977 U-boat

[joegrundman]

I recently read this pretty good book, U-boat 977 by Kaleun Heinz Schaeffer

it's available as free pdf download here and i fully recommend it :

http://www.archive.org/details/977uboat001463mbp

however i made a few notes that I think would be of general interest here, but i do appreciate that this is only one source, and not necessarily to be considered definitive:

1. A description of the TDC, which the author refers to as the "attack table"

The torpedo-officer at the attack-table reports "Lined-
up" and the switch is made by which the attack-table
is connected with the gyro-compass and the attack-
sight. The mechanism churns around and two red lamps
indicate that the process of calculating the information
which has been fed in to it is not yet completed. The
lights go out after a few moments, and the petty-officer
at the attack-table reports the resulting settings to the
torpedo officer. From this point onwards our own
alterations of course are of little importance, being allowed
for automatically. The target must simply be held in
the crosswires of the attack-sight in order that the apparatus
can do its job. The torpedo-officer gives the
order "Follow" to the attack-table. A lamp glows, and
the attack-table is now controlling the binoculars on
the bridge. Meanwhile the constantly changing firing-
settings are being transmitted automatically to the
torpedoes and set on their angling mechanism. With this
system we can fire at any moment and on any course,
provided that the 90-degree limiting angle is not exceeded. The torpedoes will run to a pattern that spread
over roughly a ship's length by the time they reach the
range of the target. We turn to our attacking course.

pp87-88

From this it appears there was a time delay between programming the TDC and it being ready, but once ready updates by changing periscope angle are instantaneous - this would be akin to a 5 sec (for example) delay between selecting auto-update on the TDC and it being ready for use.

I understand that the real TDC had input for target course rather than AOB, and hence presumably the submarines' own heading would be fed in automatically from the gyrocompass - this would account for his statement that changes on own course would be automatically factored in.

This important functionality is missing from the SH3 TDC

however this line "The torpedo-officer gives the
order "Follow" to the attack-table. A lamp glows, and
the attack-table is now controlling the binoculars on
the bridge." confuses me.

2. The sound of ASDIC

The convoy was steaming away now, its propellers
barely audible. But three destroyers were after us, and
before long the sound of their Asdic,like fingernails
run over a comb, grew all too familiar. Another of their
Asdic devices rattled like peas in a tin, a third screeched
like an ancient tramcar taking a curve. We weren't likely
to forget this experience. I thought of the man who went
out to discover what fear meant He should have been
there.

pp103

only the third variation he describes could be considered similar to the sound we are familiar with. I like the idea of a mod changing it for the comb or peas effect

3. Pitch and roll in heavy weather

FOR FOUR weeks the wind had been howling
from every quarter at 55 to 60 miles an hour, with heavy
rain and the thermometer only a few degrees above zero.
I was up on the bridge. There was of course no protec
tion there, just the icy steel bulkheads, so it was impos
sible to work up any warmth. Lashed to the rail as I was,
the leather safety-belt reinforced with steel bit deep
into my ribs. It had been known for the watch on the
bridge to be washed overboard in heavy seas in one
boat the relief had gone up to take over and just found
no one there. The force of the seas breaking over us
now was terrific, but the boat shot on nevertheless like
an arrow, with very little pitching or rolling and the
waves over us over a breakwater.

pp117

the final sentence is of interest here - the author suggests that U-boats were really quite stable in even very rough weather

4. radar decoys

couldn't help thinking this superfluous, for inside the
boat it was as good as pitch dark anyhow. Next the Asdic
decoys were thrown out, and we began to fill balloons
with metal strips attached, which were to be released
when we surfaced to float low over the water and fox
the enemy radar.

pp143

radar decoys!! i never knew - this would be nice in game!