Here we are in the control room of a Type IXC U-boat: see below. We're looking to port and forward at where the navigator spent a great deal of his time. The clock at the left of the picture, just above the chart table, was always set to Central German time. Note that the framed cover over the chart table is not original, but placed there by the museum. Another alteration you can see is that instead of the normal hatchway forward of the chart table the museum has cut a full size doorway into the bulkhead for easier access by tourists. The remains of the original circular hatchway can be seen on the left side of the lower doorframe.

At the station in this photograph the navigator and the commander have every piece of information crucial to navigation available to them: speed, course and helm. Furthermore there is a sophisticated piece of equipment taking pride of place over the table.

A question often asked about U-boat operations is "How did a submerged U-boat crew know if they were going to hit the bottom?" One answer is that by reading the boat's depth, the navigator could then consult a chart for the area he was in, read off the known water depth in the boat's position (presuming he knew where he was) and then by arithmetic get an estimate. Indeed this is how the first U-boats had to operate.

Yet it wasn't always possible to know exactly where you were and charts were sometimes unreliable. When in doubt technology came to the rescue. Just as the allies used sound impulses (ASDIC or SONAR) to locate a submerged U-boat, the U-boat could use sound waves to detect the distance to the sea floor.

How does this work? Briefly, sound reflects from objects such as a wall, or the ocean floor, or a U-boat. By emitting a sound, and measuring how much time the sound echo took to 'bounce' back, the distance to whatever that sound had reflected from could be calculated by comparing against the speed of sound.

The instrument featured in close up below dominates the port side of the control room as it is mounted right above the chart table and projects further out than surrounding equipment. Even the non German speaker can have a good guess at its function by looking at the title of it: "ATLAS-ECHOLOT". Produced by Atlas Werke, it's a forerunner of today's sophisticated depth sounding equipment.

By reading this dial it was possible to get an accurate idea of how far the bottom was from the boat. The main dial of the echo sounder is calibrated in 1 meter increments up to a distance of 120m or about 394 feet. The legend above the dial tells us it measures the depth under the keel. The Atlas-Echolot was sophisticated technology for its day, and U-boat commanders and their navigators relied quite heavily on this instrument especially when patrolling along an unfamiliar coast - for example the American Eastern seaboard. The ability to keep a reasonable depth was a sound defensive strategy. In case of attack, the boat's best defense was to be able to go deep, as the deeper the boat, the closer a depth charge needed to explode to do damage to the boat.

As we move through the boat you will notice other systems by Atlas Werke. German systems manufacturers usually displayed their name prominently on their instruments much like today's weapons systems manufacturers do. Atlas Werke continued to be involved in Submarine design and technology after the war.

To the right of the Echolot you can't miss the valve wheels for controlling the negative buoyancy tanks. These are the tanks that are flooded to help the boat dive. Once the boat is dived, they are pumped out again. In effect they are there to 'kick start' the boat's dive by adding extra weight.

Notice that the electrical demands of a U-boat were high: the junction box to the left of the Echolot gives us an idea of the impressive amount of electrical power present in some circuits: 300 Volts and up to 25 Amps can run through this junction. This is enough power to run several bar heaters. Notice the hinge which allows quick access for fuse replacement.

Underneath the junction box is a gyrocompass repeater. The gyrocompass is an electro-mechanical device quite different to a traditional magnetic compass. We will see the actual gyrocompass later. You will notice many duplicated instruments within U-505. This makes sense: crew don't need to move too far to read an instrument on a different panel or bulkhead somewhere. "Repeaters" were used liberally so the crew always had access to important data.

Underneath the Echolot is a red switch: to the left of it, you will notice the helm repeater: it shows which way the rudder is pointed. As with standard international maritime practice, red is port, green is starboard. Also underneath the Echolot, mounted underneath the red switch is a clipboard for holding pens used by the navigator or commander when working on plots at the chart table.

Underneath the helm repeater are the tachometer repeaters pictured above for the twin screws (propellers) that drive the boat. Once again, red and green tell us which sides the dials indicate. Abbreviations of the German for Port (Bb) and Starboard (Stb) feature within the tachos. If the needles swung to the outside of the dials - the black numbers - the direction of thrust is forwards. The inner numbers (red) indicate reverse. The legends voraus and zurück also make matters clear. Under the dim lighting conditions frequently experienced in a boat's operations, colours on instruments could be unclear so the legends help prevent any confusion. The tachometers tell us the rotation speed of the screws in revolutions per minute. Although they go up to 600rpm, we will see later that the diesel-room tachometers top out at 550rpm. The tachos here were produced by De Th Horn, of Leipzig.

The light fitting aided with working at the charts. I'm not sure what has been removed from the fitting to the left of the tachometers - note the four empty brackets.
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