Federal Aviation Administration, DOT Section 25.341 for 0 -s -2H where - s = distance penetrated into the gust (feet); Uds = the design gust velocity in equivalent airspeed specified in paragraph (a)(4) of this section; and H = the gust gradient which is the distance (feet) parallel to the airplane-s flight path for the gust to reach its peak velocity. (3) A sufficient number of gust gradient distances in the range 30 feet to 350 feet must be investigated to find the critical response for each load quantity. (4) The design gust velocity must be: ( spaschal on DSK3GDR082PROD with CFR ) 16 where - Uref = the reference gust velocity in equivalent airspeed defined in paragraph (a)(5) of this section. Fg = the flight profile alleviation factor defined in paragraph (a)(6) of this section. (5) The following reference gust velocities apply: ) Where: Fgz = 1 - U - - s - - U = ds -1- Cos-" - - - H - 2 - U ds = U ref Fg H 350 ( Fg = 0.5 Fgz + Fgm Z mo Fgm = R 2 Tan - - R1 = R2 = ; 250000 R1 - 4-; Maximum Landing Weight Maximum Zero Fuel Weight 12:50 Apr 30, 2019 Jkt 247046 PO 00000 Frm 00249 Fmt 8010 ; Maximum Take-off Weight Zmo = Maximum operating altitude defined in Section 25.1527 (feet). (7) When a stability augmentation system is included in the analysis, the effect of any significant system nonlinearities should be accounted for when deriving limit loads from limit gust conditions. (b) Continuous turbulence design criteria. The dynamic response of the airplane to vertical and lateral continuous turbulence must be taken into account. The dynamic analysis must take into account unsteady aerodynamic characteristics and all significant structural degrees of freedom including 239 VerDate Sep<11>2014 ; Maximum Take-off Weight Sfmt 8010 Y:\SGML\247046.XXX 247046 EN08MR96.004 Section 25.341 Gust and turbulence loads. (a) Discrete Gust Design Criteria. The airplane is assumed to be subjected to symmetrical vertical and lateral gusts in level flight. Limit gust loads must be determined in accordance with the provisions: (1) Loads on each part of the structure must be determined by dynamic analysis. The analysis must take into account unsteady aerodynamic characteristics and all significant structural degrees of freedom including rigid body motions. (2) The shape of the gust must be: ER09FE96.019 [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-23, 35 FR 5672, Apr. 8, 1970] (i) At airplane speeds between VB and VC: Positive and negative gusts with reference gust velocities of 56.0 ft/sec EAS must be considered at sea level. The reference gust velocity may be reduced linearly from 56.0 ft/sec EAS at sea level to 44.0 ft/sec EAS at 15,000 feet. The reference gust velocity may be further reduced linearly from 44.0 ft/ sec EAS at 15,000 feet to 20.86 ft/sec EAS at 60,000 feet. (ii) At the airplane design speed VD: The reference gust velocity must be 0.5 times the value obtained under Section 25.341(a)(5)(i). (6) The flight profile alleviation factor, Fg, must be increased linearly from the sea level value to a value of 1.0 at the maximum operating altitude defined in Section 25.1527. At sea level, the flight profile alleviation factor is determined by the following equation: ER09FE96.018 (1) May not be less than Section1.0 at speeds up to VC; and (2) Must vary linearly with speed from the value at VC to zero at VD. (d) Maneuvering load factors lower than those specified in this section may be used if the airplane has design features that make it impossible to exceed these values in flight.