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 exhibited three modes of movement: a non-periodic mode called the spiral mode, which could be either divergence or subsidence; a heavily damped non-periodic mode called the roll subsidence; and a short-period oscillation, often poorly damped, called the Dutch roll mode.