665
Federal Aviation Administration, DOT
§ 27.685
§ 27.681
Limit load static tests.
(a) Compliance with the limit load
requirements of this part must be
shown by tests in which—
(1) The direction of the test loads
produces the most severe loading in the
control system; and
(2) Each fitting, pulley, and bracket
used in attaching the system to the
main structure is included.
(b) Compliance must be shown (by
analyses or individual load tests) with
the special factor requirements for
control system joints subject to angu-
lar motion.
§ 27.683
Operation tests.
It must be shown by operation tests
that, when the controls are operated
from the pilot compartment with the
control system loaded to correspond
with loads specified for the system, the
system is free from—
(a) Jamming;
(b) Excessive friction; and
(c) Excessive deflection.
§ 27.685
Control system details.
(a) Each detail of each control sys-
tem must be designed to prevent jam-
ming, chafing, and interference from
cargo, passengers, loose objects or the
freezing of moisture.
(b) There must be means in the cock-
pit to prevent the entry of foreign ob-
jects into places where they would jam
the system.
(c) There must be means to prevent
the slapping of cables or tubes against
other parts.
(d) Cable systems must be designed
as follows:
(1) Cables, cable fittings, turn-
buckles, splices, and pulleys must be of
an acceptable kind.
(2) The design of the cable systems
must prevent any hazardous change in
cable tension throughout the range of
travel under any operating conditions
and temperature variations.
(3) No cable smaller than three thir-
ty-seconds of an inch diameter may be
used in any primary control system.
(4) Pulley kinds and sizes must cor-
respond to the cables with which they
are used. The pulley cable combina-
tions and strength values which must
be used are specified in Military Hand-
book MIL-HDBK-5C, Vol. 1 & Vol. 2,
Metallic Materials and Elements for
Flight Vehicle Structures, (Sept. 15,
1976, as amended through December 15,
1978). This incorporation by reference
was approved by the Director of the
Federal Register in accordance with 5
U.S.C. section 552(a) and 1 CFR part 51.
Copies may be obtained from the Naval
Publications and Forms Center, 5801
Tabor Avenue, Philadelphia, Pennsyl-
vania, 19120. Copies may be inspected
at the FAA, Rotorcraft Standards
Staff, 4400 Blue Mount Road, Fort
Worth, Texas, or at the National Ar-
chives and Records Administration
(NARA). For information on the avail-
ability of this material at NARA, call
202–741–6030, or go to:
http://
www.archives.gov/federal
lregister/
code
loflfederallregulations/
ibr
llocations.html.
(5) Pulleys must have close fitting
guards to prevent the cables from being
displaced or fouled.
(6) Pulleys must lie close enough to
the plane passing through the cable to
prevent the cable from rubbing against
the pulley flange.
(7) No fairlead may cause a change in
cable direction of more than 3
°
.
(8) No clevis pin subject to load or
motion and retained only by cotter
pins may be used in the control sys-
tem.
(9) Turnbuckles attached to parts
having angular motion must be in-
stalled to prevent binding throughout
the range of travel.
(10) There must be means for visual
inspection at each fairlead, pulley, ter-
minal, and turnbuckle.
(e) Control system joints subject to
angular motion must incorporate the
following special factors with respect
to the ultimate bearing strength of the
softest material used as a bearing:
(1) 3.33 for push-pull systems other
than ball and roller bearing systems.
(2) 2.0 for cable systems.
(f) For control system joints, the
manufacturer’s static, non-Brinell rat-
ing of ball and roller bearings must not
be exceeded.
[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27–11, 41 FR 55469, Dec. 20,
1976; Amdt. 27–26, 55 FR 8001, Mar. 6, 1990; 69
FR 18803, Apr. 9, 2004]
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