212
14 CFR Ch. I (1–1–14 Edition)
§ 23.335
§ 23.335
Design airspeeds.
Except as provided in paragraph
(a)(4) of this section, the selected de-
sign airspeeds are equivalent airspeeds
(EAS).
(a)
Design cruising speed, V
C.
For
V
C
the following apply:
(1) Where W/S
′
=wing loading at the
design maximum takeoff weight, V
c
(in
knots) may not be less than—
(i) 33
√
(W/S) (for normal, utility, and
commuter category airplanes);
(ii) 36
√
(W/S) (for acrobatic category
airplanes).
(2) For values of
W/S more than 20,
the multiplying factors may be de-
creased linearly with
W/S to a value of
28.6 where
W/S=100.
(3)
V
C
need not be more than 0.9
V
H
at
sea level.
(4) At altitudes where an
M
D
is estab-
lished, a cruising speed
M
C
limited by
compressibility may be selected.
(b)
Design dive speed V
D.
For
V
D,
the
following apply:
(1)
V
D
/M
D
may not be less than 1.25
V
C
/M
C
; and
(2) With
V
C min,
the required minimum
design cruising speed,
V
D
(in knots)
may not be less than—
(i) 1.40
V
c
min
(for normal and com-
muter category airplanes);
(ii) 1.50
V
C
min
(for utility category
airplanes); and
(iii) 1.55
V
C min
(for acrobatic category
airplanes).
(3) For values of
W/S more than 20,
the multiplying factors in paragraph
(b)(2) of this section may be decreased
linearly with
W/S to a value of 1.35
where
W/S=100.
(4) Compliance with paragraphs (b)(1)
and (2) of this section need not be
shown if
V
D
/M
D
is selected so that the
minimum speed margin between
V
C
/M
C
and
V
D
/M
D
is the greater of the fol-
lowing:
(i) The speed increase resulting when,
from the initial condition of stabilized
flight at
V
C
/M
C,
the airplane is assumed
to be upset, flown for 20 seconds along
a flight path 7.5
°
below the initial path,
and then pulled up with a load factor of
1.5 (0.5
g. acceleration increment). At
least 75 percent maximum continuous
power for reciprocating engines, and
maximum cruising power for turbines,
or, if less, the power required for
V
C
/
M
C
for both kinds of engines, must be as-
sumed until the pullup is initiated, at
which point power reduction and pilot-
controlled drag devices may be used;
and either—
(ii) Mach 0.05 for normal, utility, and
acrobatic category airplanes (at alti-
tudes where M
D
is established); or
(iii) Mach 0.07 for commuter category
airplanes (at altitudes where M
D
is es-
tablished) unless a rational analysis,
including the effects of automatic sys-
tems, is used to determine a lower mar-
gin. If a rational analysis is used, the
minimum speed margin must be
enough to provide for atmospheric
variations (such as horizontal gusts),
and the penetration of jet streams or
cold fronts), instrument errors, air-
frame production variations, and must
not be less than Mach 0.05.
(c)
Design maneuvering speed V
A.
For
V
A,
the following applies:
(1)
V
A
may not be less than
V
S
√
n
where—
(i)
V
S
is a computed stalling speed
with flaps retracted at the design
weight, normally based on the max-
imum airplane normal force coeffi-
cients,
C
NA
; and
(ii)
n is the limit maneuvering load
factor used in design
(2) The value of
V
A
need not exceed
the value of
V
C
used in design.
(d)
Design speed for maximum gust in-
tensity, V
B
. For V
B
, the following apply:
(1) V
B
may not be less than the speed
determined by the intersection of the
line representing the maximum posi-
tive lift, C
NMAX
, and the line rep-
resenting the rough air gust velocity
on the gust V-n diagram, or V
S1
√
n
g
,
whichever is less, where:
(i) n
g
the positive airplane gust load
factor due to gust, at speed V
C
(in ac-
cordance with § 23.341), and at the par-
ticular weight under consideration; and
(ii) V
S1
is the stalling speed with the
flaps retracted at the particular weight
under consideration.
(2) V
B
need not be greater than V
C
.
[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as
amended by Amdt. 23–7, 34 FR 13088, Aug. 13,
1969; Amdt. 23–16, 40 FR 2577, Jan. 14, 1975;
Amdt. 23–34, 52 FR 1829, Jan. 15, 1987; Amdt.
23–24, 52 FR 34745, Sept. 14, 1987; Amdt. 23–48,
61 FR 5143, Feb. 9, 1996]
VerDate Mar<15>2010
10:12 Mar 18, 2014
Jkt 232046
PO 00000
Frm 00222
Fmt 8010
Sfmt 8010
Y:\SGML\232046.XXX
232046
pmangrum on DSK3VPTVN1PROD with CFR