A disk assembly for a gas turbine engine, the assembly comprising: a disk; a cover plate (68, 69) providing a cavity at a first axial side of the disk; a notch in at least one of the disk and the cover plate (68, 69); a passageway including: an inlet provided by the notch in fluid communication with the cavity, and; an exit provided at the second axial side of the disk opposite the first axial side, wherein the exit is in fluid communication with the inlet, the passageway is configured to provide fluid flow from the cavity to the exit and includes an upper surface of the disk, and the passageway extends from the inlet to the exit; a first blade including a first blade shelf; a second blade including a second blade shelf, wherein the first blade shelf and the second blade shelf are radially outward of the upper surface, the first blade further includes a first blade platform, the first blade shelf is radially inward of the first blade platform; and a first blade slot in the disk receiving the first blade, and a second blade slot in the disk receiving the second blade, wherein the upper surface extends circumferentially between the first and second blade slots (80, 82), the first blade shelf extends circumferentially from an upper portion of a root of a first blade, and the second blade shelf extends circumferentially from an upper portion of a root of the second blade; the first blade shelf, the second blade shelf and the upper surface provide the passageway; the assembly being characterised in that: the first blade shelf extends from the first axial side of the disk to the second axial side of the disk, and the second blade shelf extends axially from the first axial side of the disk to the second axial side of the disk; and the exit is provided by recesses in at least one of the first and second blade shelf (92, 96). a disk; a cover plate (68, 69) providing a cavity at a first axial side of the disk; a notch in at least one of the disk and the cover plate (68, 69); a passageway including: an inlet provided by the notch in fluid communication with the cavity, and; an exit provided at the second axial side of the disk opposite the first axial side, wherein the exit is in fluid communication with the inlet, the passageway is configured to provide fluid flow from the cavity to the exit and includes an upper surface of the disk, and the passageway extends from the inlet to the exit; an inlet provided by the notch in fluid communication with the cavity, and; an exit provided at the second axial side of the disk opposite the first axial side, wherein the exit is in fluid communication with the inlet, the passageway is configured to provide fluid flow from the cavity to the exit and includes an upper surface of the disk, and the passageway extends from the inlet to the exit; a first blade including a first blade shelf; a second blade including a second blade shelf, wherein the first blade shelf and the second blade shelf are radially outward of the upper surface, the first blade further includes a first blade platform, the first blade shelf is radially inward of the first blade platform; and a first blade slot in the disk receiving the first blade, and a second blade slot in the disk receiving the second blade, wherein the upper surface extends circumferentially between the first and second blade slots (80, 82), the first blade shelf extends circumferentially from an upper portion of a root of a first blade, and the second blade shelf extends circumferentially from an upper portion of a root of the second blade; the first blade shelf, the second blade shelf and the upper surface provide the passageway; the assembly being characterised in that: the first blade shelf extends from the first axial side of the disk to the second axial side of the disk, and the second blade shelf extends axially from the first axial side of the disk to the second axial side of the disk; and the exit is provided by recesses in at least one of the first and second blade shelf (92, 96). the first blade shelf extends from the first axial side of the disk to the second axial side of the disk, and the second blade shelf extends axially from the first axial side of the disk to the second axial side of the disk; and the exit is provided by recesses in at least one of the first and second blade shelf (92, 96).