The Vought XSO2U was an American observation floatplane developed by Vought-Sikorsky for the United States Navy during the late 1930s.
Intended to replace the Curtiss SOC Seagull in service as a scout aboard cruisers, it proved superior to the Curtiss SO3C in evaluation, but failed to win a production contract due to Vought’s lack of manufacturing capacity.
In the late 1930s the United States Navy developed a set of specifications for a new scout-observation aircraft to operate from its cruisers in the reconnaissance and gunnery spotting roles.
Intended to replace the Curtiss SOC biplane, the requirements included that the aircraft should have folding wings, have a superior range and speed to that of the SOC, and that the new type should be powered by the Ranger V-770 inline engine.
Designs were submitted in response to the Navy’s specifications by Vought-Sikorsky and Curtiss-Wright.
The Vought design, designated Model 403 by the company, was similar to the company’s OS2U Kingfisher, which was then under development to replace the SOC aboard U.S. Navy battleships, but had its monoplane wing moved higher on the fuselage than that of the Kingfisher, and differed in the attachment method used by its single-float landing gear.
In addition, the radial engine of the OS2U was replaced by an inline Ranger V-770 in a squared-off cowling.
Capable of being operated with either the float as a seaplane or with a conventional taildragger undercarriage as a landplane, the XSO2U utilised all-metal construction, with the exception of its control surfaces which were fabric-covered.
The wings folded to the rear for storage in a manner similar to that of the Grumman TBF Avenger torpedo bomber.
The aircraft was capable of performing dive bombing and could be fitted with a single bomb or depth charge on a hardpoint under each wing for the mission, or for anti-submarine warfare.
Gun armament consisted of two M2 Browning machine guns, one mounted in a fixed position firing forwards through the propeller using synchronizer gear, while the other was in a flexible position in the observer’s cockpit for rear defence.
Specifications
Crew
2
Length
36 ft 1 in (11.00 m)
Wingspan
38 ft 2 in (11.63 m)
Height
15 ft 11 in (4.85 m)
Wing area
300 sq ft (28 m2)
Empty weight
4,016 lb (1,822 kg)
Max take-off weight
5,624 lb (2,551 kg)
Fuel capacity
128 US gallons (480 l; 107 imp gal)
Powerplant
1 × Ranger XV-770 inline engine, 450 hp (340 kW)
Propellers
2-bladed Hamilton Standard constant-speed
Performance
Maximum speed
190 mph (310 km/h, 170 kn) at 9,000 feet (2,700 m)
Service ceiling
22,200 ft (6,800 m)
Armament
Guns
2 x M2 Browning machine guns, one fixed forwards-firing, one flexible rear-firing.
Bombs
Two light bombs or depth charges on under wing racks.
