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If an aircraft have two vertical tails then pilot push in the rudder pedal the rudders will not be deployed at the same angle.It is used throughout the all envelope of flight or is it possible only for low speed? Why and which ones is more deflected? enter image description hereenter image description here

George Geo
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    You know for a fact that all fighters with twin tails deflect the rudders at different angles? Because I think you may be making a faulty assumption. But, if you have a specific and verifiable example, please share details. – Michael Hall Oct 10 '19 at 20:58
  • Yes, I seen that. The out of the turning rudder is more deflected than the other one. – George Geo Oct 11 '19 at 05:17
  • It is used throughout the all envelope of flight or is it possible only for low speed? – George Geo Oct 11 '19 at 05:26
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    Do you see that in which aircraft in which situation? You ask as if it was true of all of them, but it is unlikely the same in all types. Do you mean F-14? MiG-29? F/A-18? De Havilland Sea Vixen? Su-27? De Havilland Venom? F-22? F-35? Very different designs, with very different requirements, made by different companies… – Jan Hudec Oct 11 '19 at 05:28
  • The aerodynamics is the same for all of those rudders. If they are spaced enough then it will be deflected at the different angles. – George Geo Oct 11 '19 at 05:47
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    I wouldn't take that picture as evidence of different rudder deflections: the picture isn't taken from exactly head on. The nose looks like it skews to our left, and whereas external fuel tank on our right is pointed straight forward, the one on our left looks pointed outward. I highly doubt that the nose is asymmetrical and the left fuel tank was mounted at an angle; we're just seeing the plane from a bit of an angle. I think that may account for the rudder's perceived deflection, too. – yshavit Oct 11 '19 at 06:27
  • of course even if they're not meant to, a malfunction can cause this to happen. And my guess is it'd cause the pilot some headaches before he figured out how to compensate for the asymetric rudder deflection just as a faulty rudder would cause trouble with an aircraft having only one. – jwenting Oct 11 '19 at 06:55
  • There's others in flight – George Geo Oct 11 '19 at 07:25
  • Somewhat related – Rsf Oct 11 '19 at 12:29
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    Rudder toe in or out it's used for pitching or as brake device. But this is differential deployment left /left not left /right pathern – George Geo Oct 11 '19 at 13:21
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    This feature may be quite different for parallel rudders (e.g F15) and V-shaped one (e.g. F22, or in the opposite direction the A12), for fly-by-wire aircraft (in which you can virtually deflect any surface in any direction independently) and for conventional transmission (e.g. P38) (in which there are physical links limiting independent deflection of both rudders) – Manu H Nov 05 '19 at 16:18
  • True, the F22 doing the pedal turn definitely not uses the rudders in their symetrical way, or F117 in pitch up. – George Geo Nov 05 '19 at 21:28

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The jet in the top picture is turning slightly left using nose wheel steering, which is generally the same control as the rudder. I'm not aware of any fighter jet that has a tiller. Therefore the computer has commanded the rudders to deflect left. This is likely combined with a "toe in" (a characteristic of some fighters that aids in stability) of the rudders so it looks like only one has moved.

In the bottom picture, the flight control computer has decided that the best way to maintain the pilot's commanded attitude is to asymmetrically deflect the rudder. Flight control computers move surfaces in fly-by-wire systems, not pilots. Pilots just ask the computer if it is okay to do that. The computer decides if it is okay and how. It will use a combo of all the available surfaces to achieve the desired attitude within the programmed flight envelope and it doesn't have to do it symmetrically.

Craig
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    The toe-in not "tow in " it is for pitching up or rotate .The toe out it is used for airbrake some fighters (F22 ,Superhornet ,F35). – George Geo Jun 07 '20 at 12:42