An Introduction to Rotorcraft Aerodynamics

Explore momentum theory as a simple rotor model that links hover thrust, induced velocity, and power, using actuator disc assumptions and metrics like disc loading and power loading.

Apply conservation laws—continuity, momentum, and energy—to relate rotor thrust, induced velocity, slipstream area, and hover power under momentum theory, with Mars and Earth examples.

Analyze hover power for a four-rotor helicarrier using momentum theory. Estimate 53 gigawatts per rotor for 26-meter rotors and 100 million kg mass, deeming hover infeasible.

Explore the figure of merit as a non-dimensional rotor efficiency metric, comparing ideal momentum theory power to actual power and detailing factors like P0, profile power, and induced loss factor.

Learn how blade element theory estimates profile power and rotor thrust in hover by blending momentum theory with blade section lift and drag, using solidity and figure of merit.

Apply momentum theory to climb and descent, derive thrust, induced velocity, and power relationships, and contrast climb and descent flow models within rotorcraft aerodynamics.

Explore how momentum theory explains rotor inflow with the universal inflow curve across climb, descent, and intermediate zones, including vortex ring and windmill break states, and auto rotation dynamics.

Apply momentum theory to forward flight, linking rotor tilt, V infinity, alpha, slipstream, and induced velocity via conservation of mass, momentum, and energy for rotorcraft aerodynamics.

Introduce advanced ratio to clean up the transcendental induced velocity equation. Analyze forward-flight asymmetry, reverse-flow regions, and high Mach zones, including a universal power curve.

Shift from momentum theory to blade element theory, linking lift and drag on independent two-dimensional blade sections to rotor thrust and power.

Explore how lift and drag coefficients vary with angle of attack for symmetric and non-symmetric airfoils, stall behavior, and implications for rotorcraft blade design.

Explain how thrust and power coefficients depend on local airfoil characteristics and inflow. Discuss linear lift and quadratic drag models, angle of attack reduction by inflow, and iterative hover solutions.

Combine blade element and momentum theory into blade element momentum theory to analyze inflow variations and rotor efficiency across the disk.

Explore how solidity and blade pitch variation shape the induced inflow and induced power coefficient for hover, and why uniform inflow is considered ideal in momentum theory.

Explore blade element momentum theory for rotorcraft, aiming for uniform inflow and constant lambda, and compare ideal and optimum rotors with hyperbolic twists and angle of attack alpha.

Examine the limits of blade element and momentum theory with tip losses. Learn how tip-induced flow lowers thrust and how the printing method models it.

Explore rotorcraft performance through a power economy that combines induced, profile, and parasitic power, plus climb and tail rotor losses, to determine hover and forward flight limits.

Analyze rotorcraft power economy, including induced and parasitic losses, to estimate Gazelle-inspired helicopter performance. Explore max speed around 250 km/h, hover ceiling near 7,000–7,500 ft, climb rate, and payload limits.