Patent ID: 7997872

Claim:
A fan blade arrangement for a gas turbine engine, the arrangement comprising: a first blade having a leading edge, a trailing edge and a suction surface extending between the leading edge and the trailing edge; a second blade adjacent and generally parallel to the first blade; a covered passage defined by the first blade and the second blade, wherein the blade arrangement is subject to an air flow generally parallel to the suction surface and in a direction generally from the leading edge towards the trailing edge, the air flow giving rise to a shock wave associated with the leading edge of the second fan blade, the shock wave impinging on the suction surface of the first blade at a shock wave position, and a suction surface blade angle of the first blade progressively reduces in a direction generally from the leading edge towards the trailing edge along part of the suction surface so that the cross-sectional area of the covered passage between the first and second fan blades increases over an entire length of the covered passage such that the shock wave can move smoothly into and out of the covered passage.