L R一 L sin(a)=R sin(g) ng Figure 2-2: Torsional pendulum experimental setup to determine roll axis inertia, Ixc, for the trainer aircraft. The period of oscillation of a roll angle perturbation, is measured to parameterize the aircraft inertia. The angle a is the small angle deviation of the supporting cables from the vertical position. This experiment was also repeated for the pitch and yaw axes to determine Iyy and Izz respectivel For rotational perturbations applied to the airframe, the product of interior angles and distances must be constant 2 where o is the aircraft roll angle perturbation and a is the small angle deviation of the supporting cables from the vertical position. The differential equation describin the motion of the torsional pendulum is governed by a torsional inertia term and the restoring moment due to tension forces Irao+ 2TRsina=0Figure 2­2: Torsional pendulum experimental setup to determine roll axis inertia, Ixx, for the trainer aircraft. The period of oscillation of a roll angle perturbation, φ, is measured to parameterize the aircraft inertia. The angle α is the small angle deviation of the supporting cables from the vertical position. This experiment was also repeated for the pitch and yaw axes to determine Iyy and Izz respectively. For rotational perturbations applied to the airframe, the product of interior angles and distances must be constant Rφ = Lα (2.2) where φ is the aircraft roll angle perturbation and α is the small angle deviation of the supporting cables from the vertical position. The differential equation describing the motion of the torsional pendulum is governed by a torsional inertia term and the restoring moment due to tension forces ¨ Ixxφ + 2T R sin α = 0 (2.3) 34