SIFT Army Aviation Information Practice Test

What are the main forces acting on a helicopter?

1. Induced lift, mass, thrust, and form drag

2. Lift, weight, thrust, and drag

3. Lift, gravity, air resistance, and rotor vortex drag

4. None of the above

The correct answer is: Lift, weight, thrust, and drag

The primary forces acting on a helicopter are lift, weight, thrust, and drag, which are fundamental to understanding helicopter flight dynamics. Lift is the upward force that allows the helicopter to rise and is generated by the rotor blades as they move through the air. The design and angle of attack of these blades are crucial in maximizing lift. Weight is the force due to gravity acting on the helicopter. It must be countered by lift for the helicopter to ascend or maintain altitude. Thrust is the forward force produced by the helicopter's engines, primarily when the rotor blades spin. This thrust propels the helicopter through the air and is essential for maneuverability. Drag is the resistive force acting opposite to the direction of flight, caused by air resistance against the helicopter's body and rotor blades. Understanding and managing drag is integral to maintaining efficiency and performance. While other forces such as induced lift and various types of drag (for instance, form drag) are considerations in flight dynamics, they are components or effects rather than the fundamental forces themselves. The distinctions between these forces help clarify how helicopters operate, making the answer focused on the essential forces pertinent to helicopter mechanics clear and accurate.