CA1296970C - Aircraft fire protection system - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An aircraft fire protection system which includes a plurali-ty of water spray nozzles spaced along a plurality of longitudi-nal conduits all cross-connected by a plurality of transverse conduits, with "choking" type flow restrictors spaced between groups of spray nozzles to limit flow following conduit rupture, Conduits are connected to the aircraft on-board water supply sys-tem via a pump and non-return valve in series and, additionally or alternately, a plurality of externally mounted self-sealing couplings are interconnected to the conduits, one of which cou-plings should be accessible to fire-fighting personnel for fire tender hose hookup regardless of aircraft orientation and atti-tude. A two-way flow restrictor includes a housing with a cap-tured ball valve element with flutes by-passing opposing seating shoulders for the ball to provide two predetermined "choked" flow rates for normal and reverse flow modes.

Description

1;~96970 8AC~GRQyND OF T~E r NVE~T~ON

E,iel~ o~ the Invent~n:
ThQ present inventlon relate5 to systems ~or the preventlon of fire~ aboard slreraft~ including aircraft whlch have crashed.

~escri~ti~n of the P~Qr ~t:
There are two principal major ~ire hazards in a1rcraft ca~insl namely:
(a~ ~n-fligh~ fire in the ca~in spaçes; and (b) Fire on th~ ground, following a crash, which ~pre4ds into the ca~in.
Both of these involve combustion of the fabric ~nd ~r-nishing~ i~side the airc~aft ~nd the ~mission o~ toxic fumes.
~and-held fire ex~lngu~shers are of limite~ ~se in the in-flight flres and totally ineffeetive in ~he ma jor f lres w~lch f~llow crashes. Internal spray systems have been proposed for commer-cial and milit~ry aircraft, but they have not been adopted 4eça~se they require ~he air~r~ft ~o carry l~r~e quantitie5 of water or other nontoxic extinguishing liquids and the weight pen-alty is ~naccept~bl~.
~o The majority o~ survivable crashes occur within the per~e-ter of an airield and f ir~ ~en~rs are abl~ to extinguish exter-nal ~i~es wi~hin a matter of minutes. aut in ~his brief period, a large number of passengers will have died from the ef~ects of:

1~969~
(a~ Toxic fumes given off by the burning furnishings;
(b) External fumes ducted through the aircraft by the chimney effect;
(c) Flash-over fires in the aircraft furnishings; and (d) High temperature in the cabin.

SUMMARY OF THE INVENTION
The present invention makes it possible to operate a cabin spray system without the need to carry large additional quantities of water or other fluid in the aircraft. This is achieved by:
(a) The use of the aircraft's domestic water supply (fresh and used) to cope with in-flight fires during the immediate period following a crash; and/or (b) Pumping water from the ordinary hoses of the fire tenders into special connectors mounted at the extremities of the aircraft, one of which is certain to be accessible to the firefighters.

Each of these two capabilities individually and especially in combination will provide the time necessary for safe aircraft evacuation. Some airlines or aircraft regulatory bodies may prefer to use a system having one or the other of the capabilities, but a system having the capabilities in combination would be expected to dramatically increase the chances for survival compared to aircraft without such protection.

1 ~fi~7() In a broad aspect, the present invention relates to a fire protection system for an aircraft of the type having an on-board water supply system, the fire protection system comprising: a) a plurality of spray nozzles dispersed throughout the aircraft passenger cabin; b) a plurality of distribution conduits interconnecting said plurality of spray nozzles; c~ means for selectively connecting said distribution conduits to the aircraft on-board water supply system; and d) means for optionally connecting said distribution conduits to a source of pressurized water external to the aircraft, said external source connection means being positioned to be accessible to fire-fighting personnel outside the aircraft regardless of the orientation of the aircraft; wherein said external water source connecting means comprises a plurality of self-sealing couplings distributed about the external fuselage of the aircraft and connected to said distribution conduits, and wherein said distribution conduits are configured for providing a flow path to each of said plurality of spray nozzles from each of said self-sealing couplings.
Preferably, the distribution conduits are configured to supply each of the plurality of spray nozzles along at least two alternate flow paths whereby a redundancy is achieved.
It is also preferred that the fire protection system further comprises means for limiting the flow of water in the distribution conduits in the event of a rupture of one of the distribution conduits upstream of one or more of the plurality of spray nozzlès.

