Measurement of the yawing moment of inertia of an aircraft (HP 115) in flight

Abstract

The yawing moment of inertia has been obtained by measuring the acceleration in yaw resulting from the release of a wing-tip parachute. Lateral accelerometers mounted near the fore and aft extremities of the aircraft on a line parallel to the principal axis of inertia were used to measure the yawing acceleration. The principal axis is known in this case from previous ground measurements, but it is shown that 1 degree error in axis inclination would only produce an error of about 3 per cent in the measured inertia. The results obtained from the flight tests are encouraging and are about 3½ per cent lower than earlier measurements on a ground rig and about 2½ per cent greater than the manufacturer's original estimate. Operational problems are discussed and some improvements to the parachute equipment are also suggested.