Quest for Performance: The Evolution of Modern Aircraft
Chapter 3: The Lean Years, 1918-26
[67] The pace of aircraft development and production was extremely slow during the time period from the armistice in November 1918 until about 1926. World War I was thought to be the war "to end all wars," the war "to make the world safe for democracy." Postwar military appropriations, including funds for new aircraft, were accordingly small. The primary financial base underlying the development and production of new aircraft and advanced technology had dried up. The military made use of leftover and modified aircraft from World War 1, of which the DeHavilland DH-4, previously described, was a prime example. In fact, the DH-4 continued to serve in various capacities in the Army Air Corps of the United States until the early 1930's. There was, of course, some development activity sponsored by both the Army and the Navy, and a number of prototypes of new aircraft were produced. These prototypes, however, usually followed the familiar biplane formula that emerged from World War I. Some small production contracts, generally, no more than 15 or 20 aircraft, were placed with the existing manufacturers for some of these prototypes. Hence, the industry did not entirely collapse.
The requirements of civil aviation during this time period presented little incentive for advanced aircraft developments. No airlines devoted to the transportation of passengers existed in the United States; however, the Government operated a primitive airmail service that linked various cities in the United States, and the first coast-to-coast airmail service was established in 1921. The aircraft employed for carrying the malls consisted mostly of surplus World War I aircraft, with the ubiquitous DH-4 as the mainstay of the operation. Many modifications were made to the DH to make it more suitable for airmail service, and the aircraft was so utilized until at least 1927 or 1928.
[68] General aviation as we know it today existed only in the form of barnstormers. These gypsy pilots roamed the country from town to town offering 5- to 10-minute rides for sums of around $5.00. The aircraft that served as the workhorse for the gypsy pilot was the Curtiss JN-4 or jenny. This aircraft was a trainer that served during World War I to introduce thousands of neophytes to the mysteries of flying. In the decade following World War I, many young people, children and teenagers alike, were introduced to the wonderful world of flight by the sight of a Jenny gracefully gliding to a landing in a pasture close to the family homestead. Once seen and heard, the sight and sound of this ancient biplane with its slow-turning engine and the whistling noise of the wind through the bracing wires made an indelible impression on many young people in the 1920's and served as a springboard for their later entry into some aspect of aviation. The jenny was similar in configuration and construction to the DH-4 shown in figures 2.26 and 2.27 (chapter 2), but, instead of having an engine of 400 horsepower, it was equipped with the 90-horsepower Curtiss OX-5 or the 150-horsepower Wright-Hispano. Most models of the jenny used by barnstormers had the 90-horsepower engine and were designated JN-41). The aircraft was quite slow and had a cruising speed that did not differ very much from the stalling speed. By today's standards, the handling characteristics of the jenny would be considered unacceptable (shown by the data in ref. 101). The Curtiss Jennys, however, were available in large numbers following the end of World War I and could be purchased for as little as a few hundred dollars. Obviously, no new aircraft suited to the demands of the barnstormers could be developed and provided no market for the development and production of new aircraft.
A Curtiss JN-4H with the Wright-Hispano engine is shown in figure 3.1, and the characteristics of this version of the Jenny are given in table II (appendix A).

2 Curtiss JN-4H trainers
Figure 3.1 - Curtiss JN-4H Jenny trainer; 1918. [NASA]