A significant weight reduction was realized in the sealing of integral fuel tank structures manufactured during a recent manufacturing technology program conducted by General Dynamics/Fort Worth Division for the Air Force Materials Laboratories.
In the 1950s, General Dynamics/Convair Division successfully developed and used a nitrile phenolic thermosetting adhesive film, Scotch-Weld, for sealing fuel tank faying surfaces. Manufactured by 3M, Scotch-Weld was used or the F-102 and F-106 military aircraft and was subsequently adapted for General Dynamics’ 880 and 990 commercial transports. In all, 1364 of these aircraft were produced using the Scotch-Weld system.
Although these aircraft had an excellent service history of minimal downtime and maintenance cost related to fuel leaks, the fuel tank sealing process did not receive widespread recognition. Perhaps the modest acclaim stemmed from the absence of documented manufacturing cost – which were generally assumed to be very expensive due to the rigid processing constraints established by Convair.
USAF interest in the adhesive sealing process revived upon an intensive performance review of all sealing systems used in-service aircraft, including bombers, transports, and fighters. Overall, the F-106 aircraft had the best performance record, with nearly 30 years of service.
The program conducted by General Dynamics/Fort Worth Division was a two-part effort which was structured to update and qualify the adhesive sealing system for use on current aircraft. During Part I. the original Scotch-Weld system and a modification of that system were evaluated in side-by-side comparisons to verify that the modified system would provide equal performance at a lower manufacturing cost than the original.
During Part II, two full-scale fuselage integral fuel tank assemblies were manufactured using the updated adhesive sealing system. These F-16 aircraft assemblies were manufactured alongside production F-16 tanks with no break in production flow. In addition, a comprehensive cost comparison was conducted to evaluate both the production and the adhesive fuel tank sealing methods.