FAA Federal Aviation Regulations (FARS, 14 CFR)

Secondary controls, such as wheel brake, spoiler, and tab controls, must be designed for the maximum forces that a pilot is likely to apply to those controls. The following values may be used:

             Pilot Control Force Limits (Secondary Controls)
------------------------------------------------------------------------
Control                        Limit pilot forces
------------------------------------------------------------------------
1  1  Miscellaneous:                         1+R
*Crank, wheel, or                         [lpar5]___[rpar5] x 50 lbs.,
but
lever.                                   3
not less than 50 lbs. nor
more than 150 lbs.
(R=radius). (Applicable to
any angle within 20°
of plane of control).
Twist.....................................  133 in.-lbs.
Push-pull.................................  To be chosen by applicant.
------------------------------------------------------------------------
*Limited to flap, tab, stabilizer, spoiler, and landing gear operation
controls.