Revolutionary Control Philosophy
George Spratt's Model 107 represented the culmination of nearly three decades of controlwing research that began in 1939. Unlike conventional aircraft that relied on movable control surfaces, the Model 107 employed two parasol-mounted wings that could independently vary their angle of attack. Spratt claimed this design made the aircraft impossible to stall or spin, with 75 percent less susceptibility to turbulence compared to traditional configurations.
The prototype, registered N2236, began construction in 1962 with assistance from Elliot Dalland. The aircraft featured a speedboat-like hull constructed from polyurethane foam and covered with fiberglass, topped by fiberglass wing panels. After five years of development, the Model 107 achieved first flight in 1967, powered by a modified Mercury 800 marine engine producing 80 horsepower.
Unique Control System
The Model 107's control scheme eliminated conventional ailerons, elevators, and rudders entirely. Pilots operated the aircraft through three primary controls: a helicopter-style collective that adjusted both wings' angle of attack simultaneously, a control wheel that varied wing angles differentially for banking and turning, and an auxiliary pitch stick mounted low that controlled throttle and vertical flight. The aircraft's wide, fixed V-shaped tail functioned purely for stability, containing no movable surfaces.
This revolutionary system enabled remarkable flight characteristics. The Model 107 could perform hands-off takeoffs and landings using power adjustments alone. During the mid-1960s to mid-1970s, two Spratt controlwing flying boats operated in the Chesapeake Bay area, accumulating hundreds of accident-free flight hours. The prototype N910Z was soloed by more than 100 pilots and frequently demonstrated from Spratt's personal aircraft carrier—a 55-foot steel vessel anchored over shallow sandbars.
Limited Production and Variants
Rather than pursuing commercial manufacturing, Spratt marketed construction plans to homebuilders during the 1970s. Only three plans-built Model 107 flying boats were ever completed and flown. The original prototype N2236 was joined by a second aircraft built in the late 1990s and registered N107GW, which remains the sole Spratt controlwing aircraft in the current FAA registry. A third aircraft was completed but later lost in operational use.
The later aircraft incorporated different powerplants, with N107GW using an 85-horsepower Mercury 850 engine modified according to Spratt's specifications. Other builders experimented with Volkswagen automotive engines, though these installations proved less successful. Plans-built aircraft using wooden construction typically weighed 250 to 275 pounds more than Spratt's all-composite prototype.
Technical Specifications and Performance
The Model 107's compact dimensions reflected its experimental nature and single-seat configuration, though a passenger could be accommodated. With a 24-foot wingspan and 96 square feet of wing area, the aircraft achieved a maximum gross weight of 1,000 pounds. The pusher propeller configuration, driven by the modified marine engine, provided adequate performance for the aircraft's intended role as a technology demonstrator.
The controlwing concept extended beyond flying boats. Spratt developed land-based variants, including a Subaru-powered prototype currently housed in the Mid Atlantic Air Museum at Reading, Pennsylvania. A Rotax-powered ultralight version with a single rubber float was built but never fully developed into a practical design.
Legacy and Current Status
Despite promising flight characteristics, the controlwing technology failed to achieve widespread adoption. Development stalled when the builder of N107GW lost medical certification just as flight testing began, leaving no other experienced controlwing pilots available to continue the program. The design's complexity and unconventional control scheme likely deterred potential builders despite its claimed safety advantages.
Reports suggest controlwings have been spotted in Canada, and discussions about developing modern controlwing kits continue among experimental aircraft enthusiasts. However, no significant revival of the technology has materialized. The Model 107 remains a fascinating footnote in aviation history, representing one of the most radical departures from conventional flight control philosophy ever to achieve successful flight testing.
George Spratt's controlwing concept demonstrated that alternative approaches to aircraft control could work effectively, even if they failed to displace traditional designs. The Model 107's legacy lies not in production numbers or operational success, but in proving that innovative thinking could challenge fundamental assumptions about how aircraft should be controlled and flown.