Section 25.495 14 CFR Ch. I (1-1-19 Edition) WT - fSectionAE - -B + - A+B- A + B + SectionE - Where: VN = Nose gear vertical reaction. WT = Design takeoff weight. A = Horizontal distance between the c.g. of the airplane and the nose wheel. B = Horizontal distance between the c.g. of the airplane and the line joining the centers of the main wheels. E = Vertical height of the c.g. of the airplane above the ground in the 1.0 g static condition. Section = Coefficient of friction of 0.80. f = Dynamic response factor; 2.0 is to be used unless a lower factor is substantiated. In the absence of other information, the dynamic response factor f may be defined by the equation: - - - f = 1 + exp-" - -" 1 - 2 - - - spaschal on DSK3GDR082PROD with CFR Where: x is the effective critical damping ratio of the rigid body pitching mode about the main landing gear effective ground contact point. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-23, 35 FR 5673, Apr. 8, 1970; Amdt. 25-97, 63 FR 29072, May 27, 1998] Section 25.497 Tail-wheel yawing. (a) A vertical ground reaction equal to the static load on the tail wheel, in combination with a side component of equal magnitude, is assumed. (b) If there is a swivel, the tail wheel is assumed to be swiveled 90Section to the airplane longitudinal axis with the resultant load passing through the axle. (c) If there is a lock, steering device, or shimmy damper the tail wheel is also assumed to be in the trailing position with the side load acting at the ground contact point. Section 25.499 Nose-wheel yaw and steering. (a) A vertical load factor of 1.0 at the airplane center of gravity, and a side component at the nose wheel ground contact equal to 0.8 of the vertical ground reaction at that point are assumed. (b) With the airplane assumed to be in static equilibrium with the loads resulting from the use of brakes on one side of the main landing gear, the nose gear, its attaching structure, and the fuselage structure forward of the center of gravity must be designed for the following loads: (1) A vertical load factor at the center of gravity of 1.0. (2) A forward acting load at the airplane center of gravity of 0.8 times the vertical load on one main gear. (3) Side and vertical loads at the ground contact point on the nose gear that are required for static equilibrium. (4) A side load factor at the airplane center of gravity of zero. (c) If the loads prescribed in paragraph (b) of this section result in a nose gear side load higher than 0.8 times the vertical nose gear load, the design nose gear side load may be limited to 0.8 times the vertical load, with 252 VerDate Sep<11>2014 12:50 Apr 30, 2019 Jkt 247046 PO 00000 Frm 00262 Fmt 8010 Sfmt 8010 Y:\SGML\247046.XXX 247046 ER27MY98.018 VN = Section 25.495 Turning. In the static position, in accordance with figure 7 of appendix A, the airplane is assumed to execute a steady turn by nose gear steering, or by application of sufficient differential power, so that the limit load factors applied at the center of gravity are 1.0 vertically and 0.5 laterally. The side ground reaction of each wheel must be 0.5 of the vertical reaction. ER27MY98.017 drag force of 0.8 times the vertical reaction cannot be attained under any likely loading condition. (d) An airplane equipped with a nose gear must be designed to withstand the loads arising from the dynamic pitching motion of the airplane due to sudden application of maximum braking force. The airplane is considered to be at design takeoff weight with the nose and main gears in contact with the ground, and with a steady-state vertical load factor of 1.0. The steadystate nose gear reaction must be combined with the maximum incremental nose gear vertical reaction caused by the sudden application of maximum braking force as described in paragraphs (b) and (c) of this section. (e) In the absence of a more rational analysis, the nose gear vertical reaction prescribed in paragraph (d) of this section must be calculated according to the following formula: