Removable air filter assemblies for aircraft

1. An air intake system for an engine of an aircraft, the air intake system comprising:

an air duct having an inlet port, the air duct providing fluid communication between the inlet port and the engine; and

a removable air filter assembly configured to interface with the inlet port of the air duct and a skin of the aircraft, the removable air filter assembly including:

an air filter frame having an outer wall and an inner wall, the outer wall of the air filter frame forming an air filter slot;

a bypass door forward of the air filter slot of the air filter frame;

an air filter insertable into the air filter slot of the air filter frame; and

an air plenum formed by the walls of the air filter frame, the air filter and the skin of the aircraft;

wherein, the bypass door is movable between a plurality of door positions including a closed door position and an open door position, air flowing to the inlet port of the air duct via the air filter in the closed door position and bypassing the air filter in the open door position.

2. The air intake system as recited in claim 1 wherein the inlet port of the air duct forms a convex filter interface edge and an aft end of the removable air filter assembly forms a concave inlet port interface edge.

3. The air intake system as recited in claim 1 wherein the inner wall of the air filter frame forms a cutout including one or more edges configured to couple to the skin of the aircraft to at least partially form the air plenum.

4. The air intake system as recited in claim 3 wherein the removable air filter assembly further comprises a seal at the one or more edges of the cutout configured to seal the removable air filter assembly against the skin of the aircraft.

5. The air intake system as recited in claim 1 wherein the outer wall of the air filter frame forms a bypass slot, the bypass door coupled to the bypass slot, and wherein air flows to the inlet port of the air duct via the bypass slot in the open door position.

6. The air intake system as recited in claim 1 wherein the bypass door opens toward the skin of the aircraft in the open door position.

7. The air intake system as recited in claim 1 wherein the bypass door is rotatably coupled to the outer wall of the air filter frame by a hinge at a forward end of the bypass door.

8. The air intake system as recited in claim 1 wherein the removable air filter assembly further comprises a bypass door actuator configured to move the bypass door between the plurality of door positions.

9. The air intake system as recited in claim 1 wherein the bypass door further comprises a spring loaded bypass door biased to the closed door position, the spring loaded bypass door moving to the open door position when airflow against the spring loaded bypass door exceeds a threshold.

10. The air intake system as recited in claim 1 wherein the removable air filter assembly further comprises an aft bypass door aft of the air filter slot.

11. The air intake system as recited in claim 1 wherein the removable air filter assembly further comprises an aft seal insertable into the inlet port of the air duct.

12. The air intake system as recited in claim 1 further comprising a lock configured to interface with a forward end of the removable air filter assembly to secure the removable air filter assembly against the inlet port.

13. The air intake system as recited in claim 1 further comprising a lock configured to interface with an aft end of the removable air filter assembly to secure the removable air filter assembly against the inlet port.

14. The air intake system as recited in claim 1 further comprising an alignment tab and groove subsystem configured to align the removable air filter assembly with the inlet port of the air duct.

15. The air intake system as recited in claim 14 wherein the inner wall of the air filter frame includes one or more alignment tabs and the skin of the aircraft forms one or more alignment grooves, the one or more alignment tabs slidable along the one or more alignment grooves.

16. An aircraft comprising:

an airframe having a skin;

an engine disposed within the airframe; and

an air intake system configured to receive air for the engine, the air intake system comprising:

an air duct having an inlet port, the air duct providing fluid communication between the inlet port and the engine; and

a removable air filter assembly configured to interface with the inlet port of the air duct and the skin of the airframe, the removable air filter assembly including:

an air filter frame having an outer wall and an inner wall, the outer wall of the air filter frame forming an air filter slot;

a bypass door forward of the air filter slot of the air filter frame;

an air filter insertable into the air filter slot of the air filter frame; and

an air plenum formed by the walls of the air filter frame, the air filter and the skin of the airframe;

wherein, the bypass door is movable between a plurality of door positions including a closed door position and an open door position, air flowing to the inlet port of the air duct via the air filter in the closed door position and bypassing the air filter in the open door position.

17. The aircraft as recited in claim 16 wherein the aircraft is a helicopter including a fuselage and a main rotor system powered by the engine, the air duct coupled to the fuselage.

18. The aircraft as recited in claim 16 wherein the aircraft is a tiltrotor aircraft including a fuselage supporting a wing having outboard ends and a nacelle including the engine and the air duct coupled to one of the outboard ends of the wing.

19. The aircraft as recited in claim 16 wherein the removable air filter assembly is shaped to contour the skin of the airframe.