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ANTONY PRESTON, JOHN BATCHELOR
This was the first of the blunders made by Dönitz and his advisers, for skilled air crew did not take long to devise tactics which neutralised the so-called "aircraft trap". They simply flew around the U-Boat out of range, while calling up the nearest warship to come and sink her; if at any time the
U-Boat started to dive, the aircraft then rapidly switched to the attack. This led to the "Battle of Seconds", the U-Boat crews' term for the vital 30-40 seconds needed to clear decks before diving, and many inexperienced U-Boat personnel died simply because they could not get below fast enough.
The second error made by the Germans was a more technical one. Faced with disturbing reports from U-Boat commanders about attacks from aircraft at night when the Metox receiver had given no indication of a radar search, the German scientists refused to consider the possibility of centimetric wave-bands on the grounds that they had already tried this idea without success. A similar reluctance to accept the existence of H/F-D/F in 1942 had caused casualties, but in the spring of 1943 such a mistake was deadly.
The problem was not helped when a captured British bomb-aimer casually revealed that aircraft could track the emissions from a Metox set. When the Germans found that the Metox set did produce emissions which could be tracked, they jumped to the wrong conclusion, and blamed the Metox for all their problems.
However, a new receiver which cured the fault did nothing to halt the sinkings, and only when it was too late to affect the outcome did the Germans discover that however many signals were emitted by the Metox, the centimetric wave-band of the ASV set gave far more accurate bearings, and it was this which was causing the losses.
The collapse of the U-Boat campaign was dramatic. In May a pair of convoys like SC-122 and HX-229 reached Britain without loss, having sunk six U-Boats on the way. In the same month escorts achieved a record, with more U-Boats than merchant ships sunk, and the figures show how savagely the escorts were mauling the U-Boats in revenge:
Month Shipping sunk U-Boats sunk
Dönitz had no choice but to withdraw his U-Boats from the battle and concede a temporary defeat, while his technicians and scientists worked on the new weapons which were under development.
German Type XVIIB U1407/Meteorite. U1407 was one of the peroxide-engined Type XVIIB U-Boats which fell into British hands in 1945. As HMS Meteorite she was run for four years to gain experience with the Walther propulsion system, and although a speed of 20 knots was reached she proved highly dangerous
German Type XVIIB U1407/Meteorite. Displacement: 312 tons surfaced. Armament: Two 21-in torpedo-tubes (4 torpedoes carried). Speed: 8 knots (surfaced) 20 knots (submerged)
The new acoustic torpedoes have been mentioned, but there was also the "Schnorchel", that half-forgotten Dutch device for running diesels at periscope depth. It was hurriedly introduced into service, and was made a Standard fitting for new construction as a move to reduce the crippling losses from aircraft. There were passive devices as well, such as the "Pillenwerfer" or Submarine Bubble Target (SBT), which was a chemical compound released from a torpedo-tube; it acted like a giant Alka-Seltzer to produce bubbles which gave a false Asdic echo, but rarely fooled an experienced operator. Periscopes and even hulls were coated with rubber compounds which it was hoped would absorb Asdic and radar pulses, but again these measures were only partially effective.