A redesigned continuous flow passenger oxygen mask was tested for its ability to deliver an adequate supply of oxygen at an altitude of 40,000 feet above sea level. Four male subjects participated in the study. Blood oxygen saturation (SaO2) baseline levels for hypoxic exposure were established for each subject. Immediately prior to high altitude exposure, subjects prebreathed 100% oxygen for two hours through a pressure demand type mask. The hypobaric chamber was then decompressed to a simulated altitude of 35,000 feet. Subjects switched to the passenger oxygen mask. The initial oxygen flow rate to the passenger mask came from manufacturer production performance test data. Once heart and respiratory rates and SaO2 level stabilized, chamber altitude was increased to 40,000 feet. Descent to ground level was performed in steps of 5,000 feet with SaO2 levels being established for each altitude and recommended oxygen flow. Subjects remained at each test altitude for a minimum of three minutes or until SaO2 levels stabilized. At no point during the testing did SaO2 levels approach baseline levels for hypoxic exposure. This mask design would appear to offer protection from hypoxia resulting from altitude exposure up to 40,000 feet.

The passenger emergency oxygen system presently used onboard USAF transort aircraft is a phase dilution continuous flow system, and is similar to that on commercial aircraft. The mask is certified for emergency use up to 40,000 ft, when provided with an oxygen flow in accord with military specifications (MIL-D-19326F). We have evaluated the effect on arterial hemoglobin saturation (SaO2), of reductions in oxygen flow (below those specified) to the emergency mask; the volunteer subjects were exposed to simulated altitudes of 40, 35, 30 and 25 thousand feet. At reduced oxygen flows to the emergency pasenger mask, SaO2, was: 88 + or - 2.8%, 92 + or - 3.5%, 98 + or - 1.2%, and 97 + or - 1.0%; at 40, 35, 30, and 25 thousand ft respectively. Although halving the oxygen flow to the mask at 25,000 ft and 30,000 ft resulted in acceptable levels of SaO2, reductions in flow--at 35,000 ft and, especially, at 40,000 ft--were not as well tolerated. at 40,000 ft and, to a lesser extent, 35,000 ft, inboard leakage of ambient air around the face and through the anti-suffocation valve seriously compromised SaO2, Because passengers suddenly exposed to a 40,000-ft cabin altitude would undboubtedly suffer from anxiety and would tend to hyperventilate, and because of limitaions inherent in continuous flow oxygen systems, we recommend that oxygen flow to the passenger mask (as specified in MIL-D-19326F) be reduced with great caution. Keywords: Air breathing equivalency; Arterial hemoglobin saturation; Dixie Cupmask; Emergency passenger mask; Hyperventilation; Hypoxia; Loss of consciousness; Steady-state.

Designed as a stopgap measure to provide overhead reconnaissance capability during the early years of the Cold War, the versatile U-2 has since evolved to meet changing requirements well into the 21st century. Though many authors have documented the airplane's operational history, few have made more than a cursory examination of its technical aspects or its role as a NASA research platform. This volume includes an overview of the origin and development of the Lockheed U-2 family of aircraft with early National Advisory Committee for Aeronautics (NACA) and National Aeronautics and Space Administration (NASA) involvement, construction and materials challenges faced by designers and builders, releasable performance characteristics and capabilities, use of U-2 and ER-2 airplanes as research platforms, and technical and programmatic lessons learned.

Covering all the essentials of turbine aircraft, this guide will prepare readers for a turbine aircraft interview, commuter ground school, or a new jet job.