1937 saw the United States Navy looking for a replacement aircraft for its Curtiss SOC Seagull series of biplane floatplane aircraft. The requirement was circulated to US manufacturers in early 1933, resulting in proposals from Curtiss, Douglas and Vought, but it was the XO3C-1 prototype, company-designated Curtiss Model 71, ordered on 19 June 1933 and first flown in April 1934, which was ordered into production as the SOC-1 (Model 71A). This changed official designation reflected the combination of scout and observation roles.
When first flown the prototype was equipped with amphibious landing gear, twin main wheels being incorporated in the central float. However, standard production aircraft were built as floatplanes, with non-retractable tailwheel landing gear optional; in any event they were easily convertible from one configuration to the other. Construction was mixed, with the foldable wings and tail unit of light alloy, a welded steel-tube fuselage structure, and a mixture of light alloy and fabric covering. The pilot and gunner/observer were accommodated in tandem cockpits, enclosed by a continuous transparent canopy with sliding sections for access. To provide a maximum field of fire for the flexibly-mounted gun in the rear cockpit, the turtleback could be retracted.
Deliveries of the first SOC-1 production aircraft began on 12 November 1935. These were powered by Pratt & Whitney R-1340 Wasp engines, and the first squadrons to become fully equipped with the type comprised Scouting Squadrons VS-5B/ -6B/ -9S/ -10S/ -11S. Production of 135 SOC-1s was followed by 40 examples of the SOC-2 (Model 71B) with wheeled landing gear, detail improvements and R-1340-22 Wasp engines. A total of 83 examples of the SOC-3 (Model 71E) was built, these being generally similar to the SOC-1. SOC-2s and SOC-3s, after modification to install arrester gear during 1942, became redesignated SOC-2A and SOC-3A respectively. Curtiss also built three aircraft virtually the same as the SOC-3 for service with the US Coast Guard: these SOC-4 (Model 71F) aircraft were acquired by the US Navy in 1942 and equipped with arrester gear to bring them up to SOC-3A standard. In addition to the SOC Seagulls built by Curtiss, 44 were produced by the Naval Aircraft Factory at Philadelphia, Pennsylvania. Basically the same as the Curtiss-built SOC-3, these were designated SON-1 or, if fitted with arrester gear, SON-1A.
Following termination of SOC production in early 1938, Curtiss became involved in the development and manufacture of a successor, designated SO3C Seamew. However, when the operational performance of the Seamew proved unsatisfactory it was withdrawn from first-line service; all available SOCs then reverted to operational status, continuing to fulfil their appointed role until the end of the war.

Curtiss SOC-1 Seagull
Engine: 1 x Pratt & Whitney R-1340-18 Wasp, 447kW / 600 horsepower.
Wingspan: 10.97 m / 35 ft 12 in
Wing area: 31.77 sq.m / 341.97 sq ft
Length: 8.08 m / 26 ft 6 in
Height: 4.50 m / 14 ft 9 in
Maximum Speed: 157mph (253kmh; 137kts)
Cruise speed: 214 km/h / 133 mph
Maximum Range: 954miles (1,535km)
Rate-of-Climb: 1,000ft/min (305m/min)
Service Ceiling: 14,895ft (4,540m)
Armament:
1 x 0.30 cal (7.62mm) fixed, forward-firing machine gun.
1 x 0.30 cal (7.62mm) trainable machine gun in flexible mount in rear cockpit.
2 x 100lb bombs held underwing.
Accommodation: 2
Hardpoints: 2
Empty Weight: 3,508lbs (1,591kg)
Maximum Take-Off Weight: 5,437lbs (2,466kg)

Among the evaluations of the Model 73 XF12C-1 was a dive bombing test in September of 1934 that resulted in a failure of the parasol monoplane wing assembly. Though the pilot and machine were wholly spared, the prototype was nonetheless heavily damaged. Testing had shown that the parasol wing assembly was generally unfit for the stresses of what the new aircraft would be called upon to achieve. As a result, the US Navy ordered a new prototype to fall in line with stricter requirements. Curtiss once again delivered an answer, this time the Model 77, to which the US Navy affixed the designation of XSBC-2.
With a biplane wing, Wright R-1510-12 Whirlwind radial and three-bladed propeller, the first flight of the XSBC-2 was on December 9th, 1935. In March of 1936, a Pratt & Whitney R-1535-82 Twin Wasp Junior radial piston engine was fitted to the airframe, resulting in the revised company designation of “Model 77A” and the revised US Navy designation of “XSBC-3”.

