Resettable overpressure indicator for aircraft

1. A passive pressure or overpressure indicator apparatus for use in a compartment of an aircraft engine nacelle, the indicator apparatus comprising:

a housing configured for attachment within the interior of the compartment of the aircraft engine nacelle;

a pressure sensing element disposed within the housing, the pressure sensing element having access to the exterior of the compartment via at least one venting passage disposed within the housing in order to detect a pressure differential between the interior and exterior of the compartment wherein the venting passage is configured to meter ambient air to the pressure sensing element;

an indicator element movably coupled to the pressure sensing element between a nominal position and a triggered position, in which a distal end of the indicator element is caused to move exterior of the compartment in the triggered position to provide a visual indication when a predetermined pressure differential between the interior and the exterior of the compartment indicative of an overpressure condition is detected by the pressure sensing element; and

a reset mechanism for resetting the indicator element to the nominal position, the reset mechanism including at least one reset feature that can only be accessed by opening the compartment of the aircraft engine nacelle.

2. The pressure or overpressure indicator apparatus according to claim 1 , wherein the pressure sensing element is a diaphragm.

3. The pressure or overpressure indicator apparatus according to claim 2 , further comprising a pair of magnets disposed on opposing sides of the diaphragm and initially disposed in attraction with one another at a predetermined distance wherein expansion of the diaphragm due to an overpressure condition increases the distance between the magnets and causes a release of the indicator element, thereby moving the indicator element from the nominal position to the triggered position.

4. The pressure or overpressure indicator apparatus according to claim 1 , wherein the indicator element is biased by a spring.

5. The pressure or overpressure indicator apparatus according to claim 1 , wherein the pressure sensing element is a bellows.

6. The pressure or overpressure indicator apparatus according to claim 5 , further including an assist spring used in combination with the bellows to release the indicator element to the triggered position.

7. The pressure or overpressure indicator apparatus according to claim 6 , further including at least one feature within the housing configured to release the assist spring when the bellows has moved a predetermined distance due to an overpressure condition.

8. The pressure or overpressure indicator apparatus according to claim 1 , wherein the at least one reset feature is disposed transverse to the indicator element.

9. The pressure or overpressure indicator apparatus according to claim 1 , in which the at least one venting passage includes at least one restriction to enable vibrational damping.

10. The pressure or overpressure indicator apparatus according to claim 1 , in which the at least one reset feature includes at least one transverse pin engageable with the indicator element.

11. The pressure or overpressure indicator apparatus according to claim 1 , in which the at least one reset feature includes a latch member.

12. A method for detecting overpressure conditions within a jet aircraft nacelle compartment, the method comprising:

providing a housing with a pressure sensitive element;

connecting an output of the pressure sensitive element to an indicator member movably retained within the housing;

mounting the housing within the nacelle compartment; and

enabling the indicator member to move between a nominal position and a triggered position based on the output of the pressure sensitive element such that an end portion of the indicator member extends external to the compartment in order to provide a visual indication of an overpressure condition when a predetermined pressure differential between the interior and the exterior of the compartment is exceeded as detected by the pressure sensitive element, and wherein the housing includes at least one venting passage extending from the interior to the exterior of the compartment wherein the at least one venting passage is configured to meter ambient air to the pressure sensitive element; and

providing a reset mechanism configured to reset the indicator member to the nominal position following detection of the overpressure condition, the reset mechanism being accessible only by first opening the nacelle compartment.

13. The method according to claim 12 , further comprising enabling disposing at least one reset feature of the reset mechanism on the housing within the nacelle compartment.

14. The method according to claim 13 , in which the at least one reset feature is one of a pin or a latch member.

15. The method according to claim 12 , in which the pressure sensitive element is one of a diaphragm or a bellows.

16. The method according to claim 12 , in which the pressure sensitive element is a bellows and in which the method further comprises providing an assist spring to facilitate release of the indicator member to the triggered position when the predetermined pressure differential is exceeded.

17. The method according to claim 12 , further comprising:

providing at least one restriction in the at least one venting passage to enable vibrational damping.