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129~,9~;~o It is still further preferred that the fire protection system further comprises means for optionally connecting the distribution conduits to a source of pressurized water external to the aircraft, the external source connection means being positioned to be accessible to fire-fighting personnel outside the aircraft regardless of the orientation of the aircraft.
In accordance with the invention as embodied and broadly described herein, the fire protection system for an aircraft to be supplied with pressurized water from a source external to the aircraft comprises a plurality of spray nozzles dispersed through the aircraft passenger cabin; conduit means located internal to the aircraft interconnecting the plurality of spray nozzles; and at least one self-sealing coupling mounted on the external fuselage of the aircraft and being interconnected with the plurality of spray nozzles by the conduit means.
Further in accordance with the invention as embodied and broadly described herein, the apparatus for restricting the flow of a fluid in a conduit to a predetermined maximum value for a given fluid flow pressure drop comprises a flow restrictor housing having a through-bore, an enlarged bore portion within the housing, and an internal housing shoulder positioned at the juncture of the enlarged bore portion and the downstream part of the enlarged through-bore. The apparatus further includes a valve body positioned within the enlarged bore portion and movable by the action of the flowing fluid into abutment with the shoulder. Still further, the t, ~ ', 1~!9fi97(~
apparatus includes a set of flutes formed in the housing and spaced about the inner periphery of the enlarged bore position, the set of flutes by-passing the shoulder. The flutes are sized so that the combined cross-sectional flow area yields the desired fluid flow rate value for the given fluid flow pressure drop.

BRIEF DESCRIPTION OF THE DRAWING
The appended drawing, which is considered a part of the present specification and which, in conjunction with the written portion of the specification, serves to explain the principles and operation of the aircraft fire control system of the present invention, includes the following figures:
Figure 1 is an overall schematic view of one embodiment of the aircraft fire control system, made in accordance with the present invention;
Figure 2 is a schematic showing a portion of the aircraft fire control system depicted in Figure l; and Figure 3 is a schematic detail of the flow restrictor element of the aircraft fire control system depicted in Figure 1.
Summarizing the description of the aircraft fire protection system shown in the figures, and operation thereof depending upon the aircraft body size, preferably three or more longitudinal conduits 32, 34 are installad on each side within cabin 14. Sited at intervals along these pipes are spray nozzles 28, so disposed to provide complete coverage of the aircraft interior with finely dispersed droplets of water.

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The longitudinal conduits are supplied with water from feed inlets at the extremities of the aircraft. Thus, there are two self-seal-ng couplings 66 forward and two aft of the fuselage, and one self-sealing coupling 68 at each wing tip, each able to be supplied from the airfield fire tender's hose pipes, these being fitted with matching self-sealing couplings. The aircraft's couplings are installed in non-pressurized parts of the aircraft. Feeder pipes 67 from the couplings to the interior sprinkler system are led through standard bulkhead fittings where they pass through the pressurized bulkheads.
The longitudinal conduits 32,34 and transverse conduits 36 in the cabin are of titanium to save weight. The flexible conduits 70 in the wings are of plastic, their flexibility making it easier to pass them through existing lightening holes in the wing ribs.
Self-sealing couplings 66,68 are disposed so that some of the couplings will be accessible, r~gardless of the attitude of the aircraft. They will be supplied with water from the first tender to arrive on the scene of the accident, at a normal pressure of 9 bar (110 psi). However, the sprinkler system is effective provided the pressure is no less than 2.3 bar (35 psi~.
Should one or both wings be sheared off in the accident, and plastic flexible conduits 70 thus become damaged, non-return valves 72 in the wing roots where the conduits join the internal conduit distribution system will close when water is applied to one or more of the other external hose couplings ,~L~ ,', ~, ~.~9~i~7(~
which remain serviceable. If the wing is intact, ~ut on fire, then the plastic conduit will survive if it is full of water.
If the plastic conduit 70 is destroyed by fire before it is filled with water via its respective coupling 58, then, again, any of the other couplings 66 can be used by the firefighter to drench the cabin.
Should the accident cause a fracture of the conduits within the cabin, it will still be possible to achieve drenching of the cabin via the separate system parts. The sprinkler nozzles are arranged in groups along longitudinal conduits 32.34, with flow restrictors 38 between those groups.
The flow restrictors "choke", limiting the quantity of water which can spill from the fractured conduit ends to that quantity which would normally have been supplied to the sprayers on the broken-off section. This will ensure that all spray nozzles 28 supplied with water will function as intended. Flow restrictors 38 are of a novel but simple and reliable design which enables them to restrict to two different flow values, depending upon the direction of water flow. Thus it is possible to ensure successful drenching of the cabin 14, no matter where along the conduit length a fracture occurs.
The weight of the system 10 is estimated as 45 kg (100 lb) for a Boeing 737 installation, and this low figure would be acceptable to any airline interested in passenger safety.

