hello WWII vets and enthusiasts, I had a general question about the on board oxygen tanks found in most fighter aircraft. I wanted to know how long a pilot could rely on a tank of oxygen, and if they carried more than one tank. I've searched the internet for information on this topic, but there's isnt too much info on how long these tanks would last until they had to use another tank or drop altitude. Maybe it was never an issue because one tank could last the entire flight. thanks Bill
I found some information regarding oxygen tanks and systems used in WWII: understanding hypoxia ...During the first two decades of this century there seems to have been great expansion and embellishment but little original thought on aspects of hypoxia, despite great leaps in aviation and the first world war. The theories of Paul Bert and Hermann von Schrotter were used as the basis of most considerations of aviation hypoxia during the first world war. It should be realised, however, that despite the development of aviation in warfare (Spanish Civil War and First World War) very few aviators during this period actually flew higher than 10,000 ft. and when they did it was for relatively short periods. Perhaps this is an unfair statement as certainly there was a great deal of experimentation on hypoxia and much development and refinement of equipment during the great war. However, after the innovative works and theories of the likes of Bert and Schrotter the wartime progress seems (to me) somewhat mundane and repetitive. In 1917 Barley submitted a minute to the British War Office detailing his observations of a variety of aircrew performance impairments that he attributed to hypoxia. He claimed that hypoxia was the cause of increased aircrew fatigue after flights at higher altitudes as well as the many reports of inappropriate or irrational aircrew actions when at altitude. He also proposed subtler degrees of impairment at relatively low altitudes and the relief of all these difficulties by breathing Oxygen. Birley, and others, were aware that hypoxia was able to impair aircrew performance and a variety of experimental methods were devised attempting to investigate their observations. In Britain two researchers independently devised simple, inexpensive methods of simulating altitude exposure. One of these, the 'Flack' apparatus (named after it's inventor GPCAPT Martin Flack) involved a five litre re-breathing bag with a chemical CO2 scrubber. The approximate height at which hypoxic symptoms develop could be estimated by sampling the gas in the re-breathing bag at the commencement of symptoms while using the apparatus. Using the Flack apparatus a number of researchers demonstrated that some people were more resistant to the effects of hypoxia than others, and concluded that selecting for these more resistant candidates would enhance the safety and performance of the Royal Flying Corps (RFC). Flack devised a number of tests that selected for the personnel more resistant to hypoxia, and these tests were in use up to the commencement of the second world war. Flack's empirical tests were very effective in identifying people with poor respiratory responses to hypoxia but it is debatable whether rejection of these folk enhanced the performance of the RFC/RAF. During the first world war there was, in Britain at least, some considerable aircrew resistance to the use of Oxygen. A variety of factors probably played a part, for example it was considered, by some, a 'soft' option (like parachutes, initially forbidden for RFC aviators). Others thought that shooting down an enemy while 'hiding' behind a mask was unsportsmanlike, and the Oxygen masks of the day were, almost universally, uncomfortable and unreliable. Another development in 'hypoxia technology' around this time was the invention of various 'economiser' circuits and apparatus to reduce the proportion of wasted Oxygen. These Oxygen economizers (as designed by J.S. Haldane, 1917, and produced by Siebe Gormon for use by aviators at around the same time) were initially unreliable and bulky, they employed a flexible reservoir bag supplied with constant flow rate Oxygen. During inhalation Oxygen passed from the reservoir bag to the pilot's mask and when he exhaled the bag refilled with Oxygen while his breathe passed out of the mask via a rubber flap valve. Early Oxygen regulators were, also, somewhat rudimentary and cumbersome, not to mention unreliable. During the first world war LTCOL Dreyer RFC improved on the contemporary regulator design with it's manually selected settings for certain altitudes by designing an aneroid unit that automatically adjusted the amount of Oxygen delivered as the altitude increased. Other advances in regulators at this time reflected the desirability of knowing how much Oxygen was left in the tank and how fast you were using it - various meters were incorporated in the basic regulator design. The Germans