The legendary Grumman F-14 Tomcat is widely considered the best fleet air superiority fighter the U.S. Navy ever put to sea. But the Navy wasn't the only one to fly F-14s, NASA had two of the formidable fighters too, and together the planes helped provide valuable flight test research that helped fix a dangerous problem ve the Tomcat fleet.
The video above shows NASA 991, an F-14 assigned to the space organization's Dryden Flight Research Center at Edwards Air Force Base, California. NASA 991 belonged to the Navy but was borrowed back to Grumman to perform flight testing, whereupon it became known as F-14 (1X). The fighter was flown by NASA pilots, then Grumman pilots, and later by Navy test pilots.
The Navy's F-14 fleet had a problem: The fighters, while preparing to land on an aircraft carrier at sea, were suddenly going into a spin. The F-14, when configured for landing with its variable geometry "swing wings" extended and flying at a high angle of attack, would suddenly start to —that is, it would start turning on its vertical axis. An inadvertent yaw problem was bad enough, but having it happen while the pilot was trying to land on a moving, pitching aircraft carrier at sea was dangerous. According to NASA, F-14s had been lost in spin accidents, prompting the Navy to ask NASA for help.
NASA traced the problem back to the aileron rudder interconnect and laminar air flow. Air was not flowing smoothly over the F-14's wings while it was configured for landing, creating an opportunity for the plane to suddenly yaw left or right. Using feedback from more than 200 test flights, engineers made improvements to the plane's high angle of attack flying qualities, improving the plane's ability to resist sudden spin, and reducing "wing rock," the tilting of the aircraft from one side to the other. A fix for the yaw problem was devised that involved cleaning up the surfaces of the Tomcat's wing, making air flow more smoothly over them at subsonic speeds.
991 conducted a total of 212 flights flown by NASA/Grumman between 1979 and 1985 before being returned to the U.S. Navy. You can read about the experiments , with a more advanced technical paper available .