Explain the 'Centrifugal Unseating' failure in external rings and how it manifests in high-speed gearbox inspections.

Centrifugal unseating occurs when the rotational speed $N$ exceeds the ring's design limit, causing it to expand and lift out of the groove. In a gearbox, this is usually catastrophic as the ring flies off and enters the gear mesh. During inspection, if the ring hasn't failed yet, 'unseating' can be identified by: 1) Wear marks on the OD of the ring from contact with the housing; 2) A 'loose' fit of the ring when the shaft is stationary; and 3) Fretting on the groove floor. To remediate, a 'Self-Locking' ring or a ring with a higher 'cling' (lower free diameter) must be used.