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U.S.S. Wyoming 6 2"/50
U.S.S. Arkansas 12 2"/50
U.S.S. California 12 14"/50
U.S.S. Tennessee 12 4"/50

1. Although this system is obsolescent, its simplicity makes it excellent as- an. introduction to main battery fire control installations. At this point it is timely to caution the student that there has been a gradual change in fire control nomenclature. For example, the instrument now called "Gun Train Indicator" in all installations was called "Single Target Turret Indicator" in the Sperry "installation, and what is now called "Gun Order" was called "Corrected Target Bearing".

2. The Sperry-Ford System of Main Battery Fire Control was developed piecemeal in our Navy, and comprises some apparatus that was originally designed when director fire first made its appearance (1913-15) and some that resulted from subsequent experience. Various parts of this system were designed by personnel of the Bureau of Ordnance, by the Ford Instrument Co., and by the Sperry Gyroscope Co., and the system as a whole is sometimes referred to as the "Bureau-Ford-Sperry System", although it is commonly known as the "Sperry System". The elevation system, which comprises apparatus of Bureau and Ford Design, is also referred to as the "United States Navy type" of director firing installations. All apparatus of the train system is of Sperry design.

3. The Elevation System, using Ford instruments, employs the Ford Transmission System1 which is self-synchronous but has a limited number of steps. The Train System is Step-by-Step, and is not-self-synchronous.


4. The accompanying diagram (Plate 1) illustrates the instruments involved in the gun elevation system, the lines with arrows indicating the paths of the two elements affecting gun elevation - namely:

1Not to be confused with the later Ford "DCS" system.


Plate 1


5. Advance Range (in yards) is obtained from the range keeper Advance Range Dial (or, from the Plotting Board). This range is set by handcrank into the Range Converter, where it is converted to the corresponding elevation in minutes (or "eight depression"), to be combined with the Director Correction of the Firing Director.

6. The-mechanism for converting Gun Range to "Range in Minutes" sight depression) consists of a hand crank geared to a drum. The drum is graduated for range in yards in such, a way that when the range is set on the drum, the drum; is thereby turned angularly through the corresponding "range in minutes" given in the range table. Actually the drum, has two sets of graduations, one for "full charge" and the other for "reduced charge".

7. Director Correction is transmitted from the Firing Director by the Director Correction Transmitter to the Range Converter, where it registers in the upper left hand window (Plate 1). Here by mean of a hand crank, the Director Correction is transferred1 by the Converter Operator to the corresponding lower left hand dial of the Converter, which operation combines this Director Correction with the Sight Depression and indicates the resultant Gun Elevation Order.

8. The Gun Elevation Transmitter (located in the Range Converter) transmits automatically the above resultant Gun Elevation Order to the Gun Elevation Indicators at the Gun Stations. The Gun Elevation Indicators are controlled from the switch board in the Plotting Room, allowing each Gun Elevation Indicator to be throvm in circuit with either Gun Elevation Transmit ter. Thus either Gun Elevation Transmitter can control the elevation of all turrets, or, for divided fire, each group of turrets may be controlled separately.

9. Gun Elevation Indicators receive mechanically from the auxiliary gun elevation rack the angle of elevation of the gun. Actual Gun Elevation is corrected for Roller Path Inclination and, on later mounts, it may be corrected for erosion of the guns. Thus, by matching pointers in the Gun Elevation Indicator, the guns can be laid to the desired angle of elevation, i.e.: GUN ELEVATION ORDER + EROSION CORRECTION + ROLLER PATH CORRECTION.

1The Range Converter has included in its mechanism a "follow the pointer" system to enable the Operator to keep the proper Director Correction set at all times without actually reading the Director Correction.



10. The accompanying diagram (Plate 2) illustrates the instruments involved in the Gun-train system. Lines with arrows indicate the path of the bearing signal from the Target Bearing Transmitter to the indicator at the turret trainer's station.

