The Douglas C-39 was basically the end result of a development process that began with the XC-32 in 1935. The XC-32 was a military version of the Douglas DC-2 civilian airliner. The XC-32 led to an order for 18 similar aircraft with the C-33 designation. The first C-33 built was held back at the Douglas factory and modified with a DC-3 tail assembly and designated C-38. The C-38 led to an order for 35 similar production versions which were designated C-39 by the Air Corps.
The C-39 was a mixture of DC-2, DC-3 and military specific parts and assemblies. The plane used a basic DC-2 forward and center fuselage section mated to a DC-3 style aft fuselage and tail. The wing consisted of a DC-3 center section and DC-2 outboard wings. The landing gear was based on the design developed for the Douglas B-18 bomber. Because the C-39 was essentially a hybrid of DC-2 and DC-3 assemblies, it was unofficially known as the DC-2½.
The first C-39 was delivered in December 1938 and the remaining planes were received in 1939. The museum has the 14th C-39 built (S/N 38-515) in its collection.
Interior of the C-39 The C-39 interior was specifically designed for carrying cargo but could also be configured with 12 passenger seats (six rows of two). The floor of the cabin had numerous tie down points for securing cargo -- primarily with ropes. At maximum loading, the plane could carry nearly two tons of cargo.
The C-39 carried a crew of three -- the pilot, co-pilot and radio operator. Previous versions of the plane (C-32, -33 and -38) had just a pilot and co-pilot. The radio operator's station was at the rear of the cabin opposite the cargo loading door. In cases where the plane was carrying a maximum load, the aisle way to the cockpit could potentially be blocked with cargo so the radio operator could act as a load master to make sure the cargo did not shift in flight and open the cargo doors after landing and begin the unloading process while the flight crew finished its post flight checks and paperwork in the cockpit.
C-39 in Operational Service The Army Air Corps received the last of the 35 C-39s ordered in mid-1939. These planes, combined with the C-33s already in service, comprised the bulk of the Air Corps cargo transport fleet until late 1940. The C-39s were assigned to several units within the United States.
Until the early 1940s, it was common practice to assign a few cargo planes to Army air fields with large pursuit or bomber units. When it became apparent that the Army would need thousands of transport planes to move men and material during the anticipated war, several transport groups were formed. One such unit, designated the 10th Air Transport Group (later re-designated 10th Air Depot Group), was formed at the Fairfield Air Depot at Patterson Field in Ohio. One of the missions of this group was to conduct scheduled delivery service between several Army depot air fields in the United States. The C-39 was capable of being converted to carry litter patients and was sometimes used as a hospital ship during exercises and occasionally for actual medical evacuations.
Several C-39s (and a few C-33s) were assigned to Clark Field, Philippines in the early 1940s. When it became apparent that the Japanese attack was imminent, the Philippines-based C-39s were used to evacuate personnel to Australia. These planes continued to fly cargo/transport missions until late in the war -- some in Australia and at least one in India.
The C-39s remained in service until 1944 when several planes (including the museum's C-39) were declared surplus and sold to other governments.
TECHNICAL NOTES: Engines:Wright R-1820-55 radials of 975 hp each Maximum speed: 210 mph Cruising speed: 156 mph Range: 1,600 miles Service ceiling: Approx. 20,600 ft. Span: 85 ft. 0 in.
Length: 61 ft. 6 in.
Height: 18 ft. 8 in. Weight: 21,000 lbs. maximum gross weight Crew: Three (pilot, co-pilot and radio operator) Passenger capacity: 12 passengers or 3,600 lbs. of cargo Serial numbers: 38-499 to 38-501; 38-504 to 38-535