The United States Navy contracted the company on August 29th, 1936, to deliver 83 SBC-3 “Helldiver” production aircraft. Initial deliveries occurred on July 17th, 1937 to Squadron VS-5 of the carrier USS Yorktown. By all reports, the SBC proved a rather pleasant airframe to control, however, the constantly changing world of technology in the late 1930s solidified the SBC as an out-of-date design, forcing the fighter to undertake second-line duties in the training of upcoming airmen out of Florida. The biplane dive-bomber soldiered on for a time longer with both US Navy and Marine Corps branches aboard such active carriers as the USS Hornet. The SBC Helldiver would lead a short active life with the US Navy and officially meet her end by October of 1944, being replaced by much-improved and modern types.
The SBC Helldiver was the last biplane aircraft to be purchased by the United States Navy.
The design was characterized by its staggered, uneven span biplane wing arrangement with outboard struts, cabling and skeletal inboard struts holding the wings in place. The fuselage was metal clad. The undercarriage, while retractable, still sported its visible wheels tucked in alongside each forward fuselage side. The crew of two sat in tandem under a glazed canopy. The cockpit was set at amidships, aft of the both wing assemblies.

Curtiss worked on improving the base SBC-3 series design and set one airframe aside for testing. The resulting tests yielded the new Model 77B, US Navy designation SBC-4. Fitted with a more powerful Wright R-1820-22 Cyclone 9 series radial piston engine of 850 horsepower, the US Navy signed a production contract on 5 January 1938 for 174 examples, 1938 with the first deliveries beginning in March of 1939.

France desperately attempted to counter the German advance by quickly improving their military inventory, even contracting American aircraft firms for whatever they could make available. In early 1940, the United States Navy rerouted some 50 of its actively serving SBC-4 Helldiver aircraft to the French Navy with a total of 90 on order for France. Aircraft were repainted via French standards and the 0.30 caliber armament was upgraded to a more potent pairing of 2 x 0.50 caliber. All American instruments were replaced by French-labeled ones and Curtiss employees would be involved in delivering the aircraft to the French carrier Bearn by way of Nova Scotia. The Bearn eventually accepted the aircraft and made her way across the Atlantic back to France.
This delivery would arrive too late to be of much use in combat and the nation of France eventually capitulated. The Bearn moved south to the Caribbean island of Martinique where the remaining forty-nine SBC-4s fell victim to the corrosive effects of the tropical environment, destined never to fight.
At least five SBC-4s were accepted into the inventory of the Royal Air Force under the designation of Curtiss “Cleveland” Mk.I and generally used to train ground personnel out of Little Rissington, UK.

The US Navy secured a revised SBC-4 model with the addition of self-sealing fuel tanks, and a total of 175 were built by April 1940, of which 117 were in service by December 1941.
By the time the USA became involved in World War II, the SBC-3s had become obsolescent, but SBC-4s were then in service with US Navy Squadrons VB-8 and VS-8 on board the USS Hornet and with US Marine Squadron VMO-151.
Overall production for the series was 308 aircraft.

XSBC 3
Engine: 825 hp Pratt & Whitney R¬-1535 82 Twin Wasp Junior
Armament: 2 x 0.30 in (7.62 mm), 227 kg (500 lb) bomb

XSBC-4
Engine: Wright R 1820 22 Cyclone

Curtiss SBC-4 Helldiver
Engine: 1 x Wright R-1820-34 Cyclone radial, 671kW / 950 horsepower.
Wingspan: 10.36 m / 34 ft 0 in
Length: 8.57 m / 28 ft 1 in
Height: 3.17 m / 10 ft 5 in
Wing area: 29.45 sq.m / 317.00 sq ft
Take-off weight: 3211 kg / 7079 lb
Empty weight: 2065 kg / 4553 lb
Max. Speed: 377 km/h / 234 mph
Cruise speed: 282 km/h / 175 mph
Service Ceiling: 7315 m / 24000 ft
Rate-of-Climb: 1,630ft/min (497m/min)
Range w/max.payload: 652 km / 405 miles
Maximum Range: 590miles (950km)
Armament:
1 x 7.62mm forward-fixed M1919 Browning machine gun, 1 x 454 kg / 1,000lb bomb
1 x 7.62mm trainable machine gun in rear cockpit.
Crew: 2
Hardpoints: 1