The Vought SB2U Vindicator is an American carrier-based dive bomber developed for the United States Navy in the 1930s, the first monoplane in this role.
Vindicators still remained in service at the time of the Battle of Midway, but by 1943, all had been withdrawn to training units.
It was known as the Chesapeake in Royal Navy service.
In 1934, the United States Navy issued a requirement for a new Scout Bomber for carrier use and received proposals from six manufacturers.
The specification was issued in two parts, one for a monoplane, and one for a biplane.
Vought submitted designs in both categories, which would become the XSB2U-1 and XSB3U-1 respectively.
The biplane was considered alongside the monoplane design as a “hedge” against the U.S. Navy’s reluctance to pursue the modern configuration.
The XSB2U-1 was of conventional low-wing monoplane configuration with a retractable conventional tailwheel landing gear, the pilot and tail gunner being seated in tandem under a long greenhouse-style canopy.
The fuselage was of steel tube construction, covered with aluminium panels from the nose to the rear cockpit with a fabric-covered rear fuselage, while the folding cantilever wing was of all-metal construction.
A Pratt & Whitney R-1535 Twin-Wasp Junior radial engine drove a two-blade constant-speed propeller, which was intended to act as a dive brake during a dive-bombing attack.
The use of propeller braking was not entirely successful, and in practice US Navy Vindicators lowered the aircraft’s undercarriage to act as a speed brake and dived at shallower angles.
A single 1,000 lb (450 kg) bomb could be carried on a swinging trapeze to allow it to clear the propeller in a steep dive, while further bombs could be carried under the wings to give a maximum bombload of 1,500 lb (680 kg).
The SB2U was evaluated against the Brewster XSBA-1, Curtiss XSBC-3, Great Lakes XB2G-1, Grumman XSBF-1 and Northrop XBT-1.
All but the Great Lakes and Grumman submissions were ordered into production.
Designated XSB2U-1, one prototype was ordered on 15 October 1934 and was delivered on 15 April 1936. Accepted for operational evaluation on 2 July 1936, the prototype XSB2U-1, BuNo 9725, crashed on 20 August 1936.
Its successful completion of trials led to further orders, with 56 SB2U-1s ordered on 26 October 1936, and a further 58 of a slightly modified version, the SB2U-2, on 6 October 1938.
The SB2U-3 was a more heavily modified version, intended as a long-range scout bomber, capable of being fitted with a conventional wheeled undercarriage, for operations from aircraft carriers or land airbases, or with floats.
To give the required increased range, the fuselage fuel tank fitted to the SB2U-1 and -2 was supplemented by integral wing tanks, while the aircraft’s tail had an increased span.
The prototype XSB2U-3, converted from the last SB2U-1, flew in February 1939, and after testing as both a landplane and floatplane, 57 SB2U-3s were ordered on 25 September 1939, mainly for the US Marine Corps.
The SB2U is prominently featured in the 1941 film Dive Bomber.
There were 260 examples of all Vindicator variants produced, and a single example is preserved at the National Naval Aviation Museum at NAS Pensacola, Florida.
Variants
XSB2U-1
Single prototype, powered by a 750hp R-1535-78 engine.
SB2U-1
Initial production version powered by an 825hp R-1535-96 engine, 54 built.
SB2U-2
Same as SB2U-1 but with minor equipment changed, 58 built.
XSB2U-3
Single prototype of the extended-range version with twin floats, converted from the SB2U-1.
SB2U-3
Similar to the SB2U-2 but fitted with an 825hp R-1535-102 engine, crew armour and two 0.5in guns, 57 built.
V-156F-3
Export version for the French Navy, 40 built.
V-156B-1
Export version similar to the SB2U-3 and powered by a 750hp R-1535-SB4-G engine for the British Royal Navy. Designated Chesapeake Mk.I, 50 built.
V-167
The V-156 company demonstrator was fitted with a more powerful Pratt & Whitney R-1830 engine and redesignated V-167.
It remained a one-off.
Specifications
Crew
2
Length
33 ft 11+3⁄4 in (10.357 m)
Wingspan
41 ft 10+7⁄8 in (12.773 m)
Height
14 ft 3 in (4.34 m) (tail down, propeller vertical)
Wing area
305.3 sq ft (28.36 m2)
Empty weight
5,634 lb (2,556 kg)
Gross weight
7,474 lb (3,390 kg)
Max take-off weight
9,421 lb (4,273 kg)
Fuel capacity
370 US gal (310 imp gal; 1,400 L) internal fuel
Powerplant
1 × Pratt & Whitney R-1535-02 Twin Wasp Jr 14-cylinder two-row air-cooled radial engine,
825 hp (615 kW) (take-off power): 750 hp (560 kW)
(Continuous power)
Propellers
2-bladed Hamilton Standard constant-speed propeller, 11 ft 0 in (3.35 m) diameter
Performance
Maximum speed
211 kn (243 mph, 391 km/h) at 9,500 ft (2,900 m)
Cruise speed
132 kn (152 mph, 245 km/h) (range cruise)
Range
970 nmi (1,120 mi, 1,800 km) (main and wing centre-section tanks only), 1,000 lb (450 kg) bomb load
Ferry range
2,130 nmi (2,450 mi, 3,940 km)
(Max internal and external fuel)
Service ceiling
23,600 ft (7,200 m)
Rate of climb
1,070 ft/min (5.4 m/s)
Time to altitude
17.5 min to 15,000 ft (4,600 m)
Armament
Guns
1 × forward firing 0.50 in (12.7 mm) M2 Browning machine gun in starboard wing
1 × 0.50 in (12.7 mm) machine gun in flexible mount in rear cockpit
Bombs
1 × 1,000 lb (450 kg) or 500 pounds (230 kg) bomb under fuselage
2 × 100 lb (45 kg) and 8 × 30 lb (14 kg) bombs under wings
