What is thrust in the context of helicopter flight?

In the context of helicopter flight, thrust specifically refers to the force that propels the helicopter forward, allowing it to achieve horizontal movement. The primary source of thrust in a helicopter is generated by the rotor system. The rotor blades create lift as they spin, but they also produce a forward component of thrust when they are tilted forward, enabling the helicopter to move in that direction.

It's important to distinguish thrust from lift, which is primarily the upward force produced by the rotor blades to counteract gravity. While lift is crucial for maintaining altitude, thrust is essential for moving forward or backward. Understanding the roles of these forces helps clarify how helicopters maneuver in the air.

The other concepts in the choices, like resistance during descent, torque from the rotor system, and the upward lift due to rotor blades, do not accurately define thrust and pertain to other dynamics of helicopter flight.