Helicopter & Propeller Design Basics

Study Notes

Rotors serve as rotating airfoils, generating lift similar to fixed-wing aircraft wings by creating negative pressure above their curved surfaces.

Helicopters are composed of several major components: airframe, fuselage, main rotor system, tail rotor, and powerplant.

Constructed from various materials including metal, wood, composites, and titanium to ensure reliability and performance.
Designs vary from tubular to sheet metal structures, integrating engineering and materials technology.

Acts as the main body of the helicopter, enclosing the cabin, crew, passengers, cargo, engine, avionics, and flight controls.
Can be built using truss-type or semi-monocoque structures and often incorporates advanced composites for strength and weight savings.
Visibility from the cockpit is vital due to the multidirectional nature of helicopter flight.

The main rotor system is essential for lift; it comprises a mast, hub, and rotor blades.
The mast is a hollow cylindrical shaft that connects to the transmission, with the hub at its top serving as the attachment point for rotor blades.
Main rotor systems can be categorized as rigid, semirigid, or fully articulated based on the rotor blade design.

Regulates thrust to maintain directional control as the main rotor torque changes or to adjust headings while hovering.
Typically driven by the transmission to ensure control in the event of engine failure.
Fenestron design employs a shrouded series of rotating blades within a vertical tail, enhancing safety by reducing the risk of contact with objects or personnel.
Notar system uses a fan system that generates low-pressure airflow, providing directional control while being resistant to foreign object damage (FOD).

Reciprocating engines (piston engines) are commonly used in smaller helicopters due to their simplicity and cost-effectiveness.
Turbine engines are more powerful, suitable for various helicopter types, and deliver high power relative to size, though they are generally more costly to operate.

Turbine engines feature components like a compressor, combustion chamber, turbine, and accessory gearbox assembly.
The compressor draws in and compresses air, which is mixed with fuel and ignited to create expanding gases that drive the turbine wheels.
In most turbine setups, the first and second stage turbines operate independently on separate shafts, referred to as a "free turbine," maximizing efficiency and power distribution.