THE serious nature of difficulties which might be encountered in tail spins, was brought forcibly to the attention of the Material Division of the U.S. Army Air Corps, in the Spring of 1926, when Lieutenant E. H. Barksdale lost his life in attempting to determine the cause of difficult recovery from spins in a military aeroplane being flight tested at Dayton, Ohio. Trouble in recovery from spins had been encountered in several instances in foreign countries, and one or two cases had occurred in the United States: however, the problem was not considered as one generally applicable to all aeroplanes, because, in most cases of previous trouble, the aeroplanes concerned possessed unusual design features which were thought to be mainly responsible for their abnormal behaviour. Prior to this time, general conjectures had been made, regarding probable reasons for difficult recovery from spins, but very little in the nature of systematic investigation had been attempted, consequently no generally applicable principles had been determined. Numerous studies had been made in wind tunnels, and it was recognised that the normal aerofoil would rotate automatically under certain conditions, but the magnitude of the forces involved, and therefore the ability of an aeroplane to recover a normal attitude by use of the controls, could not be readily determined by wind tunnel tests. A few flight tests had indicated that the centre of gravity location, with respect to the resultant air force vector on the lifting surfaces, influenced the type of spin and the case of return to a normal attitude.
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