British Director Firing Systems
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The Royal Navy's Director Firing Systems grew from a complete system which centralised elevation, training and firing of the main batteries of capital ships which was being fitted as the war began. As resources and opportunity permitted this system inspired less comprehensive systems suitable to cruisers, flotilla leaders and eventually event destroyers.
Tripod Director System
The first system produced, and the priority for deployment, was a comprehensive elevation-and-training system based upon the Vickers tripod directors in "light aloft towers" or in armoured hoods. On ships featuring both types, the light aloft director was deemed the primary director in recognition of its higher placement in the ship and the presumably better view it enjoyed.
Design
The two devices were similar, but the light aloft director tower's design included the cylindrical tower and its slightly domed roof, and the armoured tower one sat within a hood whose construction and operation were intrinsic to the ship's.
The directors were tilt corrected for range and dip to the guns was also accounted for. Moreover, drift was precisely corrected by a cam rather than the approximate correction achieved in most cases by inclining the sight.
The crew sat within a rotating tub that spun within a fixed base, facing inward to a large articulated gun sight on a tripod. It was much like a small gun mount without a gun.
Crew
There were four men within the light aloft director: a talker with a set of Telaupads and a voicepipe to the spotting top above (in some installations, he used a Navyphone), a Director Layer who elevated the sight and fired the guns, a Director Trainer who rotated the tower with either a large slewing handle or a smaller training handle, and a Sight Setter who applied the range and deflection being signaled to his F.T.P. receivers from the Transmitting Station.
In the armoured tower, a separate man below the director revolved the armoured hood by separate hydraulic means; the director itself was mechanically separate and spun within the hood, loosely matching its angle of training. Simple interlocks prevents the hood from training further off the director's angle that might cause damage to the sighting scopes.
Outputs
Elevation and training was transmitted to the guns by Step-by-Step circuits to F.T.P. elevation and training receivers; elevation in steps of 1.5 arc minutes, and training angle in steps of 4 arc minutes or in a slewing mode in steps of 2 degrees azimuth which had to be used in blocks of 6 degrees.[1]
The circuits could reliably handle 1000 steps per minute (16.67 per second), which effectively limited elevation speed to less than a half degree per second, and training to 1 degree per second and thereby eliminated the possibility of continuous aim in most conditions. Moreover, 1 degree per second in training might be so modest that firing under helm would be impossible, especially when turning against the bearing rate. Slewing mode could achieve 30 degrees per second, which would be ample for any scenario.
Firing was done by either a main or aux trigger at the director layer's hand to any number of guns that were switched in at a gun ready board worked by the talker.
Lightweight Pedestal System
For smaller ships such as light cruisers or for use in the secondary batteries of capital ships, the large tripod directors gave way to a compact pedestal-mounted director whose crew stood around it rather than sat upon it.
Destroyer System
The destroyer system was similar to the lightweight director, but was a training-only director with gyroscopic firing to fire the guns "on the roll". The guns would be elevated to one of several fixed index marks on a scale, and the director set to the same elevation so that the gyroscope's action would accomplish the desired elevation for firing. Unlike the elevation-and-training systems Britain was employing in capital ships, the destroyer director was manually cross-leveled by a dedicated crewman. This innovation would allow the destroyer to correct for the considerable cross-tilt that such a lively platform as a destroyer was prone to, as the destroyer's pitch would affect firing on the beam, or her rolling would affect firing well ahead or astern.
Homebuilt Systems
A number of ships developed their own director firing systems, although the detail on these is regrettably scanty. Lieutenant-Commander Arthur T. Johnstone was commended by the Admiralty in May 1915: "T.L. [Their Lordships] express their appreciation of the zeal & ingenuity displayed in the fitting of extempore director firing installation in H.M.S. Defence."[2]
See Also
Footnotes
- ↑ Director Firing Handbook, 1917, p. 151.
- ↑ Johnstone service record. The National Archives. ADM 196/142/593.
Bibliography
- Admiralty, Gunnery Branch (1917). The Director Firing Handbook. O.U. 6125 (late C.B. 1259). Copy No. 322 at The National Archives. ADM 186/227.
- 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.
- Admiralty, Technical History Section (1919). The Technical History and Index: Fire Control in H.M. Ships. Vol. 3, Part 23. C.B. 1515 (23) now O.U. 6171/14. At The National Archives. ADM 275/19.
- Brooks, John (2005). Dreadnought Gunnery and the Battle of Jutland: The Question of Fire Control. Oxon: Routledge. ISBN 0714657026. (on Amazon.com and Amazon.co.uk).
