The Champion Submarine-Killing Submarine of World War Two


Virtual Tour

Tour Main

Exterior - Bridge


Exterior Tour (Bridge Section)


This is the area that houses and support for both periscopes and both the SD and SJ radar masts.  Also seen are the lookout platforms, RD Loop and VHF antenna and the search light.  On the forward part of the bridge was one of the two TBT and the hatch to the conning tower.


Periscopes (right):

The after scope is the attack scope and features an optical range finder for determining the range of a target. The forward scope is the general observation scope.





SJ Radar (below):

Unlike the SD unit, the SJ was a directional radar, which could be used to sweep the surrounding sea for targets. The primary limitation on range was the height of the retractable mast, radar being limited to line-of-sight.  The fleet boats' SJ radar was designed for search, ranging, and navigation.  In addition to conducting surface searches, the radar masts could also be extending above the water before surfacing, to check the area for enemy warships and aircraft.




T.B.T. (above):

Target Bearing Transmitter.  These were used to indicate the angle, or bearing, of a target from the submarine, and to relay that information to the torpedo data computer in the conning tower to establish the gyro angles for the torpedo run. There were two TBTs, one on the bridge and one mounted on a stand by the 40mm gun on the after gun deck.  The mounting for the one on the bridge still exists.

  Search Light (above):

Used mostly for communication and for searching the surface after an attack.  If the situation would arise, a submarine would surface at night and search the wreckage for survivors and/or material to salvage such as papers, maps, etc.

SD Radar (left):

This was a very basic unit. Operated from the conning tower, the SD radar was only vaguely directional. It was capable of warning that a plane was within about 6 miles of the boat, but couldn't really pinpoint a bearing, or give much in the way of information. Late in the war, SD was replaced by SV radar.  The Batfish is shown with SD Radar.


Deck Gun (below):

Deck guns varied in location and type.  They could be placed either forward of the bridge or aft of the bridge, usually it was the commanding officers choice as to where to  mount it.  Initially, the Batfish was outfitted with a 4" gun forward.  Later in the war, the 4" gun was replaced with a 5" gun that was mounted aft of the bridge.  Currently, there are no deck guns mounted on the Batfish.


40mm Gun:


Not originally fitted to submarines, the 40-mm was added to the arsenal when commanders argued that they needed something to fill the gap between the 20-mm and the deck gun for close-in attacks on small vessels.  The single-barrel "wet" version used on submarines had seats for the aimer and trainer, who could elevate, depress, traverse, and aim the gun with hand controls.  Besides its rarely used anti-aircraft role, the 40-mm was used for attacks on supply junks and other light craft that weren't considered adequate targets for torpedoes or the main gun.  Later in the war, a 40-mm was usually installed on the cigarette deck at the aft end of the conning tower, where it replaced the original 20-mm mount.

20mm Gun:

The smallest weapon in the American arsenal firing an explosive shell, the 20-mm was a close-in anti-aircraft machine-cannon. The shells were loaded in a drum magazine, and a single gunner aimed and fired the gun. Pressure-proof storage was provided for these guns, but it was found that they could tolerate immersion reasonable well provided the barrels were changed frequently.  Most wartime production fleet submarines originally came fitted with at least one 20-mm, on the after part of the conning tower and, after the pre-war bridges were cut down, reducing the silhouette and, in the process, creating a second gun position at the front of the bridge, a second gun was fitted. When the skippers could convince the right people, these were both often replaced with 40-mm mounts, giving an increase in both range and destructive power.

Machine Guns:

Fleet submarines all had mounting points for machineguns fitted at various locations around the bridge. The guns and ammunition were stored in pressure-proof containers near the mounts, where they could be quickly extracted on surfacing. The preferred weapon was the .50 caliber Browning heavy machinegun.  Currently, there is one replica machine gun mounted on the port side of the bridge (left center of photo).