Helicopter Lesson: Translating Tendency

Introduction

• Topic: Understanding translating tendency in helicopters.
• Helicopter System: Focus on counterclockwise rotating helicopters.
• Definition: Translating tendency is the helicopter’s drift in the direction of tail rotor thrust, typically to the right for counterclockwise systems.

Causes of Translating Tendency

• Newton’s Third Law: Every action has an equal and opposite reaction.
  • Main Rotor: Turns counterclockwise, pushing the fuselage to turn clockwise (right direction) if uncompensated.
  • Tail Rotor: Acts as an anti-torque device to stabilize the helicopter's heading and counteract the rotation of the main rotor.

Effects

• Drift to the Right: Due to tail rotor thrust balancing the main rotor’s torque.
• Left Skid/Left Wheel Low: At hover, the helicopter tends to hang left to compensate for translating tendency.

Compensation Techniques

1. Rigging

   • Flight Controls: Rig controls to increase pitch and counteract right drift.
   • Transmission Offset: Shift transmission slightly left to adjust the center of gravity, counteracting right drift.

2. Flight Management System (FMC)

   • Automatically adjusts controls to maintain stationary hover.

3. Pilot Input (Manual Method)

   • Apply left cyclic input to counteract right drift.

Conclusion

• Key Takeaway: Translating tendency is the inherent drift to the right due to tail rotor thrust balancing the main rotor’s torque.
• Compensation Methods: Include rigging, flight management systems, and manual pilot input.

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Note: This lesson illustrates the dynamic physics involved and the pilot/technical adjustments necessary to maintain a stable hover in helicopters with counterclockwise rotating systems.