Torpedo: The Complete History of the World's Most Revolutionary Naval Weapon

The final development of the Great War was the specially-designed Sopwith Cuckoo (so named for the bird which lays its eggs in others’ nests), which, however, arrived too late to see active service. It was a single-seater, to allow for the weight of the torpedo. The pilot was thus deprived of the help of an observer, who was useful in judging the height above the water in order to launch at the exact correct altitude to avoid damaging the torpedo. He also lacked a rear gunner to protect his back during the low, slow approach run on a fixed line. This was just acceptable while opposing enemy ships did not carry fighter protection, but since the British had pioneered the use of ‘expendable’ fighters carried on capital ships and others, and had begun designing viable aircraft carriers, it was obvious that to survive in future the Cuckoo would need close fighter protection. It was supplied with very large span folding wings, useful for aircraft carrier stowage, but also on land in the small hangars of the day. The Cuckoo also had strengthened landing gear, with four pairs of struts, allowing it to carry the torpedo unimpeded beneath the front fuselage.

While the Fleet Air Arm fell under RAF control, and was often seen as the poor relation, the US Navy wisely kept control of its own air arm, which came to be based around the large and powerful converted battlecruisers Saratoga and Lexington, the largest carriers in the world for many years. It is sobering to reflect that the RN Hood and one of her cancelled sisters would have been much better value for money as large aircraft carriers than the converted large cruisers Courageous, Glorious and Furious.

^{A Devastator releases its Mark 13 torpedo, low and slow, as the weapon does not yet have the nose ring, tail shroud and tail box to protect it.}

^{Its Japanese contemporary, the Nakajima B5N Type 97 carrier attack bomber (Allied codename ‘Kate’) being loaded with a Type 91 torpedo. This was the plane that torpedoed the battleships at Pearl Harbor (and one high-level Kate bomber sank the Arizona).}

The Great Lakes and Martin torpedo bombers served the US Navy until the introduction of the Douglas Devastator in around 1938. But because these aircraft were thought incapable of defending themselves, at one point the US Navy considered scrapping the torpedo bomber from its inventory, relying instead on the dive-bomber, in which it led the world at the time. Nazi Germany caught on to the idea of the dive-bomber, which was to result in the Ju-87 Stuka, thanks to a personal import by Ernst Udet of a Curtiss SBC Helldiver.

Luckily, the US Navy persevered, and replaced its vulnerable biplane torpedo bombers with the Douglas Devastator. Although a modern monoplane design with retractable undercarriage, the Devastator was handicapped by the low power (850hp) of its radial engine — good for the 1930s but far outclassed in late 1941/early 1942. It did, however, carry its torpedo semi-recessed within the fuselage, which helped with the streamlining.

HIGH-SPEED, HIGH-ALTITUDE DROPS BY THE JAPANESE

In the early 1920s, retired Lieutenant Commander Frederick Bernard Fowler, RNAS, who pre-war had founded the Eastbourne Aviation Company, led a team of pilot instructors to teach the IJN how, of all things, to operate torpedo bombers and fighters from the deck of their first aircraft carrier, the diminutive Hosho (herself designed with the aid of plans of HMS Argus). The Japanese learned quickly but retained this traditional launch method up until 1941: basically, the torpedo bomber approached at a low altitude and low speed in order to not damage the torpedo on launch. In any case, the biplane torpedo bombers with fixed undercarriage of this era could not attain high speeds. The torpedo they used was the Type 91, designed in 1931.

All this changed with the introduction of the monoplane Nakajima B5N. The monoplane was difficult to handle at slow speeds and low altitudes, so the Japanese modified the Type 91 with a reinforced lower nose section so that the torpedo could be launched at higher speed from a higher altitude. Then they needed to adapt for attacks in shallow harbours. When training for the attack on Pearl Harbor, the pilots first tried lowering their flaps and landing gear, but it was extremely dangerous and they could easily lose control.

So again the Japanese modified the Type 91, adding wooden stabilising fins to control the glide angle. These broke off when the torpedo entered the water. Captain Sherman on the bridge of USS Lexington at the Battle of the Coral Sea noted that the Japanese B5Ns approached at their top speed to launch, and on one plane, shot down while still carrying its torpedo, he saw the box around the rudder. The Americans subsequently introduced a similar modification on their own aerial torpedoes.

The strengthened nose section and tail fins allowed IJN torpedo bomber pilots to drop from as high as 60m (196ft) at a speed of 300kph (160 knots), much higher and faster than contemporary naval air forces. For even faster land-based twin-engine bombers, it was found that the latest strengthened Type 91 torpedo could be dropped from as high as 120m (394ft) and at speeds up to 560 kph (302 knots).

SECOND WORLD WAR TORPEDO BOMBERS

Meanwhile, the cash-strapped British were forced to rely on biplanes such as the RAF Vildebeest intended to defend Singapore, and the Fleet Air Arm’s fabric-covered Swordfish, known to its crews as the ‘Stringbag’. To comfort themselves, they fondly clung to the belief that for their part, the Japanese had retained their old biplane torpedo bombers, and that these relics were the ones which had destroyed the US Pacific Fleet at Pearl. As the authors of the wartime Aircraft of the Fighting Powers so blithely stated: ‘The attack on Pearl Harbor … was carried out by a force of Nakajima G-96 biplane torpedo bombers having a performance no better than that of the Swordfish. A few days later … G-96 biplanes carried out a further operation … In cooperation with low-level [sic] bombers the G-96 succeeded in sinking HMS Prince of Wales and HMS Repulse.’

^{Torpedo-armed Fairey Swordfish. This obsolescent aircraft scouted the way for Warspite in the second Battle of Narvik, decimated the Italian battle fleet at Taranto, crippled the Bismarck, and flew anti-U-boat patrols off small escort carriers in all weather in the North Atlantic. They were so slow the Bismarck’s anti-aircraft directors had fused shells to burst in front of them. On the other hand, one strike launched from a carrier in the Mediterranean had to be recalled because the retreating Italians would have been safely home in harbour before the Swordfish could have caught up with them. Although this aircraft is carrying a torpedo, the lack of an observer and gunner in the rear cockpit suggests this is a training mission.}

^{A Nakajima G-96 torpedo bomber. (Based on the drawing in Aircraft of the Fighting Powers, volume III, December 1942)}

Clearly, there were two elements at work here: first, the need to persuade the public that the Japanese flew obsolescent aircraft, and when the new Allied planes were ready they would obviously sweep them from the skies; and second, to sweeten the pill of the knowledge that in December 1942, a year after the events described, the Fleet Air Arm was still using the Swordfish biplane operationally. The appearance of the twin-engined Mitsubishi G3M and G4M bombers during the devastating attack on Force Z was a very nasty surprise. (For what actually transpired at Pearl and off the coast of Malaya, see Part IV.)