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1~9~970 _SCRIPTION OF THE PREFERRED EMBODIMENT
Reference will now be made to the present preferred embodiment of the invention, an example of which is depicted in the accompanying drawing.
With initial reference to Figure 1, there is shown an aircraft fire protection system constructed in accordance with the present invention and designated generally by the numeral 10. Fire protection system 10 is shown installed in aircraft 12 (shown in dotted lines) having passenger cabin 14 disposed along the aircraft longitudinal axis 16 and wings 18, 20 defining the transverse direction. The aircraft depicted in Figure 1 is of the type having an on-board "domestic" water supply system 22. As best seen in Figure 2, domestic water supply system 22 includes clean water reservoir 24 and used water reservoir 26.
In accordance with the present invention, the aircraft fire protection system includes a plurality of spray nozzles dispersed - 7(a) -~L~ ~.

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~hrough~ut ~e aircraft cabin. As embodied here1n, and ~s best seen in Flgure l, a plurallty o~ sprlnkler head~ 2~ sre arr~yed 810ng cabin 1~ And directed to provlde coverage to all occupied parts o~ cabin l~, The indi~idual nozzles 2~ can be directed 5- from ~elow, a~ well as from the side and f~om ~ove, the passe~-ger seating positions, and ~onfi~ured and ~ized t~ pr~ide mls~
or shower-type spr~ys. Sprinkler heads should be operablQ at lea~t over the ~ange o~ ~ater supply pressures of dbo~t 35 psi co ll0 psi. One skilled ln the art would be able to construct and p~sition sui~able sp~inkler heads giv~n cu~çnt knowledge in the art ~nd the present specific~tion.
In tccordan~e with the present Invention, the ~ircraft fire protec~ion syste~ ~urthe~ inclu~es conduit me~n~ for inSerConneeting and dis~ributin~ water tO the spr~y nozzles. As lS embodied herein, and with contin~ed refe~ence tO Flgure 1 r con-dult means ~esignated generally by the nu~eral 30 lncludes a plu-rality of longitudin~l conduits 32, 34 running th~ length of c~bin 14, with ~t least one lonsitudin~l condult on each trans-verse side of axis 16. Pr~ferab1y, a plu~ality (e.~ hree or more) of longitudinAl conduits 32, 34 are used on ea~h trans~erse side, al~hough Flgure 1 only shows one each for purposes of clar-lty. ~ongitudin~l ~onduits 32, 34 should be sSrong bu~ rela-ti~ely ligh~weight, and titanium conduits are preferred. ~hese can be run along ehe non-pressurized spa~e outside the ~abin, with only the spray nozzles penetratin~ the pressurized por~lon.

