Patent ID: 8721260

Claim:
A fan retention shaft for retaining a fan within a gas turbine engine in the event of fan shaft failure, the fan retention shaft having: a first shaft which in use extends from the engine, a second shaft to which in use the fan is attached, the second shaft being coaxial with the first shaft and the first and second shafts defining an annular passage therebetween, an energy absorbing medium disposed within the annular passage, and a retaining formation for preventing the first shaft and the second shaft from moving axially with respect to one another, wherein the retaining formation is configured to release the first shaft and the second shaft from their relative axial positions when a threshold axial load is applied to the fan retention shaft, the energy absorbing medium being arranged to absorb kinetic energy from the second shaft as the second shaft moves axially with respect to the first shaft, wherein the energy absorbing medium absorbs the kinetic energy by being crushed as the second shaft moves axially with respect to the first shaft, and wherein the energy absorbing medium comprises a foam.