Fire Control Table
Fire Control Table is a generic term for machines that could automatically or semi-automatically produce a constant stream of range and deflection data for use in fire control. Examples of such equipment varied in many particulars according to manufacturer and epoch.
A machine worthy of this designation generally permitted the operator(s) to enter these inputs:
- an estimate of the range to the target
- a bearing to the target
- Speed and Heading of Own Ship
- estimated enemy speed and heading
and be rewarded by an indication of range and deflection which would slowly change over time as the hypothesis implied in the inputs evolved over time.
It was intrinsic in the approach taken that the inputs could be altered at any time as better visual observations were recorded or a change in either ship's course or speed required entry. A particularly common means of allowing generated ranges and deflections to be changed was to allow incremental spotting corrections to be applied without prejudice to what factor might have necessitated these adjustments.
Variations in Detail
The means by which the enemy's speed and heading were expressed in the table's configuration varied. Indeed, most complete tables offered a means to think of these variables in whichever manner seemed easiest from moment to moment:
- speed and heading
- speed and inclination (this drew inferences from own heading and target bearing)
- range rate and speed-across (this drew inference from own speed and heading and target bearing)
The visual indicators of internal settings as well as the means by which they were altered naturally differed from table to table. The ease with which the relationship between the two vessels could be taken by looking at the mechanism or the likely quality of the hypothesis judged often recommended one arrangement over another.
Variations in Scope
- Some tables supported the visual plotting of ranges, bearings and spotting reports (e.g.: the Dreyer tables). Others considered such methods optional or relegated their support to a larger context (e.g.: the Argo clocks).
- wind influence on the projectiles (along or across their trajectory) may or may not be corrected for (?)
- Ballistic drift may or may not be corrected for (?)
- Variations in air density may or may not be corrected for
Evolution of Design
No matter which manufacturer or nation a table belonged to, it was commonplace for improvements to be effected continually by modifying the equipment already installed or by producing tables to an improved design. Aspects most often tweaked over time were:
- improvements in indication (e.g., adding a protractor somewhere might permit enemy heading to be easily expressed relative to own heading)
- improvements to or addition of helm-free capabilities
- increased automation to eliminate rote human tasks in their operation
- Transmitting Station
- Dreyer Fire Control Table
- Argo Clock
- Ford Rangekeeper
- Le Prieur Fire Control Table
- Admiralty, Gunnery Branch (1918). Handbook of Captain F. C. Dreyer's Fire Control Tables, 1918. C.B. 1456. Copy No. 10 at Admiralty Library, Portsmouth, United Kingdom.