I once had the opportunity to hire a former boss of mine. He had once told me that he didn't have to do the necessary calculations to verify or establish aircraft structural integrity. He said he could do it by inspection that is by just looking at the drawings. The position involved was in structural analysis for aircraft repair. Do you think I approved him for employment? An old inside joke."S=MC/I in the morning and S= P/A in the afternoon. This occurred B.C. before computers.