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Within an intake for a gas turbine engine provision is provided through stator vanes 25, 45 in the stator whereby back pressure from a necessary obstruction 34, 46 can be utilised to balance forward pressure variations caused by intake droop or crosswinds in order to reduce those forward pressure de

Within an intake for a gas turbine engine provision is provided through stator vanes 25, 45 in the stator whereby back pressure from a necessary obstruction 34, 46 can be utilised to balance forward pressure variations caused by intake droop or crosswinds in order to reduce those forward pressure detriments for more efficient engine operation according to a desired objective regime. Typically the flow through the intake 20 is analysed and then an appropriate positioning of the stator vanes 25, 45 determined in order to provide approximate balance between the forward pressures and back pressures. Normally, a combination of camber variation of stator vanes 45a and stagger variation of stator vanes 45b are utilised in order to achieve a desired momentum balance around the circumference of the intake 20. It will be understood that both the forward pressures and the back pressures are differentially variable about the circumference such that one opposes the other.

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I claim: 1. A gas turbine engine comprising an intake, a low pressure compressor including a plurality of rotor blades arranged downstream of the intake, a plurality of stator vanes arranged downstream of the low pressure compressor and at least one obstruction arranged downstream of the stator van

I claim: 1. A gas turbine engine comprising an intake, a low pressure compressor including a plurality of rotor blades arranged downstream of the intake, a plurality of stator vanes arranged downstream of the low pressure compressor and at least one obstruction arranged downstream of the stator vanes, whereby in use the at least one obstruction produces a circumferentially varying back pressure on the stator vanes and the intake supplies an airflow having a circumferentially varying forward flow pressure to the low pressure compressor due to a non-axisymmetric flow of air into the intake, the stator vanes being arranged to balance the circumferentially varying back pressure from the at least one obstruction with the circumferentially varying forward flow pressure from the intake at substantially all circumferential positions, said stator vanes having variable camber and stagger configurations at different circumferential positions so as to balance the varying back pressure caused by the said at least one obstruction. 2. A gas turbine engine comprising an intake, a low pressure compressor including a plurality of rotor blades arranged downstream of the intake, a plurality of stator vanes arranged downstream of the low pressure compressor and at least one obstruction arranged downstream of the stator vanes, whereby in use the at least one obstruction produces a circumferentially varying back pressure on the stator vanes and the intake supplies an airflow having a circumferentially varying forward flow pressure to the low pressure compressor due to a non-axisymmetric flow of air into the intake, the stator vanes being arranged to balance the circumferentially varying back pressure from the at least one obstruction with the circumferentially varying forward flow pressure from the intake at substantially all circumferential positions, wherein the stator vanes at different circumferential positions have different stagger angles. 3. A gas turbine engine as claimed in claim 2 wherein the stator vanes are of the same configuration. 4. A gas turbine engine as claimed in claim 2, wherein the obstruction is a pylon or a radial drive strut. 5. A gas turbine engine as claimed in claim 4, wherein the pylon and/or radial drive strut is shaped for desired back pressure reflection response. 6. An aircraft having a gas turbine engine as claimed in claim 2 wherein the stator vane stagger angles and the stator vane camber angles are arranged such that a flow field downstream of the low pressure compressor matches a flow field upstream of the low pressure compressor, wherein the stator vane arrangement comprising fifty two equi-circumferentially spaced stator vanes, the stator vanes at different circumferential positions have different stagger angles, the at least one obstruction comprising a pylon at a first circumferential position and a strut at a second diametrically opposite position, a first stator vane is arranged upstream of the pylon and has a stagger angle of-3�� relative to a datum angle, a seventh stator vane is arranged at a circumferential angle position of 49�� from the first stator vane, the seventh stator vane has a stagger angle of +0.5�� relative to the datum angle, a tenth stator vane is arranged at a circumferential angle position of 63�� from the first stator vane, the tenth stator vane has a stagger angle corresponding to the datum angle, a fifteenth stator vane is arranged at a circumferential angle position of 98�� from the first stator vane, the fifteenth stator vane has a stagger angle of-2.5�� relative to the datum angle, a nineteenth stator vane is arranged at a circumferential angle position of 124�� from the first stator vane, the nineteenth stator vane has