The Devastator TBD-1 Torpedo-Bomber Part I

Sadly, the Douglas TBD Devastator torpedo bomber will forever be remembered for its tragic involvement during the Battle of Midway and the sacrifice of its crews. Although the aircraft was immediately removed from front-line operations, it should not be forgotten that just five years earlier it was deemed to be the most advanced aircraft of its kind anywhere in the World. As such, it was the US Navy’s first all-metal mount and the first to feature hydraulically-assisted folding wings (for improved carrier storage). It also had the distinction of being first US Navy monoplane to be fielded in quantity on its carriers.

The Douglas TBD Devastator was born out of a US Navy requirement issued in 1934 for a carrier-based torpedo bomber. The Douglas entry was one of the winners of the competition, which also saw orders placed for the Northrop BT-1 (which would evolve into the SBD Dauntless), the Brewster SBA and the Vought SB2U Vindicator.

The Devastator emerged in prototype form as the XTBD-1 to which first flight was recorded on 15 April 1935. Only a single prototype would ever be constructed and evaluated, this being powered by a single Pratt & Whitney XR-1830-60 radial piston engine. The XTBD-1 was accepted into service with the US Navy as the TBD-1 and these entered production with a Pratt & Whitney R-1830-64 series Twin Wasp radial piston engine of 850hp.

The Devastator marked a large number of `firsts’ for the US Navy. It was the first widely used carrier-based monoplane as well as the first all-metal naval aircraft, the first with a totally enclosed cockpit, the first with power-actuated (hydraulically) folding wings and in these respects the TBD was revolutionary. A semi-retractable landing gear was fitted, with the wheels designed to protrude 10in (250mm) below the wings to permit a `wheelsup’ landing which might limit damage to the aircraft. A crew of three was normally carried beneath a large `greenhouse’ canopy almost half the length of the aircraft. The pilot sat in front; a rear gunner/radio operator took the rearmost position, while the bombardier occupied the middle seat. During a bombing run, the bombardier lay prone, sliding into position under the pilot to sight through a window in the bottom of the fuselage, using the Norden Bombsight. Maximum speed was listed at 206mph with a range of 435 miles and a service ceiling of 19,700ft.

In terms of defensive armament, the TBD Devastator was limited. The pilot controlled a single forward-firing 7.62mm general purpose machine gun or 12.7mm heavy machine gun to engage targets ahead of his position, suitable for strafing actions during the bombing run. The rear gunner operated a single 7.62mm machine gun, though this was later upgraded to include a pair of 7.62mm machine guns for slightly improved defence. However, it was in its offensive prowess that a torpedo bomber would ultimately succeed or fail. As such, primary armament for the TBD Devastator family was a single 1,200lb Mark 13 torpedo for attacking ships along their broadsides.

A total of 129 of the type were purchased by the US Navy’s Bureau of Aeronautics (BuAer), and starting from 1937 began to equip the carriers USS Saratoga, Enterprise, Lexington, Wasp, Hornet, Yorktown and Ranger. In pre-war use, TBD units were engaged in training and other operational activities, but the US Navy was already aware that the TBD had become outclassed by fighters and bombers of other nations. Although a replacement was in the works, when the US entered World War 2 the Devastator was still in front-line service with over 100 operational.

With the Japanese attack on Pearl Harbor, the Devastator began to see combat action. Taking part in attacks on Japanese shipping in the Gilbert Islands in February 1942, TBDs from USS Enterprise had little success. This was largely due to problems associated with the Mark 13 torpedo. A delicate weapon, the Mark 13 required the pilot to drop it from no higher than 120ft and no faster than 150mph making the aircraft extremely vulnerable during its attack. Once dropped, the Mark 13 had issues with running too deep or simply failing to explode on impact. For torpedo attacks, the bombardier was typically left on the carrier and the Devastator flew with a crew of two. Additional raids that spring saw TBDs attack Wake and Marcus Islands, as well as targets off New Guinea with mixed results. The highlight of the Devastator’s career came during the Battle of the Coral Sea when the type aided in sinking the light carrier Shoho. Subsequent attacks against the larger Japanese carriers the next day proved fruitless.

