The Airplane - Jay Spenser [26]
But how did one go about engineering a flying machine along these lines? Was there an existing body of knowledge to draw on that would help us to cobble together a lightweight, structurally sound fuselage? Sadly, the answer was no.
In contrast to his bountiful insights elsewhere, Sir George Cayley’s sketches and models generally showed a featureless pole for the airplane’s body. He advocated streamlining, with a clarion call for “solids of least resistance,” but he did not elaborate. And while he published drawings for a manned glider late in life, these fell well short of the needs of powered flight, and most researchers were unaware of them in any event.
William Henson, aviation’s first popularizer, was likewise unhelpful, but for the opposite reason of providing too much detail. An aerial steam carriage? Why, the man must be mad! One might as well ask a boat or a train to fly, scoffed serious researchers. Visionaries dreamed of a day when aviation might achieve fully enclosed passenger cabins. However, it certainly wouldn’t start out that way because they were too heavy. No, ruthless attention to weight demanded a minimalist approach to inventing the airplane.
Looking elsewhere, people turned to nature for inspiration. Predictably enough, they found it in the bird, which suggested not just the airplane’s configuration but also its structure. Birds are vertebrates like us humans. We and they rely on bony internal skeletons to support our weight and carry the physical loads we encounter in life or subject ourselves to through muscular exertions. Vertebrate engineering is a triumph of evolution. Nature’s invention of a structurally strong spinal column is what made large land animals possible.
Just as every arch must have its keystone, so too must a skeleton have a spine. Arranged longitudinally like the keel of a ship, it is the primary structural element in any vertebrate’s body. Every other part of the body ties into this long “backbone”—actually a series of linked bones called vertebrae—and draws strength from it.
From aardvarks to zebras to just about every species in between of any size in the animal kingdom, they’re built to this winning formula, dogs, cats, lizards, rabbits, whales, snakes, birds, and human beings included. Only in the world’s oceans, with seawater to buoy their flimsy bodies, can sizable invertebrates such as the giant squid exist.
Aviation seized on this biological paradigm as the way to build an airplane (or rather its airframe, which is the aircraft minus its engine or engines). Like a bird, the airplane would have an internal load-bearing skeleton.
That led to more questions. First and foremost, what should this mechanical bird’s bones be? The natural answer was wood, that being the preferred construction material of the nineteenth century. First-generation airplane builders would favor ash, hickory, Douglas fir, and above all Sitka spruce for their excellent strength-to-weight ratios. The Wright brothers built with ash and spruce. So did their talented American rival Glenn Curtiss, who added bamboo poles to the formula.
While every first-generation flying machine—successful or not—had a wooden skeleton, wood was far from the only material flight experimenters needed, of course. Two metals destined to play major roles in flight were also readily available.
Even then, wooden ships’ hulls and rail cars were giving way to steel in a profound transformation that revolutionized global transportation on the eve of the twentieth century. Thanks to the industrial needs of this and other industries, the world had embarked on large-scale steel production. And thanks to a newly perfected method making the refining of bauxite commercially viable, aluminum too was becoming available.
As we all know, these metals—aluminum in particular—have played a crucial role in aviation. In the early