The 1930's was a period of active research in aeronautics. The
Northrop Alpha took advantage of the research of it's day with
features such as all-metal stressed-skin semimonocoque
construction, an NACA cowl and the development of wing-body
fillets which are summarized below. Considerable experimentation
went into the study of aircraft configuration and aerodynamic
fairings. The figures show below illustrate the results of wind
tunnel testing of the Northrop Alpha wing-body combination (no
empennage). The "no fillet" curves represent the Alpha without
any fillet. The "optimum fillet" shown in the figures was
developed in the GALCIT 10 foot diameter wind tunnel in May of
1931. This "optimum fillet" resulted in some drag reduction and
a dramatic increase in maximum lift. The "optimum fillet" was
flight tested in June 1931 and was utilized on the second
Northrop Beta as well as on the Gamma's. The configuration of
the "optimum fillet" and several other fillets that were
experimented with are shown below. The GAL