Hydraulic Flight Control Systems in Helicopters

Introduction

• Presenter: Jacob
• Topic: Hydraulic flight control systems in helicopters
• Categories of helicopters by hydraulic control system:
  1. No hydraulic flight controls
  2. Hydraulically assisted or boosted flight controls
  3. Fully hydraulic systems

No Hydraulic Flight Controls

• Example: Robinson R22 helicopters
• Characteristics:
  • Simple design
  • Cheap to produce and maintain
  • Lightweight
  • Great for training and light work
• Operation:
  • Use push-pull rods to move the swash plate and tail rotor
  • Require no extra mechanical advantage due to low weight
• Suitable for helicopters weighing 1,000 to 2,000 pounds

Hydraulically Assisted or Boosted Flight Controls

• Characteristics:
  • Reduces workload for pilots
  • Comparable to power steering in cars
• Operation:
  • Still possible to move controls without hydraulics, but requires more force
• Examples:
  • Robinson R44
  • Bell 206 (TH-67/OH-58 in military)
• System Components:
  • Hydraulic reservoir/manifold
  • Pump
  • Servo actuators (lateral, longitudinal, collective)
  • Return lines for closed circuit system
• Additional Features:
  • Artificial feel or force trim for feedback to pilots

Fully Hydraulic Systems

• Primarily used in military helicopters (e.g., Apache)
• Developed to overcome servo transparency phenomenon (jack stall)
• System Characteristics:
  • High pressure up to 3,000 psi
  • Allows aggressive maneuvers and g-loading
• Drawbacks:
  • No control authority if hydraulics fail
  • Requires redundant systems for reliability (multiple reservoirs, pumps, lines)

Conclusion

• Three types of hydraulic flight control systems:
  1. No hydraulics
  2. Hydraulically assisted/boosted
  3. Fully hydraulic
• Importance of understanding each system's design and functionality for safe operation

Call to Action

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• Reminder of the focus on safety in helicopter operation