Indefatigable Class Battlecruiser (1909)

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Overview of 3 vessels
Citations for this data available on individual ship pages
Name Builder Laid Down Launched Completed Fate
Indefatigable Devonport Royal Dockyard 23 Feb, 1909 28 Oct, 1909 1911 Sunk 31 May, 1916
New Zealand Fairfield Shipbuilding and Engineering Company, Govan 20 Jun, 1910 1 Jul, 1911 1912 Sold 19 Dec, 1922
Australia John Brown & Company, Clydebank
(Ship no. 402)
23 Jun, 1910 25 Oct, 1911 Jun, 1913 Scuttled 12 Apr, 1924


According to the ambitions of 1909, these ships had Service Gear Mark II wireless upon completion.[1]


Indefatigable and Australia, at least, were fitted with Siemens' No. 3 Twin Mountings for 24-in projectors. In 1914, some or all of these were to be modified to permit 90 degree elevation for use in anti-aircraft work.[2]


Main Battery

This section is sourced in The Sight Manual, 1916.[3]

The eight 12-in guns were Mark X mounted in B. VIII* turrets. The mountings could elevate 13.5 degrees and depress 5 degrees.[4]

The gun sights were cam-worked sights limited to 15 degrees elevation.

The deflection gearing constant was 67.75, with 1 knot equalling 2.42 arc minutes, calculated as 2700 fps with 4 CRH shells at 5000 yards. Range drums were provided for 2 CRH projectiles at full charge at 2625 fps, reduced charge at 2250 fps, as well as 6-pdr sub-calibre gun and .303-in aiming rifles. By some time in 1916, dials and drums were on hand for 4 CRH heads.

Muzzle velocity was corrected by adjustable scale plate. An adjustable temperature scale plate could vary between 60 to 100 degrees Fahrenheit,[Fact Check] and a "C" corrector could alter the ballistic coefficient by at least +/- 15% and possibly 20% as in other sights.[Fact Check]

Drift was corrected by inclining the sight bracket by 3 degrees with a permanent correction of 2.07 knots left.

The side position sighting lines were 37.25 inches above and 38.25 inches abreast the bore, and the central scopes were 49.25 inches above and 42 inches abreast.

The mountings had free trainers sights, though perhaps only in the centre position.

Secondary Battery

This section is sourced in The Sight Manual, 1916.[5]

Sixteen 4-in B.L. Mark VII guns on P. II* mountings were arranged for broadside fire. They were similar to the P. II and P. II* equipment fitted in the Bellerophon class, H.M.S. Neptune and other ships.

The mounting could elevate 15 degrees and depress 7 degrees, but though its sight could match the 15 degree elevation, the range dial was only graduated to 11.5 degrees (10,000 yards).

These cam-worked sights had range dials for 2750 fps, and 1-in and .303-in aiming rifles. MV could be corrected by adjustable pointer through +/- 150 fps.

The range dial may have been 14 inches in diameter with markings that came closer together at higher ranges, as in the P II. If so, the marks were 34 inch apart for 50 yards difference at 500 yards and was 18 inch for 50 yards difference at 9,000 yards.

Unlike some P. II* sights such as those on Neptune, these sights were F.T.P. sights.

The deflection gearing constant was 64.277 with 1 knot equal to 2.41 arc minutes, corresponding to 2800 fps at 2000 yards. Drift was corrected by inclining the sight 2 degrees.

The layer's sight line was 14 inches above the bore, and 15.25 inches left. The trainer's sight line was 15.25 inches above and 12.5 inches right.

The sight had a temperature corrector, but not a "C" corrector.

The layer had an open sight. The trainer's sight could be used as a free sight with a counterweight.

