§ 25.473 Landing load conditions and assumptions.

(a) For the landing conditions specified in § 25.479 to § 25.485 the airplane is assumed to contact the ground— (1) In the attitudes defined in § 25.479 and § 25.481; (2) With a limit descent velocity of 10 fps at the design landing weight (the maximum weight for landing conditions at maximum descent velocity); and (3) With a limit descent velocity of 6 fps at the design take-off weight (the maximum weight for landing conditions at a reduced descent velocity). (4) The prescribed descent velocities may be modified if it is shown that the airplane has design features that make it impossible to develop these velocities. (b) Airplane lift, not exceeding airplane weight, may be assumed unless the presence of systems or procedures significantly affects the lift. (c) The method of analysis of airplane and landing gear loads must take into account at least the following elements: (1) Landing gear dynamic characteristics. (2) Spin-up and springback. (3) Rigid body response. (4) Structural dynamic response of the airframe, if significant. (d) The landing gear dynamic characteristics must be validated by tests as defined in § 25.723(a). (e) The coefficient of friction between the tires and the ground may be established by considering the effects of skidding velocity and tire pressure. However, this coefficient of friction need not be more than 0.8.