Specialists from TsAGI named after Zhukovsky have developed an unusual propeller with folding blades for promising aircraft. The development can be useful for both light aviation and future supersonic passenger liners.
The essence of the idea is a special design of a booster propeller that operates only during takeoff and landing. After gaining altitude, the blades fold and retract into special niches, which are closed by flaps. As a result, the aircraft maintains an aerodynamic shape and does not lose speed in cruise mode.
The main feature of the patent is that the propeller is hidden not in a separate container, but actually inside an aerodynamic fairing. Moreover, the fairing itself does not rotate with the propeller. This allowed engineers to reduce air resistance and eliminate restrictions on blade size.
The patent description states that the technology is particularly interesting for supersonic civil aircraft. The nose section of such aircraft usually has free volume that is difficult to use for passengers or cargo. It is there that a large-diameter folding propeller is proposed to be integrated.
During takeoff, the flaps open, the blades unfold and create additional thrust. After reaching cruise mode, the system is deactivated: the propeller stops, the blades fold back into the niches, and the surface becomes smooth again without protrusions or gaps.
According to TsAGI calculations, the scheme allows for reduced aerodynamic drag and noise, as well as maintaining compact aircraft dimensions even with an additional power plant.
