Photographed at Seattle, Washington, USA, by Gordon S. Williams
08/31/2011. Remarks by
Johan Visschedijk: "In 1931 Curtiss designed a new observation model to Army requirements. Like the A-8 (Model 59), this had metal monocoque fuselage construction and metal-frame, metal-covered wings. A new advanced feature for Curtiss was the use of a retractable landing gear. Army development funds were meagre in the early 1930s, and only one prototype and four Service test O-40s were procured.
Y1O-40B (
"35") (
Gordon Hubbard Collection)
The single YO-40 (Model 62, s/n
32-343) was caught in the Army's transition from traditional biplane O-types to the new monoplanes and had a narrow-chord lower wing that qualified it as a true sesquiplane. To resolve the tail-heaviness problem resulting from the forward position of the lower wing and the forward position of the upper wing center section necessitated by the cockpits, the outer wing panels were swept back 10°.
The unique landing gear was attached to structure projecting slightly from the lower fuselage, and retracted inward. Power plant was a 653 hp Wright SR-1820E Cyclone radial engine fitted with a Curtiss anti-drag ring. Armament was a single 0.30 in (7.62 mm) machine gun mounted in the right upper-wing center section and a flexible 0.30 in (7.62 mm) machine gun in the rear cockpit. Delivered in February 1932, the YO-40 crashed on 20 May, 1932.
The YO-40 was returned to the factory, rebuilt to the same configuration but with stronger wings and minor refinements and was redelivered as the YO-40A (Model 62A) with the same serial number. The Service test designation was never removed; when obsolete, the YO-40A was operated as the ZYO-40A, the Z identifying it as obsolete. It was scrapped in March 1938.
Y1O-40B (
"35") (
Bill Larkins Collection)
The designation Y1O-40A was assigned to four improved versions of the YO-40A but was not used because the aeroplanes were redesigned to a degree that required a new designation. The four aeroplanes were delivered in June 1933 as monoplanes with 670 hp R-1820-27 (Y1R-1820F) engines, under the designation of Y1O-40B (s/n 32-415 to 32-418). Basically, these were YO-40As with the lower wing removed. The inward-retracting landing gear installation was the same as on the sesquiplane. Following Service test, the aeroplanes became O-40B; the last one was surveyed in 1939.
Pictured aircraft was assigned to the 22nd Observation Squadron at Brooks Field, San Antonio, Texas, USA."