had, during WW1, devised methods of controlling the rate of evaporation of liquid Oxygen and where British aircraft carried compressed gaseous Oxygen the Germans were using liquid Oxygen. At the completion of WW1 research into hypoxia, or at least landmarks in hypoxia research, seem to have focused again on the ballooning fraternity. German physiologist-physician Dr. Hubertus Strughold studied previous research into altitude physiology and began further work in the field using balloons and later learning to fly himself. One non-ballooning land mark at this time was the first attempt at developing a pressurised cabin for aircraft. It had been shown by Suring and von Schrotter that 100% Oxygen at ambient pressure would be inadequate to prevent hypoxia above a certain altitude, since shown to be 40,000ft. A pressurised aircraft cabin is one method of providing Oxygen at higher than ambient pressures, another is 'pressure breathing' where increased pressure Oxygen (absolute and partial) is provided to the airways via a tight fitting face mask. We take for granted a pressure cabin (be it Sea Level, 4,000ft., 8,000ft., or other) whenever we fly in a commercial routine passenger transport jet. In 1921 a wind driven pump was mounted to pressurise the cabin of a De Havilland biplane in the USA. The cabin was pressurised but in an uncontrolled manner maintaining a -7000ft cabin altitude when flying at +3,000ft. This idea was explored for a year, or so, then appears to have been forgotten in the USA for some time (until the American XC-35 of 1939). Post war research by the US Army Corps served to confirm Schrotter's predicted ceiling for open gondola balloons. In May 1927 US Army CAPT Hawthorne C. Gray made further attempts on the world altitude records, using open balloons and Oxygen in pressurised steel cylinders. He reached 42,470 ft. and started a descent because of hypoxia symptoms then bailed out, due to balloon malfunction, and made a successful parachute descent. A similar attempt, six months later, found him at 42,470 ft. again, commencing descent due to symptoms of hypoxia, when his Oxygen supply ran out. He was dead when his balloon landed. By 1929 free balloon and aircraft ascents had been made to 32,800 ft. and in 1931 German high altitude physiologist, Hans Hartmann had climbed to 28,200 ft. in the Kanchenjunga region of the Nepal Himalaya without using Oxygen. These ascents further enhanced our understanding on the limitations of man in an hypoxic environment, but also demonstrated the capacity to adapt or acclimatise to reduced Oxygen tensions at altitude. In accordance with von Schrotter's earlier predictions the next step in hypoxia research went hand in hand with further altitude record attempts and involved men breathing Oxygen at a pressure greater than the ambient atmospheric pressure. The concept was simple: rather than the aviators exposing themselves to the rarefied atmosphere at altitude they would take with them an atmosphere as near as possible to that found at sea level. On 27 May 1931 Auguste Piccard and Paul Kipfer took off inside a pressurised gondola suspended from a balloon and successfully reached 51,775 ft. Piccard had designed the pressure capsule to maintain a sea level pressure and the two passengers breathed air cleansed of exhaled CO2 by an alkali 'scrubber'. Piccard's pioneering work with self contained pressurised gondolas has since allowed man to fly to well in excess of 100,000 ft. using balloons. Germany, in the late 1920s, had recommenced work on the pressure cabin for fixed wing aircraft. In 1933 a Junkers 49 equipped with a pressure cabin successfully flew to 33,000ft., and in 1936 this same plane reached 41,000ft. Similarly France had developed pressure cabin technology by 1935, albeit with problems. Between the wars, it was perceived that the British (and USA) had made little progress in their development of operational aircraft Oxygen systems, while it was felt, at the time, that the Germans had made considerable advances and had an edge over the Allies in this respect. Little had been made of Haldane's and Siebe Gorman's Oxygen economiser equipment as can be seen in the 1932 British attempt (successful) on the fixed wing altitude record. For this flight, to 43,976 ft. the Bristol Aeroplane Company's test pilot, Mr. C.F. Uwins, flew the open cockpit Vickers Vesper biplane using a constant flow RAF issue Oxygen mask set to deliver 100% Oxygen. Problems experienced during the preparatory research for this flight came to the attention of SQNLDR Gerald Struan Marshall, then Director of the RAF's Physiological Laboratory, who wrote to the Director of Medical Services pointing out the discrepancies of the Oxygen systems in use. The closing line of his report was " . . . other things being equal, in a fight at over 20,000 feet, the man with the more efficient Oxygen system will win." Within weeks research was underway on new