05/31/2009. Remarks by Johan Visschedijk: "Also known as YO-22, this experimental version had sweptback upper wings and N-struts that substituted for the two parallel struts fitted to previous Douglas observation biplanes. The aircraft had corrugated metal covering on its vertical tail surfaces and was fitted with a tail wheel instead of a skid. Powered by a 450 hp Pratt & Whitney R-1340-9 radial and tested here with a Townend ring and with early NACA-type cowling. Only two aircraft were built in late 1929, s/n 29-371 and 29-372."