14.72 Main Rotor Systems

14.72.2 Describe the construction of current rotor blades.

Construction of Modern Rotor Blades

• Built around a strong spar (main structural member)
• Covered with a lightweight skin (aluminium or composite materials)
• Internal structure may include honeycomb or foam core for strength and lightness
• Leading edge often reinforced with:
  • Abrasion strips (e.g. stainless steel/titanium)
  • Protection against erosion and impact
• Blades are designed with:
  • Aerofoil shape for lift
  • Possible twist along the span for efficiency
• Fitted with balance weights to ensure smooth operation

Summary:
Modern rotor blades are lightweight, strong composite or metal structures with a spar, skin, and protective leading edge, designed for efficiency and durability.

14.72.4 Outline the basic features of the following systems:

(a) rigid rotor;

• Blades are rigidly attached to the hub (no flapping or lead-lag hinges)
• Feathering occurs via pitch bearings (mechanical hinge)
• Flapping and lead-lag are accommodated by elastic flexing of the blades and hub

Summary:
A rigid rotor has no flapping or drag hinges; blade movement is achieved through flexibility, with feathering as the only hinged motion, giving fast and direct control response.