As the fledgling U.S. Army Air Service was still figuring things out, in 1924 it created the C-Class of aircraft to include cargo and personnel transport, doing away with an earlier T-series that indicated Transport.
And C-Cargo it has been ever since, starting with the original Douglas C-1 biplane, introduced in 1925.
It was produced at the historic Douglas plant on the Santa Monica Clover Field airport in southern California.
The boxy C-1 enlarged upon designs like the Douglas World Cruiser (DWC), but a side-by-side comparison would show many differences in the two aircraft. The big fuselage made the Liberty engine in the nose of the C-1 look small. At the aft end, an unglamorously broad fin and rudder did their job.
As originally designed, the C-1 accommodated six to eight passengers in the cabin, with a pilot and copilot/mechanic sitting side-by-side in an open cockpit just below and ahead of the leading edge of the upper wing.
Ten C-1s (serials 25-425 through 25-434) served the Army. One of these was redesignated C-1A when it received a geared Liberty engine with supercharger.
Seventeen more rounded out production as nine-seat C-1C variants (serial numbers 26-421 through 26-427, and 27-203 through 212).
With its passenger seats easily removable, the C-1 could carry more than a ton of cargo, and a ventral trap door in the fuselage facilitated the loading of large and heavy items, such as aircraft engines, for transport. This may be the first purpose-built Army aircraft cargo door, embracing the utility of aircraft as important haulers for the military.
Cargo runs for the C-1s sometimes involved spare parts like engines and propellers for stranded Air Service aircraft. Mass parachute drops were tried with the C-1, and at least one also saw duty as an air ambulance aircraft, resplendent in white paint and red crosses. For the 1926 Ford Air Tour, a C-1 carried journalists and served as a pathfinder for the tour.
The salient sorties in the C-1s’ history are the use of two C-1s as makeshift tankers, relaying fuel, oil, and food to the Fokker C-2 called “Question Mark” that set an endurance record of more than 150 hours aloft over California in January 1929.
One of the tanker C-1s was crewed by Capt. Ross G. Hoyt, First Lt. Auby Strickland, and Second Lt. Irvin A. Woodring. The other tanker was operated by First Lt. Odas Moon and Second Lieutenants Andrew F. Solter and Joseph G. Hopkins.
The receiver aircraft had a dorsal trap door through which a crewmember would grasp a refueling hose dangled by the C-1 crew. The special C-1s carried extra gas tanks and a 30′ hose with a copper wire running to the receiver aircraft for grounding. The C-1 tanker approached from behind and above the “Question Mark” to make contact.
Rough air sometimes forced the crews to deviate from their intended path to find a calmer refueling location.
A phenomenon of gravity caused problems as the C-1 became lighter, and the “Question Mark” heavier, as gasoline was transferred, and this tended to pull the two planes apart if the pilots were not immediately responsive to the weight changes. The pilot of the C-1 tanker could not see the position of the C-2 “Question Mark” below him. The remedy was a string tied to the arm of the C-1 tanker pilot. A crewmember who could see the C-2 beneath him would tug once if the C-1 needed to speed up, and tug twice if the tanker needed to slow down to maintain formation.
The two C-1s made a total of 37 refueling contacts, pouring more than 5,600 gallons of gasoline into the “Question Mark” and delivering 245 gallons of oil to keep the endurance aircraft functioning properly. At one point, a C-1 even lowered a Fokker window to replace one lost on the “Question Mark.”
The Douglas C-1 used a steel tube fuselage faired with wood and covered in fabric, typical of that era’s construction. The wings relied on spruce spars and ribs, covered in fabric. Wing struts were airfoil shaped aluminum, and the landing gear used chromoly steel tubing, an alloy including chromium and molybdenum. The C-1 spanned 60′ with both upper and lower wings. Wing chord was 7′. Length was 36′, and it stood 14′ above the grass surfaces from which it flew.
The C-1’s 12-cylinder liquid-cooled Liberty engine, an aging marvel of American design from World War I, produced more than 400 horsepower. With a top speed in the range of 110-120 miles per hour, its cruise speed has sometimes been listed as 85 and other times as between 95 and 105. In the aggravating uncertainty of performance data for so many early aircraft, range of the C-1 has been listed as low as 385 miles and as high as about 600 miles.
Called simply the Douglas Transport, this design received Approved Type Certificate 14 in October 1927, according to historian Joseph P. Juptner, although he was unable to find evidence that civilian models were built.
Nonetheless, this presaged a trend over the decades in which cargo aircraft and commercial aircraft have blurred the lines, with the same basic airframes serving both the military and airlines, as with the classic C-47 and DC-3, the DC-4 and C-54, the C-69 and Constellation, and the C-97 and Stratocruiser, among others. In the 1960s, Lockheed marketed a civilian version of the Air Force’s C-141A Starlifter as a freighter, the L-300, but no sales were finalized.
In the history of the Air Force, the old Douglas C-1 of the 1920s was cast as a supporting player. The significance and capability of airlifters has grown ever since.