View source for Category:Torpedo Director

[[File:UnknownRNTorpedoDirector.jpg|thumb|480px| A British torpedo director of unknown type, possibly after alteration to a deflection sight.<br>Images of such devices are uncommon.<ref>Originally copyright International News Service with the caption "C 8776   TRYING TO TORPEDO A GERMAN BOAT.  A torpedo leaving its tube on the deck of a British Destroyer."</ref>]] 

A '''Torpedo Director''', in British service, is a calculating sight for firing torpedoes, more similar to a [[Sightsetting Equipment|settable gunsight]] than to a [[Gunnery Director|gunnery director]].  

==Nature and Function==
<video  id="xq-4Z8UDCYI" height="300" width="400" desc="Geometry and function of a Torpedo Director" position="right"/>

The ''Director Angle'' is the proper angle between the line of sight to the target and the path of the torpedo.  Helping the torpedo officer judge and discern this angle from data available to him by direct observation or external sources is the fundamental purpose of any torpedo director.  Additionally, a good torpedo director design should offer its user a quick means of judging whether the target is near enough that the torpedo will be able to reach it.

It should be noted that the proper director angle is dependent upon a proper estimation of enemy heading and speed (expressed in one of several ways), and upon the assumption that his motion while the torpedo is underway will, on average, continue about this mean heading.  It is easy to see aiming a torpedo which generally takes longer to reach its target than does a shell requires more cooperation on the part of the target!

The Royal Navy began the 20th century using torpedo directors that modeled the torpedo firing problem according to the '''Director Triangle''' &mdash; that formed by 
# the path of the torpedo
# the line of sight to the target at the moment of firing
# the path of the target between firing and impact.<ref>''Handbook of Torpedo Control, 1916'', pp. 4-5.</ref>  

As the war approached, the Royal Navy refined their hardware along lines they felt were important, issuing improved Marks or adding parts to existing directors.

==Small Innovations==

<video id="R1VFYBDCV6U" height="300" width="400" desc="The [[Tangent Bar]] in use." position="right"/>

The directors started out pretty basic.  Clever torpedomen soon thought of small changes that would make them better, and these were often viewed at the Torpedo School and the best ones standardised for proper fitting and allocation.

* A '''Radiomir Fore Sight''' (or just "Radium Fore Sight") is one with a small glass tube containing radium for use in night work.  It was often used on Pattern 2380A and the Line of Sight Director.  They proved successful, but the luminous substance itself left a desire for looking at alternatives.<ref>''The Annual Report of the Torpedo School, 1916'', p. 25.</ref>  Other directors had electrical lamps to illuminate their sights.  

* A '''Compass Ring''' was conceived in 1911 for 2006 and 2391/2392 ... an outer ring marked in Quadrant bearings that could be attached to the base of the director and set to own ship's course.  The enemy bar would be clamped to this ring. and it was thought that this ring could be adjusted manually if own ship changed course by reference to a compass near at hand or perhaps by automatic adjustment via a gyrocompass repeater.<ref>''The Annual Report of the Torpedo School, 1911'', p. 42.</ref>   It sounds like a snafu.

* A [[Longmore Disc]] was a disc that showed the inclination of the enemy to the torpedo bar (rather than the sight bar).  It was used on the 2380, but in 1915 or thereafter, it was to be replaced by a Robinson Disc.

* A '''Inclination Disc''' (or [[Robinson Disc]]<ref>''The Annual Report of the Torpedo School, 1915'', p. 59</ref> ) is a disc that rides the sighting arm and is marked 0 to 180 degrees left and right so that target [[Inclination]] is directly readable.<ref>''Handbook of Torpedo Control, 1916'', p. 17.</ref>  

* A '''Gyro Angle Base''' or "angled stand" was proposed for some directors in 1911<ref>''The Annual Report of the Torpedo School, 1911'', p. 42-43. (C of N 26/9/11.  N.S.G. 15583/14369)</ref> to support the proposed general introduction of torpedoes with angled gyros.  It consisted of a pair of discs that could rotate up to 40 degrees either side of zero against each other and lock every 10 degrees (initially) or 5 degrees (from 1916 or so) by use of a conical spring permitted them to be clicked to the same heading a torpedo set to the same [[Gyro Angle|gyro angle]] would take upon being fired.<ref>''Handbook of Torpedo Control, 1916'', p. 18.</ref>

* A [[Tangent Bar]] was a small armature which could be added to a torpedo director to offset its rear sight a short distance to make its sighting angle converge with the track of the torpedo when the director could not be located on or near the firing tube.  The idea was an example of the Royal Navy over-thinking the problem, and the service soon great disenchanted with the fragility and complexity they bestowed upon the directors.  Some time during the production of directors Pattern 2391a and 2392a, some were being sent out without tangent bars and directors of Pattern 2006 and later that were brought in for repair were sent back without their tangent bars.<ref>''Handbook of Torpedo Control, 1916'', p. 18.</ref>  The conclusion finally reached was that the lateral errors that would remain untreated without the tangent bars were apt to be vastly smaller than the other sources of error inherent in accurate torpedo fire except in very short range attacks.  These scenarios were to be treated by choosing a suitably offset aim point on the target.<ref>''Handbook of Torpedo Control, 1916'', pp. 77-78.</ref>

* A '''Central Bearing Disc''' "similar to those fitted in Patts. 2391-2" was considered in 1911 for the 2006 directors.<ref>''The Annual Report of the Torpedo School, 1911'', p. 42.</ref>

* A [[Graduated Sight Bar]] permitted the user to determine whether the target was presently within range of the torpedo to help eliminate the problem of firing when out of range.

