Why the Exulans

It can be observed that large, high-efficiency birds like the Wandering Albatross (Diomedea exulans) are not equipped with aerodynamically working controlling tails. In normal flight their tails are not spread and therefore cannot account for much controlling action nor contribute significantly towards stability.

Another field of interest in natural aviation is that of the extinct pterosaurs. Fossil findings suggest a pterosaur existed in the suborder of the pterodactyls that had a wingspan of 12m! Called Quetzalcoatlus, its fossils, found in Texas, show that like the other pterodactyls it was tailless. Its aerodynamic shape apparently had the same essential features that later the modern bird made its own. We also speculate that Quetzalcoatlus, in spite of its size, could operate without prepared runways.

This observation suggests that tailless flight, where high flight efficiency is needed, has been promoted through evolution in nature. Although the history of aviation has seen many species of tailless aircraft, selection in human aviation has mostly favored the Pénaud-type (tailed aircraft). Considering the smaller wetted area (area exposed to airstream) and lower structural weight, the tailless aircraft should be the most efficient one. However, tailless aircraft have never really established themselves in main stream aviation.

Birds use, among other mechanisms, variable wing sweep for control. The Exulans is to demonstrate that the implementation of this control strategy can reduce trim drag and requires less wing area and thereby improves overall efficiency.