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.

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.

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 setting mark on an arc. The Trainer would use his handwheel to satisfy his F.T.P. Training Receiver and keep its range pointer set to the range repoted 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

• British Adoption of the Director
• British Director Firing Systems

Bibliography

• Template:BibUKDirectorFiringHandbook1917
• Template:BibUKDirectorFiringForDestroyers1918
• Template:BibUKFireControlInHMShips1919