A new post is up at
RetroMechanix.com reproducing several early postwar reports on convertible aircraft (vehicles which can function either as a direct lift, rotary aircraft or as fixed wing airplane, with conversion from one to the other type as required) found in NACA files at the National Archives:
The reports feature a wide variety of innovative and unusual convertible aircraft projects designed by Charles H. Zimmerman (whose V-173 "Flying Wing Helicopter" is shown above), Gerard P. Herrick, Lloyd H. Leonard, Arthur M. Young, and E. Burke Wilford, among others. The article features 27 images of these unusual flying machines, several of which may be previously unpublished.
-Jared