Enemy Inclination Indicator

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Original Design[1]

The Enemy Inclination Indicator was a British device proposed by Commander Malcolm K. Grant[2] for use in surface ships and submarines that was evaluated between 1916 and 1918.

The devices used a model ship or submarine to depict the target, and to place this avatar in a place where it could be seen at the same time as the target was being observed. The model was observed through an eyepiece.[3]

Early Development

The optical device for observing the enemy was to be a pair of Service binoculars, Pattern 343. The operator would generally use but one eyepiece, however, and observe the model through a separate tube. The size of the model was such that it was hoped that it would appear the correct size as a target ship at 15,000 to 20,000 yards.[4]

In 1916, forty of the devices manufactured by H. Hughes and Sons were evaluated in light cruisers and destroyers,[5] but when the reports were received in 1917, few ships reported the instruments of any value although the concept seemed valid. The faults in execution were identified as:[6]

  • model inaccurately made
  • model appears too large in comparison to large ship at battle ranges
  • models of different ship classes are required

The present design did not make these alterations simple to effect. Vernon recommended a redesign before manufacturing any for use.[7]

Refinement for Use in Submarines

By 1918, its virtues were more immediately apparent in submarines, as in surface ships there were issues of varying the illumination and the size of the model to match the scenario being observed, prompting its pursuit for surface craft to be suspended. H. Hughes and Sons produced three modified instruments for use in submarines, where they would be mounted on the periscope so that one eye could see the model as the other eye was looking through the periscope. It was envisaged that further changes would be:[8]

  • Altering inclination angles to be off the bow rather than stern, as this is how Royal Navy submariners treated inclination
  • the vertical line would be changed to a pointer not as high as the model.
  • arrangements for different models to be easily swapped in
  • elimination of gearing and placing the model in the centre of the graduated arc

Footnotes

  1. Annual Report of the Torpedo School, 1916. Plate 2.
  2. Annual Report of the Torpedo School, 1916. p. 26.
  3. Annual Report of the Torpedo School, 1917. p. 197.
  4. Annual Report of the Torpedo School, 1916. p. 26.
  5. Annual Report of the Torpedo School, 1917. p. 197. (C.I.O. 2,442 of 1916, N.S. 25,841/16).
  6. Annual Report of the Torpedo School, 1917. p. 197.
  7. Annual Report of the Torpedo School, 1917. p. 197.
  8. Annual Report of the Torpedo School, 1918. p. 169.

Bibliography

  • H.M.S. Vernon. Annual Report of the Torpedo School, 1916. Originally C.B. 1329. Copy 4 at The National Archives. ADM 189/36.
  • H.M.S. Vernon. Annual Report of the Torpedo School, 1917. Originally C.B. 1474. Copy 7 at The National Archives. ADM 189/37.
  • H.M.S. Vernon. Annual Report of the Torpedo School, 1918. C.B. 1527. Copy 20 at The National Archives. ADM 189/38.