The Vought OS2U Kingfisher is an American catapult-launched observation floatplane.
It was a compact mid-wing monoplane, with a large central float and small stabilizing floats.
Performance was modest because of its low-powered engine.
The OS2U could also operate on fixed, wheeled, tail dragger landing gear.
The OS2U was the main shipboard observation seaplane used by the United States Navy during World War II, and 1,519 of the aircraft were built.
It served on battleships and cruisers of the US Navy, with the United States Marine Corps in Marine Scouting Squadron Three (VMS-3), with the United States Coast Guard at coastal air stations, at sea with the Fleet Air Arm of the Royal Navy, and with the Soviet Navy.
The Royal Australian Air Force also operated a few Kingfishers from shore bases.
The Naval Aircraft Factory OS2N was the designation of the OS2U-3 aircraft built by the Naval Aircraft Factory in Philadelphia, Pennsylvania. The OS2U first flew on 1 March 1938.
In the late 1930s, Vought engineer Rex B. Beisel was tasked with designing an observation monoplane aircraft for the U.S. Navy suitable for many tasks, including directing battleship fire.
In replacing the standard biplane observation aircraft with a more modern monoplane design, Beisel incorporated innovations making it the first production type to be assembled with spot welding, a process Vought and the Naval Aircraft Factory jointly developed to create a smooth fuselage that resisted buckling and generated less drag.
Beisel also introduced high-lift devices, spoilers and in a unique arrangement, deflector plate flaps and drooping ailerons located on the trailing edge of the wing were deployed to increase the camber of the wing and thus create additional lift.
For combat missions, the pilot had a .30-caliber Browning M1919 machine gun, the receiver mounted low in the right front cockpit, firing between the engine cylinder heads, while the radio operator/gunner manned another .30-caliber machine gun (or a pair) on a flexible Scarff ring mount.
The aircraft could also carry two 100 lb bombs or two 325 lb depth charges.
Additionally, the “Kingfisher”, as it was designated, served as a trainer in both its seaplane and landplane configurations.
Beisel’s first prototype flew in 1938, powered by an air-cooled, 450 hp Pratt & Whitney R-985-4 Wasp Junior radial engine.
Variants
XOS2U-1
Prototype Vought Model VS.310 powered by a 450 hp (336 kW) Pratt & Whitney R-985-4 engine, one built.
OS2U-1
Initial production variant as the prototype but powered by a 450 hp (336 kW) Pratt & Whitney R-985-48, 54 built.
OS2U-2
Production variant with minor equipment changes and powered by a 450 hp (336 kW) Pratt & Whitney R-985-50, 158 built.
OS2U-3
Based on the OS2U-2 with self-sealing fuel tanks, armour protection, two .30 cal (7.62 mm) guns (dorsal and nose mounted), and able to carry 325 lb (147 kg) of depth charges or 100 lb (45 kg) bombs, powered by a 450 hp (336 kW) Pratt & Whitney R-985-AN2 engine, 1006 built.
OS2U-4
Two aircraft converted with narrow-chord and high-aspect ratio wings, also fitted with full-span flaps.
Not developed.
OS2N-1
Naval Aircraft Factory built OS2U-3 with a 450 hp (336 kW) Pratt & Whitney R-985-AN-2 or -AN-8 engine, 300 built.
Kingfisher I
British designation for the OS2U-3, 100 delivered to the Royal Navy.
Specifications
Crew
2
Length
33 ft 7.2 in (10.241 m)
Wingspan
35 ft 10.7 in (10.940 m)
Height
14 ft 8 in (4.47 m)
Wing area
261.9 sq ft (24.33 m2)
Airfoil
Root
NACA 23015
Tip
NACA 23009
Empty weight
3,335 lb (1,513 kg)
Gross weight
4,980 lb (2,259 kg)
Max take-off weight
6,000 lb (2,722 kg)
Fuel capacity
144 US gal (120 imp gal; 545 l) in an integral wing tank
Powerplant
1 × Pratt & Whitney R-985-AN2 Wasp Junior,
9-cylinder air-cooled radial piston engine,
450 hp (340 kW) for take-off
400 hp (298 kW) at 5,000 ft (1,524 m)
Propellers
2-bladed Hamilton Standard constant-speed propeller
Performance
Maximum speed
171 mph (275 km/h, 149 kn) at 5,000 ft (1,524 m)
Cruise speed
152 mph (245 km/h, 132 kn) with 75% power at 6,000 ft (1,829 m)
Landing speed
55 mph (48 kn; 89 km/h)
Range
908 mi (1,461 km, 789 nmi) with 75% power at 6,000 ft (1,829 m)
Service ceiling
18,200 ft (5,500 m)
Rate of climb
960 ft/min (4.9 m/s) at 4,000 ft (1,219 m)
Wing loading
19 lb/sq ft (93 kg/m2)
Power/mass
0.08 hp/lb (0.13 kW/kg)
Armament
Guns
1 × fixed, forward firing .30 in (7.62 mm)) M1919 Browning machine gun with 500 rounds
&
1x .30 in (7.62 mm) M1919 Browning machine gun with 600 rounds, flexibly mounted for the observer.
