Most-conscious pilots (is there any other kind?) will tend to use resources with care. These days we don’t run around as much at full power, guzzling fuel, and by the same token, those of us who routinely carry an oxygen system for high-altitude flight often reserve its use for the times we feel its absolutely necessary. After all, getting a bottle refilled on a long trip can be a real (and expensive) pain in the, er, cannula. Shift the paradigm-say, make the oxygen available to the pilot essentially unlimited-and the usage model changes significantly. Now you don’t think twice about putting on the tube for higher-altitude flights and you can finally consider adhering to the recommendation to suck oxygen above 5000 feet MSL at night. The engine of this shift is an unassuming 7.5-pound white box called the Inogen Aviator. What, exactly, is this thing? The Inogen Aviator is a device that comes out of the medical industry and is generally known as an oxygen concentrator. Thats not to say its a simple compressor. If you think in terms of a block diagram, the Inogen takes ambient air, increases its pressure and forces it through a zeolite filter. The zeolite separates the pressurized ambient air into oxygen and nitrogen; the nitrogen is ported off and the oxygen is captured. There is nothing to refill, and in the case of the Inogen, tests have cleared the mechanism to a life of 10,000 hours. (Company spokesmen say that, actually, the life is probably quite a bit longer, but thats where testing stopped.) All the device asks for is 12-volt power-nominally around 5 amps, but up to 15 amps during maximum oxygen flow rate while the internal battery is also charging. Two types of battery pack are available, good for 3 or 6 hours of independent use. Overall size is 10.7 x 3.9 x 9.5 inches, plus a small power-converter brick with a cigarette lighter plug to connect to ships power.
Ah, Feels Good
With an inexhaustible supply of oxygen, the Inogen Aviator can meter O2 to the pilot in varying levels. Like the best electronic oxygen conserving systems, the Aviator has a sensitive pressure sensor on the machine side of the lightweight cannula. When you inhale, a slight negative pressure is generated in the line. Sensing this pressure drop, the Aviator kicks out a bolus of oxygen.
The duration and volume of the bolus depend on which of the five flow-rate settings you have selected. Setting five is maximum output, and each lower setting represents a 20 percent reduction in effective flow rate. On the lower three settings, the bolus is hardly noticeable. In fact, you need to look at the little pinwheel flow marker in the cannula line to know its working. On setting four of five, the bolus can be detected, and its relatively aggressive on the fifth level-although you gradually become unaware of it after a half hour or so.