REFERENCE DOCUMENTS & RESOURCES - OFFICIAL ADMIRALTY DOCUMENTS
ADM 239/137: C.18-Oct-2007Updated 18-Oct-2007
This document is a modern transcription of Admiralty record ADM 239/137. It concerns the state of Royal Navy gunnery as of 1939. It was transcribed by David Chessum on behalf of the the Royal Navy Flag Officers 1904-1945 website. The original file is held at the The National Archives at Kew, London. This Crown Copyrighted material is reproduced here by kind permission of The National Archives.
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2 C.B. 3001(39.)- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
CONTENTS
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Page |
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| LIST OF PLATES | |
| INTRODUCTION | |
| PART I. - General Review | |
| PART II. - Anti-Ship Gunnery | |
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42 |
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51 |
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52 |
|
80 |
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85 |
| Part III. - Anti-Aircraft Gunnery | 88 |
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88 |
|
102 |
|
111 |
| Part IV. - Shore Attack and Defence | 116 |
|
116 |
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121 |
| Part V. - Material | |
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|
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|
|
|
|
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133 |
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133 |
| APPENDIX I. - Standard Spotting Rules for Main Armaments of Capital Ships and Cruisers | 138 |
| II. - Spotting Rules for Destroyers fitted with Admiralty Fire Control | 143 |
| III. - Spotting Rules for Secondary Armaments of Capital Ships, Main Armaments of Aircraft Carriers, Escort Vessels, Modern Minesweepers, Older Destroyers, Depot and Repair Ships | 147 |
| IV. - Instructions for the Conduct of Close Range Barrage Fire | 150 |
LIST OF PLATES
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| No. | To face Page |
| 1. – Progress of Hitting Results with 4-in. Mark XVI Gun on Twin Mark XIX Mounting during 1938 .. .. .. .. | 90 |
| 2. – Variation in accuracy of Long Range H.A. Fire with Range .. | 95 |
At end of book- |
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3. – Nelson and Rodney, S.S., 16-in., Mark I, Throw-off, H.S.B.P.T., and M.A.C. at Centurion. |
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4 C.B. 3001(39.)- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
INTRODUCTION
___________
General Information and Instructions for practices were issued in Admiralty Letter M/T.S.D. 56/39/G of 3.3.39.
The new Standardised Spotting Rules were issued in Admiralty Letter M/T.S.D.320/38/G. of 5.1.39 and in C.A.F.O. 353/39.
2. Annual reports from Commanders-in-Chief should reach the Admiralty not later than the 31st December, 1939, those from the Home, Mediterranean and China Fleets in quadruplicate, and from other Commanders-in-Chief and Flag Officers of Squadrons in duplicate.
The advantages of producing Progress in Naval Gunnery early in the year require no emphasis.
3. The re-introduction of a list of “points on which information is required when obtainable from normal practices at the end of each Section has proved of value in focussing attention of specific matters discussed in the book, and in facilitating the compiling and analysing of the reports. This practice has been continued.
4. It has been decided to recommence the half-yearly issue of the confidential book containing selected reports of Gunnery practices. Detailed summaries in Progress in Naval Gunnery of important individual firings have, therefore, been discontinued.
PART I
_____
GENERAL REVIEW
_____
SUMMARY OF YEAR’S WORK - 1938
Except for the mobilisation of the navy in the September crisis, which inter alia deprived the Home Fleet of the Centurion for the autumn practices, the interference to programmes by the international situation was not so marked in 1938 as in the preceding years.
2. The effect of the inevitable changes of personnel due to expansion is still tending to increase. Methods of easing the situation, including proposals from the fleet, are constantly under consideration, but it is not clear that any improvement can be expected for the present.
3. The conclusion of the investigation of trial low angle spotting rules has been a most satisfactory feature, and it is hoped that the consequent introduction of standardised spotting rules suitable for all types of ship will simplify training at sea and in the schools.
4. This should also permit of greater attention being given to rate-keeping which, with rangefinding, is disclosed by a collective analysis as being the principal cause of poor hitting.
5. The resumption of more regular practices during 1938 made no appreciable difference to the general standard of A.A. gunnery except in the marked progress made in the use of new equipments. The more stringent cinema marking is no doubt partly responsible for the apparent lower standards of recent years, but under the circumstances the indication is that frequent changes of personnel have as much, if not more, influence on results than lack of practice.
6. Some progress has been made with close barrage fire, but at the expense of development in augmenting fire from L.A. guns.
