This aircraft was one of the original 21 Research, Development, Test & Evaluation (RDT&E) aircraft. Since swing wing concept or what is called variable geometry wing was brand new a lot of flight test went on. The F-111 wing has Flap/Slat system which basically double it's lift production for low speed flight NASA thought it was a great test bed for a new wing design to replace flap/slat with a wing which would change shape through internal actuators. I was working the Air Force F-111 test program at the time and worked with the NASA guys on general aircraft stuff. 03/21/2008 @ 04:00 [ref: 20220]