The Kelly-D is a two-seat, homebuilt aerobatic landplane designed by Dudley R. Kelly of Versailles, Kentucky. Introduced in 1981, the aircraft was intended to provide an affordable alternative to other popular sport biplanes, such as the Pitts or Christen Eagle, while focusing on manageable ground handling and modest stall speeds for the amateur pilot. A prototype of the design was documented as flying during June and July 1982, operating from grass runways ranging from 1,600 to 2,200 feet in length.
Designed as a single-bay biplane, the Kelly-D features wire-braced N-type interplane struts and inverted V center-section struts. The aircraft utilizes a wooden two-spar wing structure with fabric covering, employing a NACA 4412 wing section. To improve upon early iterations, Kelly developed a modified version that increased the wingspan by two feet and introduced a new wing section to lower landing speeds and enhance ground handling; this refined version became the sole iteration released for home building with pre-welded components. The wings are configured with a constant chord and considerable stagger, with three degrees of dihedral applied only to the lower wings.
Power is provided by a single 115 hp (86 kW) Avco Lycoming O-235 four-cylinder, horizontally-opposed, air-cooled piston engine, paired with a two-blade fixed-pitch Sensenich propeller. The aircraft has a maximum speed of 100 mph (160 km/h) and a cruise speed of 90 mph (140 km/h), with a stall speed of 40 mph (64 km/h). Its fuel system consists of a 24 U.S. gallon fuselage tank located aft of the firewall, providing a range of 275 miles. The airframe has an empty weight of 925 lb and a maximum take-off weight of 1,500 lb.
As a plans-built aircraft, the Kelly-D was not produced in a central factory but constructed by individual builders. By 1998, Dudley R. Kelly reported that 20 kits had been completed and were flying. Registration data indicates that 16 examples were registered with the FAA at one time, with 13 remaining active as of January 2014, alongside one example registered in Canada. Because it is an experimental amateur-built aircraft, its service is limited to private recreational and sport flying. Its legacy is defined by its contribution to the North American experimental aircraft movement, and it remains recognized by ICAO under the type designator KELD.