A gas turbine engine article (60, 102) comprising: an article wall (68, 168) defining a cavity (74, 174); and a cooling passage network (76, 176, 276) embedded in the article wall (68, 168) between inner and outer portions (68a, 168a, 68b, 168b) of the article wall (68, 168), the cooling passage network (76, 176, 276) having an inlet orifice through the inner portion (68a, 168a) of the article wall (68, 168) to receive cooling air from the cavity (74, 174), a sub-passage region including an array of pedestals (82, 182, 282), and at least one outlet orifice through the outer portion (68b, 168b), the array of pedestals (82, 182, 282) including first pedestals (83, 83.1, 83.2, 183.1, 183.2, 283.1, 283.2) arranged in a first row (85, 85.1, 85.2, 185.1, 185.2, 285.1, 285.2) and second pedestals (84, 84.1, 84.2, 184.1, 184.2, 284.1, 284.2) arranged in a second, adjacent row (86, 86.1, 86.2, 186.1, 186.2, 286.1, 286.2), characterised in that: the first pedestals (83... 283.2) and the second pedestals (84...284.2) defining inter-row sub-passages (87, 187, 287) there between, each inter-row sub-passage (87, 187, 287) being defined between, respectively, one of the first pedestals (83... 283.2) and one of the second pedestals (84...284.2); each of the inter-row sub-passages (87, 187, 287) has an inlet mouth (88, 188, 288), an outlet mouth (89, 189, 289), and a compound channel (90, 190, 290) connecting the inlet mouth (88, 188, 288) and the outlet mouth (89, 189, 289), the compound channel (90, 190, 290) including a first channel length (91, 191, 291) over which the inter-row sub-passage (87, 187, 287) has a constant cross-section (91a, 191a, 291a) and from which the outlet mouth (89, 189, 289) diverges, and a second channel length (92, 192, 292) over which the inter-row sub-passage (87, 187, 287) has a non-constant cross-section (92a, 192a, 292a) and into which the inlet mouth (88, 188, 288) converges; and the limits of the inlet mouth (88, 188, 288), the first channel length (91, 191, 291), the second channel length (92, 192, 292), and the outlet mouth (89, 189, 289) are each demarcated by inflections on one or both of the sides of the respective first and second pedestals. an article wall (68, 168) defining a cavity (74, 174); and a cooling passage network (76, 176, 276) embedded in the article wall (68, 168) between inner and outer portions (68a, 168a, 68b, 168b) of the article wall (68, 168), the cooling passage network (76, 176, 276) having an inlet orifice through the inner portion (68a, 168a) of the article wall (68, 168) to receive cooling air from the cavity (74, 174), a sub-passage region including an array of pedestals (82, 182, 282), and at least one outlet orifice through the outer portion (68b, 168b), the array of pedestals (82, 182, 282) including first pedestals (83, 83.1, 83.2, 183.1, 183.2, 283.1, 283.2) arranged in a first row (85, 85.1, 85.2, 185.1, 185.2, 285.1, 285.2) and second pedestals (84, 84.1, 84.2, 184.1, 184.2, 284.1, 284.2) arranged in a second, adjacent row (86, 86.1, 86.2, 186.1, 186.2, 286.1, 286.2), the first pedestals (83... 283.2) and the second pedestals (84...284.2) defining inter-row sub-passages (87, 187, 287) there between, each inter-row sub-passage (87, 187, 287) being defined between, respectively, one of the first pedestals (83... 283.2) and one of the second pedestals (84...284.2); each of the inter-row sub-passages (87, 187, 287) has an inlet mouth (88, 188, 288), an outlet mouth (89, 189, 289), and a compound channel (90, 190, 290) connecting the inlet mouth (88, 188, 288) and the outlet mouth (89, 189, 289), the compound channel (90, 190, 290) including a first channel length (91, 191, 291) over which the inter-row sub-passage (87, 187, 287) has a constant cross-section (91a, 191a, 291a) and from which the outlet mouth (89, 189, 289) diverges, and a second channel length (92, 192, 292) over which the inter-row sub-passage (87, 187, 287) has a non-constant cross-section (92a, 192a, 292a) and into which the inlet mouth (88, 188, 288) converges; and the limits of the inlet mouth (88, 188, 288), the first channel length (91, 191, 291), the second channel length (92, 192, 292), and the outlet mouth (89, 189, 289) are each demarcated by inflections on one or both of the sides of the respective first and second pedestals.