Tactics
One crucial limitation of a torpedo bomber was that it had to fly a long, straight course at a constant altitude of 30 metres (100 ft) toward the target ship before launching its torpedo. The torpedoes were very sophisticated weapons and were prone to damage when landing on water, especially on a wave; they were ideally aimed at the bottom of a wave but this was difficult in practice.
During a torpedo run, the attacking aircraft were easy targets for defending fighters from a combat air patrol. Furthermore, torpedo planes were also highly vulnerable to anti-aircraft fire, particularly the heavy anti-aircraft guns (such as the 5 inch DP) which fired into the water, creating water spouts to slap the torpedo planes.
In the 1930s, the Japanese Navy developed the best way for torpedo bombers to achieve a hit. They used an "anvil attack" in which two groups of torpedo planes approached the target ship's bow at an angle of about 45 degrees, one on each side of the ship. The torpedoes were to be launched at the same distance from the ship; this would have ensured a hit no matter where the ship tried to maneuver. In practice, this kind of attack was difficult to coordinate and therefore extremely rare. Usually, combat air patrols and anti-aircraft fire quickly broke up approaching plane formations, after which each aircraft was on its own. At Pearl Harbor attack the ships were lined up and basically stationary so the Japanese first attack wave of 40 torpedo bombers of the Imperial Japanese Navy (IJN) armed with Type 91 torpedoes, out of 183 planes, were able to hit the ships broadside with torpedoes as the defenders were caught by surprise.
Torpedo bombers were best used as part of a coordinated attack along with other types of aircraft. For instance, during the attack on the battleship Yamato, fighter planes strafed the ship with machine guns to suppress its anti-aircraft gun fire, while dive bombers tried to cause havoc and cause topside damage, thus leaving the torpedo bombers unmolested so they could make their attack runs. By contrast, if the attackers failed to achieve air superiority or surprise, torpedo bombers would suffer heavy losses regardless of whether the type was obsolete or not. This is best exemplified at the Battles of Midway where the Air Group Eight's dive bombers missed the Japanese carriers. So Torpedo Squadron 8 (VT-8, from Hornet), led by LCDR John C. Waldron sighted the enemy carriers and began attacking without any coordination with the dive bombers or fighter cover. It was followed by Torpedo Squadron 6 (VT-6, from Enterprise). Without fighter escort, every TBD Devastator of VT-8 was shot down without being able to inflict any damage, with Ensign George H. Gay, Jr. the only survivor. VT-6 met nearly the same fate, with no hits to show for its effort. The Japanese combat air patrol, flying the much faster Mitsubishi A6M2 "Zeros", made short work of the unescorted, slow, under-armed TBDs torpedo bombers. A few TBDs managed get within a few ship-lengths range of their targets before dropping their torpedoes. Also at the Santa Cruz; the Nakajima B5N Kate despite being considered outdated played a key role in sinking USS Hornet, while the brand-new TBF Avenger torpedo bomber's failed to hit a fleet carrier.
When the targets were ships able to maneuver at high speed and hence much harder to hit, torpedoes proved less effective, except in cases when the crews launching them were especially well trained. Still, even a single torpedo hit on an enemy warship could cripple it decisively, especially in the case of vessels without an armored belt (cruisers and aircraft carriers often had torpedo blisters but these were not as extensive as that of battleships). Even heavily armored battleships did not have their protective belt extending to the bow, and a hole made there could be wrenched wider from the pressure of the inrushing water which could buckle and crush bulkheads; this tactic was used against the Yamato super-dreadnought. Also, there was nothing to protect the rudder and propellers at the stern, which was demonstrated during the hunt for the Bismarck and Force Z.
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