Which type of instability is identified by progressively steeper pitch oscillations?

The type of instability characterized by progressively steeper pitch oscillations is known as longitudinal instability. This phenomenon occurs when the aircraft experiences changes in its angle of attack that are not damped quickly enough, leading to an increasing amplitude in pitch oscillations over time.

Longitudinal stability is primarily concerned with the aircraft's behavior in the pitch axis, which is influenced by the aircraft's weight distribution, center of gravity, and aerodynamic characteristics of the tailplane. If an aircraft is longitudinally unstable, any disturbance in pitch will result in a response that exacerbates the initial disturbance instead of dampening it. This results in oscillations that become progressively steeper until the aircraft is at risk of reaching a dangerous attitude.

In contrast, directional instability involves yawing behaviors, where the aircraft may not maintain a straight flight path and tends to veer off course. Lateral instability pertains to rolling motions about the longitudinal axis, often related to balance during turns or crosswinds. Vertical instability is not a standard term used in aerodynamics in this context, as all movements vertically (up and down) typically involve the pitch axis and can be encompassed within longitudinal analysis.

Understanding the nature of longitudinal instability is critical for pilots and engineers to ensure that aircraft are designed with appropriate