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If a fighter jet veers off the runaway, is nosewheel steering needed to counter, or can directional control be maintained with the rudder deflection alone? Is there a chance that the rudder deflection alone won't be enough to change the aircraft direction? Is there a speed zone or gap were the rudder deflection is not aerodynamically available, while at the same time steering of the front landing gear is ineffective due to loss of friction? Or does the max speed for nosewheel steering and minimum speed for rudder effectiveness overlap each other?

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  • $\begingroup$ Are you asking of rudder authority vs directional wheel authority during taxi, takeoff or landing rolls? $\endgroup$ – Manu H Apr 25 '20 at 20:43
  • $\begingroup$ Exactly ,and if dead zones are between this two. $\endgroup$ – George Geo Apr 25 '20 at 20:45
  • $\begingroup$ you could include relevant terms in the question (rudder authority, steering wheel authority, take off roll, taxi, and/or landing roll). $\endgroup$ – Manu H Apr 25 '20 at 20:47
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    $\begingroup$ I just made some pretty major edits to capture what I think you are asking, because I think it is a good question, (as I interpreted it...) and doesn't deserve to be closed. George, I realize that English is your second language, but you should really try to get some help with your basic grammar before making a public post on an English language site. It can be very difficult sometimes to figure out what you are asking. $\endgroup$ – Michael Hall Apr 26 '20 at 22:39
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There is some overlap in effectiveness, and therefore no real magic number, but most aircraft that don't have full time nosewheel steering will have some published airspeed at which one will be favored over the other. For example, in the EA-6B it was 80 KIAS. On take off roll you would hold the nosewheel steering button on the control stick down to maintain directional control with the nose wheel. Accellerating through 80 KIAS it was a call-out to release the NWS button and rely on the rudder effectiveness to keep control up to rotation at around 145 KIAS. The reason for this was not because the nosewheel was less effective due to less friction, (traction) but rather there was a risk of overcontrolling steering at higher speeds.

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  • $\begingroup$ Thanks for your time , now if the crosswind comes in to play have the rudder deflection the power to overcome that ,or the differential brake control the aircraft ? $\endgroup$ – George Geo Apr 26 '20 at 18:56
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    $\begingroup$ There's no single correct answer because it depends on the airplane and amount of crosswind, but I have never had to use differential braking because neither NWS nor rudder were enough. $\endgroup$ – Michael Hall Apr 26 '20 at 20:55
  • $\begingroup$ That's a good idea for me to work with. $\endgroup$ – George Geo Apr 26 '20 at 21:11
  • $\begingroup$ @Michael Hall: While my experience is limited to single-engine propellor planes, I'd have to wonder if that's really even an answerable question. I mean I don't actually think about what I'm doing, I just do it. Like riding a bike... $\endgroup$ – jamesqf Apr 27 '20 at 3:56
  • $\begingroup$ @jamesqf, yes, with full time NWS it really doesn't matter - you simply react with your feet appropriately while deflecting both rudder and nosewheel. You really don't know or care which on is having the greater effect. However, in a jet the sensitivity needed to turn sharply at slow taxi speeds is way to much for the much faster take off and landing speeds. For this reason, the switch is generally springloaded to the disengaged position and must be held down to engage steering. So I think the question is answerable. As I interpreted it... $\endgroup$ – Michael Hall Apr 27 '20 at 4:13
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Yes, the steerable nosewheel and the rudder always work together. They both contribute a yaw torque in the same direction. As to your question about a speed regime where neither is effective-- I can't really answer that from first-hand knowledge across the entire aircraft design spectrum but it seems that the answer must be "no" in most cases or else the aircraft in question would not survive for long.

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