Newly developed structural technologies developed by the Air Force Research Laboratory have solved critical cracking issues with the C-5 cargo aircraft, thereby expanding the aircraft’s serviceability.
As part of the Durable C-5 Structural Improvements Program, AFRL recently investigated cracking issues that have been occurring in C-5 cargo floor bulkhead end fittings, part of the under-floor structure in these large cargo vehicles. The cracks, caused by stress corrosion, led to increased maintenance cost, and had the potential of reducing the amount of cargo the C-5s carry.
Traditional repair methods proved insufficient because replacement fittings would often crack during the machining process, and had a shorter lifespan than original parts. To solve the problem, researchers looked into a new, more stress corrosion-resistant aluminum alloy and a new die forging process by which all 92 fitting shapes required for the C-5 bulkhead floor could be produced using only two separate forging dies.
This new process saves money, time and effort. Additionally, the reshaped fittings created by the forging process yield an optimized design less prone to cracks. The new end fittings will provide numerous benefits for the retrofitted C-5 vehicles, including a 25 percent overall cost savings, an 80 percent reduction in fabrication time, and a 60 percent increase in service life of the fittings.
This technology has been transitioned to the Warner Robins Air Logistics Center, Ga., where the new end fittings have been installed in select C-5 aircraft. Additionally, AFRL researchers say this forging process can be applied to other aircraft that experience the same cracking issues.