Compressor aerofoil

1. A compressor aerofoil comprising:

a suction surface wall comprising a suction surface and a pressure surface wall comprising a pressure surface, the suction surface wall and the pressure surface wall meet at a leading edge and a trailing edge and define a tip comprising a tip surface, the compressor aerofoil comprises a maximum thickness Tmax,

a mean camber line defined as passing through the leading edge and the trailing edge, and

a winglet at the tip and which extends from the suction surface, the winglet comprises an overhang W that comprises a perpendicular extent from the suction surface in a range 0.1Tmax to 1.99Tmax,

the winglet comprises a maximum overhang Wmax that occurs within 50% of a length of the mean camber line from the leading edge,

wherein the winglet comprises a leading portion and a trailing portion, and

wherein the trailing portion comprises a step back from the suction surface towards the pressure surface.

2. The compressor aerofoil as claimed in claim 1 ,

wherein the range is in any one of g 0.2Tmax to 1.5Tmax, 0.6Tmax to 1.0Tmax, 1.05Tmax to 1.99Tmax, or

wherein the overhang W is a distance of 0.6Tmax.

3. The compressor aerofoil as claimed in claim 1 ,

wherein the leading portion of the winglet comprises a blend out portion which extends along the suction surface a distance in the range 5% to 40% of the length of the mean camber line and is located between the maximum overhang Wmax and the trailing portion and which reduces the overhang W from the maximum overhang Wmax to zero.

4. The compressor aerofoil as claimed in claim 1 ,

wherein the leading portion of the winglet comprises a blend in portion which starts at any position within the range between the leading edge and up to 2% of the length of the mean camber line from the maximum overhang Wmax and which increases the overhang W from zero to the maximum overhang Wmax.

5. The compressor aerofoil as claimed in claim 1 , wherein in the trailing portion the perpendicular extent from the suction surface is in a range 0.1Tmax to 1Tmax.

6. The compressor aerofoil as claimed in claim 1 ,

wherein the suction surface comprises a suction surface radial extent and the winglet comprises a radial extent S, where the radial extent S is in the range 1-15% of the suction surface radial extent.

7. The compressor aerofoil as claimed in claim 6 ,

wherein the radial extent S is 1-3% of the suction surface radial extent.

8. The compressor aerofoil as claimed in claim 1 ,

wherein the winglet defines a radially outer surface and which is continuous with and forms part of the tip surface.

9. The compressor aerofoil as claimed in claim 1 ,

wherein the winglet comprises a suction rib extending along a suction surface edge of the winglet and extending radially from the tip surface.

10. The compressor aerofoil as claimed in claim 9 ,

wherein a width Wrib of the suction rib is in the range 5 to 75% of the maximum thickness Tmax of the compressor aerofoil.

11. The compressor aerofoil as claimed in claim 10 ,

wherein the width Wrib of the suction rib is 25% of the maximum thickness Tmax of the compressor aerofoil.

12. The compressor aerofoil as claimed in claim 9 ,

wherein the winglet comprises a pressure rib extending along a pressure surface edge of the winglet and extending radially from the tip surface, and the pressure rib and the suction rib define a leading gap and a trailing gap therebetween.

13. The compressor aerofoil as claimed in claim 9 ,

wherein a height of the suction rib from the tip surface is up to 4% of the length of the mean camber line.

14. The compressor aerofoil as claimed in claim 1 ,

wherein the compressor aerofoil comprises a chord line comprising a chord length defined from the leading edge to the trailing edge,

a ratio of the maximum thickness Tmax to the chord length is up to 0.1.

15. The compressor aerofoil as claimed in claim 14 ,

wherein the ratio of the maximum thickness Tmax to the chord length is up to 0.05.

16. The compressor aerofoil as claimed in claim 14 ,

wherein the ratio of the maximum thickness Tmax to the chord length is between 0.02 and 0.03.

17. The compressor aerofoil as claimed in claim 1 ,

wherein the compressor aerofoil is configured to operate in a direction of rotation from the suction surface towards the pressure surface.

18. A compressor aerofoil comprising:

a suction surface wall comprising a suction surface and a pressure surface wall comprising a pressure surface, the suction surface wall and the pressure surface wall meet at a leading edge and a trailing edge and define a tip comprising a tip surface, the compressor aerofoil comprises a maximum thickness Tmax,

a mean camber line is-defined as passing through the leading edge and the trailing edge, and

a winglet at the tip and which extends only from the suction surface, the winglet comprises an overhang W that comprises a perpendicular extent from the suction surface in a range 0.1Tmax to 1.99Tmax,

wherein the winglet comprises a maximum overhang Wmax that occurs within 50% of a length of the mean camber line from the leading edge,

wherein the winglet comprises a leading portion and a trailing portion,

wherein the leading portion of the winglet comprises a blend in portion which starts at any position within the range between the leading edge and up to 2% of the length of the mean camber line from the maximum overhang Wmax and which increases the overhang W from zero to the maximum overhang Wmax, and

wherein the leading portion of the winglet comprises a blend out portion which extends along the suction surface a distance in the range 5% to 40% of the length of the mean camber line and is located between the maximum overhang Wmax and the trailing portion and which reduces the overhang W from the maximum overhang Wmax to zero.

19. A gas turbine engine, comprising:

a compressor comprising the compressor aerofoil of claim 18 .