14.60 Forward Flight

14.60.2 Identify the forces acting on the helicopter in steady forward flight.

Forces in Steady Forward Flight

• Lift:
  Acts upwards, produced by the rotor, balancing weight
• Weight:
  Acts downwards, due to gravity
• Thrust:
  Acts forward, produced by the rotor (tilted forward)
• Drag:
  Acts rearward, opposing motion through the air

Summary:
In steady forward flight, lift = weight and thrust = drag.

14.60.4 Explain the following;

(a) dissymmetry of lift;

• Occurs in forward flight due to unequal airflow across the rotor disc
• Advancing blade:
  • Moves into the airflow
  • Higher relative airspeed → more lift
• Retreating blade:
  • Moves away from the airflow
  • Lower relative airspeed → less lift
• This creates an imbalance of lift across the rotor disc

Correction:

• Flapping and cyclic feathering:
  • Advancing blade flaps up → reduces angle of attack
  • Retreating blade flaps down → increases angle of attack