Oxygen regulators and other equipment and over the ensuing few years the RAF Type D mask/regulator system evolved. Despite the type D mask not living up to expectations it did pave the way for further advances in masks, regulators, and economisers early in the second war. As had been previously pointed out by von Schrotter (vice supra) and Haldane [41] altitude exposure in excess of 33,000 ft. resulted in falling arterial Oxygen saturation, even with the use of 100% Oxygen. This had recently been overcome by Piccard using pressurised balloon gondolas and Struan Marshall's Physiological Laboratory set about developing a more portable pressurised environment, the pressure suit. In conjunction with the Siebe Gorman Company a deep sea diver's suit was modified to produce a pressure suit. During the period 1933 - 1935, this suit was developed and tested to 90,000 ft. in pressure chambers. In 1936 the suit was successfully flown to 54,000 ft.. It was found to be cumbersome, unwieldy, and have a variety of unanticipated technical and practical problems. Despite the problems at the time, and it's operational difficulties such a suit can be clearly seen as one of the forerunners of our modern astronaut's pressure suits used for intra and extra -vehicular travel. An American, Wiley Post, also designed and built a pressure suit in 1935. He used this suit in 1934 and 1935 in attempting to break the trans-American speed record, no further details can be found on his flights. Concurrent pressure suit research was underway in France (1935, Dr. Garsaux and Naval Surgeon Rosentiel), Italy (1937, Pezzi achieved record altitude of over 51,000ft.), and Germany (Draegerwerke). An interesting aside is the conclusion of some independent Russian research during this period. One paper stated that a degree of hypoxic protection was afforded by "...the emotional factor and the socialistic tendency of the Soviet flyer, along with physiologic compensatory mechanisms..." . The textbook quoted provides a very up to date (in 1939) treatise on Aviation Medicine [46]. Subsequent research has, however, failed to demonstrate any degree of protection against hypoxia being afforded by Socialist tendencies. In the years immediately preceding WWII the feeling that the Allies trailed in Oxygen research prompted the decision that the development of new Oxygen supply systems should be given the highest priority in British Aviation Medical research (1939). Throughout the war research attention was concentrated upon the practicalities of Oxygen use by combat aviators. Problems addressed included; how to produce and carry Oxygen, how to ensure reliable, controlled delivery of Oxygen to the aircrew, how to design a mask system that ensured the Oxygen went where it was supposed to - into the lungs, and how to minimise the effects of hypoxia during flight at high altitude. Extensive decompression chamber examination of the efficacy of a variety of Oxygen equipment was performed at the RAF's Physiological Laboratories between 1939 and 1945. The various equipment's effect was monitored by end expiratory gas analysis on machines designed by Haldane, a laborious process to say the least, especially when the research was punctuated by alarms and everyone diving for the air-raid shelters. I have no documentation of parallel research in the USA, Germany, France or USSR but assume similarities because this series of British tests assessed a number of mask/regulator sets from Germany and USA, while France, Germany, Italy, Russia, and USA all had operational decompression chambers by the mid 1930s. The war demonstrated potential problems for aircrew bailing out at high altitude. The work of FLTLT Pask demonstrated the need for a 'bail-out' bottle of Oxygen if an air-crewman was to reliably survive high altitude egress from his aircraft (Barostat release parachutes were apparently not available at this time, or at least not operational). The need for portable Oxygen systems, allowing aircrew mobility within bombers or other large aircraft was also appreciated and the precursor to our present 'Loadie's bottle' was developed and designated 'Portable Oxygen Set Mark 1A'. This equipment was found deficient and a priority improvement research tasking of 1943 brought results too late to benefit operational aircrew (1945). The problems of hypoxia in passengers was also addressed after some disastrous high altitude transatlantic flights in loaded Liberators. Around 1940 the RAF also looked seriously at alternative forms of Oxygen storage and transport. At this time pressurised cylinders of gaseous Oxygen were generally used, liquid Oxygen (LOX) being abandoned soon after the first war due to inefficiency in the equipment of that time (The Germans had, apparently, continued using LOX). The sheer weight needed to load a non-pressurised passenger aircraft with sufficient Oxygen cylinders for a long flight made research into more