Submarines and their Weapons - Aircraft of World War II

SUBMARINES AND THEIR WEAPONS
that, combined with its effectiveness, surely meant
that it could be improved. There was certainly the
possibility of giving it much greater endurance and
straight-line performance, but increasing the range
always resulted in a lowering of the strike rate, since
the torpedoes had no self-directive capability. There is
reason to believe that scientists in Germany had actually
perfected a passive acoustic homing device to
steer a torpedo towards a submarine sound source by
1936, and that the new weapon had been kept back
from production to preserve its secrecy.
FOXING THE 'FOXER'
The relatively simple first-generation devices, which
were restricted to fairly low speeds, proved effective
against slow-moving targets such as merchant ships,
but less so against warships, which often simply outpaced
them. Towed noise-makers (known as 'Foxers';
originally no more than two lengths of iron pipe,
Below: U14Q6, one of the few operational Type XVII
Walter-engined boats to be completed. She was scuttled
in May 1945 but was salvaged and taken to the United
States. A sister-boat, U1407, went to the UK.
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chained loosely together so that they constantly
crashed into each other) could also dupe these
devices, and it was September 1943 before German
scientists perfected a means of outwitting them.
When a torpedo fitted with the second-generation
T5 or 'Zaunkönig' ('Wren') passive acoustic seeker
detected a sound source in a small arc ahead of it, a
subsidiary circuit operated a simple solenoid switch
to actuate the small rudder vane. This caused the torpedo
to turn sharply to starboard and run in a circular
path for a predetermined period (long enough, in fact,
for it to describe a semi-circle) before turning sharply
to starboard once more and setting off on its original
track again. In this way, the torpedo skirted the noisemaker
and homed in on the propeller noise of the ship
towing it instead. Then, on encountering the noise of
the ship dead ahead, the torpedo turned to perform the
circling manoeuvre once more. The diameter of the
semi-circular track the torpedo described being less
than the length of the ship plus the distance the latter
covered in the intervening period, it would strike the
target from the beam. It has been estimated that 700
T5s were fired in anger, and that 77 (11 per cent)
scored hits. The US Navy introduced the similarly