Code of Federal Regulations - Title 14

214

14 CFR Ch. I (1–1–14 Edition)

§ 23.345

High lift devices.

(a) If flaps or similar high lift devices

are to be used for takeoff, approach or
landing, the airplane, with the flaps
fully extended at V

, is assumed to be

subjected to symmetrical maneuvers
and gusts within the range determined
by—

(1) Maneuvering, to a positive limit

load factor of 2.0; and

(2) Positive and negative gust of 25

feet per second acting normal to the
flight path in level flight.

(b) V

must be assumed to be not less

than 1.4 V

or 1.8 V

, whichever is

greater, where—

(1) V

is the computed stalling speed

with flaps retracted at the design
weight; and

(2) V

is the computed stalling speed

with flaps fully extended at the design
weight.

(3) If an automatic flap load limiting

device is used, the airplane may be de-
signed for the critical combinations of
airspeed and flap position allowed by
that device.

the airplane as a whole, thrust, slip-
stream, and pitching acceleration may
be assumed to be zero.

(d) The flaps, their operating mecha-

nism, and their supporting structures,
must be designed to withstand the con-
ditions prescribed in paragraph (a) of
this section. In addition, with the flaps
fully extended at V

, the following con-

ditions, taken separately, must be ac-
counted for:

(1) A head-on gust having a velocity

of 25 feet per second (EAS), combined
with propeller slipstream cor-
responding to 75 percent of maximum
continuous power; and

(2) The effects of propeller slipstream

corresponding to maximum takeoff
power.

[Doc. No. 27805, 61 FR 5144, Feb. 9, 1996]

§ 23.347

Unsymmetrical flight condi-

tions.

(a) The airplane is assumed to be sub-

jected to the unsymmetrical flight con-
ditions of §§ 23.349 and 23.351. Unbal-
anced aerodynamic moments about the
center of gravity must be reacted in a
rational or conservative manner, con-

sidering the principal masses fur-
nishing the reacting inertia forces.

(b) Acrobatic category airplanes cer-

tified for flick maneuvers (snap roll)
must be designed for additional asym-
metric loads acting on the wing and
the horizontal tail.

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as
amended by Amdt. 23–48, 61 FR 5144, Feb. 9,
1996]

§ 23.349

Rolling conditions.

The wing and wing bracing must be

designed for the following loading con-
ditions:

(a) Unsymmetrical wing loads appro-

priate to the category. Unless the fol-
lowing values result in unrealistic
loads, the rolling accelerations may be
obtained by modifying the symmet-
rical flight conditions in § 23.333(d) as
follows:

(1) For the acrobatic category, in

conditions A and F, assume that 100
percent of the semispan wing airload
acts on one side of the plane of sym-
metry and 60 percent of this load acts
on the other side.

(2) For normal, utility, and com-

muter categories, in Condition A, as-
sume that 100 percent of the semispan
wing airload acts on one side of the air-
plane and 75 percent of this load acts
on the other side.

(b) The loads resulting from the aile-

ron deflections and speeds specified in
§ 23.455, in combination with an air-
plane load factor of at least two thirds
of the positive maneuvering load factor
used for design. Unless the following
values result in unrealistic loads, the
effect of aileron displacement on wing
torsion may be accounted for by adding
the following increment to the basic
airfoil moment coefficient over the ai-
leron portion of the span in the critical
condition determined in § 23.333(d):

=¥0.01

where—

is the moment coefficient increment; and

d is the down aileron deflection in degrees in

the critical condition.

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as
amended by Amdt. 23–7, 34 FR 13088, Aug. 13,
1969; Amdt. 23–34, 52 FR 1829, Jan. 15, 1987;
Amdt. 23–48, 61 FR 5144, Feb. 9, 1996]

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