Federal Aviation Administration, DOT

Section 25.701

(b) Each kind and size of pulley must
correspond to the cable with which it is
used. Pulleys and sprockets must have
closely fitted guards to prevent the cables and chains from being displaced or
fouled. Each pulley must lie in the
plane passing through the cable so that
the cable does not rub against the pulley flange.
(c) Fairleads must be installed so
that they do not cause a change in
cable direction of more than three degrees.
(d) Clevis pins subject to load or motion and retained only by cotter pins
may not be used in the control system.
(e) Turnbuckles must be attached to
parts having angular motion in a manner that will positively prevent binding
throughout the range of travel.
(f) There must be provisions for visual inspection of fairleads, pulleys, terminals, and turnbuckles.
Section 25.693

Joints.

Control system joints (in push-pull
systems) that are subject to angular
motion, except those in ball and roller
bearing systems, must have a special
factor of safety of not less than 3.33
with respect to the ultimate bearing
strength of the softest material used as
a bearing. This factor may be reduced
to 2.0 for joints in cable control systems. For ball or roller bearings, the
approved ratings may not be exceeded.
[Amdt. 25-72, 55 FR 29777, July 20, 1990]

spaschal on DSK3GDR082PROD with CFR

Section 25.697 Lift and drag devices, controls.
(a) Each lift device control must be
designed so that the pilots can place
the device in any takeoff, en route, approach, or landing position established
under Section 25.101(d). Lift and drag devices
must maintain the selected positions,
except for movement produced by an
automatic positioning or load limiting
device, without further attention by
the pilots.
(b) Each lift and drag device control
must be designed and located to make
inadvertent operation improbable. Lift
and drag devices intended for ground
operation only must have means to
prevent the inadvertant operation of
their controls in flight if that operation could be hazardous.

(c) The rate of motion of the surfaces
in response to the operation of the control and the characteristics of the
automatic positioning or load limiting
device must give satisfactory flight
and performance characteristics under
steady or changing conditions of airspeed, engine power, and airplane attitude.
(d) The lift device control must be
designed to retract the surfaces from
the fully extended position, during
steady flight at maximum continuous
engine power at any speed below VF +
9.0 (knots).
[Amdt. 25-23, 35 FR 5675, Apr. 8, 1970, as
amended by Amdt. 25-46, 43 FR 50595, Oct. 30,
1978; Amdt. 25-57, 49 FR 6848, Feb. 23, 1984]

Section 25.699

Lift and drag device indicator.

(a) There must be means to indicate
to the pilots the position of each lift or
drag device having a separate control
in the cockpit to adjust its position. In
addition, an indication of unsymmetrical operation or other malfunction in
the lift or drag device systems must be
provided when such indication is necessary to enable the pilots to prevent
or counteract an unsafe flight or
ground condition, considering the effects on flight characteristics and performance.
(b) There must be means to indicate
to the pilots the takeoff, en route, approach, and landing lift device positions.
(c) If any extension of the lift and
drag devices beyond the landing position is possible, the controls must be
clearly marked to identify this range
of extension.
[Amdt. 25-23, 35 FR 5675, Apr. 8, 1970]

Section 25.701

Flap and slat interconnection.

(a) Unless the airplane has safe flight
characteristics with the flaps or slats
retracted on one side and extended on
the other, the motion of flaps or slats
on opposite sides of the plane of symmetry must be synchronized by a mechanical interconnection or approved
equivalent means.
(b) If a wing flap or slat interconnection or equivalent means is used, it
must be designed to account for the applicable unsymmetrical loads, including those resulting from flight with the

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