Naval Anti-Aircraft Guns and Gunnery. Norman Friedman
learned how to operate multi-carrier Task Groups, whose extra decks were a better solution. Conversely, the Royal Navy accepted many compromises, even in aircraft performance, because it assumed that its ships could accommodate so few aircraft. When it wanted more aircraft per carrier, it adopted double hangars, with their limited head-room (which made post-war modernisation of some wartime-built ships impossible). Saratoga is shown recovering her T4M torpedo bombers in the early 1930s. Unlike later US carriers up to 1945, she had a British-style closed hangar. That in turn made gasoline vapour explosions more devastating – and one such explosion doomed her sister-ship Lexington (the Japanese closed-hangar Taiho suffered a similar fate). Later US carriers had open hangar decks, which made it possible to warm up engines on them; that in turn made for faster launching of aircraft which had to be held below because they did not fit the parking area on the flight deck (whose size was set by the required take-off run).
The one ship-killing air weapon used during the First World War was the air-dropped torpedo, first employed by the Royal Navy and intended for mass use against the German High Seas Fleet had the war continued. This US Navy torpedo bomber has just dropped its weapon off Pensacola, 28 April 1920 – and it has porpoised. In 1922 the shore-based Torpedo and Bombing Squadron of the Atlantic Fleet successfully attacked the battleship Arkansas when she was steaming at full speed 70 miles from Norfolk. They made at least seven hits on her, and a miss hit the battleship North Dakota. This exercise demonstrated that air-launched torpedoes could be made to run straight, apparently an issue at the time.
It took time for navies to develop effective air-launched torpedoes and the tactics which went with them. Even then, the torpedo was by far the heaviest bomb load navies contemplated, and until the advent of engines in the 1000 and 1500hp class in the 1930s, torpedo bombers were invariably heavy and slow. The first production US Navy torpedo bomber, the T4M-1 of 1928, had a maximum speed of 114mph and required 14.1 minutes to climb to 5000ft. The Depression precluded replacement of the T4M, or even an upgrade with the new R-1820 engine, as proposed in 1931. The T4M could carry a torpedo or 1500lbs of bombs, and that became the standard for the next torpedo bomber, the Douglas Devastator. Given the combination of heavy bombing and torpedo attack in one aircraft, the inter-war US Navy assumed that carrier air strikes would mix the two types of attack, which would be combined with dive bombing by other aircraft. These T4Ms are shown on board the carrier Saratoga.
Reconnaissance was always the first step in an air attack: the sea is broad, and even a large convoy or fleet is only a small speck on it. Attackers with heavy loads had insufficient endurance for any kind of search. Instead, reconnaissance aircraft or ‘snoopers’, often cued by other intelligence, found the target and homed the attackers.8 Destroying a snooper might prevent an attack altogether. Since ships could generally be seen and shadowed from well beyond anti-aircraft gun range, it took fighters to deal with snoopers.9
Torpedo bombing
During the First World War, torpedo attack was the only form of air attack which actually sank moving ships at sea. It was practiced by both the British and the Germans, and in 1918 the British planned a mass torpedo attack against the German High Seas Fleet in harbour, to be mounted from aircraft carriers. The war ended before the plan could be executed.
To be effective a torpedo had to be relatively massive. Until the Second World War, engines suitable for carrier aircraft were not powerful enough to give a large enough aircraft an impressive performance. In the early 1930s the US Navy nearly abandoned the torpedo as an air weapon, reversing its position only with the advent of the Douglas TBD-1 Devastator – whose performance might have seemed sparkling in 1936, but was decidedly unimpressive a few years later. High bomber performance introduced a new problem. A torpedo dropped at high speed from a relatively high altitude typically oscillated as it fell towards the water. If it hit the water at the wrong angle, it would dive and it might also roll. A roll would cause its elevators, which were set to make it rise out of its initial dive, to act as rudders and cause it to hook. Something had to be done to stabilise the torpedo in flight so that it hit the water at the desired angle. The solutions were air tails which guided a torpedo into the water at the right angle, often coupled with breakaway protection for the nose of the torpedo.10 Relatively few wartime photographs show air tails of any type; presumably each user considered the concept secret.
The Regia Aeronautica, the Italian Royal Air Force, developed torpedo tactics before the war, but in line with its view that air power was general-purpose it did not form specialised torpedo bomber squadrons. The primary torpedo bomber was the Savoia-Marchetti SM 79 Sparviero, which could carry two torpedoes, as shown, although in practice they typically carried one. After SM 79s made successful torpedo attacks in 1940, special torpedo attack squadrons, the Aerosiluranti (Siluranti were torpedoes), were formed. They received enormous wartime publicity. (Philip Jarrett)
Throughout the mid-1930s carrier aircraft capable of lifting and carrying torpedoes had to be so large that they could not match dive bomber performance. For a time the US Navy planned to drop them altogether in favour of total reliance on dive bombers (the carrier Ranger was built without torpedo stowage). The fleet recommended not only elimination of torpedoes but restriction to two 500lb bombs for horizontal bombers; in 1932–4 BuAer retained both because it considered the performance penalties involved in carrying a torpedo or a third bomb were negligible. When it sketched a design prior to opening a new bomber competition in 1934, BuAer found that biplane configuration would limit it to 170mph, whereas a monoplane could reach 186mph; it included speed in the specification it released in 1934. This competition in effect saved the aerial torpedo in the US Navy, because it produced a torpedo bomber with high enough performance to have a reasonable chance of surviving enemy fighters: the Douglas Devastator. The rules of the 1934 competition embodied the speed BuAer estimated such an aircraft could reach; the Devastator actually made 206mph, and it proved remarkably free of mechanical defects. As a result, 114 were immediately ordered. Had the Devastator not been developed, further US carriers would probably have been built without torpedo stowage, their attackers limited to dive bombing. It would have been effective against carriers and cruisers, but not, the US Navy thought, against battleships – it took torpedoes to sink the huge Japanese Yamato and Musashi, for example. In addition to its modern design, the Devastator had the US Navy’s first hydraulically-folded wings. Unfortunately aircraft, particularly engine, technology was moving so fast that within a few years it was obsolete. The TBD was powered by a 900hp R-1830 (an abortive version offered in 1940 to the Dutch used a 1200hp R-1820; note the difference in output in an engine of about the same size). According to a post-war BuAer history of attack aircraft development, further development of the TBD suffered because the navy came to emphasise dive bombing instead. Once the fighters and dive bombers exceeded the performance of the Devastator (in 1938), BuAer ran a competition for a faster new torpedo bomber, which became the Grumman Avenger. This time it wanted 50 per cent higher speed and a bomb bay sufficient for a torpedo, three 500lb bombs, or fuel for a range of 3000 miles (during design the bomb bay was enlarged to accommodate an additional 500lb bomb). Like other US (and Japanese) torpedo bombers, the TBD could also be used as a level bomber, typically carrying a single 1000lb or three 500lb bombs. For that purpose it, and the Avenger which succeeded it, had a Norden bombsight. In its case the bombardier’s window was under the belly, normally covered by doors for streamlining (it could not be used if the torpedo was carried). After making a good showing (as a level bomber) in carrier raids on the Mandated Islands in February 1942, and (as a torpedo bomber) at the Coral Sea in May, Devastators were nearly wiped out at Midway. One reason why was that they carried their torpedoes tipped down at a 9° angle. This flight deck photograph suggests the reason why: the torpedoes were carried parallel to the deck, presumably for loading, but the aircraft was tipped back. The Mk 13 torpedo had to be dropped