Martin Kitten K-III

The Martin K-III Kitten was designed in 1917 by James V. Martin for the U.S. Army as a high-altitude fighter. It was fitted with oxygen tanks behind the pilot's seat and provisions for electrically heating the pilot's clothing. Unfinished at the war's end, Martin shifted his goals for the K-III toward the post-war civilian light airplane market. About sixty test flights were made in the summer of 1919, but with little success.

Despite its failure as a practical airplane, the K-III had several interesting design features. It is generally recognized as the first airplane in the United States to be equipped with an in-flight-operated retracting landing gear. The "K-strut" wing truss was intended to equalize the moments and forces acting on the wing support, as well as to save weight and to reduce drag. Although the K-III was a failure (only one was built), it does illustrate one pioneering aeronautical engineer's novel attempts to solve rudimentary aircraft design problems.