1947. NACA's ramjet flying test stand

 

First photo of ramjet flight test shows NACA 20 in. design mounted on retractable support under B-29 belly. Although the ramjet engine is designed for operation at supersonic speed, these 300 m.p.h. tests determine thermodynamic data and the  effect of altitudes up to 40,000 ft. In secret operation for more than a year, this flying test stand is used for a variety of jet engine tests at NACA Flight Propulsion Research Laboratory, Cleveland, Ohio. (NACA photo) 

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Aviation Week | December 15, 1947