The general history of the flight engines used by the Wright Brothers is quite fascinating and fortunately rather well recorded.[1] The individual interested in obtaining a reasonably complete general story quickly is referred to three of the items listed in the short bibliography on page 69. The first, _The Papers of Wilbur and Orville Wright_, is a primary source edited by the authority on the Wright brothers, Marvin W. McFarland of the Library of Congress; a compact appendix to volume 2 of the _Papers_ contains most of the essential facts. This source is supplemented by the paper of Baker[2] and the accompanying comments by Chenoweth, presented at the National Aeronautics Meeting of the Society of Automotive Engineers on 17 April 1950. Aside from their excellence as history, these publications are outstanding for the manner in which those responsible demonstrate their competence and complete mastery of the sometimes complex technical part of the Wright story. [Footnote 1: An extensive bibliography, essentially as complete at this time as when it was compiled in the early 1950s, is given on pages 1240-1242 of volume 2 of _The Papers of Wilbur and Orville Wright_, 1953.] [Footnote 2: Max P. Baker was a technical adviser to the Wright estate and as such had complete access to all of the material it contained.] The consuming interest of the Wrights, of course, was in flight as such, and in their thinking the required power unit was of only secondary importance. However, regardless of their feeling about it, the unit was an integral part of their objective and, due to the prevailing circumstances, they very early found themselves in the aircraft engine business despite their inexperience. This business was carried on very successfully, against increasingly severe competition, until Orville Wright withdrew from commercial activity and dissolved the Wright Company. The time span covered approximately the twelve years from 1903 to 1915, during the first five years of which they designed and built for their own use several engines of three different experimental and demonstration designs. In the latter part of the period, they manufactured and sold engines commercially, and during this time they marketed three models, one of which was basically their last demonstration design. A special racing engine was also built and flown during this period. Accurate records are not available but altogether, they produced a total of something probably close to 200 engines of which they themselves took a small number for their various activities, including their school and flying exhibition work which at one time accounted for a very substantial part of their business. A similar lack of information concerning their competition, which expanded rapidly after the Wright's demonstrations, makes any comparisons a difficult task. The Wrights were meticulous about checking the actual performance of their engines but at that time