Windecker Industries - Eagle Prototype

Eagle Prototype

The certification Eagle prototype, incorporating retractable landing gear, crashed during spin testing for certification by the Federal Aviation Administration. After a redesign of the empennage, the Eagle AC-7 became the first composite airplane to receive FAA certification, in December 1969. (A number of composite sailplane designs had been certified by the FAA as early as 1967). Windecker went on to produce six civilian Eagles in the early 1970s.

The Eagle was faster than the high-performance airplanes it was designed to compete against. With the same gross weight (3,400 lbs), wing area (176 sq ft) and engine (285 hp Continental IO-520) as its competitors, the Eagle prototype was emblazoned with silhouettes of a Beech Bonanza, Cessna 210, and Bellanca Viking, testimony to outrunning those airplanes in side-by-side tests. Windecker results of back-to-back flight tests showed the Eagle to be 10 mph (16 km/h) faster than the Beech V35 Bonanza, even though it was almost 11 inches wider and over 2 ft (0.61 m) longer. This speed advantage was due primarily to the optimum aerodynamic contours of the molded composite airframe. Additionally, the rigid sandwich-construction of its composite material skins prevented wrinkling and buckling under loads (a common occurrence with the thin aluminum skins of metal aircraft) which causes additional parasitic drag. The Eagle's low aspect ratio (of 5.82) rectangular wing, chosen for docile low-speed handling, probably reduced the Eagle's top speed. In 1970, a tapered, higher aspect ratio wing was under development that was calculated to add 10 miles per hour to the Eagle's maximum speed.

Because of its unfamiliarity with composites, the Federal Aviation Agency required the Eagle be 20% stronger than airplanes made with aluminum. This resulted in the Eagle being 100 lb (45 kg) heavier than its non-composite competitors. Interestingly, the retractable-gear Eagle is no heavier than current production fixed-gear composite airplanes, such as the Cirrus SR22 and Cessna (formerly Columbia) 350, both certified in 1998.