J-20 5th Gen Fighter Thread IV (Closed to posting)

[latenlazy]

Exactly. If you use TVC, which forces the nose to move extra, it will result in extra drag cause the rest of the body is resisting it. So often it is handy in low speed and high AOA but STR is a different story. Then again why would you add so much weight (TVC) if you do NOT want to go close in with your very very expensive stealth? F22 is intermediate solution between a optimized stealth and air superiority fighter. Just look at the next generation of stealth.

I mean, at the end of the day I still suspect that TVC can be a difference maker in certain situations, but I don't think it should be depended on indiscriminately like the IAF. I'll just leave it to the PLAAF to figure out potential tactical advantages and decide whether the tradeoffs are worth it.

 

[MiG-29]

Establishing a turn rate without also establishing at what speed it can maintain that turn rate, and what the speed penalties are for achieving that turn rate are all meaningless if we're trying to measure performance. Turn rates alone tell us nothing without proper context.

You are simply not changing the fact Thrust vectoring increases turn rate or roll rate or pitch rate.

niether the highest turn is always for the aircraft with the lower corner speed or higher load factor.

But here you just going away from what we were talking, does J-20 needs TVC nozzles? and the answer it depends in its weapons system, but definitively if J-20 has TVC nozzles its turn rate will increase.

You like it or not Thrust vectoring increases turn rates because it reduces drag and increases lift.

and the answer of that is simple the jet deflect less its aerodynamic surfaces in example canards or tailplanes, plus it adds a vector parallel to lift.


But with HHOBS it does not need to have TVC nozzles, J-20 wil be able to hit targets without even turning or rolling.

 

[MiG-29]

Exactly. If you use TVC, which forces the nose to move extra, it will result in extra drag cause the rest of the body is resisting it. So often it is handy in low speed and high AOA but STR is a different story. Then again why would you add so much weight (TVC) if you do NOT want to go close in with your very very expensive stealth? F22 is intermediate solution between a optimized stealth and air superiority fighter. Just look at the next generation of stealth.

That is not true, simple because a TVC nozzles fitted fighter deflect less the aerodynamic surfaces, thus becomes more stealthy at cruise flight and it generates less drag in a turn simply for the same reason, it deflects less its aerodynamic surfaces, so it will reduce drag to turn too.

 

[Munir]

That is not true, simple because a TVC nozzles fitted fighter deflect less the aerodynamic surfaces, thus becomes more stealthy at cruise flight and it generates less drag in a turn simply for the same reason, it deflects less its aerodynamic surfaces, so it will reduce drag to turn too.

TVC is added to already moving surfaces... It is not just the TVC. Just imagine what happens with drag if you not only use surface but also thrust to change to high AOA... You push your plane beyond a normal flight attitude (compared to flight direction). That is a well known basic fact.

 

[rhino123]

That is not true, simple because a TVC nozzles fitted fighter deflect less the aerodynamic surfaces, thus becomes more stealthy at cruise flight and it generates less drag in a turn simply for the same reason, it deflects less its aerodynamic surfaces, so it will reduce drag to turn too.

Wait... now I am confuse. How can a TVC nozzles fitted fighter deflect less aerodynamic surfaces? I thought that TVC nozzles aid in the maneuverability of an aircraft and not deflection? Granted that canard might reduce stealth and increase the surface area for radar detection, conventional enginesaircraft without carnard and TVC would not increase the aerodynamic surface, even if maneuverability might be compromised.

 

[Quickie]

Wait... now I am confuse. How can a TVC nozzles fitted fighter deflect less aerodynamic surfaces? I thought that TVC nozzles aid in the maneuverability of an aircraft and not deflection?

Actually, this is some sort of a myth. If 2 aircraft are heading towards each other with one of them at a lower or higher altidude, not deflecting the carnards or the conventional horizontal elevators actually exposes more of their surfaces to the radar than it would be for the case if the control surfaces are deflected at an angle towards the opponent aircraft.

 

[plawolf]

Wait... now I am confuse. How can a TVC nozzles fitted fighter deflect less aerodynamic surfaces? I thought that TVC nozzles aid in the maneuverability of an aircraft and not deflection? Granted that canard might reduce stealth and increase the surface area for radar detection, conventional enginesaircraft without carnard and TVC would not increase the aerodynamic surface, even if maneuverability might be compromised.

