<p>Last in a long line of designations applied to Douglas' highly successful observation biplane family begun with the O-2, the O-38 was the main radial-engined version to see service. The O-38 was based on the O-25, which had introduced a revised machine gun mount for the observer in the rear cockpit, but featured a Pratt & Whitney R-1690-3 Hornet radial engine with a Townend cowling ring. The O-38 also resembled the O-29 and O-32, which had been powered by Wright Cyclone and Pratt & Whitney Wasp radials, respectively.
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<p>Forty-six O-38s were built (30-407/30-419, 31-349/31-379, 31-406/31-407) for the US Army's observation squadrons, although one was completed as an unarmed staff transport for the National Guard as the O-38A. The O-38B designation covered 63 aircraft (31-409/31-438, 32-102/32-116, 32-325/32-342) which had R-1690-5 engines of 525 hp and other minor improvements. Of these 33, were for the National Guard. A single O-38C (32-394) was procured on behalf of the US Coast Guard.
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<p>A major redesign occurred with the O-38D (one made, 33-001), which featured a widened and deepened fuselage with enclosed cockpits, full engine cowling, new tail surfaces and single-strut undercarriage. The production version was the O-38E, of which 37 were built (33-002/33-016, 34-001/34-022). Eight similar aircraft were procured as O-38Fs (33-322/33-329) with further improved canopies and R-1690-9 engines. These were unarmed and served with the National Guard on staff transport duties.
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<p>Serving as well in the observation role as the O-2s, O-25s and O-32s before them, the O-38s were replaced mainly by the next Douglas family of observation types, the parasol O-43/46. However, a handful of O-38s remained active with the National Guard into 1942, used mainly for target towing. The A-6 designation was reserved for O-38s modified for use as pilotless targets, but this program was never put into effect.
