A fan casing arrangement for a gas turbine engine having a propulsive fan, the arrangement having a fan case and a fan track liner and being configured to circumscribe the fan, wherein the fan track liner is provided around the inside of fan case so as to adopt a radial position between the fan and the fan case. The fan track liner includes an elongate member which is helically-wound against the inside of the fan case in a plurality of turns. A method of installing a fan track liner in a fan casing arrangement for a gas turbine engine having a propulsive fan, the method involving: providing a fan case to circumscribe the fan, providing a flexible and elongate liner member, and helically winding the liner member against the inside of the fan case in a plurality of turns to define at least part of the fan track liner.