Mounting arrangement for an electrical harness

1. A mounting arrangement for an electrical harness, wherein the arrangement is part of a gas turbine engine having an axial direction and a radial direction, the arrangement comprising:

an elongate tray internally mounted adjacent but not in contact with a first casing of the engine and outward of a second casing of the engine, the tray having a base and raised sides to define a channel extending along the axial direction, the electrical harness mounted within the channel; and

a cooling air source outward of the first casing in the radial direction, the source configured to provide cooling air into the channel to cool the electrical harness,

wherein the electrical harness includes a first type of cable disposed within the tray and a second type of cable comprising a material different from the first type of cable, the second type of cable extending beyond the tray,

wherein a tubular cooling air duct extends from the first casing into the channel in the radial direction, wherein the cooling air duct has a plurality of spaced outlet holes configured to eject the cooling air provided by the cooling air source from the cooling air duct into the channel in the radial direction and in the axial direction, and

wherein the first type of cable extends from a first region and the second type of cable extends into a second region, the first region being a cooler region than the second region.

2. The arrangement of claim 1 , wherein a proximal surface of the first casing forms a fourth wall for the channel.

3. The arrangement of claim 1 , wherein the cooling air duct passes through the first casing.

4. The arrangement of claim 3 , wherein the base of the tray is secured to the second casing.

5. The arrangement of claim 4 , wherein the first casing is formed by a nacelle or a thrust reverser of the engine and the second casing is a core casing of the engine.

6. The arrangement of claim 5 , wherein the cooling air source is within the nacelle or the thrust reverser.

7. The arrangement of claim 5 , wherein the cooling air source is a bypass duct of the engine.

8. The arrangement of claim 5 , wherein the tray extends along the axial direction.

9. The arrangement of claim 8 , wherein the cooling air duct is one of a plurality of cooling air ducts spaced in the axial direction.

10. The arrangement of claim 9 , wherein there is an annular space between the first casing and the second casing, and an upstream end of the tray has an opening configured to receive a portion of a ventilation flow from the annular space.

11. The arrangement of claim 1 , wherein the tray is narrower at an upstream end of the tray than at a downstream end of the tray.

12. The arrangement of claim 1 , wherein the first type of cable is polytetrafluoroethylene-insulated cable and the second type of cable is mineral-insulated cable.

13. The arrangement of claim 1 , wherein the plurality of spaced outlet holes are provided at an end region of the cooling air duct.

14. A gas turbine engine including the arrangement of claim 1 .