Scale drawings by Paul Matt for the 2000 Waco book, "Waco, Symbol of Courage & Excellence, Vol. 2" http://www.aviation-history.com
The Waco UPF-7 is an unusual airplane. This is not due to any outstanding technical features but to timing. It was built in quantity at a time when the open cockpit biplane for civilian use was waning, however it slipped into service unnoticed as a training plane.
As new lower-powered monoplanes rapidly took their place in the schools and in private aviation, the U.S. Army and Navy were principal customers for this type of biplane trainers in succeeding years. While Waco did not have a share of this market, it was one of the few firms that continued to supply open cockpit biplanes to private owners. This group was mainly comprising of what could be considered "a custom trade". Yet the UPF-7, introduced in the late twilight of the biplane era, was built in greater quantity than any single Waco model that preceded it. Approximately 600 came out of the Troy, Ohio factory between 1937 and 1942.
The UPF-7 standardized on the 220 hp Continental W-670-6A, civil equivalent of Continental's R-670 military engine.