Federal Aviation Administration, DOT
Section 27.673

Section 27.685

Primary flight control.

Primary flight controls are those
used by the pilot for immediate control
of pitch, roll, yaw, and vertical motion
of the rotorcraft.
[Amdt. 27-21, 49 FR 44434, Nov. 6, 1984]

Section 27.674

Interconnected controls.

Each primary flight control system
must provide for safe flight and landing
and operate independently after a malfunction, failure, or jam of any auxiliary interconnected control.

Section 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 angular motion.

[Amdt. 27-26, 55 FR 8001, Mar. 6, 1990]

Section 27.675

Stops.

(a) Each control system must have
stops that positively limit the range of
motion of the pilot-s controls.
(b) Each stop must be located in the
system so that the range of travel of
its control is not appreciably affected
by - 
(1) Wear;
(2) Slackness; or
(3) Takeup adjustments.
(c) Each stop must be able to withstand the loads corresponding to the
design conditions for the system.
(d) For each main rotor blade - 
(1) Stops that are appropriate to the
blade design must be provided to limit
travel of the blade about its hinge
points; and
(2) There must be means to keep the
blade from hitting the droop stops during any operation other than starting
and stopping the rotor.
(Secs. 313(a), 601, 603, 604, Federal Aviation
Act of 1958 (49 U.S.C. 1354(a), 1421, 1423, 1424),
sec. 6(c), Dept. of Transportation Act (49
U.S.C. 1655(c)))
[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27-16, 43 FR 50599, Oct. 30,
1978]

spaschal on DSK3GDR082PROD with CFR

Section 27.679

Control system locks.

If there is a device to lock the control system with the rotorcraft on the
ground or water, there must be means
to - 
(a) Give unmistakable warning to the
pilot when the lock is engaged; and
(b) Prevent the lock from engaging in
flight.

Section 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.
Section 27.685 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 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 thirty-seconds of an 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 which must
be used are specified in Military Handbook MIL-HDBK-5C, Vol. 1 Section Vol. 2,

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