At Midway, a total of 41 Devastators, the majority of the type still operational, were launched from Hornet, Enterprise and Yorktown to attack the Japanese fleet. The Devastator proved to be a death trap for its crews. It lacked manoeuvrability, had light defensive weaponry and poor armour relative to the weapons of the time. Moreover, its speed on a glide-bombing approach was a mere 200mph (320km/h), making it easy prey for fighters and defensive guns alike. Tragically, during the battle, only four TBDs made it back to Enterprise, none to Hornet and two to Yorktown, without scoring a torpedo hit. This brought the aircraft’s combat career to an inglorious end.

In the wake of Midway, the US Navy withdrew its remaining TBDs and squadrons transitioned to the newly arriving Avenger. The 39 TBDs remaining in the inventory were assigned to training roles and by 1944 the type was no longer in the US Navy’s inventory.

Reputation I

The reputation of the Douglas TBD Devastator has been somewhat blackened by circumstance. It was a very early monoplane design with ludicrously inadequate power. While its performance was still better than that of the Swordfish, it faced much tougher defenses. Moreover, USN doctrine for its employment was inadequate, in that it did not sufficiently stress delivery of a massed, coordinated attack by dive bombers and torpedo bombers. Finally, it was lumbered with a torpedo which, while fundamentally adequate, was not very effective in 1942 due to several problems.

The Devastator story is limited by the aircraft’s small production run, but within the careers of those 130 airframes that were built is a surprising variety of trivia. For instance, barely half of all TBDs were assigned to Pacific Fleet squadrons between the climactic events at Pearl Harbor and Midway. Of those 76, more than threequarters (59) were lost to combat or operational causes.

For such a well-known aircraft, the TBD logged surprisingly little combat. In fact, the 178 sorties that resulted in enemy contact equate to barely one mission for every aircraft produced. On average, each wartime Devastator assigned to a Pacific Fleet squadron flew 2.2 combat sorties between 1 February and 6 June 1942. The highest individual mission count probably belonged to VT-5’s BuNo 0354, which logged perhaps six combat sorties, including a Japanese submarine contact.

Overall, the five PacFleet TBD units launched 132 aircraft with torpedoes, of which about 95 (72 per cent) dropped their `fish’. However, only ten hits were recorded – 7.5 per cent of the aircraft launched and 10.5 per cent of Mk 13s dropped. By far the most successful mission was the combined Lexington-Yorktown strike of 7 May, when full co-ordination with SBDs saw 36.8 per cent hits from 86 per cent of the aircraft launched.

At Midway, VT-3 and -6 each got about 42 per cent of their TBDs to the drop point despite severe opposition from fighters and anti-aircraft gunfire. Torpedo Eight, poorly positioned from the start, managed just one known drop from 15 TBDs. The overall performance figures were further skewed when VT-6’s three pilots followed orders and jettisoned torpedoes rather than attack the cruisers Mogami and Mikuma on 6 June.

Although primarily a torpedo aircraft, the TBD flew nearly one-quarter of its sorties with bombs. A further five sorties resulting in contact with the enemy were made with depth charges. The 112 torpedo sorties resulted in four Mk 13s jettisoned or failed to release. Thus, 108 effective sorties resulted in about 95 torpedoes dropped, with ten hits on four ships, of which two were sunk.

The Japanese Navy was disappointed with the B2M design so it turned to its own resources in designing a replacement. The First Naval Air Technical Arsenal’s engineers, led by Suzuki Tamefumi, designed the three-seater biplane Type 92 Carrier Attack Bomber (also known as the B3Y1) that entered service in 1933. Wing structure was of wood and the fuselage structure of welded steel tube. Powered by a 750-horespower Type 91 water-cooled engine, the B3Y1 had a top speed of 136 miles per hour and a range of 500 miles. This model’s engine also proved unreliable and the performance, especially in range, was unsatisfactory, so a new design was prepared by Kawasaki Sanae at the First Naval Air Technical Arsenal that entered service in early 1937 as the Type 96 Carrier Attack Bomber (or B4Y1). The new design married the wings of the successful E7K1 shipboard floatplane to a new fuselage and tail unit to produce a three-seater biplane with all-metal structure. Powered by an 840-horsepower Nakajima Hikari radial engine, it had a maximum speed of 173 miles per hour and a range of 978 miles, both markedly superior to any of its precursors or any similar machine in service, although this superiority was cut short by the introduction of Douglas’s monoplane TBD-1 later in 1937.

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