7. It is desired that special attention should be given to obtaining improved accuracy in all forms of A.A. gunnery, particularly in small ships fitted with new equipment. Constant investigation is resulting in the development and production of better equipment, but it is considered that existing equipment is capable of better results than have hitherto been attained.
8. Defence against M.T.Bs. has again suffered for want of suitable targets. The target raft towed by the D/C M.B. did not proved satisfactory, and four D/C motor boats of small size and protected to a limited degree against 2 pdr. practice shot have now been ordered. When delivered t is intended that trials should proceed both in Excellent and in one of the Main Fleets, firing direct at these target boats.
6 C.B. 3001(39.)- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
Principal Object for 1939 Practices
9. Except for the large scale fleet firings, referred to later, this remains the same as for 1938. The development of fire control organisation and procedure on the lines indicated in C.B.3001/38 and amplified in this book, and the attainment of proficiency in the use of the standardised spotting rules is to take precedence over new problems.
Competitive Firings
10. This type of firing has largely been superseded by efficiency tests, and in 1938 was carried out on the China Station only, in addition to efficiency tests by some units. The Commander-in-Chief remarks as follows:-
“A low angle competitive firing was carried out on 23rd August by three 8-in. cruisers, this being the culminating point of individual day practices at Weihaiwei. For the second year in succession this was won by Suffolk.
The question as to the advisability of retaining this practice in the year’s programme is still under consideration. On the China Station, when ships are inevitably separated for a part of the year, such a practice has definite advantages and is preferred to the system of awarding gunnery problems.
Owing to the differences in armament of ships, the high angle competitive firing hitherto carried out, has been put in abeyance, and a squadron firing substituted in lieu. All available ships took part in this practice in 1938 and it was carried out at high speed with ships firing both sides, and culminated in a runner torpedo attack on the firing line, when full avoiding action was taken.”
Efficiency Tests
11. The value of efficiency tests has again been confirmed on stations where circumstances have permitted of their being carried out.
12. A tendency on the part of Officers of Quarters to go into local control as soon as breakdowns begin, instead of first trying intermediate and more efficient methods, has been brought to light. While undue waste of time trying alternatives should be avoided, the much greater efficiency of main control with director firing demands that it should be continued as long as possible, and that opportunities of reverting to it after breakdowns have been dealt with should be looked for.
13. It has been suggested that a prolonged sub-calibre firing in an efficiency test would be valuable for exercising breakdowns. This
type of practice is recommended when difficulties arise in arranging a full calibre efficiency test, and when it is desired to conserve the ammunition allowance for other practices.
Efficiency Badges
14. The award of badges for gunnery efficiency has been adopted generally in the Mediterranean Fleet and for sloops on the Africa Station. Other stations have not adopted the scheme, and the Commanders-in-Chief make no comment, except the Commander-in-Chief, America and West Indies, who considers that the award of efficiency badges would provide an incentive.
Prolonged Firings
15. These practices continue to give value from both the control, ammunition supply and material points of view for the expenditure of ammunition entailed.
16. This year it has been necessary to omit the 8-in. cruisers to avoid complications arising in the relining programme for worn guns. Capital ship main armaments have also been omitted from the programme of prolonged firings in view of the large scale fleet firings which, it is hoped, will be carried out instead.
Large Scale Fleet Firing (C.B.3001/38, page 8).
17. Since the fleet programmes will not permit of concentrating the two main fleets at Malta this year, it has been decided that each fleet should stage their own large scale fleet firing, making the best use of the reduced number of ships for the investigation.
18. An outline of the type of practice proposed including the distribution of fire to be used in the various phases of a fleet action has been received from the Commanders-in-Chief, Home and Mediterranean Fleets. Both fleets intend to carry out the practice in the autumn with a firing line of five capital ships, extended possibly by two cruisers in the Home Fleet. The target line will consist of about five targets, some fast and some slow, and fire will be opened, after approach and deployment, with divisional concentration. Fire will be re-distributed while closing and conclude with a general engagement. Relief spotting aircraft will be employed and W/T jamming introduced.
19. The reduction of the battle line from the original proposal for a combined fleet firing will considerably reduce the strain on communications and the difficulties of the aircraft, but the proposals which are generally concurred in, should provide a more searching test of communications in battle that has hitherto been carried out, as well as a more comprehensive gunnery practice than has been staged for many years.