efficient, lighter methods seem mandatory. One method around this weight problem was taken by researchers at the Royal Society Mond Laboratory at Cambridge who, between 1939 and 1941, developed a number of machines that could produce concentrated Oxygen from the surrounding air. These machines, or 'separators' as they were then called, worked by compressing air, allowing it to cool and liquefy, and then distilling off gaseous Oxygen by selective warming. This separator unit (popularly known as the 'ice-cream machine' at this time) was fitted to some aircraft, running off their engines, and operated effectively at 25 - 27,000 ft. This equipment was not followed up to it's fullest potential, partly due to weight considerations, improvements in pressure cabins, and electrical equipment already making substantial demands on aircraft powerplants, until the Americans reopened research into similar "On Board Oxygen Generator Systems (OBOGS)" in the 1970s. Another problem, the substantial waste of Oxygen by the systems available early in the second war was addressed by developing advanced Oxygen economisers along the lines of those developed by Haldane and Siebe Gorman Co. around 1917 (vide supra). These "Puffing Billy" Economisers (RAF Oxygen Economiser Mk. 1) were trialed extensively throughout 1940, found to be effective above 30,000ft. and substantially reduce the amount of Oxygen (cylinders) needed for long flights. The Mark 1 Oxygen Economiser was pressed into service for fighter and bomber aircrew later in 1940 with the Mark 2 to follow in March 1941. The economiser subsequently proved to be a very effective and reliable piece of equipment. While the British were fitting all their production aircraft with Mark 2 Economisers (April 1942) the Germans and American were developing slightly different methods of 'economising' on the finite Oxygen stores that an aircraft could carry. Considerable advances were made in the design of 'demand' regulators that only permitted Oxygen to flow to the crewmember in response to his inspiratory effort. The initial demand regulators displayed a considerable breathing resistance, found tiring by aircrew, but subsequent development has improved the resistance of the system and in particular the demand valve making demand Oxygen systems commonplace, almost passé, in modern military aircraft. Towards the end of the second war acceleration atelectasis started to become a problem for military aviators. Although not entirely appropriate to an essay on 'hypoxia' this problem was certainly potentiated by methods employed to prevent hypoxia. The pilot's symptoms of coughing and chest pain, due to closure of smaller airways in the base of the lungs due to increased acceleration (g-forces), were made worse when he had been using 100% Oxygen (As RAF aircrew had been instructed to do). The explanation behind this was provided by J. Ernsting and D. Glaister who postulated that the 100% Oxygen is absorbed from pulmonary lobules distal to the G-induced atelectatic obstruction thus worsening the collapse. A parallel mechanism to delayed otic barotrauma. During the war extensive research effort was directed at refining the Oxygen masks being used by airmen. The RAF progressed from their A-mask of the 1920s to the H-mask of 1944, which has since undergone minor improvement in it's evolution to the P/Q masks in use today, and the W mask that may see service in the near future. Another major field of development in the prevention of hypoxia was the expansion of experience and expertise in pressure cabin technology. As mentioned above the first usage of a pressure cabin occurred in the USA in the early 1920s and further developments were made by the Germans and the French during the following two decades. The French had a pressurised twin engined aircraft in 1940, that could maintain a cabin altitude of 9,700ft. when flying at 30,000ft. Fuelled by Germany's successes with pressure cabins the RAF approached the problem with some urgency in the immediate pre-war years. In 1940 the RAF had successfully pressurised their Vickers-Armstrong Wellington bomber using engine mounted compressors that could be controlled by a crewmember. 