xture that will not ignite Nitrogen-inerting has been accomplished several ways Adding nitrogen to fuel tank(s) from a ground source before flight; Discharging onboard supplies of compressed or liquefied nitrogen in flight; The use of on-board inert gas generation systems that separate air into nitrogen and oxygen. Nitrogen-inerting, using a ground source of nitrogen, might prevent explosions such as that occurred to the TWA800 aircraft. But Nitrogen-inerting may not prevent an explosion after the fuel tanks have been emptied during flight through fuel consumption, or when ullage is exposed to warmer air as an aircraft descends. The development and installation of such systems are expensive and may be impractical because of system weight and maintenance requirements in some airplanes (Velotti, 1997, p60). However, since these studies were conducted, advances in technology for separating nitrogen from air and instances of tank ignition may now make it possible to show that inerting of fuel tanks is cost beneficial. C-17 OBIGGS system is an example used by McDonnell Douglas that use an on-board inert gas generation systems that separate air into nitrogen and oxygen.4.1.1 C-17 OBIGGS NITROGEN INERTING SYSTEMThe aircraft company of McDonnell Douglas (Dornheim,, 1997, p63) has designed and built an on-board system for the C-17 (OBIGGS) which generates nitrogen and uses the gas to inert fuel tanks. The OBIGGS system bleeds air from inboard engines, separates oxygen from the nitrogen, stores the nitrogen and, dispenses it, to inert the tanks as needed. The system is designed to keep the ullage oxygen fraction below 9% by volume, less than the 9.5% - 12 % minimum required for an explosion. It weighs 2,000 lb. and costs approximately $1.5 million per unit. The space of the aircraft that the system takes up is approximately 80 cu. ft. of space on the aircraft.Obiggs has no effect on tank capacity, and its bleed air requ...
