Throughout the 1950s and 1960s, aviation engineers struggled to overcome an important issue: that planes became increasingly difficult to control, the closer they got to the sound barrier. It wasn’t until NASA strapped a pair of custom-made wings onto this fighter that supersonic flight became not just feasible, but downright commonplace.
See, as a plane approaches the speed of sound, it’s travelling so fast that the air in front of it can’t get out of the way fast enough, and acts as an impediment against the plane moving any faster. This is caused by too much air travelling over the top side of the wing, in turn creating excessive drag and causing the plane to lose stability (known as mach tuck). Planes of this era had trouble even getting to mach .9, much less breaking the sound barrier. This was a problem for both the military and commercial enterprises, the latter of which was looking to supersonic aircraft as the next logical step in the evolution of passenger air travel.
So, in the early 1960s, Richard T. Whitcomb — chief of the Transonic Aerodynamics Branch at Langley Research Center — began experimenting with modifications to the wing’s shape, or airfoil. It would eventually lead to the NASA Supercritical Airfoil, which is seen on high subsonic passenger aircraft like the Boeing 777, as well as supersonic military and commercial aircraft like the B-1B Lancer and the Concorde.
Compared to existing wings of the time, the NASA Supercritical Airfoil was flatter on top, rounder on the bottom, and incorporated a little lip on the trailing edge. These minor structural changes had a huge effect on how the air flowed past them, causing far less mach tuck and only at significantly higher speeds, which allowed pilots to retain control over the aircraft well past the sonic boom. It also provided a higher cruising speed, improved fuel efficiency, and greater flight range.
After testing his new wing design in Langley’s eight-foot transonic pressure tunnel, Whitcomb’s team strapped them to the fuselage of the Navy’s Vought F-8A Crusader, a single-engine supersonic fighter. This plane was chosen because, being a carrier-based aircraft, its wings could easily be removed and swapped out at will.
Tests on the wings (which cost $US1.8 million dollars to construct) began in March 1971 at the Dryden Flight Research Center at Edwards AFB. Using pressure sensors mounted on the wings, these test flights supported the modelled data that Whitcomb’s team collected from the earlier wind tunnel tests. While the first successful supersonic flight using the wings took place in May of that year, research continued until 1973.
1973 saw the start of the oil embargo, which caused airlines to lose interest in the prospect of supersonic flight in favour of more fuel efficient planes. But despite the drop off in demand at the time, the NASA Supercritical Airfoil has nevertheless become ubiquitous on modern high-speed commercial aircraft — which have enjoyed a 15 per cent jump in fuel efficiency thanks to the wings — in the three decades since. Now if there were just something we could do about that damnable head-cracking turbulence. [NASA 1, 2 – Wiki – Space – Air and Space Museum]