11. The Target Bearing is observed by the Target Bearing Trans mitters any of which can transmit this relative bearing to a Target Turret Transmitter in Plot, where it registers on a pair of dials as observed Target Bearing. There are two Target Turtet Transmitters (T.T.T.s)in the Plotting Room, one for each group of Turrets. In the Target Turret Transmitter the setting of the Deflection and of the Present Range (from the Range Keep er) apply to the observed bearing a correction which not only introduces the Deflection but also compensates for Convergence. (i.e., Horizontal Parallax).1

12. Operation of the Target Turret Transmitter. (See Plate 3). Observed Target Bearing from the Target Bearing Transmitter enters the instrument and registers on the two (coarse and fine) bearing dials, at the same time being introduced into a parallax mechanism, whose other input is the range as set in the instrument. The Range is taken from the "Present Range Dial" of the Rangekeeper and set by handcrank. The output of the parallax mechanism moves the Deflection scale of the instrument, so that when the Operator sets the Deflection pointer by hand he applies the combined correction for horizontal parallax and deflection, through a differential, to the Observed Target Bearing. The output of this differential is "Corrected Target Bearing" or Gun Train Order.

13. "Target Turret Indicators", (i.e., Train Indicators). The 'Corrected Target Bearing" (Gun Train Order) is transmitted by transmitters in the Target Turret Transmitter to the Target Turret Indicator's in the Turrets. The Train of the Turret is transmitted by the Turret Train Transmitter (located near the training rack of the turret) and registers on the dials of the Target Turret Indicators. By proper matching of pointers the turret will now be trained to the firing bearing.


14. Control Instruments. The Sperry-Ford System affords control from three stations in Train; namely:

1Each Group of Turrets is converged on the Target. Therefore the Target Turret Transmitters are not interchangeable.


Plate 2


Plate 3


  1. Target Bearing Transmitter #1 in Foretop.
  2. Target Bearing Transmitter #2 in Main Top.
  3. Target Bearing Transmitter #3 in Fire Control Tower.

and six stations in Elevation:

  1. Director #1 in Foretop.
  2. Director #2 in Maintop.
  3. Director #3 in Fire Control Tower.
  4. Director #4 in Forward High Turret.
  5. Director #5 in After High Turret.
  6. Director #6 (Stable Zenith) in Plot.

15. In Plot there are also two Rangekeepers, two combined range converters and transmitters, two target turret transmitters, and certain auxiliary instruments.

16. Divided Fire. The Sperry-Ford System is very flexible in Elevation, it being possible to use any one of the five directors in conjunction with either Range Converter and Gun Elevation Transmitter for controlling part of the battery, and any other director with the otter Range Converter and Gun Elevation Transmitter for the remainder of the battery. In Train, however, due to the non-interchangeability of the Target Turret Transmitters, the battery can only be divided into two groups (forward group and after group), though any one of the three Target Bearing Transmitters can control either or both groups. Consequently, Divided Fire for the Sperry-Ford System consists of:

Group 1 - Forward Turrets controlled by Director #1, #3 or #4, T.B.T. #1 or ,#3, and the "forward" group" of plot, consisting of the forward rangekeeper, converter, and T.T.T.

Group 2 - After Turrets controlled by Director #2, #3 or #5. T.B.T. #2 or #3, and the "after group" of plot, consisting of the after rangekeeper, converter, and T.T.T.

17. Indirect Fire. Indirect Fire may be carried out with this system using the Stable Zenith Instrument (Director, Mark IX)1 mounted in Plot as the Firing Director, and the Target Designator System for controlling in train. A Target Designator is mounted on each Target Bearing Transmitter. It consists of a galvanometer with a needle1 which indicates "train right", "train left", or "on". The needle may be controlled by either Rangekeeper in plot. If the Rangekeeper is properly set up, and the director trainer keeps his designator "on", his telescope will stay pointed at the target. In this way a rangekeeper may control the battery in train, if the target is obscured.

1The Stable Zenith was not developed by Sperry-Ford.


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Transcribed and formatted by Thomas Wildenberg