Staff Writer (Updated: 6/25/2015):
Externally, the Model 18 was a basic design featuring a short nose assembly, framed cockpit position, tapered fuselage, low-set wing assemblies and a n H-style tail unit. The engines were fitted into streamlined nacelles at each wing leading edge. The undercarriage consisted of a tail-dragging arrangement to include two main landing gear legs and a tail wheel. Power was served through the pairing of Pratt & Whitney R-985 Wasp Junior radial piston engines of 450 horsepower each powering twin-bladed propellers. This supplied a maximum speed of 225 miles per hour with a cruising speed nearing 211 miles per hour. Range was out to 1,200 miles with a service ceiling of approximately 18,500 feet. The standard operating crew for a single C-45 was two pilots and up to nine passengers depending on the internal cabin configuration. Additionally, the cabin space could also be optimized for photo-reconnaissance equipment, MEDEVAC and light cargo-hauling. Overall, however, there proved no notable differences between the military C-45 and civilian Model 18 airframe.
The US Army Air Corps eventually placed orders for over 1,300 C-45 aircraft and, of these, most (1,137) were delivered in the C-45F configuration (seven-seat passenger transport). Other variants included the original C-45, the C-45A, C-45B, C-45C, C-45D, C-45E, C-45G and C-45H models - differing mainly in internal configuration and expected role. The "Expeditor II" and "Expeditor III" names were given to British (Royal Navy) and Canadian (Air Force) examples, respectively, under Lend-Lease.
After World War 2 and into the volatile 1950s, the US military charged Beechcraft with refurbishing some 900 C-45 airframes and these were reconstituted into USAF service as the C-45G (autopilot, R-985-AN-3 radial engines) and C-45H (sans autopilot, R-985-AN-14B engines) of which many went on to serve into the 1960s (approx. 1963). Some were assigned to Strategic Air Command (SAC).
Every branch of American service eventually fielded some form of the Model 18, such was the reach of this fine little airplane.