The Douglas SBD Dauntless was the main US Navy dive bomber during the crucial years of the Second World War. It played a crucial part in the battle of Midway, accounting for four Japanese fleet carriers in a single day.
The SBD was a development of the Northrop BT-1, a dive bomber that had entered service in 1938. The BT-1 had not been a great success, and Northrop had devoted a great deal of attention to improving the design. The prototype XBT-2 underwent testing in a full sized wind tunnel at Langley, Virginia, followed by six months of constant tests and modifications.
By this point, Northrop was a fully owned subsidiary of Douglas. John Northrop left during 1939 to found his own company (Northrop Aircraft Inc.), and the XBT-2 was redesignated as the XSBD-1. The change from Bomber to Scout Bomber was the result of a Navy decision to reserve the Bomber designation for multi-engined aircraft.
The new aircraft was aerodynamically cleaner than the BT-1. Most obvious was the change from the partially retracted landing gear of the BT-1 to fully retracted landing gear. Like the BT-1 it was a low winged monoplane of all metal construction apart from the fabric covered control surfaces. The prototype and the dash-one was powered by a 1,000hp Wright XR-1820-32 Cyclone radial engine.
The SBD-1 could carry a single 1,600lb bomb under the centreline, and a 100lb bomb or a depth charge under each wing. It carried two .50 calibre machine guns mounted in the engine cowlings and one .30 calibre machine gun in the radio operations position. The crew of two sat under a greenhouse canopy in the single cockpit.
The SPD-1 entered service with the Marines, in June 1940. One Dauntless unit, Marine Air Group 21, was based on Hawaii and lost seventeen aircraft destroyed and twelve damaged during the Japanese attack on Pearl Harbor, losing its entire strength of aircraft in one day.
The SPD-2 had just entered carrier service in December 1941. On 7 December eighteen SBD-2s from the USS Enterprise were caught up in the attack on Pearl Harbor having been dispatched ahead of the carrier. Seven of the eighteen were lost, but did claim two Japanese aircraft destroyed, the type’s first victories of the war. Three days later an SBD-2 of the USS Enterprise scored the type’s first naval victory, sinking a Japanese submarine during the hunt for the Japanese fleet that had launched the Pearl Harbor attack.
During the first few months of 1942, the US Navy’s carriers undertook a series of raids on Japanese held positions in the Pacific. The SBD’s first significant contribution came during the battle of the Coral Sea (May 1942), where the type was given credit for sinking one Japanese carrier, the Shoho and disabling the Shokaku. The battle stopped a Japanese attempt to capture Port Moresby, and secured the safety of Australia.
The SPD achieved its greatest success at the battle of Midway. The crucial moment of the battle came between 9.00 and 10.30 AM on the morning of 4 June. First a force of TBD Devastator torpedo bombers made an attack on the main force of three Japanese carriers. They were intercepted by Zero fighters, and massacred. The Devastator was soon taken out of the front line.
The disaster that befell the Devastators gave the Dauntless its chance. Just as the torpedo bomber attack ended, the dive bombers arrived over the Japanese fleet. The Zeros were horribly out of position, down at sea level. This gave the SPD pilots the chance to make a virtually unopposed on three Japanese fleet carriers. They took their chance, and within minutes the Akagi, Kaga and Soryu were on fire and sinking. A fourth carrier, the Hiryu, had been sailing at a distance from the main fleet, and survived the carnage of the morning. Aircraft from the Hiryu inflicted critical damage on the Yorktown, which eventually sank, but at 15.00 the Hiryu was herself critically damaged by a force of Dauntlesses. The next day she had to be scuttled.
The Dauntless was the most successful naval aircraft of 1942, sinking more Japanese ships than every other type combined. It continued as a front line dive bomber throughout 1943, taking part in all of the main carrier battles of the Pacific War as well as equipping an increasing number of ground based squadrons. Finally, in 1944 it was replaced by the Curtis SB2C Helldiver.
Fifty seven aircraft were delivered as SBD-1s. They were followed by 87 SBD-2s, which carried extra fuel, increasing the range of the aircraft to 1200 nautical miles.
The SBD-3 appeared in early 1942. It was originally developed for the French, but was retained by the navy after the collapse of France. The dash three was the first truly combat ready version of the aircraft, featuring self-sealing fuel tanks, crew armour and an armoured windscreen, all features that had been revealed as necessary by the fighting over Europe. The SPD-3 was powered by an R-1820-52 providing the same horsepower as the earlier engine. Some 584 SBD-3s were produced.
The SBD-4 was very similar to the SPD-3. It carried twin .30 calibre machine guns in the radio operations position, a feature introduced during the production run of the SBD-3. Otherwise the main change was the upgrading of the electrical system from 12 to 24 volts, to cope with the ever increasing complexity of electrical systems needed in combat aircraft. Seven hundred and eighty SBD-4s were produced between October 1942 and April 1943.
The SPD-5 was the last version to see significant service from aircraft carriers. 2,965 aircraft were produced between February 1943 and April 1944. The main change was the use of a more powerful engine – the 1,200 hp R-1820-60 Cyclone – which made up for the ever increasing weight of equipment carried.
The final variant, the SPD-6, appeared in March 1944, by which time it was approaching obsolescence. It was powered by an even more powerful R-1820-66 Cyclone, giving 1,350 hp, which increased the top speed of the aircraft to 262 mph. However, by now the next generation of naval aircraft had finally appeared, and so the 450 SPD-6s spent most of their careers outside the combat zone.
Despite a reputation for being somewhat sluggish, the Dauntless was undoubtedly the most import naval bomber of the Second World War. Its record against Japanese shipped earned it the nickname “Slow But Deadly”
Engine: Wright R-1820-66 Cyclone
Span: 41 ft 6 in
Length: 33 ft 0 in
Max Speed: 255 mph at 14,000 feet
Cruising Speed: 185 mph
Ceiling: 25,200 ft
Range: 733 miles as scout bomber
Armament: Two forward firing .50 calibre machine guns in cowling, two .30 calibre machine guns in rear cockpit
Bomb load: One 1,600lb bomb under fuselage, up to 650lbs of bombs beneath the wings.