A method of inspecting the fan track liner of a gas turbine engine of a type having a rotatable propulsive fan circumscribed by a fan track liner and having a plurality of fan blades extending radially outwardly from a central hub, the method comprising the steps of: affixing at least part of an inspecting device to the fan so as to be directed towards the fan track liner; and rotating the fan within the fan track liner to move said at least part of the inspecting device circumferentially relative to at least a region of the fan track liner to thereby scan said region of the fan track liner with said at least part of the inspecting device, wherein said step of affixing at least part of the inspecting device to the fan involves positioning said at least part of the inspecting device adjacent the fan track liner via a support extending radially outwardly from the hub of the fan, such that said step of rotating the fan is effective to move said at least part of the inspecting device across the radially innermost surface of the fan track liner, wherein said inspecting device comprises an ultrasonic transducer which is affixed to said fan, and wherein the transducer is provided within an assembly which, when affixed to said fan, is supported in sliding contact with the radially innermost surface of the fan track liner during the or each said step of rotating the fan, wherein said assembly comprises a resilient ultrasonic couplant material arranged between the ultrasonic transducer and the fan track liner and for sliding contact with the fan track liner during the or each said step of rotating the fan to facilitate the transmission of ultrasonic energy from the transducer into the fan track liner, and wherein the method comprises directing an ultrasonic couplant liquid between the transducer and the fan track liner during the or each step of rotating the fan. affixing at least part of an inspecting device to the fan so as to be directed towards the fan track liner; and rotating the fan within the fan track liner to move said at least part of the inspecting device circumferentially relative to at least a region of the fan track liner to thereby scan said region of the fan track liner with said at least part of the inspecting device, wherein said step of affixing at least part of the inspecting device to the fan involves positioning said at least part of the inspecting device adjacent the fan track liner via a support extending radially outwardly from the hub of the fan, such that said step of rotating the fan is effective to move said at least part of the inspecting device across the radially innermost surface of the fan track liner, wherein said inspecting device comprises an ultrasonic transducer which is affixed to said fan, and wherein the transducer is provided within an assembly which, when affixed to said fan, is supported in sliding contact with the radially innermost surface of the fan track liner during the or each said step of rotating the fan, wherein said assembly comprises a resilient ultrasonic couplant material arranged between the ultrasonic transducer and the fan track liner and for sliding contact with the fan track liner during the or each said step of rotating the fan to facilitate the transmission of ultrasonic energy from the transducer into the fan track liner, and wherein the method comprises directing an ultrasonic couplant liquid between the transducer and the fan track liner during the or each step of rotating the fan.