Fireproof pressure relief assembly

1. A pressure relief assembly ( 24 ) comprising:

an aircraft engine cowl ( 26 ) including radially outer and inner skins ( 28 , 30 ) having an opening therethrough;

a door frame ( 32 ) fixedly joined around the perimeter of said opening and extending laterally therefrom to define a door seat ( 34 ) surrounding a central portal ( 36 ) and facing radially outwardly;

a pressure relief door ( 38 ) pivotally joined to said cowl ( 26 ) for being deployed outwardly from a stowed closed position covering said portal ( 36 ) to a deployed open position uncovering said portal ( 36 );

said door ( 38 ) having radially opposite inner and outer surfaces ( 40 , 42 ) terminating in a perimeter rim ( 44 ), with said inner surface of said rim ( 44 ) overlapping said door seat ( 34 ) to define a primary seal ( 46 ) in said door stowed position; and

a fireproof secondary seal ( 48 ) bridging said door inner surface ( 40 ) and said frame ( 32 ) around the inner perimeter of said primary seal ( 46 ) to pre-seal flow to said primary seal ( 46 ).

2. An assembly according to claim 1 further comprising:

a hinge ( 50 ) pivotally joining said door ( 38 ) to said cowl ( 26 );

a pressure relief latch ( 52 ) latching closed said door ( 38 ) in said stowed position and having a predetermined release load at which said latch ( 52 ) releases said door ( 38 ) to permit deployment thereof;

said door seat ( 34 ) and said door rim ( 44 ) being in direct contact to define a sealed lap joint thereat; and

said secondary seal ( 48 ) including an inner perimeter terminating closely adjacent to said door frame ( 32 ) to maximize surface area of said door inner surface ( 40 ) uncovered by said secondary seal ( 48 ) to in turn maximize pressure load against said door ( 38 ) for reaching said predetermined release load of said latch ( 52 ).

3. An assembly according to claim 2 wherein:

said door outer surface ( 42 ) is aerodynamically smooth and disposed aerodynamically flush with said cowl outer skin ( 28 ) in said stowed position;

said door ( 38 ) further includes a structurally thick central panel ( 54 ) from which said door rim ( 44 ) extends laterally for providing a thin rim ( 44 ) surrounding said door central panel ( 54 ); and

said secondary seal ( 48 ) terminates outboard of said central panel ( 54 ) to maximize said uncovered surface area.

4. An assembly according to claim 3 wherein:

said cowl ( 26 ) and door ( 38 ) are circumferentially arcuate, and said door frame ( 32 ) varies in curvature around the circumference thereof to locally match said cowl ( 26 ) and door ( 38 ); and

said secondary seal ( 48 ) includes an inner sealing lip ( 56 ) extending in a cantilever laterally inwardly from said door frame ( 32 ) and varying in flexibility around said inner perimeter thereof for effecting an unwrinkled compression seal against said door rim ( 44 ).

5. An assembly according to claim 4 wherein:

said cantilever inner lip ( 56 ) has a length (A) and an original inclination angle (B) preselected for being elastically compressed shallower in direct contact against said stowed door rim ( 44 ) to effect a preloaded compressive interference sealed fit therewith.

6. An assembly according to claim 4 wherein:

said door frame ( 32 ) includes forward and aft circumferentially arcuate legs ( 32 a ) and circumferentially opposite longitudinal legs ( 32 b ) surrounding said portal ( 36 ) and having an inside corner ( 58 ); and

said inner lip ( 56 ) includes a complementary inside corner ( 60 ) having an inclination angle (B) less than the inclination angle (B) outside said lip inside corner ( 60 ) to permit unwrinkled lateral contraction of said lip inside corner ( 60 ) when compressed against said door rim ( 44 ).

7. An assembly according to claim 6 wherein said inner lip inclination angle (B) is constant along said lip inside corner ( 60 ).

8. An assembly according to claim 4 wherein said secondary seal ( 48 ) further comprises a fire blanket ( 62 ) fixedly attached to said door frame ( 32 ) and integrally supporting said cantilever inner lip ( 56 ) in suspension upon said door rim ( 44 ).

9. An assembly according to claim 8 wherein said fire blanket ( 62 ) comprises thermal insulation for thermally protecting said door frame ( 32 ) and minimizing thermal distortion of said primary seal ( 46 ) and thereby minimizing size of said inner lip ( 56 ), with said inner lip ( 56 ) having a thickness (T) substantially less than the thickness (T 2 ) of said fire blanket ( 62 ).

10. An assembly according to claim 8 further comprising a narrow retainer ( 66 ) fixedly clamping said fire blanket ( 62 ) to said door frame ( 32 ) by a plurality of fasteners ( 64 ) extending through said door seat ( 34 ).

