The determination of an accurate value of a moment of inertia plays a vital role in designing decent mechanical parts as general such as a flight control system for aircraft. This why an accurate value for moment of inertia is needed. A test rig was designed and made form cardboard and then developed for wood. Experiments were carried out, to get to the final shape and product for the test rig, and it was manufactured with dimensions of 2.7x2.5 meters and with a holder dimension of 60x60 cm that bears up to 10 kg. Moreover, an electronic circuit has been used to measure the period of oscillations. The moment of inertia of a rectangular block of wood and a UAV is found. The moment of inertia was measured analytically and experimentally for the block of wood, and by comparing the values it founds that the error ratio from 1%to5% in X axis and -6% to 7% in Y axis. For the UAV the moment of inertia’s error ratio in X axis from 2% to 5% and in Y axis from 11% to 14%. It is noticed that the greater the additional weight, the greater the accuracy of the device.