British Destroyer Director Firing System
The British Destroyer Director Firing System was deployed late in the war to provide their destroyers and flotilla leaders with the benefits of director firing. It used a crew of three at the director and a fixed elevation angle for firing on the roll.
Nature
The smaller ships of the Royal Navy were not amenable to the bulky equipment that comprised the director firing systems for the capital ships, but some simplifications and compromises were seen as helpful in preserving the basic benefit in a suitable form.
The director could also signal the training angle for the ship's searchlights.
Director
The director was pedestal-mounted and, like the capital ship system, transmitted slewing and training angle to the gun mounts, and in the same step-sizes: 4 arc minutes for training, and 2 degrees per step for slewing. Firing impulses were likewise transmitted to the guns, always firing on the roll.
Unlike the larget system, however, elevation angles were not transmitted at all; the guns were all elevated to a fixed index-mark so they would match the sighting angle of the director's telescope. Henderson Firing Gear was provided if the director layer wished to use it.
The gearing was set up such that the slewing handle rotated the director fifteen times as fast as the training handle did.[1]
Director Crew
The director required a crew of three.
Director Layer
The director layer on this device both trained and elevated the director as well as working the firing pistol and adjusting the Henderson gyroscope. Since the Henderson gear would keep his horizontal wire on the target, he could concentrate on keeping the scope always on for training.[2]
Sightsetter
The sightsetter only set the deflection as directed; the gunsights at the guns worked in concert with the mechanical elevation indexes to establish the proper elevation for the range. The director's deflection drum featured a movable pointer which would be adjusted for the range in use, and this would correct for drift.
Cross-Level Operator
This man kept an open sight arranged 90 degrees off the scopes in azimuth on the horizon. This action corrected the director's line of sight due to trunnion tilt. At night, he additionally acted as sightsetter for the searchlight deflection dial.
Gun Crews
The gun crews functioned as usual, except as follows.
Rather than keeping his crosshairs on the target and firing when they came on, the gunlayer would use his handwheel to keep a newly-fashioned pointer attached to the trunnion in line with a given index mark on an arc. The arc had a series of indices arrayed at one degree intervals numbered 6 through 14. 10 was the mark ordinarily used, and corresponded to the director's scopes being in the same plane as the guns; the other marks could allow for super-elevation or firing at different points on the roll.[2]
The Trainer would use his handwheel to satisfy his F.T.P. Training Receiver and keep its range pointer set to the range reported by his sightsetter, as this would achieve the convergence correction.
Searchlight Crew
The man training each searchlight would have a bearing receiver very similar to the training receiver used at the guns, except that the deflection sent to the training receivers would be factored out at the director from its signals. The bearing receiver also corrected for convergence.
See Also
Footnotes
Bibliography
- Template:BibUKDirectorFiringHandbook1917
- Admiralty, Gunnery Branch (1918). Director Firing For Flotilla Leaders and Destroyers. Pub. No. B.R. 934 (late O.U. 6127 and C.B. 1461 and 1461(A). The National Archives. ADM 186/234.
- Template:BibFCHMShips
