Section 25.341

14 CFR Ch. I (1-1-19 Edition)

H(W) = the frequency response function, determined by dynamic analysis, that re-

Where - 
W = reduced frequency, radians per foot; and
L = scale of turbulence = 2,500 ft.

(3) The limit turbulence intensities,
U, in feet per second true airspeed required for compliance with this paragraph are - 
(i) At airplane speeds between VB and
VC:
U = Uref Fg
Where - 

spaschal on DSK3GDR082PROD with CFR

Uref is the reference turbulence intensity
that varies linearly with altitude from 90
fps (TAS) at sea level to 79 fps (TAS) at
24,000 feet and is then constant at 79 fps
(TAS) up to the altitude of 60,000 feet.
Fg is the flight profile alleviation factor defined in paragraph (a)(6) of this section;

(ii) At speed VD: U is equal to 1-2 the
values
obtained
under
paragraph
(b)(3)(i) of this section.
(iii) At speeds between VC and VD: U
is equal to a value obtained by linear
interpolation.

(2) Values of A must be determined
according to the following formula:

lates the loads in the aircraft structure
to the atmospheric turbulence; and
F(W) = normalized power spectral density of
atmospheric turbulence given by - 

(iv) At all speeds, both positive and
negative incremental loads due to continuous turbulence must be considered.
(4) When an automatic system affecting the dynamic response of the airplane is included in the analysis, the
effects of system non-linearities on
loads at the limit load level must be
taken into account in a realistic or
conservative manner.
(5) If necessary for the assessment of
loads on airplanes with significant nonlinearities, it must be assumed that
the turbulence field has a root-meansquare velocity equal to 40 percent of
the U values specified in paragraph
(b)(3) of this section. The value of limit
load is that load with the same probability of exceedance in the turbulence
field as AU of the same load quantity
in a linear approximated model.
(c) Supplementary gust conditions for
wing-mounted engines. For airplanes
equipped with wing-mounted engines,
the engine mounts, pylons, and wing
supporting structure must be designed

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ER11DE14.026</GPH>

Where - 

Where - 
PL = limit load;
PLSection1g = steady 1g load for the condition;
A = ratio of root-mean-square incremental
load for the condition to root-meansquare turbulence velocity; and
U = limit turbulence intensity in true airspeed, specified in paragraph (b)(3) of this
section.

ER11DE14.025</GPH>

rigid body motions. The limit loads
must be determined for all critical altitudes, weights, and weight distributions as specified in Section 25.321(b), and all
critical speeds within the ranges indicated in Section 25.341(b)(3).
(1) Except as provided in paragraphs
(b)(4) and (5) of this section, the following equation must be used:
PL = PLSection1g Section UA