Rotor Blade Designs Overview

Rotor Blade Designs

• Symmetrical blades have a better aerodynamic pitch characteristic.
• Asymmetrical blades produce more lift for the same surface area; they have more camber on one side. Engineered asymmetric blades can achieve the same advantages as symmetrical blades through blade edge sweeping.
• Symmetrical blades are more common due to the instability of asymmetrical design.
• Two main blade planform types: parallel (uniform) and tapered.
• Uniform planforms have parallel leading and trailing edges and create more lift due to the consistent chord length.
• Tapered planforms have converging leading and trailing edges, decreasing chord length, causing more uniform lift across the blade.
• Manufacturers prefer uniform blades because of cost-effectiveness; only one rib part number is needed.
• Tapered blades require different rib numbers due to varying chord length.
• Tapered blade designs provide more equal lift across the blade by featuring negative twist, allowing for higher angles of attack at the root (where rotation is slower) to ensure the same lift across the entire blade span.

Rotor Blade Construction

• Bonded construction is preferred for strength and avoids drilling holes in the blade.
• Single-pocket construction is quicker to build but is more difficult to repair if damage occurs; multi-pocket construction allows easier repair.

Rotor Blade Balance and Trim

• Balance weights are added to specified locations on the blade for proper balance and flight characteristics.
• Weights added to the blade's leading edge make the helicopter fly lower, while adding weight to the trailing edge makes it fly higher.
• Trim tabs provide an easier way to adjust the blade's pitch than balance weights and rely on airflow velocity.
• Adjusting trim tabs higher will lower the flight of the helicopter, and vice versa.
• Hydraulics need to be turned off during rigging to remove residual pressure before connecting the collective and throttle controls together.
• The collective and throttle are connected via correlator or auto-throttle linkage.
• Rigging of collective is done initially, and then throttle is correctly connected.
• Helicopter is tested with ground runs, hovers, and full flight tests, finishing with an autorotation check at minimum gross weight.

Rotor Blade Features

• Erosion protection capping (stainless steel) is used for the leading edges of rotor blades.
• Rotor blades are painted matte black to reduce glare for the pilot.
• Composite materials for blades offers static discharge abilities, and are inspected via a tap test.
• Additional double plates are implemented at the root and tip for increased structural strength, without increasing blade weight.

This quiz covers the fundamental concepts of rotor blade designs, focusing on symmetrical and asymmetrical blades. It examines their aerodynamic characteristics, different planform types, and the advantages of each design. Ideal for those studying aerospace engineering or rotorcraft design.