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Federal Aviation Regulations

Sec. 23.397 — Limit control forces and torques.

(a) In the control surface flight loading condition, the airloads on movable surfaces and the corresponding deflections need not exceed those that would result in flight from the application of any pilot force within the ranges specified in paragraph (b) of this section. In applying this criterion, the effects of control system boost and servo-mechanisms, and the effects of tabs must be considered. The automatic pilot effort must be used for design if it alone can produce higher control surface loads than the human pilot.

(b) The limit pilot forces and torques are as follows:

ControlMaximum forces or torques for design weight, weight equal to or less than 5,000 pounds1Minimum forces or torques2
Stick67 lbs40 lbs.
Wheel350 D in.-lbs440 D in.-lbs.4
Stick167 lbs100 lbs.
Wheel (symmetrical)200 lbs100 lbs.
Wheel (unsymmetrical)5100 lbs.
Rudder200 lbs150 lbs.

1For design weight ( W ) more than 5,000 pounds, the specified maximum values must be increased linearly with weight to 1.18 times the specified values at a design weight of 12,500 pounds and for commuter category airplanes, the specified values must be increased linearly with weight to 1.35 times the specified values at a design weight of 19,000 pounds.

2If the design of any individual set of control systems or surfaces makes these specified minimum forces or torques inapplicable, values corresponding to the present hinge moments obtained under §23.415, but not less than 0.6 of the specified minimum forces or torques, may be used.

3The critical parts of the aileron control system must also be designed for a single tangential force with a limit value of 1.25 times the couple force determined from the above criteria.

4D=wheel diameter (inches).

5The unsymmetrical force must be applied at one of the normal handgrip points on the control wheel.

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as amended by Amdt. 23–7, 34 FR 13089, Aug. 13, 1969; Amdt. 23–17, 41 FR 55464, Dec. 20, 1976; Amdt. 23–34, 52 FR 1829, Jan. 15, 1987; Amdt. 23–45, 58 FR 42160, Aug. 6, 1993]

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