Volume 8 No 3 Jun 1957.pdf - Lakes Gliding Club

the lower clouds took the form of S(;ud butwere evid_endy a roll cloud. High overheadwas a stratus cloud which had a beautifulcleanly defined leading edge, beyond whichthe sky was blue. The photograph, whichwas take\l at 20,000 ft., shows the leadingedge of the arch at the top of the picture.Thc lowcr cloud lying about 10-15,000 ft.was extensive in thc Mackenzie Basin butdid not exist east of those shown, or east ofthe sailplane's flight path. Landing time was17.15. The 6t hr. flight was done in relativecomfort owing to· the roomy and cQmfortableSkylark cockpit. The most importantfactor against cold was that it was draughtproof.SAFETY HIGHThe Diluter Demand Oxygen SystemHE development of aircraft oxygenT equipment has progressed from a crude"pipestem"-which literally dcliveredoxygen straight into the victim's mouthviacontinuous flow, with its mask andeconomiser or rebreather bag, to themodern "demand" system.sailplane pilots are already familiar withthe continuous flow design, and numerousexamples are to be found on gliders all overthe world.A lightweight mask has a continuousflow of oxygen delivered to it. Attached tothis mask is a rebreather bag, whichcaptures the initial portion of each exhaledbreath consisting primarily of unusedoxygen. Rebreathing makes it possible toeconomise in two ways, by using up thisotherwise unused oxygen, and by supplyinga reservoir to collect oxygen delivered fromthe regulator to the mask during eachperiod of exhalation. The mask itself isfitted with a valve through which the finalportion of the exhaled gases are blown off.In order that the supply of oxygen may'beadjusted according to altitude, the oxygenby I>avid [neecondition as if he were breathing air at10,000 ft. Since the continuous flow system,under maximum flow conditions, supplies100% oxygen, it may be assumed that40,000 It. is about the upper limit for theuse of this equipment. Although this is.basically true when the user is at rest, anymovement or activity may result in failureofthe mask to seal itself to the face and in"... any movement or activity"overbreathing of gas in the rebreather bag.regulator is provided with a manually The resultant inboard or inward maskoperated flow controller.leakage will dilute the oxygen supply withThe demand system is less weU known. air, making hypoxia very probable. As longThis was developed during the last war, as a as its limitations are observed, continuousresult of certain inherent drawbacks in flow is a good method of supplying oxygencontinuous flow which, although they do for flights at moderate altitudes, and it isnot concern us directly here, are neverthe- interesting that the American Militaryless interesting when comparing the merits Aviation Ceiling for this type of equipmentof the two designs.is 25,000 ft. The demand system was devisedBriefly, a man breathing 100% oxygen at40,000 ft. will be in approximately the sameprimarily to overcome this problem. As itsname suggests, this delivers oxygen only-119-