Casing for a propulsion unit

1. A dual-flow aircraft propulsion unit comprising:

an engine;

a nacelle including an axisymmetric casing delimiting an air flow path; and

at least one pre-cooler heat exchanger for supplying air to the aircraft, wherein the pre-cooler heat exchanger includes an air scoop for drawing air from a secondary flow of the dual-flow propulsion unit and a flow adjustment valve, mounted downstream of the air scoop,

wherein said casing has at least two openings,

wherein each of the openings being closed by a removable and interchangeable panel, and

wherein the at least one pre-cooler heat exchanger is attached to a respective one of the removable and interchangeable panels.

2. The propulsion unit as claimed in claim 1 , wherein the openings are located substantially in a single transverse plane, the transverse plane oriented transverse to a longitudinal axis of the casing, the openings being offset in relation to one another by a predetermined angle in relation to the longitudinal axis of the casing.

3. The propulsion unit as claimed in claim 1 , wherein the openings are located in a recesses of the casing.

4. The propulsion unit as claimed in claim 1 , wherein at least one of the panels forms the recesses for the pre-cooler heat exchanger.

5. The propulsion unit as claimed in claim 4 , wherein the panel carrying the pre-cooler heat exchanger, on the side of the flow path, an aerodynamic surface provided with an opening, and wherein the component is a pre-cooler heat exchanger including a surface heat exchange plate that closes the opening and of which the surface on the flow path side is continuous with said aerodynamic surface.

6. The propulsion unit as claimed in claim 1 , wherein the air scoop is attached to one of the panels.

7. The propulsion unit as claimed in claim 6 , wherein the scoop is partially embedded in the casing or the panel and includes a protruding portion on the internal surface of the casing or the panel.

8. The propulsion unit as claimed in claim 1 , wherein the openings are substantially identical.

9. A system for a propulsion unit as claimed in claim 1 , including the pre-cooler heat exchanger and the two removable panels designed to close the openings of the axisymmetric nacelle casing, characterized in that the pre-cooler heat exchanger is rigidly attached to one of said panels.

10. An aircraft propulsion unit comprising:

an engine;

a nacelle including an axisymmetric casing delimiting an air flow path; and

at least one pre-cooler heat exchanger,

wherein said casing has at least two openings, each of the openings being closed by a removable and interchangeable panels,

wherein at least one of the panels carry the pre-cooler heat exchanger on the side of the flow path, and an aerodynamic surface being provided with the openings, and

wherein the pre-cooler heat exchanger includes a surface heat exchange plate that closes the opening and of which the surface on the flow-path side is continuous with the aerodynamic surface of the panel.