Passive internal ice protection systems for engine inlets

1. A flush type engine inlet comprising an ice protection apparatus comprising:

a frame surrounding a mesh screen, the frame comprising a first part and a second part;

the first part extending in a first direction from a back edge to a front edge;

the second part connected to the back edge of the first part and extending in a second direction at a folding angle to the first part;

the second part configured to be attached to the flush type engine inlet such that the first part and the second part are below an opening of the flush type engine inlet; and

the first part configured to be smaller than the opening such that a portion of the opening remains uncovered at all times.

2. The flush type engine inlet of claim 1 , wherein the folding angle comprises an obtuse angle, an acute angle or about 90 degrees.

3. The flush type engine inlet of claim 1 , wherein the portion of the opening that remains uncovered comprises about 50% of an area of the opening.

4. The flush type engine inlet of claim 1 , wherein:

the first part further comprises a first side edge and a second side edge; and

the second part is connected to first side edge of the first part-and extending in the second direction.

5. The flush type engine inlet of claim 1 , wherein the mesh screen is configured to catch and hold a particular size of ice with a suction generated by an air flow into an engine, wherein the particular size of ice is larger than a size certified for the engine.

6. The flush type engine inlet of claim 1 , wherein the mesh screen comprises a plurality of pores each having a pore size of about 0.25 inch up to 0.50 inch.

7. The flush type engine inlet of claim 1 , wherein:

the mesh screen comprises stainless steel; or

the frame comprises fiberglass.

8. The flush type engine inlet of claim 1 , further comprising:

an engine cover forming the flush type engine inlet, the engine cover comprising a body having inside edges that define a front end and a back end of the opening;

the second part attached to the inside edge of the back end of the opening;

the first direction comprises from the back end of the opening towards the front end of the opening; and

the second direction comprises upwards from the first part towards the back end of the opening.

9. The flush type engine inlet of claim 8 , wherein the body of the engine cover is curved in accordance with a contour of a rotorcraft.

10. The flush type engine inlet of claim 8 , further comprising a filter positioned below the opening between the first part and an engine.

11. The flush type engine inlet of claim 8 , wherein the first part further comprises one or more folding lines parallel to the first direction to accommodate a shape of the engine cover.

12. The flush type engine inlet of claim 10 , further comprising one or more brackets configured to hold the first part under the one or more folding lines and be fastened to the second part and further to the engine cover.

13. A method comprising:

providing a flush type engine inlet on a rotorcraft, the flush type engine inlet comprising an ice protection apparatus comprising:

a frame surrounding a mesh screen, the frame comprising a first part and a second part,

the first part extending in a first direction from a back edge to a front edge,

the second part connected to the back edge of the first part and extending in a second direction at a folding angle to the first part,

the second part configured to be attached to the flush type engine inlet such that the first part and the second part are below an opening of the flush type engine inlet, and

the first part configured to be smaller than the opening such that a portion of the opening remains uncovered at all times;

operating the rotorcraft wherein air flows downstream into an engine through the opening and the ice protection apparatus; and

preventing ice with a particular size from entering into the engine using the ice protection apparatus.

14. The method of claim 13 , wherein the folding angle comprises an obtuse angle, an acute angle or about 90 degrees.

15. The method of claim 13 , wherein the portion of the opening that remains uncovered comprises about 50% of an area of the opening.

16. The method of claim 13 , wherein:

the first part further comprises a first side edge and a second side edge; and

the second part is connected to first side edge of the first part and extending in the second direction.

17. The method of claim 13 , wherein the particular size of ice is larger than a size certified for the engine.

18. The method of claim 13 , further comprising filtering the air flowing into the engine using a filter positioned below the opening between the first member and an engine.

19. The method of claim 13 , wherein the ice protection apparatus further comprises:

an engine cover forming the flush type engine inlet, the engine cover comprising a body having inside edges that define a front end and a back end of the opening;

the second part attached to the inside edge of the back end of the opening;

the first direction comprises from the back end of the opening towards the front end of the opening; and

the second direction comprises upwards from the first part towards the back end of the opening.

20. The method of claim 13 , wherein the first part further comprises one or more folding lines parallel to the first direction to accommodate a shape of the engine cover.