Design Innovation and Development
Eugene L. "Gene" Turner began developing the T-40 in 1958 with ambitious goals for the homebuilt market. As a former World War II P-47 Thunderbolt pilot from Squadron 45G and experienced aeronautical engineer who had worked on projects including the Bell XV-3 Convertiplane and Boeing 737-200, Turner understood both pilot needs and engineering constraints. His design incorporated advanced NACA 65-215 laminar flow airfoils typically reserved for high-performance aircraft, paired with an innovative wing-folding mechanism that reduced hangar width requirements from 22 feet to just 7 feet 10 inches.
The prototype first took flight on Turner's birthday, April 3, 1961, powered by a Continental A65 engine producing 65 horsepower. Turner replaced this with an 85-horsepower Continental C85 after nine months of testing, significantly improving performance. The aircraft featured all-wood construction using Douglas fir spars and ribs with plywood skinning, making it accessible to amateur builders while maintaining structural integrity.
Recognition and Competition Success
The T-40 prototype, christened "Ophelia Bumps" and registered as N115ET (originally N10T), dominated homebuilt aviation competitions in the early 1960s. It captured the 1961 EAA Outstanding Design Award and placed second in the 1962 EAA Design Competition. Additional honors included the Lockheed-Marietta Georgia Award for Outstanding Workmanship and the EAA Outstanding Canopy Design Trophy, accumulating 18 EAA trophies total between 1961 and 1962.
The aircraft's success stemmed from its impressive performance specifications. With the 85-horsepower Continental C85 engine driving a two-bladed Beech-Roby controllable-pitch propeller, the T-40 achieved a maximum speed of 170 mph and cruised at 145 mph. It climbed at 1,100 feet per minute and had a service ceiling of 15,000 feet, remarkable figures for such a lightweight design weighing just 850 pounds gross.
Variants and Evolution
Turner developed several variants to expand the design's appeal. The T-40A, which first flew in March 1969, stretched the fuselage to accommodate two occupants side-by-side while retaining conventional landing gear. The T-40B offered the same two-seat configuration with tricycle landing gear, first built by Bill Betts in Watkinsville, Georgia. The Super T-40AS featured a bubble canopy and accepted engines up to 125 horsepower, achieving cruise speeds of 155 mph with a range of 505 miles.
Later variants accepted increasingly powerful engines, with some installations using Lycoming O-235 engines producing up to 150 horsepower. These high-performance versions achieved top speeds between 170 and 175 mph while maintaining the design's excellent short-field characteristics of 600-foot takeoffs and 470-foot landings.
Manufacturing and Production
Unlike mass-produced aircraft, the T-40 was marketed as plans for homebuilders starting in 1961. Turner Aircraft, Inc. never manufactured complete aircraft but provided detailed construction drawings and ongoing builder support. The exact number of T-40s constructed remains unknown, as individual builders completed aircraft at their own pace without centralized reporting.
Turner Aircraft, Inc. remained active through at least the 1970s as Gene Turner continued developing variants like the swept-tail T-77. When Turner Aircraft ceased operations, Adams Aeronautics Company acquired rights to the plans and continues offering them to modern homebuilders, ensuring the design's availability for new construction projects.
Technical Innovation
The T-40's laminar flow wing design represented advanced aerodynamic thinking adapted for amateur construction. The NACA 65-215 airfoil section, combined with a dual-spar structure and 6.35 aspect ratio, provided exceptional efficiency. Stall speeds of 55 mph clean and 49 mph with flaps deployed gave pilots comfortable low-speed handling characteristics.
The wing-folding mechanism solved a persistent problem for homebuilders with limited hangar space. Simple yet robust, the system allowed one person to fold the wings for storage while maintaining structural integrity for flight operations. Turner's attention to pilot comfort included a cockpit width of 24 inches and canopy design influenced by the experimental NACA X-2 research aircraft.
Legacy and Preservation
Two notable T-40 examples reside in museums today. The original prototype "Ophelia Bumps" is displayed at the Saxon Aerospace Museum in Boron, California, while another example nicknamed "Tail End Charlie" - painted in Turner's World War II squadron colors - is preserved at the Minter Field Air Museum in Shafter, California.
The T-40's influence on homebuilt aviation extends beyond its competition victories. It demonstrated that sophisticated aerodynamic features like laminar flow wings could be successfully incorporated into amateur-built designs, inspiring subsequent homebuilt aircraft development. Adams Aeronautics' continued support ensures that Gene Turner's innovative design remains available to new generations of aircraft builders, perpetuating its legacy in experimental aviation.