Rotor Blade Designs Overview

Rotor Blade Designs

• Symmetrical blades have better aerodynamic pitch characteristics, while asymmetrical blades produce more lift for the same surface area. Asymmetrical blades have a higher camber on one side compared to the other. Engineers achieve the same pitching characteristics in asymmetrical blades by sweeping the edges 3 degrees upwards for stability. Symmetrical designs are more common due to asymmetrical designs' instability.
• Blade designs are categorized as either parallel (uniform) or tapered. Uniform designs have parallel leading and trailing edges, producing greater lift due to the chord line. Tapered designs have converging leading and trailing edges, decreasing chord length. Manufacturers favor uniform designs due to cost-effectiveness (single stamping). Tapered designs require more complex machining due to varying chord length.
• Tapered blades produce more consistent lift throughout the blade since speed varies. A negative twist is applied to the blade to compensate for increasing angle of attack from root to tip and equal lift at root and tip.
• Construction methods include bonded construction (stronger, no holes), single-pocket (quicker to produce), and multi-pocket (easier to repair). Single-pocket design is more prone to damage if a rib is damaged.
• Balance weights are used (tip and chordwise) to control blade behavior/flight path. Adjusting these weights can raise or lower the blade position within its plane of rotation

Blade Construction and Features

• Bonded construction is used for increased strength and lack of holes.
• Single-pocket construction is more efficient to produce
• Multi-pocket construction is easier to repair
• Blade tips include balance weights for stability and aerodynamic control.
• Stainless steel coverings (cappings) on the leading edge protect against erosion.
• Rotor blade color is matte black to reduce glare. Composite blades also have an ability for static discharge.
• Tap testing is a primary inspection method for composite blades.

Rotor Blade Inspection and Maintenance

• Multi-pocket construction is more expensive to manufacture, but more reparable if damaged
• Additional double plates increase structural strength and stiffness at the root and tip without increasing blade weight.

Helicopter Control Systems

• Hydraulics are used for control systems before assembly and remain in operation until use.Collective is connected to the throttle and is rigged first.
• Trim tabs on the trailing edge help control the plane of rotation
• Servo flaps positioned towards the trailing edge are helpful when eliminating the need for hydraulic systems.
• The servo flap system does provide greater aerodynamic reactions and improves the use of servo tabs.

This quiz covers the fundamental concepts of rotor blade designs, including the differences between symmetrical and asymmetrical blades, uniform and tapered designs, and their aerodynamic properties. Understand how these designs influence lift and stability in engineering applications.