600
14 CFR Ch. I (1–1–14 Edition)
Pt. 25, App. G
N
N
y
y
y
y
one
one
γ
( )
−
−
=
∑
−
−
⎛
⎝
⎜⎜
⎞
⎠
⎟⎟ +
−
−
⎛
⎝
⎜⎜
⎞
⎠
⎟⎟
⎡
⎣
⎢
⎢
⎤
⎦
⎥
⎥
t
o
P
b A
P
b A
g
g
1
1
2
2
exp
exp
where—
t=selected time interval.
y=net value of the load or stress.
Y
one
=
g
=value of the load or stress in one-g
level flight.
N(y)=average number of exceedances of the
indicated value of the load or stress in
unit time.
è=symbol denoting summation over all mis-
sion segments.
N
o
, A
¯ =parameters determined by dynamic
analysis as defined in paragraph (c)(2) of
this appendix.
P
1
, P
2
, b
1
, b
2
=parameters defining the prob-
ability distributions of root-mean-square
gust velocity, to be read from Figures 1
and 2 of this appendix.
The limit gust loads must be read from the
frequency of exceedance curves at a fre-
quency of exceedance of 2
×
10¥5 exceedances
per hour. Both positive and negative load di-
rections must be considered in determining
the limit loads.
(4) If a stability augmentation system is
utilized to reduce the gust loads, consider-
ation must be given to the fraction of flight
time that the system may be inoperative.
The flight profiles of paragraph (c)(1) of this
appendix must include flight with the sys-
tem inoperative for this fraction of the flight
time. When a stability augmentation system
is included in the analysis, the effect of sys-
tem nonlinearities on loads at the limit load
level must be conservatively accounted for.
(d)
Supplementary design envelope analysis.
In addition to the limit loads defined by
paragraph (c) of this appendix, limit loads
must also be determined in accordance with
paragraph (b) of this appendix, except that—
(1) In paragraph (b)(3)(i) of this appendix,
the value of U
s=85 fps true gust velocity is
replaced by U
s=60 fps true gust velocity on
the interval 0 to 30,000 ft. altitude, and is lin-
early decreased to 25 fps true gust velocity
at 80,000 ft. altitude; and
(2) In paragraph (b) of this appendix, the
reference to paragraphs (b)(3)(i) through
(b)(3)(iii) of this appendix is to be understood
as referring to the paragraph as modified by
paragraph (d)(1).
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