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Swingin'' on a spar: the birth and development of variable--geometry aircraft.

Article Excerpt
Grumman's pudgy XF10F-1 Jaguar was the Navy's first swing-wing jet in 1952, but being rather early In the grand scheme of things, its performance was less than stellar, Hence, for his beautiful chaseplane view of the Jaguar landing, aviation artist Gerry Asher chose the appropriate title One Fat Lazy Cat,

Author's Note: The Gs were brutal. Grunting heavily as we entered the vertical during ACM in a Grumman F-14B Tomcat, I realized this was as good as it got while rivulets of sweat formed inside my helmet and the oxygen mask pressed deeply into my face. The G-suit was pneumatically squeezing my gut and legs while an 800-pound Gorilla was sitting firmly in my lap, yet through it all I became keenly aware that as the airspeed was bleeding off and our kinetic energy was rapidly being absorbed, there was absolutely no change whatsoever in the big jet's overall aerodynamic demeanor. We were slowing down dramatically and I was now lying on my back staring straight into the sun, but there was absolutely no buffet. No shaking. No telltale hint from our jet subtly telling us that it was about to depart controlled flight. It was a type of flying quite literally impossible in any earlier-generation jet fighter.

The secret to the ease with which we were maneuvering that day was held deep within the very heart of the airplane, as a massive forging guided thousands of pounds of moving metal, swiftly computer-controlled to react to the forces and speeds at which we were flying, and moving faster than a pilot could control manually while still flying the jet. Attached to those large fittings were the aircraft's wings, changing position and sweep angle from nearly straight out at slow speed to nearly straight back at speeds approaching Mach 2, and every possible variation in between. I was experiencing the aerodynamic magic of variable geometry--wings that changed their very own planform inflight. These smooth evolutions were made possible by this complex but now well-harnessed technology that gave the Tomcat a special place in aviation history. Here now is the story of how all that evolved, and the amazing aircraft that were built to take advantage of this highly advanced concept.

Whether you're standing at the edge of a small grass strip watching a Cessna 150 leap from the ground while performing a short-field takeoff, or standing next to Runway 31L at New York's Kennedy Airport watching the Concorde rip past as it rotates at 245 knots (when they were in service), you are ultimately seeing the effect of wing shape and size. The wing 011 that little 150 is festooned with barn-door-size flaps, figuratively speaking, yet the Concorde's tapered double-delta is devoid of any flaps whatsoever, relying instead on brute force, blinding speed, and a high angle of attack to make the wing work at the lower end of its performance envelope. What would happen, theoretically at least, if you could combine the best attributes of both aircraft's wings in one machine that could change back and forth between the two?

This is the general concept behind variable geometry, or the 'swing wing' in pilot parlance. The best of both worlds, a variable geometry aircraft can take off and land at amazingly slow airspeeds with its wings extended and an assortment of lift-augmenting devices doing their work, then accelerate to supersonic speeds even at low altitude with its wings swept back at fairly dramatic angles. Even more important, the aircraft can maneuver effortlessly through the entire spectrum of air combat scenarios as the changing wing sweep and size allows safe stable flight throughout every attitude, airspeed, and G-load. As a result of this new technology, sobering images of dog-fighting jets tumbling out of control while wrapped up in a steep turn at low altitude as the pilot ran out of energy, airspeed, and ideas would become a thing of the past.

Fact is, variable geometry aircraft have been flying since the early-1950s, and the first operational American jet aircraft to use this technology went into service during the late-1960s. The first carrier-based swing-wing jet flew in 1972, and various foreign countries have been using these types of aircraft...

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