Control of engine intake door

1. An air induction system for an aircraft engine having a power activated door for controlling flow of intake air, the system comprising:

a housing having a hollow interior and an opening in the housing comprising an entryway for receiving intake air into the housing;

said door, the door being pivotable between a closed position wherein said opening is closed and an open position wherein intake air enters the housing through said opening;

an actuator cylinder for pivoting the door, the cylinder being linearly movable in a stroke having a range of motion extending between a first end position corresponding with the door being open and a second end position corresponding with the door being closed; and

linkages which operatively connect the actuator cylinder to the door for transferring linear motion of the cylinder into rotational motion of the door, the linkages being configured such that movement of the cylinder through a distance produces a corresponding angular rotation of the door,

wherein the second end position is within a portion of the stroke defining a dwell range wherein movement of the cylinder produces substantially no rotation of the door.

2. An air induction system as set forth in claim 1 wherein said linkages comprise first and second bellcranks mounted for pivotal motion, a link which interconnects the bellcranks, and a rod extending between the second bellcrank and the door.

3. An air induction system as set forth in claim 2 wherein the linkages are arranged such that, at the second end position of the cylinder, movement of the cylinder causes rotation of the first bellcrank but no rotation of the second bellcrank.

4. An air induction system as set forth in claim 1 wherein the opening comprises a first opening, the door comprises a first door, and the rod comprises a first rod, and wherein the system further comprises a second opening in the housing, a second door, and a second rod, and wherein simultaneous movement of the first door and second door is effected by said actuator cylinder.

5. An air induction system as set forth in claim 1 wherein said opening in the housing comprises a bypass opening for receiving intake air into the housing that augments or replaces primary intake air.

6. An air induction system as set forth in claim 5 further comprising a primary opening formed in the housing comprising a primary entryway, and a barrier filter having a porous media mounted across the primary entryway.

7. An air induction system as set forth in claim 6 wherein the housing has four of said primary entryways and four corresponding barrier filters, and wherein each of the four barrier filters has the same shape and size such that the four filters are interchangeably usable.

8. An air induction system as set forth in claim 7 wherein said barrier filters include at least one substantially horizontal filter at a top of said housing and at least one substantially vertical filter at a lateral side of said housing, and wherein said substantially vertical filter at said lateral side is oriented to face partially in a forward direction.

9. An air induction system for an aircraft engine having a power activated door for controlling flow of intake air, the system comprising: a housing having a hollow interior and an opening in the housing comprising an entryway for receiving intake air into the housing; said door, the door being pivotable between a closed position wherein said opening is closed and an open position wherein intake air enters the housing through said opening; an actuator for pivoting the door, the actuator having a range of motion; and linkages which operatively connect the actuator to the door;

the linkages comprising first and second bellcranks mounted for pivotal motion, a link which interconnects the bellcranks, and wherein movement of the actuator at said first position causes rotation of the first bellcrank and a corresponding rotation of the second bellcrank to thereby pivot the door, and movement of the actuator at said second position causes rotation of the first bellcrank but substantially no rotation of the second bellcrank and substantially no pivoting of the door.

10. An air induction system as set forth in claim 9 wherein the linkages further comprise a rod extending between the second bellcrank and the door.

11. An air induction system as set forth in claim 10 wherein the opening comprises a first opening, the door comprises a first door, and the rod comprises a first rod, and wherein the system further comprises a second opening in the housing, a second door, and a second rod, and wherein simultaneous movement of the first door and second door is effected by said actuator cylinder.

12. An air induction system as set forth in claim 9 wherein the second position is within a portion of said range of motion defining a dwell range wherein movement of the actuator produces substantially no rotation of the door.

13. An air induction system as set forth in claim 9 wherein the actuator is operated remotely.

14. An air induction system as set forth in claim 9 wherein said opening in the housing comprises a bypass opening for receiving intake air into the housing that augments or replaces primary intake air.

15. An air induction system as set forth in claim 14 further comprising a primary opening formed in the housing comprising a primary entryway, and a barrier filter having a porous media mounted across the primary entryway.

16. An air induction system as set forth in claim 15 wherein the housing has four of said primary entryways and four corresponding barrier filters, and wherein each of the four barrier filters has the same shape and size such that the four filters are interchangeably usable.

17. An air induction system as set forth in claim 16 wherein said barrier filters include at least one substantially horizontal filter at a top of said housing and at least one substantially vertical filter at a lateral side of said housing, and wherein said substantially vertical filter at said lateral side is oriented to face partially in a forward direction.

18. A helicopter comprising:

an engine;

an air induction system including:

a housing having a hollow interior and an opening in the housing comprising an entryway for receiving intake air into the housing;

a power activated door for controlling flow of intake air, the door being pivotable between a closed position wherein the opening is closed and an open position wherein intake air enters the housing through the opening;

an actuator cylinder for pivoting the door, the cylinder being linearly movable in a stroke having a range of motion extending between a first end position corresponding with the door being open and a second end position corresponding with the door being closed; and

linkages that connect the actuator cylinder to the door, the linkages comprising first and second bellcranks mounted for pivotal motion, and a link which interconnects the bellcranks,

the stroke of the cylinder including a dwell range wherein movement of the cylinder produces no rotation of the door, the dwell range being adjacent the second end position; and

wherein movement of the actuator at said first position causes rotation of the first bellcrank and a corresponding rotation of the second bellcrank to thereby pivot the door, and movement of the actuator at said second position causes rotation of the first bellcrank but no rotation of the second bellcrank and no pivoting of the door.

19. The helicopter of claim 18 wherein the dwell range includes about 0.25 inches of cylinder travel and corresponds to about 15 degrees of rotation of the first bellcrank.

20. The helicopter of claim 18 wherein the first bellcrank has first and second arms that extend at an oblique angle relative to each other.