Development and Design Philosophy
Chris Heintz conceived the CH-640 as a solution to the homebuilt aviation market's lack of practical four-seat aircraft. Beginning design work on January 2, 2001, Heintz adapted his proven type-certificated AMD Alarus design, expanding the wing and stabilator span to accommodate increased weight and a larger powerplant. The prototype N640Z completed its maiden flight just two months later on March 1, 2001, making its public debut at Sun 'n' Fun in April 2001.
The design philosophy centered on creating a simple four-seat aircraft capable of full-capacity cross-country flights while maintaining construction simplicity for amateur builders. Heintz achieved remarkable efficiency by retaining 90 percent parts commonality with the two-seat CH 2000 fuselage, simply repositioning the cabin rear wall to accommodate additional seating. The wings represented entirely new engineering, incorporating high-lift airfoils optimized for the aircraft's increased gross weight.
Construction and Manufacturing
Zenair Ltd., founded by Chris Heintz and based in Canada, manufactured the CH-640 using 6061-T6 aluminum construction with aviation-grade blind rivets. The company offered two kit configurations: a standard kit requiring approximately 1,250 construction hours, and a quick-build variant reducing assembly time to 750 hours. Initial 2001 pricing established the standard kit at $24,800, with the quick-build option at $35,190, both excluding engine, propeller, instruments, and interior components.
By 2011, kit prices had increased to $28,995 for the standard version, with completed aircraft costs ranging from $45,000 to $99,000 depending on engine selection and avionics installations. The aircraft's 6061-T6 aluminum construction provided durability while maintaining reasonable weight, contributing to its impressive 1,000-pound useful load capacity.
Performance and Specifications
The CH-640's recommended powerplant was the Lycoming O-360, a 180-horsepower air-cooled, horizontally-opposed four-cylinder engine. This engine selection provided optimal performance for the aircraft's 2,200-pound gross weight, though acceptable engine power ranged from 150 to 240 horsepower. The O-360's reliability and widespread availability made it an ideal choice for homebuilders.
Performance specifications positioned the CH-640 as a capable cross-country tourer. Maximum speed reached 160 mph, with cruise speeds of 150 mph and an initial climb rate of 950 feet per minute. The aircraft's stall speed of 47 mph with flaps deployed provided excellent short-field capabilities, while its 510-mile range enabled substantial cross-country flights with full seating capacity.
Market Position and Pilot Appeal
The CH-640 distinguished itself in the homebuilt market through conventional handling characteristics and familiar control systems. Unlike many kit aircraft utilizing control sticks, the CH-640 featured dual yoke controls, easing transitions for pilots familiar with Cessna or Piper aircraft. Its 46-inch cabin width provided spacious accommodations, while dual gull-wing doors facilitated easy entry and exit.
The aircraft's heavier weight compared to typical homebuilts actually became an advantage, providing stability and handling characteristics that appealed to pilots transitioning from certified aircraft. Wing loading of 14.6 pounds per square foot contributed to smooth flight characteristics, while structural G-limits of +5.7/-2.9 ensured adequate strength margins for normal operations.
Production History and Market Challenges
Zenair maintained CH-640 production from 2001 through early 2020, with approximately 50 completed aircraft flying by December 2011. Despite the design's capabilities, production faced challenges common to four-seat experimental aircraft. The homebuilt market traditionally favored two-seat designs due to lower costs and complexity, while four-seat requirements demanded larger engines, increased materials, and substantially higher completion costs.
Several hundred aircraft remained under construction when Zenair discontinued new kit production in early 2020, citing economic reasons and persistently slow demand for four-seat experimental aircraft across the industry. The company continued supporting existing builders and aircraft owners through parts and sub-kit availability.
Legacy and Continuing Influence
The CH-640 represented an important chapter in homebuilt aviation by demonstrating that affordable four-seat kit aircraft could achieve certification-level engineering standards. Its adaptation from the type-certificated CH 2000 provided builders confidence in the design's proven foundation, while modern construction techniques made assembly accessible to amateur builders.
AeroNews Network praised the completed aircraft as "a tremendously stable little airplane and a fair amount faster than what you might think," highlighting its performance capabilities. The design's contribution to expanding homebuilt aviation options beyond traditional two-seat configurations established precedents for future four-seat kit developments.
Today, completed CH-640 aircraft continue operating in private hands, serving as cross-country tourers and demonstrating the viability of Chris Heintz's vision for accessible four-seat homebuilt aviation. While production has ceased, the aircraft's engineering legacy influences continuing developments in the experimental aircraft market.