Systematic Configuration Variations

Spin researchers recognized quite early the problems in forming engineering gen­eralities for spinning airplanes. During all spin phases – the entry, the developed spin, and the recovery – airplanes operate in nonlinear ranges of angle of attack, control surface angle, and angular velocities, not to mention inertial moments. Nonlinear behavior means that general­izations require a large body of data obtained by systematic variations in design parameters.

Not long after the NACA 20-foot spin tunnel was put into operation, the veteran spin investigators Oscar Seidman and Anshal I. Neihouse began that process of systematic spin data collection. In a series of NACA Technical Notes and a technical report dating from 1937 to 1948, they reported on the effects of systematic wing, tail, relative density, and mass distribution changes on spin characteristics and recoveries.

With the coming of jet – and rocket-powered airplaneshaving long, slender, heavily loaded fuselages this group, now augmented by Walter J. Klinar and Stanley H. Scher, again picked up the problem of generalizing on spin characteristics by making systematic variations in design parameters. In the new series, the effects of mass distribution were again reviewed, but also the complex aerodynamics of long noses, strakes, and canards (Neihouse, Klinar, and Scher, 1960).