The lateral motion had three modes of motion: an aperiodic mode called the spiral mode that could be a divergence or subsidence, a heavily damped aperiodic mode called the roll subsidence, and a short-period oscillation, usually poorly damped, called the Dutch roll mode.
The lateral motion had three distinct modes of movement: a non-repeating mode known as the spiral mode, which could be either upward or downward; a heavily dampened non-repeating mode called the roll subsidence; and a short-term oscillation, often poorly damped, called the Dutch roll mode.