassing the hot thinner air going through the turbojet inner tube so it is called bypass air and when it comes out the rear of the engine because it is relatively cold it mixes with the turbojet air and speeds up cooling. Look at the engines hanging off a Boeing and you will see the big wide short fan at the front that is the bypass section and sticking out the back is the hot turbojet engine... this is a very high bypass engine that generates most of its thrust from the bypass air. The turbojet is just there to turn the big fan that blows a large volume of air.
These engines can have enormous thrust ratings but the thrust they generate is from enormous amounts of cold air not moving at high supersonic speed so the aircraft that use these engines can't fly past the speed of sound. For a military aircraft a turbofan engine is very good because all that bypass air is oxygen rich so the afterburner or reheat can be much more effective at generating thrust than with a standard turbojet.
The problem is that while a high bypass turbofan has a much lower IR signature than a low bypass turbofan or turbojet if you want to supercruise then you need very high exhaust velocities and you only get that from a turbojet or low bypass turbofan.
The best compromise would be a variable cycle high/low bypass turbofan where high bypass could be used for more efficient subsonic flight with low IR signature, but when supercruise or supersonic flight is needed it can operate in a low bypass mode as well.
The other method of reducing IR signature was using an armoured nozzle inside the exhaust nozzle as used on the Su-25 CAS aircraft. This conceals the rear of the engine hot section from view and it can be partially cooled by bypass air, but I rather doubt it could be used on a stealth fighter simply because it might make an afterburner impossible.
Obviously the talk about S shaped intakes so a radar can't see the front of the fan blades of the engine directly also apply to the rear having a big long snake like 3D rectangular engine nozzle might further improve IR signature.
China Clones, Sells Russian Fighter Jets
These reports come out on a regular basis, the thing is that the Russians have moved on. The aircraft they sold China were basically not much different from the Su-27SM. Certainly more advanced than the Su-27 base model, but also not Su-30MKIs either.
As long as Russia can stay a generation ahead I see no real problem.
The Chinese are trying to master and copy Russian material of a generation Russia probably can't sell now anyway. No one seems to be interested in buying Su-27SMs or Mig-29SMTs any more.
The Suggestion that China will suddenly steal all of Russias remaining markets is amusing to say the least. Russia has the problem that it has lost the market of the former soviet republics to a degree and eastern europe as well. Of the other Soviet customers few have much money and were better considered donor clients that accepted Soviet Aide. Russia has worked to cultivate new export opportunities and will continue to do so, but the idea that China will replace them seems a stretch when China continues to buy RD-93 engines for aircraft it exports to Pakistan. The RD-93 is an RD-33 with its gearbox shifted from the top to the bottom to suit the aircraft it is to be installed in. If they can't copy a jet engine from the 1980s then what chance of improving on it?
The reality is that China as an enormous population and labour is plentiful and cheap but most high tech stuff are not manufactured in sweatshops by kids earning a dollar a week so the labour advantage doesn't continue. Later on workers will start to realise they are being used and that pay and conditions are poor and they might start demanding better conditions and better pay for a better living standard.
China has enormous potential, but Russia has changed its market... it is going for high tech, while China seems to be more in the cheap and simple Soviet market.