THE EFFECT OF VARIATIONS IN MX4EXCS OF INERTIA ON SPIN AND

An investigation has been conducted in the Langley 15-foot free-spinning tunnel on a research model, representative of a present-day trainer or a four-place cabin monoplane, with varied moments of inertia. The tests were made for ei&t different wing arrangements and four different tail arrangements, including a twin tail. The momsnts of inertia about the three airpLane axes were increased or decreased by a constant percentage and the results were compared. Comparison is also made between these results and those previously presented for conditions with the airplane relative density varied. The results of variation of moments of inertia indicated that, within the range of the present tests, uniformly decreasing the moments of inertia led to steeper spins, higher angular and vertical velocities, and faster recoveries. Comparison of these results with results of previous tests indicated that adding weight at the center of savity up to 50 percent of the basic weight led to higher rates of descent and rotation, had little effect upon recoveries when the eievators were up, and generally had a somewhat adverse effect upon recoveries when the elevators were neutral or down. The results also indicated that the twin-tail configuration was a very effective arrangement as regards spin recovery