Fa2004 16.33348 Oo or yo Horizontal Down Figure 1: Perturbed Axes. The equilibrium condition was that the aircraft was angled up by eo with velocity VTo=Uo. The vehicle's motion has been perturbed(Xo- X)so that now 0=00+0 and the velocity is VT+ vro. Note that Vr is no longer aligned with the X-axis, resulting in a non-zero u and w. The angle y is called the flight path angle, and it provides a measure of the angle of the velocity vector to the inertial horizontal axis� Fall 2004 16.333 4–8 W C.G. 0 VT VT0 = U0 XE X0 X q � Z Z0 ZE � Θ � or �0 �0 �0 Horizontal U = U + u Down Figure 1: Perturbed Axes. The equilibrium condition was that the aircraft was angled up by Θ0 with velocity VT0 = U0. The vehicle’s motion has been perturbed (X0 → X) so that now Θ = Θ0 +θ and the velocity is VT = VT0. Note that VT is no longer aligned with the X­axis, resulting in a non­zero u and w. The angle γ is called the flight path angle, and it provides a measure of the angle of the velocity vector to the inertial horizontal axis