Swearingen SX-300



The Swearingen SX-300 is a high-performance homebuilt aircraft, featuring two seats and developed by Ed Swearingen during the 1980s.

The aircraft was offered as a kit, but this was not a comprehensive kit like contemporary designs, and its construction was beyond the abilities of the average amateur aircraft builder. The airplane features a 300 hp six-cylinder engine.

Design and development
Citing the lack of advancement in aircraft performance since the 1930s, Swearingen started a new company to develop faster light aircraft designs. The new design was intended to be developed as a kit aircraft initially and then later to be type certified, although certification was never completed.

The aircraft was designed in 1983, first flown on July 1, 1984 and initially designated as the S29-300, for Swearingen, 29th design, 300 horsepower. The official company designation for the production kit aircraft is SX300, although some owners have registered them as SX-300 and SX 300.

The SX300 is fabricated from all-metal aluminum sheet, but with an emphasis on reducing aerodynamic drag. The wings are made from 0.040 in aluminum sheet, while the tail is 0.020 in sheet, with all metal joints butt-ended rather than overlapped and secured with countersunk rivets. The wing leading edge is stretch-formed over machine dies and then wrapped around the wing to achieve a smooth surface. The leading edge is reinforced with foam. The wing has a tapered planform, but with a straight leading edge. The fuselage has hydroformed structural members, with stringers and sheet metal covering. The wings have 3° of washout to improve the stall characteristics. The ailerons are differential and counter-weighted. The engine cowling is made from composite material and is based on Swearingen's design he employed in the Piper PA-30 Twin Comanche. The canopy is forward hinged and secured with six latches. The Lycoming IO-540 powerplant is mounted using a 7.25 in propeller extension and is offset 2° right and 1.5° down for P-factor effects. The fuel is contained in two wet wings and capacity is 30 u.s.gal per side. The tricycle landing gear is retractable rearwards and fuselage-mounted. The right hand main landing gear includes a retractable step. The aircraft is stressed for +6/-3 g.

Kits went on sale in 1986 and ceased sales in 1989. The company indicated that production ended due to lack of progress in type certifying the design, but Apfelbaum indicates "the more likely reason is that a turboprop prototype shed its wings, leading to a fatal accident during a demonstration, which ultimately diminished the interest of the military."

The kit was very difficult to construct, even for experienced builders and many were not completed. It is estimated that 80 to 90 kits were sold but only 48 sets of landing gear were made. About 45 SX-300s were actually completed and flown with about 30 reportedly still flying in 2023.

Operational history
In a 2023 review for AVweb, Johnathan and Julia Apfelbaum concluded, "the SX300 doesn’t just look like a thoroughbred rocket ship of an aircraft—it really is. We would have to say this aircraft is certainly one of Swearingen’s finest achievements."

Accidents and incidents
The design has had a high accident rate, with at least seven fatal accidents recorded by the US NTSB. At least five were also damaged in landing gear collapses due to failures of the landing gear main leg trunnions.