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Supercritical means more speed — the Crusader with the $1.8 million wing

10 October 2012

F-8 Supercritical Wing in flight — NASA photo

Flying has more than one apparent paradox. Flaps provide lift but also drag so one flies more slowly while also descending more steeply. Bernoulli’s principal has the design of a wing with a curved upper surface and a flat lower surface. This airfoil design does not work well near Mach speeds though superbly at low speeds. Flying faster and flying better meant the design of the supercritical wing — one with a flat upper surface and curved lower surface. Yes, going faster means inverting the surfaces though it is a bit more complicated — with a curved trailing edge as well.

Wing tunnel testing at Langley in the early 1960s by Richard Whitcomb led to the NASA Supercritical Airfoil. Yes, the same man who developed Area Rule (the coke bottle shaping of the F-102 and F-106 as prime examples) also developed the supercritical wing which has the effect of delaying the shock wave formation on the upper surface as well as reducing its power. Overall, as much as fantastic 15% efficiency increase. A breakthrough by any measure.

NASA modified a TF-8A Crusader with a wing at a cost in 1969 dollars of USD$1.8 million for full scale flight testing. The test period lasted until mid 1973 and proved that delayed shock waves resulted in higher cruise speeds and longer range for the same power and fuel load. One calculation, using 1974 dollars, showed a 280 plane fleet of medium sized airliners would save USD$78 million (~USD$384 million in 2012 dollars).

It is no surprise that high subsonic speed aircraft like airliners and business jets now have supercritically designed airfoils.

Essentially:

Cost of supercritical wing — $1.8 million

Improvement — priceless

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NASA’s fact sheet is here.

The photogenic Supercritical Wing Crusader is displayed on Edwards AFB. Although a civilian cannot simply obtain base access it can be seen on Google Earth imagery at these coordinates: 34º 57′ 08.25″ N / 117º 53′ 18.12″ W

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