Patent ID: 8578697

Claim:
A fan section of a gas turbine engine comprising: a fan having a rotational axis and radially extending fan blades from which ice may be shed in a first direction having a radial and an axial component during operation of the engine, and all or part of a blade of the blades may become detached so as to be ejected from the fan in a second direction having a radial and a circumferential component during operation of the engine, and a fan casing liner panel comprising a first sheet element of composite material and a second sheet element of cellular material having a septum layer on one surface of the cellular material, the first sheet element being bonded in face to face relationship to the septum layer of the second sheet element, wherein the septum layer is perforated, and the perforations comprise holes disposed in a plurality of rows to form lines of preferential weakness to ease passage of the blade or part thereof into the liner panel, each of the plurality of rows extending circumferentially about the rotational axis of the fan in a plane extending perpendicular to the rotational axis, each of the holes being spaced further apart from the nearest hole in an axial direction than from the nearest hole in the circumferential direction, the lines of preferential weakness being aligned with the circumferential component of the second direction, the holes being spaced further apart in a direction at an angle to the lines of preferential weakness to thereby provide lines of enhanced resistance to fracture by impact of ice shed in the first direction.