Code of Federal Regulations - Title 14

333

Federal Aviation Administration, DOT

Pt. 23, App. A

particular items are installed in the air-
plane. The engine mount, however, must be
designed for a higher side load factor, if cer-
tification in the acrobatic category is de-
sired, than that required for certification in
the normal and utility categories. When de-
signing for landing loads, the landing gear
and the airplane as a whole need only be in-
vestigated for the category corresponding to
the maximum design weight. These sim-
plifications apply to single-engine aircraft of
conventional types for which experience is
available, and the Administrator may re-
quire additional investigations for aircraft
with unusual design features.

A23.7

Flight loads.

(a) Each flight load may be considered

independent of altitude and, except for the
local supporting structure for dead weight
items, only the maximum design weight con-
ditions must be investigated.

(b) Table 1 and figures 3 and 4 of this ap-

pendix must be used to determine values of
n

, and

, corresponding to the max-

imum design weights in the desired cat-
egories.

used to determine values of

and

cor-

responding to the minimum flying weights in
the desired categories, and, if these load fac-
tors are greater than the load factors at the
design weight, the supporting structure for
dead weight items must be substantiated for
the resulting higher load factors.

(d) Each specified wing and tail loading is

independent of the center of gravity range.
The applicant, however, must select a c.g.
range, and the basic fuselage structure must
be investigated for the most adverse dead
weight loading conditions for the c.g. range
selected.

(e) The following loads and loading condi-

tions are the minimums for which strength
must be provided in the structure:

(1)

Airplane equilibrium. The aerodynamic

wing loads may be considered to act normal
to the relative wind, and to have a mag-
nitude of 1.05 times the airplane normal
loads (as determined from paragraphs A23.9
(b) and (c) of this appendix) for the positive
flight conditions and a magnitude equal to
the airplane normal loads for the negative
conditions. Each chordwise and normal com-
ponent of this wing load must be considered.

(2)

Minimum design airspeeds. The minimum

design airspeeds may be chosen by the appli-
cant except that they may not be less than
the minimum speeds found by using figure 3
of this appendix. In addition,

Cmin

need not

exceed values of 0.9

actually obtained at

sea level for the lowest design weight cat-
egory for which certification is desired. In
computing these minimum design airspeeds,
n

may not be less than 3.8.

(3)

Flight load factor. The limit flight load

factors specified in Table 1 of this appendix

represent the ratio of the aerodynamic force
component (acting normal to the assumed
longitudinal axis of the airplane) to the
weight of the airplane. A positive flight load
factor is an aerodynamic force acting up-
ward, with respect to the airplane.

A23.9

Flight conditions.

(a)

General. Each design condition in para-

graphs (b) and (c) of this section must be
used to assure sufficient strength for each
condition of speed and load factor on or
within the boundary of a

V¥n diagram for

the airplane similar to the diagram in figure
4 of this appendix. This diagram must also be
used to determine the airplane structural op-
erating limitations as specified in
§§ 23.1501(c) through 23.1513 and § 23.1519.

(b)

Symmetrical flight conditions. The air-

plane must be designed for symmetrical
flight conditions as follows:

(1) The airplane must be designed for at

least the four basic flight conditions, ‘‘A’’,
‘‘D’’, ‘‘E’’, and ‘‘G’’ as noted on the flight en-
velope of figure 4 of this appendix. In addi-
tion, the following requirements apply:

(i) The design limit flight load factors cor-

responding to conditions ‘‘D’’ and ‘‘E’’ of fig-
ure 4 must be at least as great as those speci-
fied in Table 1 and figure 4 of this appendix,
and the design speed for these conditions
must be at least equal to the value of

found from figure 3 of this appendix.

(ii) For conditions ‘‘A’’ and ‘‘G’’ of figure 4,

the load factors must correspond to those
specified in Table 1 of this appendix, and the
design speeds must be computed using these
load factors with the maximum static lift
coefficient

determined by the applicant.

However, in the absence of more precise
computations, these latter conditions may
be based on a value of

1.35 and the de-

sign speed for condition ‘‘A’’ may be less
than

Amin.

(iii) Conditions ‘‘C’’ and ‘‘F’’ of figure 4

need only be investigated when

W/S or

W/S are greater than

W/S or

W/S of this

appendix, respectively.

(2) If flaps or other high lift devices in-

tended for use at the relatively low airspeed
of approach, landing, and takeoff, are in-
stalled, the airplane must be designed for the
two flight conditions corresponding to the
values of limit flap-down factors specified in
Table 1 of this appendix with the flaps fully
extended at not less than the design flap
speed

Fmin

from figure 3 of this appendix.

(c)

Unsymmetrical flight conditions. Each af-

fected structure must be designed for unsym-
metrical loadings as follows:

(1) The aft fuselage-to-wing attachment

must be designed for the critical vertical
surface load determined in accordance with
paragraph SA23.11(c)(1) and (2) of this appen-
dix.

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