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Aviation History
1944
1944 - 1482.PDF
•68 F LIG HI JULY 20TH, 1944 FIRE RISK IN AIRCRAFT Where F = force produced on aircraft structure in lb. W = weight of petrol and tanks, in lb. V and S as above. 87-octane fuel weighs 7\ lb. per gal., and the tank i| lb. per gal. Then W = (50 x 75) x (50 x 1.25) = 437.5 lb. Therefore F =t 437.5 x 6 = 2,620 lb. from which it will be seen that under the influence of 6g. the load which the tank and its supports are subjected to is fairly considerable. If the tank can be so mounted that the sudden shock does not rupture the shell but pulls the mounting away from the aircraft structure, then no risk due to spilt contents will be present. / 5HEAB WASHES SHEAR WA3HE.B BREAKS UNDER LOAD - COUPLING\ 13 PULLED APART AMD ITS OPEN END§ UO. INSTAKTKlf * Sst>M.EL>. Fuel and Oil Lines Regarding fuel and oil pipes; if these pipes had to break, a sealing valve could come into operation and stop the flow of liquid. In fact, a weak point could be incorporated to ensure the pipe/ breaking, if it had to break, at the sealing valve. An Avery coupling, suitably modified as shown in the author's sketch, would admirably answer this problem. Fuel pipes should also be kept as far as possible from any component that would be likely to cause a fire in the event of a leakage. The operations of refuelling or jettisoning of fuel whilst flying involve very great fire risks unless certain precautions are observed in the design of the systems. . Static discharges can cause fire when jettisoning fuel where it is likely to contaminate the surface of the aircraft adjacent to the dis charge port. This can be nullified by ensuring that the discharge nozzle is so designed that contamination could not take place. Design requirements are in being recom mending that the volume of fuel left in the tank after jet tisoning the bulk, is not to be less than 1 per cent, of the volume of the tank, so as to prevent the formation of an explosive mixture. Sometime* when landing a local ex plosion occurs in the dischpdfge pipe. This is not serious An Avery coupling, modified as shown, would make a self-sealing weak point ;n fuel and oil pipe lines. to be a worth-while contribution towards the problem of fire prevention. Exhaust manifold systems are probably the worst offenders, and a shielding system could be de«L, vised whereby, if petrol or oil were spilt near the exhaust' systern/the parts with which it would come into contact woura not "flash" it off. Short Circuits Short-circuits in the electrical system can be protected by such methods as shielding, or prevented by isolating the main source of electrical supply, which is the battery and the engine-driven generator. Some means of imme diately stopping the magneto and the generator, render ing the battery incapable of producing a spark, are required. The magneto and engine-driven generator could be stopped by stopping the engijte, which seems to be a case for either the featheringy&irscrew or the airscrew brake. _^^^ -=____ The battery cotld be autocratically jettisoned just before an immine|t:"-£ras\ or the ^feetfti so shielded that it would provided the closing valve "wiir prevent the explosion fbe impossirMe\|orViy shrflt |;ircuit to cause a fire. The reaching the tanks, and the discharge pipe is strong enough \ Battery cOBlM|e de'pnvjfl of the means of causing a spark to withstand such an explosion.! With regard to refuel- by short-circilting umffer the electrolyte, and if a battery ling, there is a scheme in existence whereby methyl-bro- of the NIFE tvpc jflth metal plates and caustic electro- mid'e is released when the, refuelling connection is broken. lyte was usedJfcnTMramage would result if the battery was so that the fesultant petrW vapolr" \S needed again. Another is rendered non-inflamrasMe by fie •••••H — WM method would be to discharge rawing of the chemical with it/ the electrolyte from the bat- ^skelding and lagging of rArts tery. This is another case for which are liable to 'become/hot H!^m the battery with no cedar- enough to ignite petrol br oil/eems £. f^Pm wood separators which could \ / B^fcsMaJt '\ """"llljp '.j, hold a certain amount of \ i^Wf g RP^^^^hliHte: Hi liquid. The automatic sys tem could be operated by mechanism similar to that of ^^jypp"5*^SgSi**'!'"^^••-•••jma^^'',: J^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^B the Graviner fire-extinguisher system. Accumulators should be provided with adequate ventilation to prevent the accumulation of explosive gases. Electrical Equipment The use of electrically oper ated fuel gauges, pumps, etc., which are adequately protected against sparking is advisable. The Waymouth I-- »* Gauges and Instruments, AJ?'?L gf u Ltd., when describing their SStSSSiiSS *** g-f- state that there itself on fire. The » ™ electrical connection rush of air in the between the tank and the dive put the fire out. electrical supply—it is via a
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