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Aviation History
1989
1989 - 1273.PDF
Endless 02 frees new fighters by Kieran Daly Normalair-Garrett is to supply onboard oxygen generating equipment for the Lockheed YF-23 Advanced Tactical Fighter prototype. Trials of the ATF unit have begun at Brooks AFB, Texas. Oxygen stored for aircraft use is bulky, weighty, and unpleasantly hazardous. Its supply is a prime limiting factor in dispersed and extended- range fighter operations. The US Navy, concerned about its carriage on aircraft carriers in particular, is determined to minimise its use. The next generation of com bat aircraft, however, should be able to dispense with stored gas as the primary crew oxygen source. Instead, on board oxygen generation systems (OBOGS), specifically molecular sieve oxygen- generating systems (MSOGS), will "strain" oxygen from engine bleed air and feed it to the crew. Already the B-1B carries a system supplied by Normalair- Garrett, and the company is to provide further units for the British Aerospace EAP fighter demonstrator. The system works by drawing conditioned bleed, air through a bed of Zeolite to filter out the nitrogen, carbon dioxide, and trace gases. Only oxygen and inert argon pass through the Zeolite molecular lattice. Zeo lite is a synthetic alumino- silicate in a ceramic binder, produced as small beads. The oxygen/argon mixture in atmospheric proportions of 21:1 is compressed to form a breathable product containing 95 per cent oxygen. Back pressure from the product is used to purge the waste gas left Schematic of Normalair-Garrett three-bed MSOGS Pressure-relief [ -TrfiSiSmMmWmMMmMm valve | Oxygen-enriched product gas [ I Conditioned engine bleed air Above How MSOGS makes oxygen Sizes range from this six-bed MSOGS, above, to a compact concentric device in the Zeolite bed. In the three- bed system illustrated, the bed cycles are overlapped to provide a steady flow. NGL says that the 95 per cent-rich mixture meets maximum operational oxygen 1 1.. Jt ll . h • . HiP-. ./ >/^.,:W:;'.:'V.-: ,"•::• .V ' . ' No-nav routing The McDonnell Douglas Pilot's Associate offers automatic airborne route planning, calculating the safest way to and from a target by gathering data from the threat warning systems requirements under normal conditions. The company has developed two types of sensor to check that the product gas is of the correct composition. The fluidic sensor NEWS IN BRIEF • Asironaulics joins LRAACA itics is to supply the n electronic flight lay system for the US Navy's Lockheed P-7 long- ••- air ASW c aircraft (LRAACA) The US company will supply cockpit sets for Lockheed's systems integration laboratory and two prototypes to be completed by the end of 1992. I) i" nation from any of ihr< e • • >sing units, compares the viscosity and rate of flow of product and reference gases through capillaries to measure the partial pressure of oxygen pressure. In the second, a piece of Zirconia is heated to 750°C and the two gases are passed either side, which generates a measurable electrical potential across the material. This type of sensor will be used in the EAP. It is still not possible to dispense entirely with stored oxygen, because an emergency bottle must be carried in case of engine or electrical power failure. If cabin decompression occurs above a pre-set altitude, the system reverts automatic ally to emergency oxygen. Operators can specify manual or automatic reversion in the event of other emergencies. If, for example, the engine restarted after a. failure, so would the MSOGS. Operators can also specify the ability to deselect the emergency supply in such a case. As with conventional oxygen systems, the ejection seat has its own emergency bottle for use in crew ejections. NGL's standard MSOGS uses three Zeolite beds, arranged in line or in a triangle, and weighs 551b. The latest model has the beds arranged concentrically, and weighs only 251b. NGL claims a unit life of around ll,000hr and extremely low maintenance requirements. The company now has a teaming arrangement with Pall Safety Atmospheres of Tampa, Florida, partly to gain access to the US market and also to take advantage of a Pall-developed process to "fix" the Zeolite granules to prevent the for mation of dust. the system will allow a two- crew fiightdeck. •:." • : • SI on Tornado MLU Smiths Industries is to provide a mi ise head-down y for ihe Royal An [ a Tornado GR.l mid-life update. The raster/cursive displ.i\ will be lent full-colour d moving maps and monochrome electro-optical sensor images. The order is potentially worth £\l million. FLIGHT INTERNATIONAL, 6 May 1989 27
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