Section 29.681

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

(a) Automatically disengage the lock
when the pilot operates the controls in
a normal manner, or limit the operation of the rotorcraft so as to give unmistakable warning to the pilot before
takeoff; and
(b) Prevent the lock from engaging in
flight.
Section 29.681 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 angular motion.

spaschal on DSK3GDR082PROD with CFR

Section 29.683 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.
Section 29.685 Control system details.
(a) Each detail of each control system must be designed to prevent jamming, chafing, and interference from
cargo, passengers, loose objects, or the
freezing of moisture.
(b) There must be means in the cockpit to prevent the entry of foreign objects 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, turnbuckles, splices, and pulleys must be of
an acceptable kind.
(2) The design of 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 1-8 inch diameter may be used in any primary
control system.
(4) Pulley kinds and sizes must correspond to the cables with which they
are used. The pulley-cable combinations and strength values specified in
MIL-HDBK-5 must be used unless they
are inapplicable.
(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 three degrees.
(8) No clevis pin subject to load or
motion and retained only by cotter
pins may be used in the control system.
(9) Turnbuckles attached to parts
having angular motion must be installed to prevent binding throughout
the range of travel.
(10) There must be means for visual
inspection at each fairlead, pulley, terminal, 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 rating of ball and roller bearings may not
be exceeded.
[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as
amended by Amdt. 29-12, 41 FR 55471, Dec. 20,
1976]

Section 29.687

Spring devices.

(a) Each control system spring device
whose failure could cause flutter or
other unsafe characteristics must be
reliable.
(b) Compliance with paragraph (a) of
this section must be shown by tests
simulating service conditions.

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