Machine Design
Sagita Helicopters model doublerotor  Sagita Helicopters

Innovative copter sports double-rotor design

Sagita  takes a unique approach to helicopter design by using dual counter-rotating rotors each powered by separate concentric turbines.

Sagita RC Model Helicopter REDT
Sagita has built an RC model of its concept.

A new helicopter concept with less complex mechanics aims to make aviation safer, simpler, and easier to maintain. Sagita Helicopters in Belgium is behind the design known as REDT (Direct Turbine Driven Rotor).

Unlike contemporary helicopters that use a tail rotor and gearbox, REDT needs neither of these components. At this point Sagita has only built an RC scale model of its concept, not a full-sized version. The concept uses a fuselage-mounted compressor to pressurize air for two concentric turbines that drive counter-rotating blades. The use of two rotors that spin in opposite directions eliminates the need to have a gearbox that manipulates hinged blades.

Sagita Helicopters described its concept for rotor drives at the 3rd European Conference for Aero-Space Sciences. Its technical outline of diagrams and conclusion of flight tests seem to explain more of the advantages and disadvantages, though it is a work in progress.

Rotor Head Sagita Helicopter Schematic


REDT Helicopter Turbine View
Lowering the number of moving parts for the REDT helps reduce maintenance and improves mechanical reliability. One of the most common helicopter complications REDT avoids is “dead man’s curve.” Pilots flying outside of this height-velocity performance curve when the tail rotor over speeds might not be able to make a safe landing.

Other advantages include ease of handling because the rotor does not transmit torque to the fuselage, an estimated 10% more power available to the rotor because the engine is supercharged; plus no noise from a gearbox, which makes for a more comfortable flying experience.

However the engine has overheated during some flight tests and developers are looking for a cause and a cure.

Helicopter Air System Block Diagram

Watch the demo below of Sagita’s scale model’s flight test.

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