SIFT Army Aviation Practice Test 2026 – Complete Exam Prep

The correct choice is that pressure differentials between the upper and lower sides of the blades occur when a helicopter's main rotor blades rotate rapidly. As the rotor blades spin, they generate lift through the difference in air pressure created above and below the blades. The airfoil shape of the blades causes the air pressure on the upper surface to be lower than that on the lower surface, allowing the helicopter to rise. This fundamental principle of aerodynamics is crucial for the operation of rotorcraft and is directly related to how lift is generated.

When the rotor blades rotate, the angle of incidence of these blades impacts the lift generated, but the immediate effect of the rapid rotation is primarily the creation of pressure differentials. Understanding this concept is essential for grasping how rotorcraft achieve and maintain flight, as well as how changes in rotor speed and pitch can affect overall aircraft performance.