Northrop X-4 Bantam Semi-Tailless Research Aircraft Family

The Northrop X-4 Bantam comprised two small, twin-jet research aircraft built to investigate a swept-wing configuration without a horizontal tail. Elevons supplied pitch and roll control, while split flaps also served as speed brakes. First flown on December 15, 1948, the design encountered growing pitch oscillations and nose-down trim changes near transonic speeds. Researchers tested balsa strips that thickened the trailing edges of the flaps and elevons, improving handling and delaying some instability, although oscillations persisted above about Mach 0.91. The more reliable second aircraft carried most of the research; its 81st and final NACA flight was September 29, 1953. The results showed the limitations of that semi-tailless configuration with contemporary control technology.