An investigation of the four-bladed Dowty Rotol R212 propeller (NACA 16 sections) has been made at l/5th scale (0·7 metre diameter) in the RAE 1·5 metre acoustic tunnel. Propeller power absorption and thrust have been measured over a range of rotational speeds up to 8000 rev/min at mainstream speeds from 15 m/s to 60 m/s for a range of blade settings. Slipstream wake surveys show outward movement of the position of the peak pressure as propeller loading is increased.

Noise analysis demonstrates the predominance of multiple tones whose number and intensity increase with helical-tip Mach number. An empirical formula shows that the fundamental tone SPL varies with tip speed and power loading in an identical manner to that observed on a modern ARA-D section propeller.