Method of repairing a damaged abradable coating

1. A method of repairing a damaged abradable coating on a surface in an assembled engine without removing a module of the engine from the engine, the method comprising:

(a) inserting a boroscope through an aperture in a casing of the assembled engine, the boroscope carrying a conduit,

(b) directing the boroscope to the damaged abradable coating on the surface,

(c) supplying a liquid abradable glue through the conduit, and

(d) directing the liquid abradable glue onto the surface in the assembled engine to repair the damaged abradable coating,

wherein the liquid abradable glue consists of silica powder, sodium silicate and a dislocator, the dislocator being selected from the group consisting of polyester, graphite and hexagonal boron nitride.

2. A method as claimed in claim 1 further comprising heating the liquid abradable glue such that the liquid abradable glue hardens.

3. A method as claimed in claim 2 comprising running the engine for a predetermined time to harden the liquid abradable glue.

4. A method as claimed in claim 2 , comprising directing a microwave heater through the aperture in the casing with the boroscope and heating the liquid abradable glue using the microwave heater.

5. A method as claimed in claim 1 wherein the engine comprises a gas turbine engine.

6. A method as claimed in claim 5 wherein the surface is selected from the group consisting of a surface of a compressor stator component and a surface of a turbine stator component.

7. A method as claimed in claim 1 wherein the damaged abradable coating is a plasma sprayed abradable coating or a thermally sprayed abradable coating.

8. A method as claimed in claim 1 wherein the damaged abradable coating comprises aluminium, silicon and hexagonal boron nitride clad powder.

9. A method as claimed in claim 8 wherein the damaged abradable coating comprises 12 wt % silicon, 16 wt % hexagonal boron nitride and the balance aluminium.

10. A method as claimed in claim 1 wherein the damaged abradable coating comprises aluminium, silicon and polyester.

11. A method as claimed in claim 10 wherein the damaged abradable coating comprises 7 wt % silicon, 40 wt % polyester and the balance aluminium.

12. A method as claimed in claim 1 wherein the damaged abradable coating comprises McrAlY and bentonite.

13. A method as claimed in claim 1 , wherein the surface is selected from the group consisting of a radially inner surface of a compressor stator component positioned radially around a stage of compressor rotor blades and a radially inner surface of a turbine stator component positioned radially around a stage of turbine rotor blades.

14. A method as claimed in claim 1 , wherein the damaged abradable coating comprises a dislocator, the dislocator being selected from the group consisting of polyester, bentonite, and hexagonal boron nitride.

15. A method of repairing a damaged abradable coating on a surface in an assembled gas turbine engine on an aircraft without removing a module of the gas turbine engine from the aircraft, the method comprising:

inserting a boroscope through an aperture in a casing of the assembled gas turbine engine, the boroscope carrying a conduit;

directing the boroscope to the damaged abradable coating on the surface;

supplying a liquid abradable glue through the conduit; and

directing the liquid abradable glue onto the surface in the assembled gas turbine engine to repair the damaged abradable coating,

wherein the liquid abradable glue consists of silica powder, sodium silicate and a dislocator, the dislocator being selected from the group consisting of polyester, graphite, and hexagonal boron nitride, and the surface being selected from the group consisting of a radially inner surface of a compressor stator component positioned radially around a stage of compressor rotor blades and a radially inner surface of a turbine stator component positioned radially around a stage of turbine rotor blades.