Focused Modular Experimentation
Over time, several inventors focused on systemic, piecemeal experiments with components. Due to this, the developments in lift & wing design, thrust, flight stability and control, and structure are surprisingly independent. Also the Wright brothers developed components separately before combining them into an integrated structure. We now discuss historical events in component inventions (and the feedback into system design, if any) in line with the complexity-theoretic process model.
Lift and Wing Design
When it comes to lift and structural integrity of wing design, research over the nineteenth century focused on the shape of the wing, the camber and airfoil, the aspect ratio, and the number and spatial layout of planes. Much of the experimental research even continued in the decades after the Wrights first flight.
Already Smeaton and Cayley studied lift as a function of the shape and camber of a surface using the whirling arm as test device. Cayley established the importance of low pressure on the upper surface (see his trilogy “On Aerial Navigation” published in 1809-1810), and the role of the aspect ratio (span divided by chord/ breadth) of wings (Gibbs-Smith 1965). Like Cayley, also Wenham conducted bird flight studies and (already in 1859) established that wing camber increases lift and mostly near the front edge. In 1871 in the U.K., Browning constructed a wind tunnel for Wenham, who studied the effect of wingspan, the angle of attack, and which part of the wing chord provides the lift (Hallion 2003, p. 116). In the early 1880s in the U.K., Horatio Phillips built his own injector wind tunnel to extensively test lift and drag characteristics of alternative cambered airfoil concepts, ultimately patented in 1884 and 1891.
Despite these findings in the U.K, aircraft with curved and straight-line wing designs kept cropping up side by side over the decades (e.g. Ader’s Eole and Maxim’s flying machine). Inspired by Wenham’s wing superimposition (1858) and Phillips’ stacked wings configuration and using the system of Pratt trusses (he knew from bridge construction) to ensure structural integrity, Chanute and Herring built light and strong straight-line wing tri- and biplane gliders with a Cayley-type cruciform tail which may well be considered a dominant design for the wing type and configuration. Only around 1915 that dominant design was toppled when Juncker and Fokker developed the cantilever wing.
The findings of Wenham, Phillips, and Lilienthal on wing design and lift were contained in Chanute’s 1894 book “Progress in Flying Machines” read by the Wright brothers. While designing their first gliders, the Wrights were fully aware of the above mentioned findings on lift. However, notably while testing their 1901 gliders, they found out that the lift was too weak (Hallion, p. 191) and decided to redo the measurements.
At the end of 1901, they built a bicycle test rig and wind tunnel to tests 200 different wing shapes, different cambers and curvatures on 38 of them, and a range of aspect ratios of rectangles as well as different shapes. In addition, they made lift and drag measurements, tested airfoil behavior, and multiplane configurations. Ultimately, all this yielded extensive and reliable airfoil data (Hallion 2003, pp. 191-193).
After extensive wind tunnels tests in 1901, glider redesigns (notably the aspect ratio and camber) and subsequent glider tests in 1902, it was concluded that they mastered lift and longitudinal control (fore-and-aft horizontal balancing) using elevators (Hallion 2003, p. 194).