Black May by Michael Gannon

Author:Michael Gannon [Gannon, Michael]
Language: eng
Format: epub
ISBN: 9780062039460
Publisher: HarperCollins
Published: 1998-04-07T16:00:00+00:00

The secret was out, and it appeared likely that the Germans would now neutralize the centimetric wavelength in the same way that Metox had neutralized the metric. But the Telefunken Company experienced problems in replicating parts of the Allied equipment, and administrative muddles further checked what was to have been a crash program to develop a new G.S.R., with the result, astonishingly, that an effective detector called Naxos-U was not shipped to the U-boats until October, far later than the two or three months predicted by Watson Watt, and long after the issue in the Atlantic had been decided.

Raushenbush began his calculations with a review of U-boat performance figures. The optimum (as against maximum) speed surfaced for charging batteries was 12 knots. The optimum speed for running submerged was 1.75 knots. The average battery capacity on entering the 200-mile-deep transit channel was 51 miles submerged, after which a U-boat had to surface for maximum recharge for a period of 6.77 to 7.77 hours, during which it would travel 81 to 93 miles. After another 51 miles submerged, it would have to surface for charging at least once again, briefly, until completing the 200 miles (assuming a direct course) in a total traverse time of 76.37 hours.

Thus, a U-boat in transit would be on the surface and vulnerable to air attack for at least one lengthy period. Any attempt to remain underwater beyond 41 hours would exhaust the air supply, although a boat could surface for 5 to 10 minutes to ventilate. A surfaced U-boat forced to dive by aircraft would later have to charge for approximately seven minutes to compensate for the 100 ampere hours used in one cycle of crash-diving and resurfacing. Since the average density of boats in the transit area at any given time was 15.8 boats, that number together would be exposed from 1,280 to 1,470 miles during their passage. Raushenbush calculated that there would be a density of one surfaced boat per 3,800 square miles.

On the air side, Raushenbush called for an additional 160 long-range aircraft, all equipped with ASV Mark III and many with Leigh Lights, to make up a total force of 260 aircraft. Such a large, coordinated force, trained to capitalize on the Allied advantage of centimetric radar, could be expected to make 7.5 sorties per aircraft per month, to make 1.8 attacks on each of 150 U-boats entering the transit channel each month, to make a minimum of twenty-five kills per month, and to cause damage to a further thirty-four boats. Over the projected 120 operational days of this effort, 100 boats would be destroyed and 136 damaged, thus “paralyzing” the U-boat fleet and throwing it on the defensive. The damaged boats would play their role in the paralysis effect by jamming and overloading the Biscay repair bases.

There were two critical factors in the Raushenbush Plan: (1) the attack program must be put into effect promptly, before the enemy devised a centimetric search receiver; and (2) the attacking force must be

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