a stagger angle-0.25�� relative to the datum angle, a twenty fifth stator vane is arranged at a circumferential angle position of 166�� from the first stator vane, the twenty fifth stator vane has a stagger angle of-2.25�� relative to the datum angle, a twenty seventh stator vane is arranged at a circumferential angle position of 180�� from the first stator vane, the twenty seventh stator vane has a stagger angle of-1�� relative to the datum angle, a thirty third and/or a thirty fourth stator vane is arranged at a circumferential angle position of 222��/229�� from the first stator vane, the thirty third and/or the thirty fourth stator vane has a stagger angle of +2.6�� relative to the datum angle, a forty eighth stator vane is arranged at a circumferentially angle position of 325�� from the first stator vane, the forty eighth stator vane has a stagger angle corresponding to the datum angle. 7. An aircraft having a gas turbine engine as claimed in claim 2 wherein the camber angle at the tip of the stator vane for the first to fifteenth and fifty second stator vane is about +5�� relative to the datum angle, the camber angle at the mid height of the stator vane for the first to fifteenth and fifty second stator vane is about +4�� relative to the datum angle, the camber angle at the hub of the stator vane for the first to fifteenth and fifty second stator vane is about +4�� relative to the datum angle, the camber angle at the tip of the stator vane for the sixteenth, seventeenth, fiftieth and fifty first stator vane is the datum angle, the camber angle at the mid height of the stator vane for the sixteenth, seventeenth, fiftieth and fifty first stator vane is the datum angle, the camber angle at the hub of the stator vane for the sixteenth, seventeenth, fiftieth and fifty first stator vane is the datum angle, the camber angle at the tip of the stator vane for eighteenth to forty ninth stator vanes is about-5�� relative to the datum angle, the camber angle at the mid height of the stator vane for the eighteenth to forty ninth stator vanes is about-4�� relative to the datum angle, the camber angle at the hub of the stator vane for the eighteenth to forty ninth stator vanes is about-4�� relative to the datum angle. 8. An aircraft having a gas turbine engine as claimed in claim 2 wherein the pylon is vertically above an axis of rotation of the low pressure compressor. 9. An aircraft having a gas turbine engine as claimed in claim 2 wherein the stator vane stagger angles and the stator vane camber angles are arranged such that a flow field downstream of the low pressure compressor matches a flow field upstream of the low pressure compressor, wherein the stator vane arrangement comprising fifty two equi-circumferentially spaced stator vanes, the stator vanes at different circumferential positions have different stagger angles, the at least one obstruction comprising a pylon at a first circumferential position and a strut at a second diametrically opposite position, a first stator vane is arranged upstream of the pylon and has a stagger angle of-1�� relative to a datum angle, an eighth and/or ninth stator vane is arranged at a circumferential angle position of 49��/56�� from the first stator vane, the eighth and/or ninth stator vane has a stagger angle of +3�� relative to the datum angle, a twenty sixth stator vane is arranged at a circumferential angle position of 173�� from the first stator vane, the twenty sixth stator vane has a stagger angle of-3.5�� relative to the datum angle, a twenty seventh stator vane is arranged at a circumferential angle position of 180�� from the first stator vane, the twenty seventh stator vane has a stagger angle of-3�� relative to the datum angle, a thirty fourth stator vane has a stagger angle corresponding to the datum angle, a forty first stator vane is arranged at a circumferential angle position of 277�� from the first stator vane, the forty first stator vane has a stagger angle of +0.3�� relative to the datum angle, a forty fourth stator vane is arranged at a circumferential angle position of 297�� from the first stator vane, the forty fourth stator vane has a stagger angle corresponding to the datum angle, a fifty first stator vane is arranged at a circumferential angle position of 346�� from the first stator vane, the fifty first stator vane has a stagger angle of-1.7�� relative to the datum angle. 10. An aircraft having a gas turbine engine as claimed in claim 2 wherein the stator vane stagger angles and the stator vane camber angles are arranged such that a flow field downstream of the low pressure compressor matches a flow field upstream of the low pressure compressor, wherein the stator vane arrangement comprising fifty two equi-circumferentially spaced stator vanes, the stator vanes at different circumferential positions have different stagger angles, the at least one obstruction comprising a pylon at a first circumferential position and a strut at a second diametrically opposite position, a first stator vane is arranged upstream of the pylon and has a stagger angle of-1.5�� relative to a datum angle, an eighth stator vane is arranged at a circumferential angle position of 42�� from the first stator vane, the eighth stator vane has a stagger angle of +3�� relative to the datum angle, a twenty first stator vane is arranged at a circumferential angle position of 124�� from the first