2 96~97 O

~ onduie means 30 further in~ludes at least one transverse c~nduit 3~ for int~rconnecting longltudinal conduits 32, 34.
Prefera~ly, a plurality o~ t~ansverse conduits 36 (three being shown in ~igure 1), sp~ced along ~xis 16, are employed to achieve 5 ~ ~ redundancy in the water supply flow path t~ each 8pray nozzle 2~. In thls same vei~, transv~se cond~lt3 36 are closed ring-type, which act like dist~ibution plen~ms. In the event of ~~ an aircrAft crash ~ollowed by ~upture ~f one of longltudinal con-d~its 32, 3~ an~or transverse conduits 3~ there would ex~st an alternative ~low to each spray nozzle 28, as can be appreci~ted from s~dying the ~onfig~rat~Pn of conduit me~ns 30 in Flgure 1.
To assist in ~hieving the flow path r~dundancy, flo~ re-stricto~s 38 are placed in longitudinal çonduits 32, 34 bet~een groups of spray nozzles ~8 t~ timit or "~hoke" the flow that would leak out of the ruptured conduit downstream of the re-~trictor. Prefera~ly, flow restrictors 3a are sized to limit th~
rupture flow rate to approximately th~t of the combined down st~eam sp~ay nozzle çapacity, ~nd it i5 ~urther preerred that the flow restr ktors be l'two-way" to ac~ommodate the alternate redundant flow p~th design. ~ novel flow restrictor 38, whi~h is s~mple in design ~nd which ~an be cons~ructed to ha~e two differ-ent choke flow rates, depending on flow direction, is di~cussed henceforth.
In a~cordance with the present inventio~, the two-way flow restrictor includ~ a hvusing with a through-bore ~nd an enla~ged bore portion capturinsly holdinq a valve body. As embodied 12 ~6 ~7 0 herein, and with refe~ence to ~ig~re 3, flow rest~ictor ~ in-clude~ hou~lng ~0 with through-bore 42, a central portion 44 ~f which ls enlar~ed in cross-sectional dlameter. Respective inter-nal ~houl~e~s ~G, 4~ are ~ormed in th~ houslng at th~ junctures of portlons SO. ~Z of the through-bore 42 and enlarged bore por-tion 4~. Bal~-type ~lve body 5~ is positioned in enl~rged bore portion 44 an~ is movable by ac~ion of the flowin~ fluid into engagement with ei~her of shouldcrs 4~, 48, depending upon the direction of flu~d f~ow.
tmportantly, and further in accordance w~th the present lnvention, flutes a~e p~o~ided spaced about the lnternal pariph-ery of the housing and by-passinq th~ respecti~e shoulde~s to p~ovide a predetermined flow path pdst the valve body, As embod-ied herein, two sets of ~lute 5~, 58 ~re f~rm~d in the in~ernal lS periphery of houslng 40 t~ by-pass shoulders 46, 4~, respectlve-ly~ As ~epic~ed in Fi~ur~ 3, th~ f lutes in sets 56, 58 are of different size to provide a differen~ pre~elected "choke~ flow rate. Thus, the "ch~ke" flow ~atc for flu;d flow right to le~t in FigurB 3 would be gre3~er than th~ "choke" fl~w rate in the 20 opposite direction owing to the large~ sizes of the flutes in set 58 relatiYe to set 5~. Alte~natively, the n~mber o~ flutes can be varied, while the flute size is kept constant, to achie~e dif-ferent "choke" ~low ratesr as ~ne skilled in the art would im~e-diately appreciate.
2S Still f~rther in ~ccordance with the p~esent inven~ion, the ai~craft ~ire protection system includes .~eans for sele~tively l~g9~0 connect~ng said distri~ution conduits to the aircraft on-board water ~pply 8ystem. As embodled herein, and wlth initi~l refer-ence to Fi~re 1, ~electiv~ ~nnection means d~slgn~ted ~enerally ~y the numer~l 60 ls shown ~onnecting domestic w~ter supply sys-tem 22 with the cen~rally located one of transverse ring-type conduit~ 3~. Other connection locati~ns sre, of course, possible due to the interconnections of conduit means 30, as ~ell a~ ~
connection between supply sys~em 22 and on~ of lon~itudinal con-duits 32, 34. With reference no~ to ~igure ~, sele~tive eonnec-tion means 60 can, fo~ example, include wa~er pu~p ~2 and non-return valve 64 ln s~ies and changeove~ valve 64 selectively connectable to ~lean water resçrvoir 24, used wate~ re~ervolr 26, indi~idually, or both, ~imultaneously.
Further in ~ccor~nce With th~ present invention, the air-l~ craft fire protection system can also incl~de m~ans for option-ally connecting ~he distrlbution cond~its to a source of pre~sur-ized water external to the aircraft. As embodied herein, and with reference ag~in to Figure l, a plurality of s~lf-sealing couplin~s 66 are distribut~d 3bout the external air~raft fusila~e on both sides of the a~rcraft and ~re indi~idually connected via feeder pipes ~7 to transverse conduits 3~ at the front ~nd rear of the aircraft. This ~is~ribution shQuld allow at least one of self-sealing ~ouplings 66 to ~e acc~ssible to fire fighting per-sonnel for ~irtually any non-standard orientation of the air-craft, such as following a crash where the aircraft may be on its side or have 50~e fu~ilage portions da~aged, Additional 9'~() self-sealing c~uplings ~8 c~n b~ located at the win~ tips and can be connected to the central one of transverse conduits 36 vla ~lexible conduits ?0 ln which ~re dlsposed non-r~turn valves 72 located near the wing roots ~ue to tl e high propensi~y for the 5 wings to ~e sheared of f followin~ ~ crash land~ng. ~lex;ble con-duits ~n be fab~icated from plastic pip~ng to provlde the re-quired ~lexibility.

