What's it made of?

Composites are the latest thing in aviation—just as they were more than a century ago.

These days, everyone in the aviation field talks about composite aircraft. Boeing’s 787 Dreamliner is made mostly of carbon fiber composites, and the percentage of composite content in new business jet designs is on the rise. Over time, carbon fiber may, indeed, replace metal as the material of choice for aircraft. But how did we get here? 

Actually, composites represent a return to where we started. It’s not well known, but the Wright Brothers’ first airplanes consisted largely of a material Wikipedia defines as “a composite of cellulose fibers embedded in a matrix of oflignin.” Some refer to this exotic substance as…wood. Though the bicycle mechanics from Dayton, Ohio undoubtedly knew how to work with metal, they chose wood for its elasticity, light weight and high strength-to-weight ratio and because it was easy to cut and carve into shape. The brothers had studied birds’ hollow “composite” bones, and so creating a flying machine in a similar manner was a good imitation of nature.

The decade between Kitty Hawk and the start of World War I, however, rendered Orville and Wilbur’s materials obsolete: the power of airplane engines increased roughly tenfold during that time, meaning aircraft could carry more weight and fly faster—and impose greater loads on themselves. Gone were the days of gliding lightly on the breeze like a bird, and so airframes needed greater strength.

Man had been busy building stout structures for centuries—bridges in particular. So as airplanes needed more strength, designers turned to fuselages made of steel tubes trussed together like a bridge. It’s an old misconception that World War I-era airplanes were made of “sticks and cloth.” On the contrary, though they were, indeed, covered with doped fabric, the structural skeletons of most Great War aircraft were steel.

At the start of World War II in the late 1930s, the two top fighters in the British Royal Air Force were the Hawker Hurricane and the Supermarine Spitfire, both single-engine monoplanes. The former was a traditional steel-tube, fabric-covered platform, while the Spitfire wasa more advanced all-aluminum monocoque design. Its structural strength came from aluminum bulkheads to which “skins” were riveted. A lighter and more efficient design, a monocoque airplane’s skin provided much of the structural strength, whereas the covering of a steel-tube airplane represented wasted weight. The monocoque design is the way almost all airplanes—from flivvers to jet airliners—were built thereafter,until the world discovered fiberglass.

n the mid 1970s, an enterprising young aeronautical engineer named Burt Rutan turned the light-sportplane industry around with his two-seat VariEze kitplane. It was formed of fiberglass and designed with its Volkswagen engine in the back and tail feathers up front. The prototype VariEze was named “Glass-Backwards” and had a racy image painted on the side that featured a shapely female’s backside.

The relative benefits of fiberglass airplanes have been debated ever since. Rutan’s VariEze (and a family of later designs) consisted ofthe same fiberglass used in boats and surfboards, which is not much lighter than aluminum (even heavier in some cases) but is easier to form in the sleek, streamlined shapes that make airplanes more efficient.

More sophisticated carbon fiber material is not as easy to work with but offers other benefits in strength and lighter weights. 

Rutan joined Beechcraft in the 1980s and designed the Starship, a composite turboprop twin with pusher engines and a “canard” forward-wing configuration easily traced to his VariEze. The Starship suffered certification setbacks and delays, due in part to the newness of the material. For example, the FAA needed to be convinced that it would weather a lightning strike as well as a metal airplane, and Beechcraft wound up having to include a layer of metallic material to absorb the charge. That and other mandates caused the airplane to gain weight, and the final product was not a great performer.

The Starship failed commercially, but it paved the way for more advanced composites. Without Rutan and other designers who followed the composite path, the Dreamliner would have never gotten off the ground.

Mark Phelps is a private pilot and a managing editor at BJT sister publication Aviation International News.