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Do they go both up and down (with respect to a retracted position in the middle) on different fighter jets?

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    $\begingroup$ f-16.net/forum/viewtopic.php?t=11863 $\endgroup$
    – PcMan
    Jan 4 at 12:39
  • $\begingroup$ DV for lack of clarity and thought put into the question. (I.e. if something is moveable and has more than one position, why would you think it might NOT move? Barring a malfunction…) $\endgroup$ Jan 4 at 16:04
  • $\begingroup$ @MichaelHall: This is a case of the LEF going up above the retracted position; grammatically the question was correct, but I now added a [hopefully] clearer phrasing. Feel free to improve further :) $\endgroup$
    – ymb1
    Jan 4 at 20:03
  • $\begingroup$ @ymb1, OK, I understand that F-16 LEFs are a maneuvering aide, but now instead of reading like "does the landing gear go up and down?" it reads like "after the landing gear fully retracts, does it go even further up?" Better might be rephrasing to ask about movement around a default neutral, or cruise position? Anyway, I don't feel compelled to guess the intent or do Chickeny Chickens' work for them... $\endgroup$ Jan 5 at 2:36
  • $\begingroup$ Interesting topic, but I think the question can be more valuable if it also asks the 'why' question. $\endgroup$
    – ROIMaison
    Jan 5 at 14:03
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I can answer on the F-16 :)

The general system description tells us that the Leading Edge Flaps may be positioned from 2 degrees (1 inch) up to 25 degrees (12-1/2 inches) down.

I assume it is similar on the F-22 and F-35, since the Leading Edge Flap subsystem provides high lift for takeoff and landing and optimizes performance in each flight phase.

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  • $\begingroup$ Will the LEF going up have any functions? $\endgroup$ Jan 4 at 13:37
  • $\begingroup$ The LEF system is designed to optimize wing airflow. It provides special functions in the takeoff and landing configurations. $\endgroup$
    – Noddle
    Jan 4 at 14:09
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    $\begingroup$ LEF 2 degrees up primarily has use during takeoff. When there's weight on wheels (aircraft on ground), the LEFs will be in the 2 degree up position. $\endgroup$
    – Noddle
    Jan 4 at 14:11
  • $\begingroup$ At subsonic speeds, the LEF's move from 2 degrees up to 25 degrees down as a function of mach number, Angle Of Attack, and altitude. This is an automatic operation that significantly reduces buffet and drag and improves high AOA directional stability. $\endgroup$
    – Noddle
    Jan 4 at 14:13
  • $\begingroup$ Here is a video of the first F-16 flight test: youtube.com/watch?v=UR-48Kri0Tw I know the description says it was supposed to be a high speed taxi, but in reality it was supposed to fly, to test low speed stability. You can see here that the leading edge flaps are all the way down, and that the aircraft is super unstable in low speed flight. $\endgroup$
    – Noddle
    Jan 4 at 14:19

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