The Boeing C-73 was the military designation given to a number of Model 247 twin-engine transport aircrafts that were taken into military service early in the Second World War.
The Model 247 was an advanced design for its time and was the first low-wing twin-engine transport aircraft to enter production in the United States. It used features developed for the Model 200 Monomail (C-18) and the unsuccessful B-9 design. It was designed to replace the previous generation of Trimotor transports, and was lighter, faster and more reliable than those aircraft. It could carry ten passengers in a cabin located above the wing (one problem with this was that the main wing spars passed right through the middle of the passenger cabin.
The Model 247 was a commercial success. United Air Lines placed the first order, for 70 aircraft, in 1932, 11 of which were completed as the Model 247D, which had NACA engine cowlings, fabric covered tail surfaces and controllable pitch propellers. The Model 247D was much faster than the basic Model 247 and the older aircraft were upgraded to the new specification.
Twenty-seven Model 247Ds were commandeered from the airlines in 1942 as the C-73. Most retained their S1H1 Wasp engines, but others got military specification Pratt & Whitney R-1340-AN-1 engines. The C-73 had a fairly short wartime career. They were declared surplus in 1944 and nineteen were sold back into private hands. Amongst the units to use the type was the 430th Bombardment Squadron, which had it in 1943-44 when it was being used to test equipment.
The Model 247 was also used by the RCAF, which operated eight.
Engine: Two Pratt & Whitney R-1340-53 radial engines
Length: 51ft 7in
Height: 12ft 2in
Empty Weight: 9,140lb
Gross Weight: 13,650lb
Maximum Speed: 200mph
Cruising Speed: 189mph at 12,000ft
Climb rate: 1,150ft/ min
Range: 745 miles
Payload: 400lb and 10 troops