08/31/2011. Remarks by
Johan Visschedijk: "Delivered in October 1934, the last airframe (s/n 33-291) ordered under the O-43A contract was finished as the XO-46. The tubular cabane mounted on the center section and supporting the parasol wings of the
O-43A by means of steel wires was replaced by parallel streamlined struts beneath the wings. The XO-46 was fitted with a 725 hp Pratt & Whitney R-1535-7 fourteen-cylinder air-cooled radial driving a three-blade propeller, hence it was the first Douglas observation monoplane to be powered by a radial engine and to have its wing braced to the fuselage by two parallel struts.
When awarded on April 29, 1935, the O-46A production contract AC-7342 covered 71 aircraft, but two contract changes, dated October 31, 1935, and March 6, 1936, added respectively 17 and 2 aircraft. Thus, a total of 90 O-46As (s/n 35-161 to 35-231, 36-128 to 36-144 for the Air Corps, and 36-147 to 36-148 for the National Guard) were delivered between May 1936 and April 1937. These aircraft differed from the XO-46 in having their R-1535-7 engines moved forward 8.5 in (21.6 cm) to improve c.g. location and in having their canopies faired into the vertical fin."
