EARTH-FIXED REFERENCE FRAME, FE (EARTH AXES

OexeIkze)

In many problems of airplane dynamics, the rotation of the Earth relative to Fj can be neglected, and any reference frame fixed to the Earth can be used as an inertial frame. In hypervelocity and space flight this is generally not the case, however, and the angular velocity of the Earth must usually be included in the analysis. Two Earth-fixed frames are of interest, as illustrated in Fig. 4.2. FEO is the “Earth-center” frame with origin at the center of the Earth and axis directions fixed by a reference point on the equator and the Earth’s axis. This frame is useful when the Earth’s rotation must be considered. FE is an Earth-surface frame, with origin near the vehicle if possible, and with 0EzE directed vertically down. 0ExEyE is the local horizontal plane, 0ExE points north, and 0EyE east.

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