Section 25.393

14 CFR Ch. I (1-1-19 Edition)

(e) Auxiliary aerodynamic surfaces,
in Section 25.445.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-86, 61 FR 5222, Feb. 9,
1996; Amdt. 25-141, 79 FR 73468, Dec. 11, 2014]

Section 25.393 Loads parallel to hinge line.
(a) Control surfaces and supporting
hinge brackets must be designed for inertia loads acting parallel to the hinge
line.
(b) In the absence of more rational
data, the inertia loads may be assumed
to be equal to KW, where - 
(1) K = 24 for vertical surfaces;
(2) K = 12 for horizontal surfaces; and
(3) W = weight of the movable surfaces.
Section 25.395 Control system.
(a) Longitudinal, lateral, directional,
and drag control system and their supporting structures must be designed for
loads corresponding to 125 percent of
the computed hinge moments of the
movable control surface in the conditions prescribed in Section 25.391.
(b) The system limit loads of paragraph (a) of this section need not exceed the loads that can be produced by
the pilot (or pilots) and by automatic
or power devices operating the controls.
(c) The loads must not be less than
those resulting from application of the
minimum
forces
prescribed
in
Section 25.397(c).

spaschal on DSK3GDR082PROD with CFR

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-23, 35 FR 5672, Apr. 8,
1970; Amdt. 25-72, 55 FR 29776, July 20, 1990;
Amdt. 25-141, 79 FR 73468, Dec. 11, 2014]

Section 25.397 Control system loads.
(a) General. The maximum and minimum pilot forces, specified in paragraph (c) of this section, are assumed
to act at the appropriate control grips
or pads (in a manner simulating flight
conditions) and to be reacted at the attachment of the control system to the
control surface horn.
(b) Pilot effort effects. In the control
surface flight loading condition, the air
loads 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 (c)
of this section. Two-thirds of the max-

imum values specified for the aileron
and elevator may be used if control
surface hinge moments are based on reliable data. In applying this criterion,
the effects of servo mechanisms, tabs,
and automatic pilot systems, must be
considered.
(c) Limit pilot forces and torques. The
limit pilot forces and torques are as
follows:
Control
Aileron:
Stick ..............................
Wheel 1 ..........................
Elevator:
Stick ..............................
Wheel (symmetrical) .....
Wheel (unsymmetrical) 3
Rudder ..............................

Maximum
forces or
torques

Minimum
forces or
torques

100 lbs ............
80 D in.-lbs 2 ...

40 lbs.
40 D in.-lbs.

250 lbs ............
300 lbs ............
.........................
300 lbs ............

100
100
100
130

1 The critical parts of the aileron control system must be designed for a single tangential force with a limit value equal to
1.25 times the couple force determined from these criteria.
2 D = wheel diameter (inches).
3 The unsymmetrical forces must be applied at one of the
normal handgrip points on the periphery of the control wheel.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-38, 41 FR 55466, Dec. 20,
1976; Amdt. 25-72, 55 FR 29776, July 20, 1990]

Section 25.399

Dual control system.

(a) Each dual control system must be
designed for the pilots operating in opposition, using individual pilot forces
not less than - 
(1) 0.75 times those obtained under
Section 25.395; or
(2) The minimum forces specified in
Section 25.397(c).
(b) The control system must be designed for pilot forces applied in the
same direction, using individual pilot
forces not less than 0.75 times those obtained under Section 25.395.
Section 25.405

Secondary control system.

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:

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