<div class="htmlview paragraph">Turbine wheel containment on air turbine starters has been standard practice for many years. Proven methods of designing reliable containment rings combine theoretical analyses and empirical relationships derived from large-scale testing programs. The choice of design and material must consider energy absorption, piercing resistance, and the effects on the surrounding static structure due to ring expansion and movement. New concepts such as dual-alloy rings may offer improvements in weight or reliability.</div>