Designed to meet specific needs of observer. Was 3-seat monoplane and fully enclosed unlike open-cockpit Douglas O-38 which it replaced. Special features include open "station" in bottom rear of cockpit, providing excellent field of view through which guns or cameras can be used . Gear retractable. Armed with single forward-firing .30 cal Browning in starboard wing and another on fixed mount in rear cockpit. Deliveries began 1937 and soon comprised about half of aircraft in National Guard units. By the time US entered WWII, O-47s used for anti-submarine patrol off east coast, over Gulf of Mexico, and out of Panama and Australia. Others used for training or as target tow planes. A few caught overseas at time of Pearl Harbor.