stator vane, the twenty first stator vane has a stagger angle corresponding to the datum angle, a twenty eighth stator vane is arranged at a circumferential angle position of 168�� from the first stator vane, the twenty eighth stator vane has a stagger angle of-4�� relative to the datum angle, a thirtieth stator vane is arranged at a circumferential angle position of 180�� from the first stator vane, a thirtieth stator vane has a stagger angle of-2.8�� relative to the datum angle, a thirty fifth/thirty sixth stator vane is arranged at a circumferential angle position of-156��/-150�� from the first stator vane, the thirty fifth/thirty sixth stator vane has a stagger angle of +1�� relative to the datum angle, a forty seventh stator vane is arranged at a circumferential angle position of-75�� from the first stator vane, the forty seventh stator vane has a stagger angle corresponding to the datum angle, a fifty sixth stator vane is arranged at a circumferential angle position of-18�� from the first stator vane, the fifty sixth stator vane has a stagger angle of-3.2�� relative to the datum angle. 11. A gas turbine engine comprising an intake, a low pressure compressor including a plurality of rotor blades arranged downstream of the intake, a plurality of stator vanes arranged downstream of the low pressure compressor and at least one obstruction arranged downstream of the stator vanes, whereby in use the at least one obstruction produces a circumferentially varying back pressure on the stator vanes and the intake supplies an airflow having a circumferentially varying forward flow pressure to the low pressure compressor due to a non-axisymmetric flow of air into the intake, the stator vanes being arranged to balance the circumferentially varying back pressure from the at least one obstruction with the circumferentially varying forward flow pressure from the intake at substantially all circumferential positions, wherein the stator vanes have different camber configurations at different circumferential positions. 12. A method of analyzing a gas turbine engine comprising an intake, a low pressure compressor including a plurality of rotor blades arranged downstream of the low pressure compressor and at least one obstruction arranged downstream of the stator vanes, in use that at least one obstruction producing a circumferentially varying back pressure on the stator vanes and the intake supplying an airflow having a circumferentially varying forward pressure to the low pressure compressor, the method comprising the steps of: a) analyzing the aerodynamic flow through the intake, low pressure compressor, the stator vanes and the at least one obstruction to determine the effect of the non axisymmetric flows, b) arranging the stator vanes to balance the circumferentially varying back pressure from the at least one obstruction with circumferentially varying forward pressure from the intake at substantially all circumferential positions. 13. A method as claimed in claim 12 wherein step b) comprises optimizing the circumferential variation in force on the low pressure compressor during rotation as a result of pressure differentials across the low pressure compressor. 14. A method as claimed in claim 13 wherein step b) comprises optimizing the circumferential variation in flow incidence angle at the stator vane leading edge. 15. A method as claimed in claim 13 wherein step b) comprises optimizing the circumferential variation in flow speed at the stator vane leading edge. 16. A method as claimed in claim 13 wherein step b) comprises optimizing the circumferential variation in flow angle rejected from the low pressure compressor towards the stator vane leading edges. 17. A method as claimed in claim 13 wherein actuator discs represent the low pressure compressor and the stator vanes. 18. A method as claimed in claim 13 wherein step b) comprises arranging the stator vanes at different circumferential positions to have different stagger angles. 19. A method as claimed in claim 13 wherein step b) comprises arranging the stator vanes at different circumferential positions to have different camber configurations. 20. A method as claimed in claim 19 wherein step b) comprises arranging the stator vanes at different radial positions to have different camber configurations. 21. A method as claimed in claim 19 wherein step b) comprises arranging the stator vanes in groups. 22. A method analyzing a gas turbine engine comprising an intake, a low pressure compressor including a plurality of rotor blades arranged downstream of the intake, a plurality of stator vanes arranged downstream of the low pressure compressor and at least one obstruction arranged downstream of the stator vanes, in use the at least one obstruction producing a circumferentially varying back pressure on the stator vanes and the intake supplying an airflow having a circumferentially varying forward pressure to the low pressure compressor, the method comprising the steps of; a) analyzing the aerodynamic flow through the intake, the low pressure compressor, the stator vanes and the at least one obstruction to determine the effect of the non axisymmetric flows, b) arranging the stator vanes to optimize the circumferential variation in force on the low pressure compressor during rotation as a result of pressure differentials across the low pressure compressor to reduce fan forcing.