“For practical tests on certain theories relative to slow-speed airplanes.” The engines, of which several of the major parts were “common to standard automobile engines,” were built in direct-drive and geared versions. The IVD had an inlet and cowling around the cylinders to aid air cooling. The IVG had in addition a gear-driven four-bladed fan in a circular opening at the revised inlet to this cowling for additional cooling capability. The IVG was apparently the model installed in the Crouch-Bolas Dragonfly.
Dragon Type IVD
1932
65hp
214ci
4-cylinder inline
Air cooled
weight: 195 lb
Direct Drive.
Dragon Type IVG
1932
90hp
214ci
4-cylinder inline
Air cooled
weight: 245 lb
Geared Drive.
All Aero 