Heading Angular Velocity Correction and Initialization

The inertial reference for body axis heading angular velocity relative to the orbit plane in the Rockwell/Dryden formulation can be thought of as true north, defined by the local meridian. However, a local meridian cannot be used as an inertial reference unless its motion as the earth turns is accounted for. Powers and Schilling (1980, 1985) derive this correction.

The earth’s atmosphere is carried around with earth rotation, causing side winds relative to the orbit plane. This requires special initialization for starting transient response calculations at zero sideslip. Closed-form initialization formulas are available using initial angle of attack, velocity, and flight path angle.