Live Fire Testing A Legacy Wing Assessing Dry Bay Fire Potential in the C-5 Wing

The C-5 has been subjected to a much needed modernization program in the last decade. One phase of this modernization was the Reliability Enhancement and Re-Engining Program (RERP). Because of this modernization, it was determined by the Office of the Secretary of Defense (OSD) that the C-5M aircraft was a covered system for live fire test and evaluation (LFT&E). One of the areas of interest was vulnerability to dry bay fires for the C-5 legacy wings. The C-5 RERP LFT&E program addressed these questions. The C-5 legacy wing was subjected to live fire testing as part of the overall C-5 RERP LFT&E program. As a result of past lightning strikes and fires, an inerting system was added to protect the wing fuel tanks. The inerting system, called the Fire Suppression System (FSS), was plumbed to the leading edge dry bays of both wings, in addition to inerting the fuel tanks. This added FSS was never evaluated or tested to see if it would prevent or extinguish dry bay fires in the C-5 wings. The primary objectives of the current testing effort were to determine the ignition and sustained fire potential in wing dry bays, both leading and trailing edges, and assess the Fire Suppression System in preventing or extinguishing potential fires. The secondary objectives were to determine the damage of pressurized hydraulic lines within the wing and assess the extent of damage on the hydraulic systems. Five ballistic shots were performed on this unique, large wing. Three shots were performed on the leading edge and two ballistic shots were accomplished on the trailing edge to collect data for the primary and secondary objectives. The test article selected was a left hand wing section that contained the #1 Auxiliary Fuel Tank and the #1 Main Fuel Tank. This is approximately the outboard half of the overall wing, past the outboard engine pylon. Pre-tests were accomplished to assess and evaluate how long the FSS takes to get below 12% oxygen in the leading edge and how airflow travels through the leading edge dry bay of the legacy wing. This information allowed better pre-test setup and for the main ballistic testing and better conclusions. Simulated airflow, from engine bypass air, was blown over the test article at approximately 250 knots to better simulate airflow and flight conditions. The five shots on the C-5 legacy wing test article resulted in two sustained fires and one self extinguishing fire. The damage, due to both ballistics and fire, was repaired after each test event to preserve the integrity of the legacy wing for each following test. The data provided insight to the ignition and fire potential of combat threats that impacted the C-5 legacy wing, during testing. This provided valuable information to the war fighter, making them more informed, and allowing for more informed decisions. This effort also exhibited the value of risk reduction pre-tests performed prior to the live fire test events and that such activities were critical to reaching the end goals of live fire testing.