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Robert M. Pinkerton investigated airfoil aerodynamics at the National Advisory Committee for Aeronautics. He coauthored the related-section study with Eastman N. Jacobs and Kenneth E. Ward and later compared measured surface pressure distributions with potential flow calculations.^[ref][ref]

His 1937 report describes a 5-by-30-inch NACA 4412 model in a variable-density wind tunnel, with 54 pressure orifices at the middle of the span. Seventeen angles of attack, from −20 to 30 degrees, were tested at a Reynolds number of approximately$3\times 10^6$. These readings test the distribution of pressure, not merely whether the total lift happens to agree with a calculation.^[ref]

An original simplified example explains the extra information. If a thin airfoil has a constant difference $C_{p,\mathrm{lower}}-C_{p,\mathrm{upper}}=0.8$ over its chord, its surface pressure integration for airfoil lift gives the normal-force approximationWith dynamic pressure $q=500\mathrm{Pa}$ and airfoil chord $c=0.20\mathrm{m}$, the normal force per unit span is $qc{c}_n=80N/m$. A different distribution can give the same integral while producing a different pitching moment or boundary layer behavior. These are invented uniform data, not Pinkerton's measurements.

Finite pressure-tap spacing and pressure-tap position error can change the inferred integral. A measured distribution therefore offers both a stricter test of potential flow and a way to see where its assumptions cease to describe the actual fluid flow.