In February, 1913, these mountings, along with many other 4-in and 6-in mountings in various capital ships and cruisers were to have illumination added for their training index racers.[6] In August of 1913, Portsmouth Royal Dockyard was to supply head rests for the guns in Indefatigable and New Zealand, to be fitted in the dockyard when the opportunity arose. Australia was omitted from this order, presumably because she was on her Australian cruise.[7]


  • two 18-in submerged broadside tubes forward, depressed 3 degrees.[8]

In 1909, it was decided that ships of this class were to carry 10 heater torpedoes. The goal, when supplies were made good, was to have these be Mark VI* H. or Mark VI** H..[9]

In 1913, it was approved, as part of a general reallocation of 18-in torpedoes, to replace the torpedoes on these ships with Mark VII* or Mark VII** torpedoes.[10]

Fire Control

Range Dials

As of 1920, New Zealand had two Range Dial Type Bs and a single Type C. Australia had a single Type B and a single Type C.[11]


Indefatigable was completed in the same form as the Invincibles with two 9-ft rangefinders, one in each control top. The delay in bringing Australia and New Zealand along permitted them to incorporate a new wrinkle: a third 9-ft rangefinder added atop "A" turret. Indefatigable received her "A" turret rangefinder during a refit between 1911 and 1914.[12]

Rangefinders were added to the echelon turrets by at least 1917 when photos depict them on Australia.[13] Australia had a small one on her after super structure, but Indefatigable did not.[14]

Sometime during or after 1917, an additional 9-foot rangefinder on an open mounting was to be added specifically to augment torpedo control.[15]

Evershed Bearing Indicators

Only Indefatigable is explicitly mentioned in Handbook for Fire Control Instruments, 1914,[16] but the other ships were approved to receive equipment in 1916 (see their ship pages).

The transmitting positions for Indefatigable were

  • Fore control platform (transmitters to port and starboard with a local switch to select one in use)
  • "A" turret
  • "X" turret
  • Upper aft conning tower

The protocols for how her crew should handle wooding of the turrets was outlined in the Handbook for Fire Control Instruments, 1914.[17]

In 1917, it was approved that capital ships of Dreadnought class and later should have Evershed equipment added to their C.T., able to communicate with either the fore top or a control turret. If there were not enough room in the C.T., a bearing plate with open sights and 6-power binoculars would be added to the C.T.. At the same time, all directors were to be fitted with receivers and, "as far as possible", ships were to have fore top, G.C.T. and controlling turrets fitted to transmit as well as receive, though this was noted as being impossible in some earlier ships.[18]

Mechanical Aid-to-Spotter

At some point, Australia and New Zealand were equipped with a pair of Mechanical Aid-to-Spotter Mark Is, one on each side of the foretop, keyed off the Evershed rack on the director. As the need for such gear was apparently first identified in early 1916, it seems likely that these installations were effected well after Jutland.[19]

In 1917, it was decided that these should have mechanical links from the director and pointers indicating the aloft Evershed's bearing.[20]

Gunnery Control

The control arrangements were likely as follows.[21]

Control Positions

  • Fore top
  • Main top (Australia lacked one)[Inference]
  • "A" turret[Inference]
  • "Y" turret[Inference]

Some ships had C.O.S.s within the control positions so they could be connected to either T.S..[22]

Control Groups

The four 12-in turrets were separate groups, each with a local C.O.S.[Inference] so that it could be connected to

  • Forward T.S.
  • After T.S.
  • Local control from officer's position within turret


Main Battery

The ships were fitted with a tripod-type director in a light aloft tower on the foremast below their forward control top along with a directing gun in the Y turret.[23][24] The battery was not divisible into for split director firing.[25]

The turret Elevation Receivers were pattern number H. 2, capable of matching the 13.5 degree elevation limit of the mountings. The Training Receivers were the single dial type, pattern number 7.[26]

Secondary Battery

The 4-in broadside guns are not listed as ever having had directors before the war's end,[27] but in July, 1922, Australia apparently had director firing for her secondary battery, as spares were ordered to be set aside for her.[28]

Torpedo Control

By the end of 1917, common torpedo control additions to all capital ships were to be adopted where not already in place. Those for Dreadnought and later classes with 18-in tubes were to include:[29]

  • duplication of firing circuits and order and gyro angle instruments to allow all tubes to be directed from either C.T. or T.C.T.
  • navyphones from both control positions to all tube positions
  • bearing instruments between "control position, and R.F., and course and speed of enemy instruments where applicable, between the transmitting stations and the control positions."
  • range circuits between R.F.s and control positions

