Extended Speed Range of E-Props history

[Blueadventures]

For information the main development of the E-prop can be attributed to drone requirements in the area of 'Extended Speed Range' ERS design.  

 

Extract from manufacture of the drone.

 

Propeller

For the R^2 UAV, a specific propeller was designed by Hélices E-Props (French carbon propeller manufacturer) to maximize the overall performances of the engine at the various required UAV air speeds.

The propeller designed for the R^2 UAV belongs to the 3rd generation of propellers. Due to mechanical performances of the carbon fiber, new aerodynamic designs have become possible: high CL profiles, narrow chords, big diameters, special positions of the blades…

Those type of propellers present a strong ESR effect (Extended Speed Range effect). The term ESR effect is used to define a fixed pitch propeller (or ground adjustable pitch one) which behavior is near from the behavior of a variable pitch propeller.

This ESR effect has the following characteristics: it causes very small gap between the static RPM and the flight RPM, this allows to keep a strong power at take-off. It seems that the max throttle RPM stays nearly constant.

The ESR effect can improve the performances at take-off, because then the engine is running very near of its max RPM, and provides all its power during take-off.

Thanks to their geometries and their profiles, the E-Props propellers as the one developed for the innovative UAV R^2 have a very strong ESR effect, which allows to improve the performances of the aircraft at take-off and in cruise, in comparison with a standard fixed pitch propeller.

Due to the assisted launch and recovery options, the maximum propeller diameter was a design driver as well as the necessity of having a folding propeller.

Seven innovations can be found on the propeller designed for the R^2 UAV, compared with a standard propeller. The obtained performances are exceptional.

The combination of these state of the art airframe, engine and propeller results in a unique and optimal airborne platform for UAV applications.