While Boeing [NYSE: BA] officials displayed to the press last week their concept for a membrane-based system to inert the center wing tanks (CWT) of transport category aircraft, the concept has limitations, according to a recent briefing. It was presented July 8 by National Aeronautics and Space Administration (NASA) engineers to the International Aircraft Systems Fire Protection Working Group (IAFPWG) meeting in Ottawa, Canada. A $1.2 million development technology project was put in place last June; it will extend over an 18-month period. The focus is on developing on board inert gas generating systems (OBIGGS) and on board oxygen generating systems (OBOGS).

The Boeing system inerts only the CWT, not the wing tanks. The NASA brief points to inerting all tanks as protection against terrorist attacks: "Aviation security program funding possible in FY 2004 to extend OBIGGS to all tanks defending against small arms and MANPADS [man-portable air defense systems]."

Furthermore:

"Currently no suitable means for OBOGS to satisfy surge load," a reference to the need for emergency oxygen. "Higher altitude emergency depressurized cruising (20-25K ft.) "requires better membrane selectivity or PSA-type [pressure swing adsorption] enrichment."

"Combined OBIGGS/OBOGS system to spread the cost among aircraft systems is not cost-effective with membrane-based system. This concept only works for cryogenic-based system or PSA-based system." See http://www.fire.tc.faa.gov/ppt/systems/CTChangJul03%20meeting.ppt