* A [[Possible Shot Scale]] was a refinement on the graduated sight bar which allowed the firing range estimation to be resolved without resort to arithmetic.

==A Change in Thinking==

As the war began, the British were becoming increasingly dissatisfied with their directors, which they regarded as flimsy, mechanically loose, and not very easy or quick to set.<ref>''Handbook of Torpedo Control, 1916'', p. 12.</ref>  Indeed, on the latter point, in 1911 test firings, 6% of torpedoes that missed their target were attributable to errors in setting the director properly or firing the torpedo when out of range.<ref>''Annual Report of the Torpedo School, 1911'', p. 8.</ref>  In 1908, the errors made at the director accounted for a full 16% of misses!<ref>''Annual Report of the Torpedo School, 1908'', p. 7.</ref>

Other complaints were more fundamental.  The tangent bar was a particular object of disgust, making the director rickety and often being wrongly set in use.  More astonishingly, the very value of such a fixture as the tangent bar was finally receiving attention.  Why worry about the small lateral errors introduced when the director was not located directly at the torpedo tube when these errors were apt to be tiny in comparison with those caused by the enemy manoeuvring after the torpedo was fired or a failure to accurately judge his speed and heading in the first place?<ref>''Handbook of Torpedo Control, 1916'', p. 12. A better source can be found!</ref>

In 1912 and 1913, the ''Vernon'' was recording ideas about [[Deflection Plotting]] in such detail that it seems plain that a switch to using deflection as a means of setting the director angles was being actively considered.<ref>''Handbook of Torpedo Control, 1912'', p. 27.</ref><ref>''Handbook of Torpedo Control, 1913'', p. 30.</ref>

In 1915 or so, the Royal Navy was exploring, for the first time, larger questions of torpedo warfare in fleet actions &mdash; ones that seem glaringly obvious in hindsight.  One aspect of this reconsideration was that the series of torpedo directors they had relied on were to be refashioned to embody the geometry based on the '''deflection triangle''' rather than the director triangle.

The deflection triangle is that formed by 
# the path of the torpedo
# the line of sight
# a line perpendicular to the line of sight that passed through the point of impact

This last line was equivalent to the target's [[Speed-Across|speed-across]] if own ship were at rest.<ref>''Handbook of Torpedo Control, 1916'', pp. 4-5.</ref><ref>''Handbook of Torpedo Control, 1916'', Plate I.</ref>

The first step taken was to adapt the existing directors to a deflection aiming,<ref>''Handbook of Torpedo Control, 1916'', pp. 25-26.</ref> a conversion process that made all above water director become [[Torpedo Deflection Sight Mark I|T.D.S. Mark I]]s, and the line of sight directors [[Torpedo Deflection Sight Mark II|T.D.S. Mark II]]s.  The longer term step was to build [[Torpedo Deflection Sight|torpedo deflection sights]] optimised to the geometry.  These T.D.S. models (Mark III <em>et seq.</em>) would become the late-war successors to the torpedo directors described here.

==Royal Navy Torpedo Directors==

===The "Whitehead Director"===
[[File:ARTS1882Plate4.jpg|thumb|400px|A "Whitehead Director", with deflection scale in red.<ref>''Annual Report of the Torpedo School, 1882''  Plate 4.</ref>]]
Early patterns of director may have been dubbed simply, the "Whitehead Director".  There is passing mention of how practice with their use might be made in 1881, and a simple diagram seems to indicate a hemispherical shape.<ref>''Annual Report of the Torpedo School, 1881'', pp. 22, 29.</ref>  An important aspect of this director was to calculate the aftward deflection of a non-gyro torpedo fired over the beam of a moving vessel.<ref>''Annual Report of the Torpedo School, 1882'', pp. 40-1.  Plate 4.</ref>

The image shows an experimental deflection scale in red from 1882, configured for firing to port.  The torpedo is to be fired 22 degrees before the beam from a ship going 8 knots.  The deflection scale is drawn for 1.5 degrees per knot.  By bringing the red "8" to the 22 degree position, the red "0" indicates the heading the deflected torpedo will assume.

In 1896, it is implied that the director in the torpedo boats was often inside the very small conning tower, and that this might be unsuitable when conning was to be done from outside.  It was urged that these ships should contrive an alternative position outside the conning tower "or other suitable place."<ref>''Annual Report of the Torpedo School, 1896'', p. 45.</ref>

===Pattern 1192/1192a=== 
<small>([[Torpedo Director Pattern 1192|main article]])</small>

These were large, semicircular directors intended for use directing broadside fire.  They received some enhancements and alterations, but were considered obsolete by 1912.

