Abstract: A sheet metal blank for the manufacture of a casing of a gas turbine engine comprising a sheet of substantially constant wall thickness and a raised or thicker region extending along substantially the full length of the sheet metal blank. A raised or thicker region is provided between edges of the sheet metal blank. The raised or thicker region comprises at least one boss and at least one ridge extending way from the or each boss.

Abstract: A fixture (10) for supporting a workpiece (18) during a machining operation. The fixture comprising a base (12) provided with a channel (14) for receiving part (16) of the workpiece (18), the channel having a first wall (20) facing an opposing second wall (22). An inflatable diaphragm (24) is located on the first wall (20), and configured to engage with an engagement surface (36) on the workpiece and bias the workpiece against the second wall. The diaphragm comprises a deformable portion (26) spaced apart from the first wall of the channel, the deformable portion having ends (28,30) which provide a seal with the first wall to define a chamber (32) enclosed by the first wall and diaphragm.

Abstract: A component such as a casing of a gas turbine engine has an array of holes distributed around a flange. The casing may distort when unsupported, but nevertheless the position accuracy of the holes may be checked by manipulating measured hole positions to lie with known deviations from a best-fit circle. The maximum load and stress required to bring the hole array into conformity with the best-fit circle is calculated and compared with a predetermined maximum. The deviation of the hole positions associated with the best-fit circle from nominal positions can also be calculated.

Abstract: A fixture (10) for supporting a workpiece (18) during a machining operation. The fixture comprising a base (12) provided with a channel (14) for receiving part (16) of the workpiece (18), the channel having a first wall (20) facing an opposing second wall (22). An inflatable diaphragm (24) is located on the first wall (20), and configured to engage with an engagement surface (36) on the workpiece and bias the workpiece against the second wall. The diaphragm comprises a deformable portion (26) spaced apart from the first wall of the channel, the deformable portion having ends (28,30) which provide a seal with the first wall to define a chamber (32) enclosed by the first wall and diaphragm.

Abstract: The present invention provided a method of manufacturing a duct for a gas turbine engine or the like from sheet metal material; the method comprising the steps of: fabricating a duct from sheet material (10,12,14) including rolling or folding metal sheet along ruled lines to form a ruled surface geometry approximately corresponding to at least part of a desired irregular final duct geometry; welding corresponding rolled or folded parts of the duct skin together and positioning the duct on a heat treatment fixture (30) having a shape corresponding to the said desired irregular duct geometry; the material of the heat treatment fixture having a greater thermal expansion coefficient than the duct material; heating the duct and fixture substantially to a stress relieving temperature of the duct material such that differential thermal expansion of the duct and fixture at the said stress relieving temperature causes the duct to distort and adopt the shape of the exterior surface of the fixture on which the duct is l

Abstract: A sheet metal blank for the manufacture of a casing of a gas turbine engine comprising a sheet of substantially constant wall thickness and a raised or thicker region extending along substantially the full length of the sheet metal blank. A raised or thicker region is provided between edges of the sheet metal blank. The raised or thicker region comprises at least one boss and at least one ridge extending way from the or each boss.

Abstract: The present invention provided a method of manufacturing a duct for a gas turbine engine or the like from sheet metal material; the method comprising the steps of: fabricating a duct from sheet material (10,12,14) including rolling or folding metal sheet along ruled lines to form a ruled surface geometry approximately corresponding to at least part of a desired irregular final duct geometry; welding corresponding rolled or folded parts of the duct skin together and positioning the duct on a heat treatment fixture (30) having a shape corresponding to the said desired irregular duct geometry; the material of the heat treatment fixture having a greater thermal expansion coefficient than the duct material; heating the duct and fixture substantially to a stress relieving temperature of the duct material such that differential thermal expansion of the duct and fixture at the said stress relieving temperature causes the duct to distort and adopt the shape of the exterior surface of the fixture on which the duct is l