The Boeing Y1C-18 was the military designation given to a single Boeing Monomail (Model 200) that was evaluated by the USAAC.
The Monomail was an advanced aircraft for its period. It was a low wing monoplane, powered by a radial engine with anti-drag ring, and with a retractable undercarriage. It had a metal semi-monocoque fuselage and all-metal wings. The cargo and mail compartment was placed in the centre of the fuselage, while the pilot sat in an open cockpit just above the wing trailing edge.
The basic design was repeated on the Model 221 Monomail of 1930, and that could carry six passengers in the nose as well as 750lb of mail. The single Model 221 was later extended to allow it to carry eight passengers, and the Model 200 was converted into the same eight-seat configuration.
The USAAC was sufficiently impressed with the Monomail to place an order for a single aircraft, and then in 1931 borrowed the original Model 200 for evaluation with the designation Y1C-18. For some reason the Model 200 didn't impress the Air Corps. The order for an aircraft was cancelled and the Model 200 was returned to Boeing.
Power: Pratt & Whitney Hornet B
Span: 59ft 1.5in
Length: 41ft 2.47in
Empty Weight: 4,758lb
Gross Weight: 8,000lb
Maximum Speed: 158mph
Cruising Speed: 135mph
Climb rate: 850ft/ min
Range: 530 miles