1993 Discover Awards: Aerosapce: Gust Busters

Friday, October 01, 1993


Hugh SchmittIe, Freewing Aircraft

When a small commuter plane lurches through choppy air, the marvel of air travel loses some of its luster. As their stomachs defy gravity, passengers may silently curse the Wright brothers for putting fliers at the mercy of turbulence.

The problem is simple physics: when sudden gusts hammer an airplane, the wings catch the forces, getting shoved this way and that. The plane’s fuselage, which is fixed securely to the wings, gets pushed about as well. Isn’t there some way to isolate the fuselage from the movements of the wings, the way a suspension system isolates a car body from the ups and downs of a road surface? A plane with such a system would not only provide smoother flights but would also suffer far less structural stress.

A fledgling company in College Park, Maryland, is poised to take flight with just such an aircraft. Called a freewing, the plane harks back to an aircraft concept that fell into obscurity when the Wrights’ fixed- wing fliers took off. Its key feature: a single wing that pivots freely back and forth on hinges mounted behind its leading edge.

The free-swinging wing can weather-vane its way through gusts without transferring the buffets to the fuselage. Even better, the design greatly reduces the chances of a stall, a leading contributor to air accidents. This dangerous phenomenon occurs when a wing meets oncoming air at such a sharp angle that smooth airflow over the wing, responsible for aerodynamic lift, breaks up and the plane begins to plummet helplessly. A freewing resists stalling because the wing adjusts willingly to the direction of the wind rather than maintaining a defiant angle.

The man behind this design, Hugh Schmittle, founded Freewing Aircraft Corporation after spending years as a Pentagon foreign-military sales specialist. In his spare time, Schmittle became entranced with the designs of a maverick aeronautical engineer named George G. Spratt. Starting in 1935, Spratt constructed a series of planes called controlwings, in which the left and right wings pivoted independently.

Spratt’s work was groundbreaking, recalls Schmittle. It provided an airplane with a lot of neat characteristics like gust absorption and stall resistance. Despite these advantages, however, the controlwing never really took off, partly because pilots looked askance at Spratt’s unorthodox cockpit accoutrements--a steering wheel and a lever, called a collective, that adjusted the wing angles. I believe very firmly that you have to give people what they expect, says Schmittle. In aviation that means a conventional cockpit: rudder pedals, a stick, and a throttle.

In 1983, Schmittle took Spratt’s rocking wings and combined them with familiar cockpit controls in a homebuilt aircraft dubbed the Freebird Mark I. The plane was a one-man ultralight, a favorite breed of aircraft among experimenters because of the ease of its lightweight skeletal construction. Although the Freebird Mark I showed off the freewing’s gust- taming capability, it also pointed up one drawback in the design. A free- floating wing can’t generate as much lift as a fixed wing--one reason the freewing scared off aviation pioneers like the Wrights. What’s more, a freewing becomes unstable if it’s fitted with the flaps that conventional planes, such as jet airliners, deploy to boost their wings’ lifting capacity during takeoff and landing. This limitation means that a conventional freewing wouldn’t suit a large aircraft whose wings must loft a heavy weight.

To solve these engineering difficulties, Schmittle founded Freewing Aircraft in 1987 and two years later established a joint research effort with the University of Maryland. After refining the Mark I with several other prototypes, Freewing Aircraft this year launched several new designs. The one that should cheer airsick fliers is the Freebird Mark V, a full-fledged two-seat airplane the size of a Piper Cub. Unlike previous freewings, the Mark V’s wing can lock into position and behave like a conventional wing, with lift-enhancing flaps, during takeoff and landing. Once airborne, the wing unlocks and begins feathering through gusts. In NASA tests, turbulence was reduced a full 75 percent.

Schmittle believes that the combination wing could be applied to an aircraft of any size. If he’s right, stormy skies will soon be safer.


Arthur Kressley, chief design engineer for the twin jet program at McDonneII DougIas in Long Beach, California, for the MD-90, an environmentally friendly passenger jetliner. Its two V2500 power plants, manufactured by the International Aero Engines consortium, are the cleanest-running combustors in their class. The MD-90 is also much quieter, reducing noise pollution during takeoff and landing and ensuring a more pleasant ride (the engines are on the rear of the fuselage, away from the 150 passenger seats). The MD-90 made its first flight on February 22, and the first delivery (to Delta Airlines) is planned for late 1994.

Bill Burcham, chief of the propulsion and performance branch of NASA’s Dryden FIight Research FaciIity at Edwards Air Force Base in California, for the Propulsion Controlled Aircraft system. This system uses engine thrust to safely land planes whose hydraulic controls fail during flight--an occurrence that causes 10 percent of all plane crashes, including the infamous Sioux City crash of a United Airlines jet in July 1989. With this ingenious new flight control system, which requires no additional hardware, a crippled jet can be controlled by a pilot’s stick movements.

John C. Mather, chief scientist at NASA’s Goddard Space FIight Center in Greenbelt, Maryland, for the Cosmic Background Explorer spacecraft. COBE has collected data that overwhelmingly support the Big Bang theory, the idea that the universe began some 15 billion years ago in a single violent cosmic explosion. A COBE instrument measured the actual spectrum of cosmic background radiation (the glow left over from the explosion) and determined that it is identical to the spectrum predicted by the Big Bang theory. The spacecraft also detected fluctuations in this radiation, which explain how matter formed into galaxies.

Dana P. Hollis, project engineering manager at Smiths Industries Aerospace in Florham Park, New Jersey, for an Electrostatic Engine Monitoring System that detects abnormal wear in aircraft engines. The system, which constantly analyzes electrically charged particles in the engine exhaust gas and compares their charges with normal levels, detects damage well before an engine is unsafe or costly to repair. The system is now in use on the Boeing-Sikorsky Comanche Helicopter and is being considered for the Boeing 777.
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