• The program is redesigning OBIGGS to address deficiencies identified in earlier fuel system simulator test series (LF-09B) to meet the vulnerability requirements during all critical segments of a combat mission and to provide an inert tank atmosphere for internal lightning protection.
• The program reported several design changes during the Phase II Critical Design Review to:
-- Fix the vent-in-during-dive problem, wherein fresh oxygen-laden air is drawn into the fuel tanks in a dive
-- More uniformly distribute the nitrogen enriched air (NEA) throughout the fuel tanks
-- Ensure NEA quality
-- Inform the pilot when the system is not inerting the ullage
• The program will conduct verification and certification testing and analyses to confirm the performance of the new OBIGGS design on all three aircraft variants. These tests are expected to begin in FY13.
• Additionally, the current fuel tank venting design is inadequate to vent the tanks during a rapid descent. As a result of the related OBIGGS and tank venting deficiencies, flight operations are currently not permitted within 25 miles of known lightning conditions. Moreover, below 20,000 feet altitude, descent rate is restricted to 6,000 feet/minute. Dive rates can be increased to up to 50,000 feet/minute but only if the maneuver includes 4 minutes of level flight for fuel tank pressurization purposes. Neither restriction is acceptable for combat or combat training.