Douglas SBD Dauntless

During great Battle of Midway US naval aircraft, spearheaded by Dauntless dive-bombers, destroyed four Japanese carriers, a cruiser and 250 aircraft, for the loss of one US carrier, a destroyer and 150 aircraft. This battle turned the tide of war against the Japanese in the Pacific.


The Dauntless was the standard shipborne dive-bomber of the US Navy from mid-1940 until November 1943, when the first Curtiss Helldivers arrived to replace it. The SBD was gradually phased out during 1944, and the 20 June 1944 strike against the Japanese Mobile Fleet in the Battle of the Philippine Sea was therefore its last major action as a carrier-borne aircraft.
In 1942-43, at the Battle of the Coral Sea, in the bitter Guadalcanal campaign and most of all in the decisive Battle of Midway, the Dauntless did more than any other aircraft to turn the tide of the Pacific War. At Midway on 4 June 1942 it wrecked all four Japanese carriers, and later in the battle sank a heavy cruiser and severely damaged another. From 1942 through to 1945, in addition to its shipboard service, the SBD saw intensive use with the US Marine Corps, flying from island bases.

In the Guadalcanal Campaign the Dauntless - operating from US carriers and from Henderson Field on the island of Guadalcanal itself - took a huge toll of Japanese shipping. SBDs sank the carrier Ryujo in the battle of the Eastern Solomons, and damaged three other carriers in the battles of Eastern Solomons and Santa Cruz. In the epic Naval Battle of Guadalcanal, 12-15 November 1942, SBDs sank the heavy cruiser Kinugasa and, supported by TBD Avengers, sank nine transports.

The Dauntless was older and slower than its Japanese opposite number, the Aichi D3A2 "Val" - but the SBD was far more resistant to battle damage, and its flying qualities perfectly suited it to its role. In particular - as its pilots testified - it was very steady in a dive.

Throughout the Pacific War, it remained the principal shipboard dive bomber available to the US Navy; it was the only US aircraft to participate in all five naval engagements fought exclusively between carriers, and deficiencies notwithstanding, it emerged with an almost legendary reputation as the most successful shipboard dive bomber of all time-albeit success that perhaps owed more to the crews that flew it in truly dauntless fashion than to the intrinsic qualities of the airplane itself. When the more modern and powerful Helldiver went into action alongside the SBD it was soon realized - particularly at the Battle of the Philippine Sea - that the new aircraft was inferior to the Dauntless. But the Helldiver was already in large-scale production and it was too late to reverse the decision that it should supplant the Dauntless in shipboard service. The SBD nonetheless continued to be used effectively by the Marine Corps right up to the end of hostilities in August 1945, notably in the Philippines campaign.

 

The genesis of the Dauntless had been complex; its gestation had been protracted. Its progenitors had been the Alpha, Beta and Gamma mail planes of the late 'twenties and early 'thirties, and its true sire had been the Northrop XBT-1, which, embodying many of the structural techniques of the commercial models, had been created by Edward A Heinemann under the aegis of John K Northrop. First flown on 19 August 1935, the XBT-l evinced sufficient promise to warrant a contract a year later, on 18 September 1936, for 54 production BT-ls, and these were to serve primarily with VS-S aboard USS Yorktown and VB-6 aboard USS Enterprise.

The BT-1 revealed few endearing characteristics; some aspects of its handling were reputedly little short of vicious, particularly at low airspeeds when lateral stability was exceptionally poor and the rudder ineffective, a torque roll as likely as not accompanying any application of power during a deck approach and several fatal crashes ensuing. On the surface, the BT-1 provided a poor basis for further development. Indeed, it is likely that evolution of the basic design would have ended with delivery of the last of the production airplanes but for an early amendment to the original contract authorizing completion of one BT-1 as the XBT-2 with an inward-folding fully-retractable undercarriage in place of the aft-folding semi-retractable and faired arrangement. This change, in itself hardly likely to translate sow's ear into silk purse, was fortuitously, to set in train an incremental modification program destined to recast the XBT-2 as the true forerunner of the Dauntless. Right testing of the XBT-2 was initiated on 22 April 1938, revealing no significant advance over the BT-1, and had barely got under way when this prototype suffered quite extensive damage as a result of a wheels-up landing. Ed Heinemann seized the opportunity presented by the return of the aircraft to the factory for repair to eradicate one of the more serious shortcomings of the XST-2, its inadequate power, seeking and obtaining authority, on 21 June 1938, to replace the Twin Wasp Junior engine and two-blade controllable-pitch propeller with a more powerful. Cyclone and a three-blade constant-speed propeller. This change produced a noteworthy improvement in speed performance but exacerbated some of the least desirable handling characteristics of the aircraft. Fixed slots were introduced on the wing to maintain aileron control at low speeds; a dozen different sets of ailerons were tested and no fewer than 21 different tail surface combinations were evaluated. The end product was an airplane possessing eminently more satisfactory handling characteristics; a high standard of maneuverability throughout the speed range, light control responses and a docile attitude towards carrier operation. In short, the prototype of the Dauntless.