11. An assembly according to claim 4 wherein:

said hinge ( 50 ) bridges said cowl ( 26 ) and said door ( 38 ) at a forward end thereof, and said latch ( 52 ) bridges said cowl ( 26 ) and said door ( 38 ) at an aft end thereof;

said seal inner lip ( 56 ) detours around both said hinge ( 50 ) and said latch ( 52 ); and

said secondary seal ( 48 ) further includes a flexible outer lip ( 68 ) along the outer perimeter thereof extending in cantilever laterally outwardly from said door frame ( 32 ) for effecting a compression contact seal against said cowl inner skin ( 30 ) to seal leakage flow through said hinge ( 50 ) and said latch ( 52 ).

12. An assembly according to claim 11 wherein said cantilever outer lip ( 68 ) has a length (C) and an original inclination angle (D) preselected for being elastically compressed shallower in contact against said cowl inner skin ( 30 ) to effect a preloaded compressive interference sealed fit therewith.

13. An assembly according to claim 12 wherein:

said door frame ( 32 ) includes forward and aft circumferentially arcuate legs ( 32 a ) and circumferentially opposite longitudinal legs ( 32 b ) surrounding said portal ( 36 ) and having an outside corner ( 70 ); and

said outer lip ( 68 ) includes a complementary outside corner ( 72 ) having a corresponding length (C) and inclination angle (D) preselected to permit elastic expansion of said outer lip ( 68 ) upon compression against said cowl inner skin ( 30 ).

14. An assembly according to claim 12 wherein:

said cantilever inner lip ( 56 ) includes a length (A) and an original inclination angle (B) for being elastically compressed shallower in direct contact against said stowed door rim ( 44 ) to effect a preloaded compression interference sealed fit therewith; and

said length (C) of said outer lip is greater than said length (A) of said inner lip ( 56 ), and said inclination angle (D) of said outer lip is greater than said inclination angle (B) of said inner lip ( 56 ).

15. An assembly according to claim 12 wherein said secondary seal ( 48 ) further includes:

a hinge dome ( 74 ) covering said hinge ( 50 ) and extending laterally between said inner and outer lips ( 56 , 68 );

a latch dome ( 76 ) covering said latch ( 52 ) and extending laterally between said inner and outer lips ( 56 , 68 ); and

a plurality of narrow retainers ( 66 ) fixedly clamping said secondary seal ( 48 ) to said door frame ( 32 ) and terminating on opposite sides of said hinge and latch domes ( 74 , 76 ).

16. An assembly according to claim 15 wherein said secondary seal ( 48 ) further comprises a fire blanket ( 62 ) extending laterally between said inner and outer lips ( 56 , 68 ) and along said hinge and latch domes ( 74 , 76 ), with said fire blanket ( 62 ) being substantially thicker (T 2 >T) than said inner and outer lips ( 56 , 68 ) for thermally protecting said hinge ( 50 ), latch ( 52 ), and door frame ( 32 ), while allowing unrestrained elastic compression of said inner and outer lips ( 56 , 68 ) cantilevered therefrom.

17. An assembly according to claim 16 wherein:

said fire blanket ( 62 ) comprises thermal insulation for thermally protecting said door frame ( 32 ), hinge ( 50 ), and latch ( 52 ), and minimizing thermal distortion of said primary seal ( 46 ); and

said inner and outer lips ( 56 , 68 ) comprise a fabric bag ( 78 ) encapsulating said thermal insulation ( 62 ), and extending laterally therefrom in thin cantilevers.

18. An assembly according to claim 17 wherein said fabric bag ( 78 ) comprises a single ply encapsulating said thermal insulation ( 62 ) and joining together in two plies to define said inner and outer lips ( 56 , 68 ) at opposite ends of said fire blanket ( 62 ).

19. An assembly according to claim 15 wherein both said hinge and latch domes ( 74 , 76 ) include a drain hole ( 80 ) covered by a corresponding flexible sealing patch ( 82 ) bonded to said domes ( 74 , 76 ) with a local interruption of said bond to seal said drain holes ( 80 ) under applied pressure and to permit liquid draining when unpressurized.

20. An assembly according to claim 15 wherein:

said cowl ( 26 ) and door ( 38 ) comprise fiber-reinforced composite materials molded to shape and having rough exposed surfaces ( 84 );

said outer lip ( 68 ) is adhesively bonded to said rough cowl inner skin ( 30 ); and

said inner lip ( 56 ) includes a seal coat ( 88 ) conforming in texture with said rough door rim ( 44 ) to improve sealing effectiveness of said inner lip ( 56 ) in interference contact with said rough door rim ( 44 ).