Transmitting Stations

Like all large British ships of the era prior to King George V and Queen Mary, these ships had 2[30]

Dreyer Table

As of 1918, the New Zealand and Australia carried Mark I Dreyer tables[31]. As to time of installation, one secondary source asserts that Indefatigable and New Zealand had Mark I tables at the Battle of Jutland,[32] but no primary source confirms this. Moreover, a first-hand account seems to suggest a manual plotting board was being used in the T.S. of New Zealand.[33]

The ships were never given Dreyer Turret Control Tables.[34]

Fire Control Instruments

The ships used Vickers F.T.P. Mark III range and deflection instruments to send data to gun sights (likely with cross-connected Mark III* range transmitters[35]), retaining Barr and Stroud (probably Mark II*[Inference]) instruments for other destinations.[36]

Target Visible and Gun Ready signals mounted in the TSes and control positions indicated which turrets could see the target and which guns were ready.[37]

See Also


  1. Annual Report of the Torpedo School, 1908. Wireless Appendix, p. 13.
  2. Annual Report of the Torpedo School, 1914. p. 52.
  3. The Sight Manual, 1916. pp. 4, 34, 106, 108-109, Plate 10.
  4. I assume the B. VIII* elevation is as in the B VIII
  5. The Sight Manual, 1916. pp. 7, 89-90, 108, Plate 39.
  6. Admiralty Weekly Orders. The National Archives. ADM 182/4. 21 Feb, 1913 entries. pp. 3-4.
  7. Admiralty Weekly Order No. 470 of 22 Aug, 1913.
  8. Addenda (1911) to Torpedo Manual, Vol. III, 1909. p. 155.
  9. Annual Report of the Torpedo School, 1909. pp. 13-4.
  10. Annual Report of the Torpedo School, 1913. p. 8.
  11. Manual of Gunnery (Volume III) for His Majesty's Fleet, 1920. p. 44.
  12. Roberts. Battlecruisers. pp. 90-91.
  13. Roberts. Battlecruisers. Photo page 30.
  14. Burt. British Battleships of World War One. p. 98.
  15. Annual Report of the Torpedo School, 1917. p. 198. (C.I.O. 481/17).
  16. Handbook for Fire Control Instruments, 1914. pp. 33-9.
  17. Handbook for Fire Control Instruments, 1914. p. 36.
  18. Annual Report of the Torpedo School, 1917. p. 230.
  19. The Technical History and Index, Vol. 3, Part 23. pp. 25-6.
  20. Annual Report of the Torpedo School, 1917. p. 230.
  21. Handbook for Fire Control Instruments, 1914. pp. 7-8. (some inferences drawn due to fundamental differences between this design and that of Orion to which it is likened).
  22. Handbook for Fire Control Instruments, 1914. p. 7.
  23. The Director Firing Handbook. pp. 88, 142.
  24. Burt. British Battleships of World War One. p. 98.
  25. The Director Firing Handbook. p. 88.
  26. The Director Firing Handbook. pp. 144, 146.
  27. The Director Firing Handbook. pp. 143.
  28. Admiralty Fleet Order 1832/1922. (G. 2475/22.—7.7.1922)
  29. Annual Report of the Torpedo School, 1917. p. 209. (C.I.O. 4212/17.).
  30. Handbook for Fire Control Instruments, 1914. pp. 6-7.
  31. Handbook of Captain F. C. Dreyer's Fire Control Tables, 1918. p. 3.
  32. Sumida, Jon. In Defence of Naval Supremacy p. 300.
  33. Midshipman Gordon Eady quoted in Steel & Hart. Jutland 1916, p. 75.
  34. Handbook of Captain F. C. Dreyer's Fire Control Tables, 1918. p. 3.
  35. Annual Report of the Torpedo School, 1910. p. 148.
  36. Handbook for Fire Control Instruments, 1914. pp. 72.
  37. Handbook for Fire Control Instruments, 1914. p. 11.


Indefatigable Class Battlecruiser
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