Correlated fuel tank leakage test - 4 hours

When testing a single fuel tank the manometer height varies due to changes to the ambient barometric pressure and temperature. The lack to trend to this variation - and the lack of bubbles in immersion and spray tests - has been used to infer the absence of leaks. A more rigorous method - without going to the additional effort of correcting for ambient changes - is to test the identical left and right tanks together. A high correlation in the manometer height variation over an extended elapsed time points to both tanks being leak free. If either thank had a leak of any significance, the manometer height trends would very clearly depart from each other. In tests here, lasting 4 hours, the ~100% correlation persisted, with no difference in trend. That both tanks are leak free is inferred.