240
14 CFR Ch. I (1–1–14 Edition)
§ 23.641
(i) For modifications to the type de-
sign that could affect the flutter char-
acteristics, compliance with paragraph
(a) of this section must be shown, ex-
cept that analysis based on previously
approved data may be used alone to
show freedom from flutter, control re-
versal and divergence, for all speeds up
to the speed specified for the selected
method.
[Amdt. 23–23, 43 FR 50592, Oct. 30, 1978, as
amended by Amdt. 23–31, 49 FR 46867, Nov. 28,
1984; Amdt. 23–45, 58 FR 42164, Aug. 6, 1993; 58
FR 51970, Oct. 5, 1993; Amdt. 23–48, 61 FR 5148,
Feb. 9, 1996; Amdt. 23–62, 76 FR 75756, Dec. 2,
2011]
W
INGS
§ 23.641
Proof of strength.
The strength of stressed-skin wings
must be proven by load tests or by
combined structural analysis and load
tests.
C
ONTROL
S
URFACES
§ 23.651
Proof of strength.
(a) Limit load tests of control sur-
faces are required. These tests must in-
clude the horn or fitting to which the
control system is attached.
(b) In structural analyses, rigging
loads due to wire bracing must be ac-
counted for in a rational or conserv-
ative manner.
§ 23.655
Installation.
(a) Movable surfaces must be in-
stalled so that there is no interference
between any surfaces, their bracing, or
adjacent fixed structure, when one sur-
face is held in its most critical clear-
ance positions and the others are oper-
ated through their full movement.
(b) If an adjustable stabilizer is used,
it must have stops that will limit its
range of travel to that allowing safe
flight and landing.
[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as
amended by Amdt. 23–45, 58 FR 42164, Aug. 6,
1993]
§ 23.657
Hinges.
(a) Control surface hinges, except
ball and roller bearing hinges, must
have a factor of safety of not less than
6.67 with respect to the ultimate bear-
ing strength of the softest material
used as a bearing.
(b) For ball or roller bearing hinges,
the approved rating of the bearing may
not be exceeded.
[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as
amended by Amdt. 23–48, 61 FR 5148, Feb. 9,
1996]
§ 23.659
Mass balance.
The supporting structure and the at-
tachment of concentrated mass bal-
ance weights used on control surfaces
must be designed for—
(a) 24
g normal to the plane of the
control surface;
(b) 12
g fore and aft; and
(c) 12
g parallel to the hinge line.
C
ONTROL
S
YSTEMS
§ 23.671
General.
(a) Each control must operate easily,
smoothly, and positively enough to
allow proper performance of its func-
tions.
(b) Controls must be arranged and
identified to provide for convenience in
operation and to prevent the possi-
bility of confusion and subsequent in-
advertent operation.
§ 23.672
Stability augmentation and
automatic and power-operated sys-
tems.
If the functioning of stability aug-
mentation or other automatic or
power-operated systems is necessary to
show compliance with the flight char-
acteristics requirements of this part,
such systems must comply with § 23.671
and the following:
(a) A warning, which is clearly dis-
tinguishable to the pilot under ex-
pected flight conditions without re-
quiring the pilot’s attention, must be
provided for any failure in the stability
augmentation system or in any other
automatic or power-operated system
that could result in an unsafe condi-
tion if the pilot was not aware of the
failure. Warning systems must not ac-
tivate the control system.
(b) The design of the stability aug-
mentation system or of any other auto-
matic or power-operated system must
permit initial counteraction of failures
without requiring exceptional pilot
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