When the F-18 Hornet does rolls, do the Leading Edge Flaps (LEFs) deflect symmetrically or is the deflection different on the left and right LEFs?


1 Answer 1


Quoting the F/A-18A,B,C,D Flight Manual A1-F18AC-NFM-000, I-2-42 Control Augmentation System (CAS) [...] The lateral control system uses ailerons, differential trailing edge flaps, differential leading edge flaps, differential stabilator, and rudders to achieve the desired roll characteristics. Scheduled air data roll rate feedback is used to augment inherent airframe roll damping. At high airspeeds, aileron travel versus stick movement is reduced and the ailerons do not deflect above 600 knots. Differential stabilator and differential trailing edge flap travel is reduced at high speed to prevent exceeding structural limits. The leading edge flaps deflect differentially up to ± 3° when below 30,000 feet and above 0.7 MACH. Differential flaps are not used in the takeoff or land modes nor above 10° AOA in the auto flaps up mode. At low airspeeds, aileron and differential stabilator travel are reduced with increasing AOA to minimize adverse yaw.

In short: Yes the F18 uses differential (asymmetric) deflections on the leading edge flaps and trailing edge flaps but the scheduling depends on angle of attack, airspeed and Mach number.

  • 1
    $\begingroup$ Hard to emulate that in my sim $\endgroup$
    – George Geo
    Nov 1, 2019 at 13:33

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