That is where FBW comes in. If you have TVC, you can have the FBW only use the TVC for small movements and keep you control surfaces locked in place.

But I agree with Quickie that it is more of a theoretical advantage, and a dubious one at that. Control surface movements will only change your RCS by a tiny amount, and will be a transitory and highly situational one, as depending on where the illuminating radar is to your plane, some control surface deflection may actually reduce the RCS the emitter is receiving.

But all of that is minor. The real issue with nit picking over control surfaces deflection makes the same logically fallacy as those insisting canards are incompatible with stealth - it completely ignores why you would deflect your control surfaces and what the plane does a split second after you do.

Using your control surfaces might produce slightly more RCS, but that is going to be a tiny faction of your RCS change when your plane turns.

Now, in a realistic combat scenario, a stealth fighter will detect an emitting enemy radar, even one operating in LPI mode if the stealth has a good modern RWR and EW systems, long before that radar can detect it. The stealth then has the opportunity to decide if it wants to go head on against that target to present its best RCS aspect and engage it in BVR, or slip past to attack from the side or the rear.

Either way, you will be making your move so far away any tiny momentary RCS spikes will be practically meaningless. If you are so close that the tiny RCS spike from your control surfaces will bring you above the detectability threshold, a) you have already done something badly wrong, and b) once you turn and present anything other than your best RCS value, you will be detected irrespective of whether you used control surfaces or TVC to turn.

 

[Engineer]

Wouldn't this imply that TVC could be decisive if both fighters have bled most of their energy in a prolonged engagement?

Not really. Altitude is traded for energy as engagement drags on. Whichever aircraft that has less energy dies first and there is no engagement to prolong after that.

Very unlikely for two good pilots to get themselves in such a situation, as they would both be sitting ducks if there was anyone else nearby.

TVC could make a big difference if you and your target were the only two planes in the sky. But in a realistic combat scenario, there will be other fighters about, and the last thing you want is to be caught without any energy.

Thrust vectoring is just a big hype anyway, and it is such a big hype because aircraft with thrust vectoring appeared to be invincible in the early days. Back then, thrust vectoring was new and pilots never have an opportunity to train against thrust vectoring aircraft. Once strategies get developed, going post-stall isn't such a good idea anymore.

 

[Engineer]

You are simply not changing the fact Thrust vectoring increases turn rate or roll rate or pitch rate.

niether the highest turn is always for the aircraft with the lower corner speed or higher load factor.

But here you just going away from what we were talking, does J-20 needs TVC nozzles? and the answer it depends in its weapons system, but definitively if J-20 has TVC nozzles its turn rate will increase.

You like it or not Thrust vectoring increases turn rates because it reduces drag and increases lift.

and the answer of that is simple the jet deflect less its aerodynamic surfaces in example canards or tailplanes, plus it adds a vector parallel to lift.


But with HHOBS it does not need to have TVC nozzles, J-20 wil be able to hit targets without even turning or rolling.

The pitch and roll rates that you mentioned are not turn rate. Turn is dependent on lift, which is an aerodynamic effect. Thrust vectoring doesn't increase lift, hence doesn't increase turn rate. You can pitch and roll all you want, but an aircraft without lift will just keep going in the same direction and downward regardless of orientation. In kiddie's term, an aircraft without wing cannot fly even with thrust vectoring, it is as simple as that.

Thrust vectoring provides non-aerodynamic mean for an aircraft to generate moment. Some aircraft needs this because they have a traditional configuration in which the tailplane becomes ineffective at high angle-of-attack. The J-20 doesn't need thrust vectoring because it has an all-moving canard which remains as an effective control surface regardless of the aircraft's angle-of-attack, not because of potnetial HMS or high off-boresight weaponaries.

 

[Deino]

.... and once again a "forth & back" discussion regarding aerodynamics, TVC, canards and powerplants ...

Especially since all I want is the unveiling of no. 2003 !! As such can we come back to the topic, gentleman ?

DEino