1941 and 1942 saw the incorporation of pressure cabins into RAF Spitfire fighters and Mosquito fighter-bombers used for high altitude photo-reconnaissance sorties. The Westland Welkin (Looking very much like the De Havilland Mosquito), produced in 1943, was the first British aeroplane with a pressure cabin integral in it's design, it did not see service before the end of the war. The other method of preventing hypoxia at altitudes above 40,000ft. is pressure breathing, as mentioned earlier. In a chronology similar to that of the pressure cabin initial research was made into pressure breathing, then shelved, only to be resurrected during WWII. In 1942 A.P. Gagge and co-workers, at Wright Field USA, developed a pressure breathing system to allow aircrew operation above 42,000ft. without pressure cabins. This equipment was successful and allowed exposure to 50,000ft. for several minutes without hypoxic problems. Canadian work on pressure breathing trailed the Americans by about a year but employed a different system, which actually provided a degree of counter pressure to the chest wall (called, by some, a pressure breathing jacket, waistcoat, or jerkin) After minor modification the Canadian equipment was teamed with a modified RAF H-mask to provide operational pressure breathing to aircrew allowing them to operate against German pressurised aircraft (e.g. The photo-reconnaissance Junkers 86) previously inaccessible to them. This equipment was flight tested to 46,000ft. in 1943 and brought into service in 1944. The Americans also adopted, and improved on this design (incorporating sleeves into the counter-pressure garment), later (1948) donating their improved version back to the RAF to assist ongoing research. After the second war, all high altitude military aircraft being fitted with pressure cabins, pressure breathing functioned in a 'get me down' emergency capacity only in case of cabin pressurisation failure. Recently, however, research has indicated the benefits of pressure breathing in reducing the incidence of Acceleration Induced Loss of Consciousness (G-LOC) [60], so much so that the USAF employs elective pressure breathing as one of the manoeuvres to enhance G-tolerance in it's modern jet fighter fleet and Ernsting proposes that future military aircraft Oxygen systems should employ an automatic selection of pressure breathing when certain levels of +Gz are reached. At the outbreak of WWII full pressure suit technology was rudimentary and not sufficient to allow operational flights above 40,000ft. In 1941 the RAF rekindled her interest in pressure suits and by 1942 had test flown one new suit. The third type of suit produced during these experiments was effective and relatively comfortable, but never actually entered service, probably due to the status of pressure cabins and pressure breathing equipment at the time. Research into full body pressure suits did, however, continue after the war fuelled by the ever-present risk of rapid (pressurized) cabin decompression and the anticipated future needs of very-high altitude air operations in which cabin pressurisation would produce an unacceptable weight penalty. Hybrids between full pressure suits and pressure jerkins were designed , and in 1957 successfully chamber flown to 140,000 ft.., John Ernsting himself being the "pilot". Russia also had spent some considerable effort, commencing in 1934 under Dr. Vladislav A. Spasskiy, on full pressure suits and their expertise probably exceeded the rest of the world by the end of WWII, although they had done no original work on partial pressure equipment. Similarly the German Drager company was involved in developing an operational pressure suit prior to the second world war. However, since then pressure cabin technology has continuously improved and pressure suits (full and partial) gradually saw less and less service. It can be seen from the above what phenomenal progress had been made in our understanding of hypoxia during the first half of this century. By the end of the second war the effects of Oxygen lack at high and very high altitude was well understood, as was the need for Oxygen administration to prevent hypoxia. The symptoms and signs of hypoxia were well recognised and documented. It had been shown, confirming previous predictions, that Oxygen at a partial pressure greater than ambient was needed to prevent hypoxia at altitudes above 40,000 ft. A wide variety of Oxygen systems had been developed around the world, variously employing high pressure gaseous Oxygen, liquid Oxygen, or generating concentrated Oxygen, while in flight, from the surrounding air. Equipment to protect from hypoxia had undergone great changes since the pre-WWI "pipe-stems" now there were face fitting Oxygen masks with demand regulators and non rebreathing (or rebreathing if required) valves and regulators that automatically altered the concentration of Oxygen supplied with altitude. Pressure breathing had been developed to prevent hypoxia at altitudes in excess of 40,000 ft. as had the partial and full pressure suits. The greatest, single, technology advance was, in my opinion, the development of cabin pressurisation systems able to sustain aircrew operations at high altitude without the cumbersome pressure suits. Of course pressure suit technology was far from redundant and played a major role in man's subsequent confrontation with space - enabling survival and activity in that most hostile of environments. I'll see what else I find.
