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Originally Posted by LukeFF
Norman Friedman mentions that two boats of the S-42 class received "Mark 14 torpedo directors" in their modernization overhaul in 1943. By that term, does he mean TBTs and if so, how did they feed data to the torpedoes?
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Luke,
I believe the brief mention on page 145 in Friedman's
U.S. Submarines Through 1945 to be a typo. I too thought he might have been refering to the Target Bearing Transmitters (TBT) mounted on the bridge to send bearing info to the tracking party. Research showed, however that the TBT was designated Mk 8.
More poking around showed that there was a Mk 14
gun director (or gun sight) that was used for 20 and 40 mm guns. This gyro stabilized sight produced a lead/lag angle for the guns which greaty improved accuracy. This is probably what Friedman was refering to. It could be that an editor mistook the Mk 14 reference to mean torpedo and changed the text.
The TBT's are essentially a pressure proof binocular mounted on a gyro repeater display. As the TBT is rotated to the target bearing, a transmitter mounted underneath sends an electrical signal to a bearing repeater in the conning tower and that repeater shows the bearing to which the TBT is pointed. On the left side of the TBT is a simple buzzer button that when pressed makes a sound in the conning tower indicating that the TBT is on the target bearing, and that the fire control team needs to use that bearing in their solution. That data is then manually fed into the TDC by the operator.
BTW, I haven't confirmed it yet, but I don't believe that the S-boats were ever fitted with TDC's. Both the control room and the conning tower were small and jam packed with gear and even the later models of the TDC would have been too big to fit. The crews of the S-boats continued to use hand held manual slide rule style devices known as the "Is-Was" and the "Banjo" to determine fire control solutions until the end of the war. An experienced and well drilled tracking party could still do well with these devices, and they were retained on the fleet boats as back up in case the TDC went down.