Claims (10)

1. A fire protection system for an aircraft of the type having an on-board water supply system, the fire protection system comprising:
a) a plurality of spray nozzles dispersed throughout the aircraft passenger cabin;
b) a plurality of distribution conduits interconnecting said plurality of spray nozzles;
c) means for selectively connecting said distribution conduits to the aircraft on-board water supply system; and d) means for optionally connecting said distribution conduits to a source of pressurized water external to the aircraft, said external source connection means being positioned to be accessible to fire-fighting personnel outside the aircraft regardless of the orientation of the aircraft;
wherein said external water source connecting means comprises a plurality of self-sealing couplings distributed about the external fuselage of the aircraft and connected to said distribution conduits, and wherein said distribution conduits are configured for providing a flow path to each of said plurality of spray nozzles from each of said self-sealing couplings.

2. The fire protection system as in Claim 1 wherein said distribution conduits include:

(i) a plurality of longitudinal conduits running along the longitudinal axis of the aircraft, at least one of said longitudinal conduits being located on each side of the aircraft, said spray nozzles being spaced along said longitudinal conduits; and (ii) at least one crossover conduit extending generally transverse to, and interconnecting with, said longitudinal conduits.

3. The fire protection system as in Claim 2 wherein said crossover conduit is a closed ring-type conduit encircling the passenger cabin.

4. The fire protection system as in Claim 3 wherein said distribution conduits include a plurality of closed ring-type crossover conduits spaced along the longitudinal axis of the aircraft.

5. The fire protection system as in Claim 1 wherein said distribution conduits are configured to supply each of said plurality of spray nozzles along at least two flow paths whereby a redundancy is achieved.

6. The fire protection system as in Claim 1 further comprising means for limiting the flow of water in said distribution conduits in the event of a rupture in one of said plurality of distribution conduits upstream of one or more of said plurality of spray nozzles.

7. The fire protection system as in Claim 5 further comprising a plurality of flow restrictors spaced along said longitudinal conduits between groups of said spaced spray nozzles.

8. The fire protection system as in Claim 7 wherein each of said flow restrictors is configured to restrict the maximum flow rate of water to a value approximately that of the combined capacity of the downstream spray nozzle.

9. The fire protection system as in Claim 4 further including at least one pair of said self-sealing couplings mounted on the external fuselage on opposite sides of the aircraft and connected to one of said transverse conduits.

10. The fire protection system as in Claim 1 wherein a pair of said self-sealing couplings are located one proximate the tip of each wing of the aircraft, the fire control system further comprising:
(i) a pair of flexible conduits one interconnecting each of said pair of self-sealing couplings to said distribution conduits; and (ii) a pair of non-return valves one positioned in each of said flexible conduits proximate the root of the respective wing.