===Pattern 1193/1193a=== 
<small>([[Torpedo Director Pattern 1193|main article]])</small>

An early director with a 60 degree arc, intended for firing ahead from torpedo craft.

===Pattern 1895/1895a=== 
<small>([[Torpedo Director Pattern 1895|main article]])</small>

A lighter version of the 1193, with a 60 degree arc for use in early torpedo craft.

===Pattern 2006/2006a=== 
<small>([[Torpedo Director Pattern 2006|main article]])</small>

These compact, circular directors first appeared for use in armoured control towers in 1904-1905, and saw service into the great war.

===Pattern 2390/2390a=== 
<small>([[Torpedo Director Pattern 2390|main article]])</small>

A 60 degree director similar to Pattern 1985, available by 1912 at least, supplied to torpedo craft with heater torpedoes.

===Pattern 2389/2389a=== 
<small>([[Torpedo Director Pattern 2389|main article]])</small>

Available by 1910 at least, it was similar to the Pattern 2390, but fitted for use from the bridge.

===Pattern 2380/2380a=== 
<small>([[Torpedo Director Pattern 2380|main article]])</small>

New in 1914 and similar to the Pattern 2390a, but larger and of improved construction.<ref>''Torpedo Drill Book, 1914'', p. 564.</ref> 

===Pattern 2387=== 
<!-- <small>([[Torpedo Director Pattern 2387|main article]])</small> -->

Available from 1910 at least.<ref>''The Annual Report of the Torpedo School, 1910'', p. 32.</ref> Same as Pattern 1192, but fitted for use from the bridge by addition of a [[Tangent Bar|tangent bar]].<ref>''Torpedo Drill Book, 1914'', p. 564.</ref>

===Pattern 2388/2388a=== 
<!-- <small>([[Torpedo Director Pattern 2388|main article]])</small> -->

Available by 1910 at least.<ref>''The Annual Report of the Torpedo School, 1910'', p. 32.</ref>  Same as Pattern 1193, but fitted for use from the bridge by addition of a tangent bar.<ref>''Torpedo Drill Book, 1914'', p. 564.</ref>  The 2388a was sturdier and had a solid sight bar, and was probably a 2388 that had been repaired to the new standard, as none of the type was directly manufactured, owing in part to new destroyers not being fitted for fore bridge firing in the 1911 era.<ref>''Addenda (1911) to Torpedo Manual, Vol. III., 1909'', pp. 170-171.</ref>  By 1916, they were considered obsolete.<ref>''Handbook of Torpedo Control, 1916'', p. 16.</ref>  Like the 1193, they were likely 60 degree arcs.{{INF}}

===Pattern 2391/2391a/2392/2392a=== 
<small>([[Torpedo Director Pattern 2391|main article]])</small>

A family of circular directors improving upon the Pattern 2006 introduced from 1909 by adding a sighting telescope and a possible shot scale.  In 1912 or so, the -a models appeared which added support for gyro angling.

===Pattern 2236=== 
<small>([[Torpedo Director Pattern 2236|main article]])</small>

Entering service in 1915 or 1916, and reflecting the disfavour accorded tangent bars, the 2236 was a modification of the 2391a with the tangent bar and the association telescopic member to offset the sighting telescope removed.  It had an inclination disc, a Radiomir fore sight and a deflection bar.<ref>''Handbook of Torpedo Control, 1916'', p. 18.</ref>

Already in 1916, plans were being drafted to convert these directors into Torpedo Deflection Sights. <ref>''Handbook of Torpedo Control, 1916'', p. 25.</ref>

===Line of Sight Director===
<small>([[Line of Sight Director|main article]])</small>

This was a circular director similar to the Pattern 2006, but with a rotating torpedo bar, intended for use on the fore bridge of a light cruiser or smaller vessel.

By mid 1917, following plans drafted in 1916,<ref>''Handbook of Torpedo Control, 1916'', p. 25.</ref> they were being converted into [[Torpedo Deflection Sight Mark II|T.D.S. Mark II]] (not Mark I, as with all other directors).<ref>''Annual Report of the Torpedo School, 1917'', p. 190.</ref><ref>''Handbook of Torpedo Control, 1916'', p. 25, Plate 12.</ref>

==Pattern 3340== 
<small>([[Torpedo Director Pattern 3340|main article]])</small>

This director was intended for use on submarines.  On the surface, it would be fitted to the head of the periscope for use on the conning tower.  When submerged, it would function as a hand-held calculator to determine the periscope angle to be used for firing.

==See Also==
*[[Torpedo Deflection Sight]]
*[[Torpedo Deflection Sight Mark I]]
* [http://vimeo.com/7565886 Video] depicting the principle of a torpedo director

==Footnotes==
{{reflist}}

==Bibliography==
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[[Category:Torpedo Control]]
[[Category:Shipboard Equipment]]