The Northrop Corporation, which had been formed in January 1932 with the Douglas Aircraft Company holding 51 per cent of the stock, had meanwhile been dissolved and had become Douglas's El Segundo Division, and when a production contract for the reworked dive bomber was placed on 8 April 1939, this change and the adoption of the all embracing classification of scout-bomber were reflected by the assignment of the designation SBD, indicating Scout Bomber Douglas.

The first production Dauntless, an SSD-1, was flown on 1 May 1940 and delivered to the US Navy on 6 September. This was almost identical to the definitive XBT-2, apart from the introduction of two 15 US gal (56,81) center section auxiliary tanks boosting total capacity to 210 US gal (795 I) and the installation of a production series Wright Cyclone engine, the R-1820-32 affording 1,000 hp at 2,350 rpm for take-off and having a normal maximum rating of 950 hp at 2,300 rpm from sea level to 5,000 ft (1 525 in).

The SBD-1 undeniably offered a capability advance over the equipment that it succeeded, but such had been the tempo of combat aircraft development during its gestation that it no longer met US Navy requirements; the service was by now relying on the Curtiss SB2C for the quantum advance that it sought. Not that the Douglas and Northrop fell short of its guaranteed performance, but the Curtiss, ordered a year earlier, on 15 May 1939, bid fair to provide 50 knots (93 km/h) more speed and tote twice the bomb load over substantially greater ranges. Thus, before its introduction to the carriers, the Dauntless was seen as being underpowered, with performance and load-carrying capabilities well below those foreseen to be demanded by the Pacific conflict now considered inevitable in most US Navy circles. It was already obsolescent.

Army version of the SBD Dauntless dive-bomber. The USAF used 948 of the 5937 Dauntlesses built. The A-24, A-24A and A-24B corresponded to the SBD-3, SBD-4, and SBD-5.

The structure of the Dauntless was extremely strong but also rather heavy, and with the chosen engine its power-to- weight ratio inevitably resulted in a rather sluggish performance, especially with a worthwhile external load. The wing, which employed the "multi-cellular" system of construction originated by John Northrop, was a duraluminium structure consisting of several false spars and plate ribs with 'top hat" section stringers supporting the flush-riveted dural sheet stressed skinning. The center section was rectangular with the outer sections tapered in chord and thickness, but an odd feature of the wing for a shipboard airplane of the era of the SBD-1, was the lack of any provision for folding, the outer panels being rigidly affixed to the center section by attaching angles and double plates, with characteristic fairing bulges covering the joints. Fixed "letter-box" slots were inserted in the wings ahead of the metal-framed fabric-skinned ailerons, and the remainder of the wing trailing edges were occupied by combined spoilers and flaps, both upper and lower halves of these split surfaces being hinged. These were hydraulically operated, and the lower halves, which continued across the center section, served in orthodox fashion for take-off and landing, the upper and lower halves being opened in unison to brake terminal velocity in a dive. These spoiler-flaps were extensively perforated with 175-in (4,45-cm) holes - an NACA Innovation - to inhibit tail buffeting.

The oval-section duralumin semi-monocoque fuselage was built up of channel-section transverse frames with extruded stringers and dural skinning. For ease of manufacture, the fuselage was split longitudinally, the upper half in one piece and the lower in three, plus a tail cone, the forward lower section including the built-in center section. Aft of the rear cockpit, sheet metal bulkheads divided the rear fuselage into a series of watertight compartments. The tail fin was built integral with the fuselage and, like the tailplane, was of metal stressed-skin construction, the rudder and elevators being metal framed and fabric skinned.

The main oleo shock-absorber legs were cantilever units with stay struts mounted on knuckle forgings which rotated on retraction, the legs hinging at the extremities of the center section and being raised hydraulically inwards, the wheels lying flat in wells forward of the main spar. The Cyclone engine was carried by a tubular steel mount and enclosed by an NACA cowling with controllable exit louvers on top of the cowling. A Hamilton Standard fully-feathering propeller was fitted, and all fuel was accommodated by unprotected center section tanks and the previously mentioned auxiliary tanks.

The pilot sat fairly high in the fuselage beneath a sliding section of a continuous "greenhouse" canopy and was provided with a pair of 0-5-in (12,7-mm) Browning machine guns, the breeches of which protruded into the cockpit where they could be cleared and cocked in the event of a stoppage. Each gun was provided with 360 rounds stowed in containers behind the fireproof bulkhead carrying the engine mount. The observer-gunner had a single drum-fed 0-3-in (7,62mm) weapon with 600 rounds and which, when stowed, was accommodated by a compartment in the top of the fuselage which was closed flush by folding doors. The pilot was provided with a three-power telescopic sight which was intended for use both in aerial gunnery and dive bombing, and a duplicate set of controls was included in the rear cockpit for emergency use. A cradle beneath the fuselage could carry a single 500-lb (226,8-kg), 1,000-lb (453,59-kg) or 1,600-lb (725,7-kg) bomb and swung forward and downward to ensure that its load cleared the propeller disc. A fixed rack for one 100-lb (45,36-kg) bomb was located under each Outer wing section.

