DD not responding to attacks?

walsh2509 · 03-03-10, 04:10 PM

ASDIC comprised a transducer housed in a dome beneath the ship that sent out a narrow beam of sound in a series of pulses that would reflect back from a submerged object within a maximum range of about 3,000 yards (2,700 m). The dome was open to the sea and was to ensure the water around the transducer was relatively still as fast moving water would destroy any signal. The echo produced an accurate range and bearing to the target. But differences in the temperatures at different depths could create false echoes, as could currents, eddies and schools of fish, so ASDIC needed experienced operators to be effective. ASDIC was only effective at low speeds. Above 15 knots (28 km/h) or so, the noise of the ship going through the water drowned out the echoes.

The early wartime Royal Navy procedure was to sweep the ASDIC in an arc from one side of the ship's course to the other, stopping the transducer every few degrees to send out a signal. Several ships searching together would be used in a line, a mile or a mile and a half apart. If an echo was detected, and if the operator identified it as a submarine, the ship would be pointed towards the target and would close at a moderate speed, the submarine's range and bearing would be plotted over time to determine course and speed as the ship closed to within 1,000 yards (910 m).

Once it was decided to attack the ship would close more rapidly, using the target's course and speed data to adjust the course. The intention was for the ship to pass a little way ahead of the submarine, then depth charges would be rolled from chutes in the stern at even intervals and depth-charge throwers would fire further charges some forty meters out on either side. The intention was to lay a depth charge 'pattern' like an elongated diamond, hopefully with the submarine somewhere inside the pattern. But to effectively disable a submarine a depth charge would have to explode within about six meters, in depth as well as in plane. Since early ASDIC equipment was poor on determining depth it was usual to vary the depth settings on part of the pattern.

There were disadvantages to the early versions of this system. Exercises in anti-submarine warfare had been restricted to one or two destroyers hunting a single submarine whose starting position was known in daylight and calm weather, rather than stormy conditions. German U-boats could dive far deeper than British or American submarines, to well below the deepest setting on the British depth charges (A dive depth of over 700 feet (210 m) against a maximum depth charge setting of 350 feet).

More importantly, early ASDIC sets could not look directly down, so the operator lost 'sight' of the U-Boat during the final stages of the attack, a time when the submarine would certainly be manoeuvring rapidly. The explosion of a depth-charge also disturbed the water so that ASDIC contact was very difficult to regain if the first attack had failed.

03-03-10, 04:10 PM	#10
walsh2509 XO Join Date: Apr 2005 Posts: 410 Downloads: 18 Uploads: 0	ASDIC comprised a transducer housed in a dome beneath the ship that sent out a narrow beam of sound in a series of pulses that would reflect back from a submerged object within a maximum range of about 3,000 yards (2,700 m). The dome was open to the sea and was to ensure the water around the transducer was relatively still as fast moving water would destroy any signal. The echo produced an accurate range and bearing to the target. But differences in the temperatures at different depths could create false echoes, as could currents, eddies and schools of fish, so ASDIC needed experienced operators to be effective. ASDIC was only effective at low speeds. Above 15 knots (28 km/h) or so, the noise of the ship going through the water drowned out the echoes. The early wartime Royal Navy procedure was to sweep the ASDIC in an arc from one side of the ship's course to the other, stopping the transducer every few degrees to send out a signal. Several ships searching together would be used in a line, a mile or a mile and a half apart. If an echo was detected, and if the operator identified it as a submarine, the ship would be pointed towards the target and would close at a moderate speed, the submarine's range and bearing would be plotted over time to determine course and speed as the ship closed to within 1,000 yards (910 m). Once it was decided to attack the ship would close more rapidly, using the target's course and speed data to adjust the course. The intention was for the ship to pass a little way ahead of the submarine, then depth charges would be rolled from chutes in the stern at even intervals and depth-charge throwers would fire further charges some forty meters out on either side. The intention was to lay a depth charge 'pattern' like an elongated diamond, hopefully with the submarine somewhere inside the pattern. But to effectively disable a submarine a depth charge would have to explode within about six meters, in depth as well as in plane. Since early ASDIC equipment was poor on determining depth it was usual to vary the depth settings on part of the pattern. There were disadvantages to the early versions of this system. Exercises in anti-submarine warfare had been restricted to one or two destroyers hunting a single submarine whose starting position was known in daylight and calm weather, rather than stormy conditions. German U-boats could dive far deeper than British or American submarines, to well below the deepest setting on the British depth charges (A dive depth of over 700 feet (210 m) against a maximum depth charge setting of 350 feet). More importantly, early ASDIC sets could not look directly down, so the operator lost 'sight' of the U-Boat during the final stages of the attack, a time when the submarine would certainly be manoeuvring rapidly. The explosion of a depth-charge also disturbed the water so that ASDIC contact was very difficult to regain if the first attack had failed.