SIFT Army Aviation Information Practice Test

The tendency of a helicopter to oscillate while in a hover is known as:

1. Ground resonance

2. Pendular motion

3. Yaw instability

4. Dynamic rollover

The correct answer is: Pendular motion

The tendency of a helicopter to oscillate while in a hover is referred to as pendular motion. This phenomenon occurs primarily due to the dynamics of how the helicopter's rotor system interacts with the surrounding air and its center of gravity. In a hover, any slight movement or displacement of the helicopter's center of gravity can lead to a pendulum-like effect, where the helicopter swings back and forth around its center of gravity, similar to how a pendulum moves. This oscillation is often a response to the rotor system's lift and uneven weight distribution, as well as external factors like wind or ground effect. Understanding this concept is critical for pilots, as they must be aware of how to counteract these oscillations to maintain stability during hover operations. Additionally, recognizing pendular motion helps in improving control inputs and ensuring safety during flight operations.