... part of the story about an aircrew The darkness was starting to fade but the wind was blowing quite hard and word came from the tower to wind down the engines as there was going to be at least a forty-five minute wait for the weather above to clear. This was very welcome news to us because we were all still a bit woozy and it gave us the opportunity to attach our oxygen masks and clear our heads and systems by inhaling the pure oxygen. (This was one of the “not listed in the manuals” ways to rapidly cure a hangover.) There we were, eight of us. Stretch out on the floor of the plane holding our oxygen masks to our faces and gradually starting to feel human again while Steve sat at his radio and monitored the tower, and Shep and Fred took turns sitting in the cockpit. After about almost an hour the call came to fire up. We all rushed to our designated positions for take-off and Shep, the pilot, would up the engines. That was when the flight engineer, checking everything out, found that we had used up so much oxygen that unless the tanks were refilled we wouldn’t have enough to last for the mission. He called the oxygen tank shop to get a truck out to our plane and refill all our on-board oxygen tanks in a hurry while Shep had to tell the tower that Owens had found a leak in one of the oxygen lines and they would have to hold up the take-ff till the oxygen crew could fix the leak and refill the tanks. Online Veterans Tribute The entire squadron had to hold position while this was taking place and there was a lot of pure hell raised by the squadron commander and all the brass, to say nothing of all the other crews and pilots who were mad as the devil at us for delaying the flight and all the planes that were already in the air from the other squadrons and groups we were to rendezvous with.
http://www.398th.org/History/Veterans/History/Welty/Interview_Welty_Merseburg.html#anchor_Welty_oxygenhttp://www.398th.org/History/Veterans/History/Welty/Interview_Welty_Merseburg.html#anchor_Welty_oxygen And, uh, up ahead I could – Oh! When we were over the target we caught a piece of flak in the air – in the oxygen system – and it emptied all the oxygen from one side of the plane. They had duel systems. We realized it but the tail gunner didn’t and he was still breathing the system that actually been drained of oxygen. [The tail gunner was Cpl. Bill Fleming.] DAVE He couldn’t tell the… BOB No you can’t tell. This is what’s called anoxia and your body has no way of signaling you that there is not enough oxygen in the air. People say well don’t you feel like you’re suffocating? No, you’re drawing in all the air you feel like you need but at twenty-eight thousand feet there are not enough oxygen molecules to keep you alive but you have no way of telling that. DAVE Oh. I see. BOB So it sneaks up on you and what – what in – by each oxygen hose there was a gadget that looked like an eye and when you were breathing oxygen that little eye would blink every time you breathed in. And about every three minutes the bombardier would come on and say “Oxygen check” and the tail gunner would say “tail gunner OK,” - “Waist gunner’s OK,” – the radioman – they’d come right up and then we’d say “OK.” And then he’d wait three minutes; that’s how fast they wanted – if somebody didn’t answer they wanted to know right away. So all through all those missions you were getting oxygen checks every three, four minutes. He made an oxygen check and the tail gunner didn’t answer. And two things could happen: he could maybe pass out or maybe the intercom had been knocked out going back to him and he couldn’t hear us. DAVE Or he could have been killed with flak. BOB Or he could have been. You didn’t know. So one of the – one of the waist gunners [either Cpl. Maury Newcomer or Cpl. Al Dougherty] crawled back there and that was difficult because you had to crawl around the tail wheel which had recessed up into the body of the plane and there wasn’t much room. You had to wiggle through there with his oxygen bottle. We had little bottles about the size of a quart, or a half gallon. And they were full of oxygen so if you wanted to walk around in the plane they were called “Walk around” bottles and you’d unplug your oxygen from the system and you’d plug it into the “Walk around” bottle which hung on your belt and you could go out and… So that’s what he [the waist gunner did] … He went back and he found him - turning blue. Found the poor tail gunner was going out. He dragged him back. I guess he gave him some air out of his out of his own oxygen bottle. Dragged him back to the waist and they were reviving him but in all that time we [the pilot and co-pilot] kept calling back, you know, “What’s going on? What’s going on?” And finally Joe [Lt. Joe Tarr, the pilot] said I can’t stand this I’m going to go back and see what’s going on. So he got up out of his seat and I’m flying and he puts on his “walk around” bottle. He crawls through – he has to go through the bomb bay, through the radio room - finally he gets back to the waist. And right about then here come the Abbeville gang.
