X-5

The Bell X-5 gave NACA and Air Force researchers a chance to test out variable-sweep wings. In this case, the sweep of the wings could be shifted--in flight, no less--between 20 degrees and 60 degrees. The more swept-back the wing angle, the less the drag and the better for flight approaching supersonic speed. The powered transition took about 20 seconds, and, if needed, the pilot could hand-crank the wings into the more forward position (more perpendicular to the fuselage) for landing.