The US Navy did not deem it advisable to deploy SBD-ls aboard its carriers, primarily because of their inadequate range, work already being in hand at El Segundo that was to increase internal fuel capacity by almost 50 per cent and a series of contractual changes allowing for the revised fuel system to be introduced with the 58th production airplane

Whereas the SBD-1 carried all fuel in welded center section tanks comprising two 90 US gal (341 1) main tanks and two 15 eliminated the auxiliary tanks and supplemented the two center section main tanks with two 65 US gal (246 I) tanks in the outer wing panels to raise maximum internal capacity to 310 US gal (1 1731). However, it was only practical to use all the additional capacity for ferrying, the maximum ferry range being raised from 1,060 nm (1 964 kin) at 123 knots (229 km/h) to 1,468 nm (2 721 kin) at 128 knots (237km/h). For operational missions, internal fuel was effectively limited to 260 US gal (9841) with which range with, for example, a single 500-lb (226,8-kg) bomb was increased by 338 nm (626 kin) to 1,172 nm (2 172 kin). This quite considerable boost in range capability was not, of course, achieved without exacting penalties on take-off distance, climb rate, service ceiling and stalling speed, and, furthermore, other reasons dictated removal of one of the 05-in (12,7-mm) cowl guns. The SBD-2 did introduce an automatic pilot, however. If unusual in so small an airplane, this piece of equipment was very desirable in view of the reconnaissance ranges of which the Dauntless was now capable.

Like the SBD-1,the SBD-2 as initially delivered to the US Navy was hardly to be considered combat worthy in that it lacked a bullet-proof windscreen, any form of armour protection or self-sealing fuel tanks - in the event, some SBD-2s were later to be fitted with aluminum alloy fuel tanks with self-sealing liners reducing total internal capacity to 260 US gal (984 1). By the time that the Japanese struck at Pearl Harbor, three US Navy squadrons, VS-6 and VB-6 aboard Enterprise and VB-2 aboard Lexington, were mounted on SBD-2 Dauntlesses, combat worthy or no, and deliveries of what can be considered the first fully combat worthy Dauntless, the SBD-3 had, in fact, begun nine months before hostilities started in the Pacific.
It was the SBD-3 that was to become the US Navy's true workhorse of the Pacific War and to carry much of the burden of that service's offensive operations until 1943, when the marginally more efficacious SBD-5 was to become available. Indeed, but for the availability of the SBD-3, the conflict in the Pacific might well have pursued a very different course during its first critical year. The SBD-3 was dubbed somewhat sardonically the Speedy Three", a caustically humorous allusion to the fact that it was anything but speedy, having taken on weight without any commensurate increase in power and all aspects of its performance suffering in consequence, although, in truth, only nominally so.
Among the best features of the Dauntless were its landing characteristics which were very easy. View for deck landing was good, and the controls crisp and effective, the flaps giving adequate drag to require a reasonable increment of engine power, which, when cut, gave a very definite deceleration, although the undercarriage was a little on the bouncy side.
The SHD-5 was not quite the end of Dauntless evolution as, somewhat belatedly, a still more powerful version of the Cyclone was applied, the R-1820-66 offering 1,350 hp at 2,700 rpm for take-off and military ratings of 1,300 hp at 2,600 rpm from sea level to 4,000 ft (1 220 m) and 1,000 hp from 11,300 to 17,500 ft (3445 to 5335 in). This power plant was installed in the final Dauntless production model, the SBD-6, but the heyday of the veteran dive bomber had long since passed and, as a result of contractual cutbacks, only 450 production SBD-6s were completed, these, with non-metallic self-sealing tanks of 284 US gal (1 075 I) total capacity and ASV radar, were delivered between March and July 1944 to bring Dauntless production to an end.

 


Douglas SBD-6 Dauntless
Dimensions:
Wing span: 41 ft 6 in (12.65 m)
Length: 33 ft 0 in (10.06 m)
Height: 12 ft 11 in (3.94 m)
Weights:
Empty: 6,535 lb (2,964 kg)
Max T/O: 9,519 lb (4,318 kg)
Performance:
Maximum Speed: 255 mph (410 km/h) @ 14,000 ft (4,265 m)
Service Ceiling: 25,200 ft (7,680 m)
Range: 773 miles (1,244 km)
Powerplant:
One Wright R-1820-66 Cyclone , 1,350 hp (1007 kw),
9-cylinder radial, air cooled engine.
Armament:
Two forward firing .50 inch (12.7 mm) machine guns
and two 0.30 inch (7.62 mm) machine guns on flexible mounts.
Fuselage mount for up to 1,600 lbs (726 kg) of bombs plus,
up to a total of 650 lbs (295 kg) of bombs carried on the wings.