Naval Anti-Aircraft Guns and Gunnery. Norman Friedman
the Devastator to adopt a nose-up attitude which in turn made for slow speed. Typically torpedoes were dropped at an altitude of no more than 100ft and at an air speed of no more than 120mph. These aircraft of VT-6 are shown on board Enterprise shortly before being launched at Midway. Only four of the fourteen launched managed to return to the ship, one being so badly damaged that it had to be thrown overboard. Of a total of forty-three Devastators launched that day, only six made it back to the carriers, two being forced to ditch. The entire squadron launched by Hornet, VT-8, was wiped out. At this time US tactics called for coordinated attacks by dive and torpedo bombers, the idea being that an enemy would be unable to deal with both at the same time. Escorting fighters were to cover the entire attack group. In fact the carrier air groups involved spread out in flight and arrived at the Japanese carriers piecemeal. It happened that the torpedo bombers arrived first, and that they drew the Japanese fighters down to their level to attack them. That left the field open to the dive bombers which soon followed. Had the three types of aircraft arrived together, the Devastator might have emerged from the battle with a far better reputation as the stablemate (with much the same engine) of the Dauntless.
As the British sought to drop torpedoes at higher speeds and from greater altitudes in the 1930s they experimented with means of stabilising them in flight.11 Ultimately they adopted the ‘air rudder’ or air tail they first saw on Norwegian torpedoes. Even then the strength of the torpedo limited drop speed. For example, a bomber approaching at higher than drop altitude had to fly level above the water for a time as it decelerated. By 1942 dive brakes were important because they minimised the level decelerating run above the water. It helped that current British naval torpedo bombers had dive brakes because they had an alternative dive-bombing role (so did the Brigand land-based torpedo bomber then under development). By late 1942 the British wanted their future air-launched torpedo to stand a 300ft drop at 250kts, which was far beyond existing capability.12
The Japanese used a wooden tail frame and special flippers for control in the water. The Germans used a wooden box air tail (three horizontal and two vertical surfaces) and an anti-roll ring using a pair of gyro-controlled fins. The Italian air tail had a longer span and incorporated an anti-roll mechanism using gyro-controlled horizontal rudders (the British monoplane air tail was also gyro-controlled).13
The US Navy seems to have come late to understanding that it needed special fittings. By 1944 its Mk 13 torpedo had a tail ring (shroud ring), a box air tail, and a wooden shroud (the ‘pickle barrel’) around its nose. Given these fittings, torpedoes could be dropped at speeds as great as 400kts and at altitudes above 2000ft.14
Torpedo attack was inherently dangerous because the pilot had to point his aircraft more or less directly at the target, using a torpedo director like that on board a ship to solve the triangle of ship course and speed and torpedo course and speed. In 1934 the Germans demanded that future aerial torpedoes be capable of angling; they may have been the first to do so.15 In 1937 an RAF officer had the same idea, and during the war British aerial torpedoes could angle, the attacker using a Type F sight.16 The Italians seem to have had the same idea. During the war the British initially rejected the US Mk 13 torpedo partly because it lacked this feature.17
The Avenger, the standard US torpedo bomber of the Second World War, arose from a 1939 design competition. Like the Helldiver designed the previous year, the Avenger was designed around the next-generation engine (the 1700hp R-2600). Its most important new feature was that the torpedo was carried internally. Like other torpedo bombers, the Avenger was also seen as a level bomber. The big internal bay could accommodate four 500lb, two 1000lb or one 2000lb bomb. In July 1942 VT-6 experimented with glide bombing. Aircraft dove at a 45 to 60° angle from 6500ft, releasing their bombs at 2500ft. They found that they could place their bombs within 40ft of a moving target. The squadron commander recommended removing all horizontal bombing gear, but BuOrd kept the Norden bombsight because it felt that under some circumstances the earlier technique might still be useful (it turned out that pilots used only the stabilised bombing approach part of the Norden, as an autopilot for use during long flights; in 1944 it was replaced in new production aircraft with an autopilot). Glide bombing did not require the displacement gear (crutch) used by dive bombers to keep their bombs away from their propellers as they dove; at a 60° angle the Avenger would not be struck by its own bomb. However, it had never been stressed for glide/dive bombing, and occasionally Avengers disintegrated during bombing dives. The aircraft could not afford the required 400–600lbs of strengthening, so Grumman added strength at what it estimated were critical points. Accelerometers were installed to indicate to pilots that they were approaching dangerous conditions. The problem was not really solved until March 1945, when Eastern Aircraft (which was producing Avengers under license), redesigned the Avenger using higher-strength alloy and at the same time redesigned the wing hinges. This TBM-4 was scheduled to enter production in August 1945, when the war ended the Avenger programme. These Avengers are shown on 15 March 1950.
There was little chance that a single torpedo bomber could hit a manoeuvring ship. Those on the target ship would see the bombers drop their weapons, and the ship was nearly as fast as the torpedoes. Evasion often succeeded. During the inter-war period, tacticians developed an answer. Aircraft would attack in groups (equivalent to firing a spread of torpedoes from one direction). At least two groups would attack together, from both bows.18 At least in theory this ‘hammerhead’ or ‘hammer and anvil’ approach would ensure that however the target ship manoeuvred, some torpedoes would hit. The faster the target, the more important to ensure that she had little or no manoeuvring time after torpedoes were in the water. That favoured minimum-range attacks at low level. Much depended on the element of surprise. The faster the attacker, the less chance the target had to evade.19 It also helped to put the torpedo into the water as close as possible to the target – but that made the attack more dangerous.
A November 1942 British description of German convoy attack tactics was that aircraft typically approached at about 150ft from astern or on the quarter of a convoy, although occasionally they circled outside gun range to gain better positions. Sometimes they turned towards the convoy individually and then turned away, to draw gunfire. Final approach and release were generally from bows or quarter at 50–80ft, with an outside limit of 180ft. Average dropping range was 1500 yds, with outside limits of 500 and 4000 yds. Attacks on convoys were generally by five or six aircraft, with a maximum of ten. Unescorted ships were generally attacked singly, though at times two or three made concerted attacks. After attacking, aircraft turned away and made off at low altitude. Typically torpedo attacks were made in conjunction with dive- and high-level bombing attacks. At times the Germans (e.g. against Russian convoys) dropped from unusually great heights. In one such attack, against Convoy PQ17 in 1942, torpedoes were seen to bounce more than their own height out of the water.
A Mk 13 torpedo about to be loaded on board a TBM-3 Avenger displays two of the three modifications which made the torpedo effective at high drop speeds and altitudes: the wooden ‘pickle barrel’ around the nose and the box tail. The third new feature, the tail ring, is hidden by the box tail. Unlike the British and the Italians, the US Navy did not adopt long-span air tails because it carried its torpedoes internally (even the Devastator carried its weapon semi-internally). This torpedo was being loaded on board the light carrier San Jacinto during the battle of Leyte Gulf, October 1944. US torpedo tactics changed radically during the war. In 1941 standard practice was to approach a low altitude. During the autumn of 1941 VT-3 developed a new tactic, in which the aircraft approached the target at high altitude, then dove to attack altitude near the target. That improved the pilots’ view of the target, and the high-speed dive to drop altitude improved protection against enemy anti-aircraft fire.
The B5N (‘Kate’) was the standard Japanese carrier torpedo bomber in 1941, the aircraft which attacked Pearl Harbor and which fought at the Coral Sea and at Midway. At the time it was the highest-performing