The C-4 was the military version of the Ford 4-AT trimotor.
The series of three-engine Ford Trimotor aircraft produced during the 1920s and 1930s were classic planes of the era. Most major airlines used these planes, especially the 4-AT, during this time, and smaller and more remote airlines around the world continued to use the plane for many more years. Some are still in use. The Trimotor's most famous single flight was Admiral Richard Byrd's flight over the South Pole on November 28, 1929, when the Floyd Bennett carried Byrd and three companions around the Pole.
The first Ford Trimotor, the 2-AT Pullman, was developed by Stout Metal Airplane Company in early 1925. In August, Ford Motor Company acquired Stout and produced the 3-AT, which was not a successful plane. Ford dismissed Stout and redesigned the plane. The new plane, the 4-AT, debuted on June 11, 1926. At the time, it was the largest civil aircraft produced in the United States. Powered by three 200-horsepower (149-kilowatt) Wright Whirlwind J4 radial engines, the 4-AT-A version of up the plane could seat up to eight passengers in its enclosed cabin, although the two pilots were exposed to the elements in their open cockpit. Called the "Tin Goose" because of its corrugated metal fuselage, it was an immediate success.
Later versions were larger and heavier, could accommodate more passengers, and used more powerful engines. Ford also switched from using the Wright engine to Pratt and Whitney Wasps. Variants of the 4-AT used different combinations of the Whirlwind and Wasp engines.
The 5-AT was the primary variant. This plane, which first flew in 1929, was larger, had more power, and could seat 13 passengers. One variant was powered by three 450-horsepower (336-kilowatt) Wasp engines, double the power of the earliest 4-ATs. The largest variant could seat 17 passengers. Some Ford Trimotors were fitted with skis or floats.
In addition to carrying passengers, the Trimotors served other purposes,
including carrying freight, crop-dusting, fire fighting, advertising,
and exploring remote areas. The military version of the 4-AT, designated
the C-4, was used to transport military troops. During its years in production,
which ended in 1933, Ford built approximately 80 4-ATs and 117 5-ATs as
well as a small number of later varieties and a few military aircraft.