Aircraft that can alter their wing configurations in mid-flight have been in development since World War II. With different wing positions allowing for greater efficiency and performance in various flight modes, these aircraft are more versatile than aircraft with fixed wings. Although a few models have made it into production, the limitations of engines, mechanics and computers have kept these aircraft from coming into widespread use. Now technology has finally caught up with the concept, and Northrop Grumman is in the process of building an unmanned shape-shifting plane: the Switchblade.
If you look at aircraft from World War I or World War II, you'll notice that the wings are almost always perpendicular to the fuselage, with only a few degrees of backwards sweep, if any. At the time, airplane engines couldn't propel the planes any faster than about 375 mph. At these low speeds, a perpendicular wing configuration allowed for maximum lift and maneuverability.
After World War II, the development of jet engines led to an enormous boost in aircraft speed. Traditional wing shapes weren't as efficient at high speeds (particularly supersonic speeds), so jet fighters began sporting tapered wings. The F-4 Phantom II is a good example of this type of wing profile. However, this increase in high-speed performance came with a trade-off -- the planes were not very effective or efficient at lower speeds.
Image courtesy U.S. Air Force
An aircraft that can alter its wing configuration in mid-flight has variable-wing geometry. This gives the plane the best possible performance characteristics at a given speed. The German Messerschmitt company first tested planes with variable wing geometry during World War II. The Messerschmitt P-1101's wings could be moved to different sweep angles, only while the plane was on the ground. Based on the Messerschmitt design, the U.S. developed a working test craft, the Bell X-5, which was slightly larger than the P-1101 and could change its wing-sweep angle while in flight.
This type of technology, also known as "swing wing," first appeared in a production aircraft in the late 1960s with the General Dynamics F-111. This plane had three different wing positions to give it maximum efficiency at all speeds. In fact, a variation of this plane, the FB-111A strategic bomber, carried the unofficial nickname "Switchblade." [ref].
Image courtesy U.S. Air Force
Several other fighter jets used variable-geometry wings in the next few decades, including the Tornado and the F-14 Tomcat. The unswept wing position made these planes exceptionally maneuverable and easier to land on the short flight decks of aircraft carriers. However, the mechanisms required to make the wing movements function were complicated and heavy. They also took up a lot of space, cutting down on efficiency and payload. Swing wings were largely abandoned for more simplistic designs.
In the next section we'll look at the Switchblade plane design.