8 C.B. 3001(39.)- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
20. Further, as some battleships in both fleets will be using G.I.C. concentration while the others use G.M.S. procedure (vide Part II. Paras. 8 to 11), these firings will provide a direct comparison of the effectiveness of the two methods of concentration under similar conditions and it is desired that the Commanders-in-Chief should remark on this question in their reports on the firings.
Duties of Control and Spotting Officers (C.B. 3001/38, pages 9 to 11)
21. Reports show that the principles enunciated have generally proved satisfactory and that opinions are unanimous on the benefits of additional observers and of the separation of the ordering of range spotting corrections from the observation of fall of shot. In some cases, however, the organisation adopted and the procedure followed show a confusion of ideas in the application of these principles, and it is considered that the meaning of some of the paragraphs in C.B. 3001/38 cannot be quite clear, particularly those dealing with the responsibility of the Control Officer.
22. That the Gunnery Officer, as Control Officer, must be responsible for the control of the main armament is not open to question, but from the emphasis which has been laid on his responsibility for the determination and application of spotting corrections, it has in some cases either been inferred that the Gunnery Officer is intended to perform this duty himself, or it has been decided that this is the only method of discharging his responsibility.
If the Gunnery Officer should assume the duty of determining the spotting corrections he will be unable efficiently to perform the more important functions of supervising rate and spotting officers, his principal duty in the control of fire. It is, therefore, undesirable that he should do so.
23. The determination and application of spotting corrections is only one element in the control of gunfire, and the delegation of this duty to the transmitting station cannot be regarded as the shelving of responsibility. Normally the control officer will either hear the corrections being given in his earphones, or he will be able to check the corrections applied by means of the repeat receivers; but he cannot be expected to exercise a degree of supervision necessary to see that every single correction is properly applied without detriment to his other duties. He may be temporarily occupied with the Captain, with the Rate Group or with some other matter connected with the armament, and it is unnecessary and unsound that firing should be delayed while he personally verifies that the drill in one detail is correct.
24. The advantages of “plot spotting” in the T.S. are touched on in paras. 31 to 33 on page 10 of C.B. 3001/38, but from the number for reports describing different procedure with “direct” and
PART 1. – GENERAL REVIEW – DUTIES OF CONTROL AND SPOTTING OFFICERS 9
with “aircraft: spotting it is evident that these need amplification. The essence of this procedure correctly followed is that it remains identical, whether the observation being made use of comes from either the main control, outlying observers, aircraft, or from a combination of any of these; and that in each case and whichever position is controlling the fullest use is made of the results of these observations and of the equipment provided to assist in controlling gunfire.
25. The investigations of trial spotting rules, lasting three years, have resulted in the drawing up of similar rules for aircraft and direct spotting, because it is now generally accepted that aircraft spotting in action will at best be intermittent and it is therefore necessary that it should not require either different rules or different procedure.
26. Consequently it is illogical and contrary to developments to adopt the system of applying spotting corrections in the control position with direct spotting, while, with aircraft spotting, these are applied in the T.S.
27. Other remarks in reports are to the effect that suitable individuals are not available in the control team for T.S. plot spotting; that the control officer wishes to maintain detailed control of range spotting; and that the control officer feels handicapped when wearing headphones by which he can listen to corrections given in the T.S., and to avoid this prefers to give the corrections himself.
28. To take the last point first, a number of other reports require that the control officer’s telephone should be fitted with a switch by which he can connect himself at will to either the rate or the spotting group. These evidently hold the view that the efficient control officer must be in direct telephone communication with all the important units in the control team. This view is fully concurred in.
29. The question of suitable individuals is largely a matter of training, for able seamen and leading seamen as well as officers have become successful spotting plot operators. The T.S. officer should not be used for this duty, but he must be trained to include the spotting plot in his supervisory duties.
30. The remaining point against T.S. plot spotting that “the control officer wishes to maintain detailed control of range spotting: shows reluctance to decentralise for fear a mistake will be made. The result of this attitude, however, is that the much more difficult rate keeping is decentralised completely beyond his control, and suffers accordingly.
31. Experience in practice firings by ships where the procedure is understood and correctly applied, is that plot spotting in the T.S. does not deprive the control officer of control of range, that it
10 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
reduces the number of mistakes made in the application of spotting corrections, that it provides a ready means of co-ordinating all information, and that it leads to better rate keeping.
Control Officer’s Plot
32. One or two reports still advocate a plot in the control position for use by the control officer. The objections to this plot are:-
(i) A suitable plot is already provided, or shortly will be, in the transmitting station and it is undesirable to duplicate equipment unnecessarily.
(ii) A plot in the control position cannot reproduce all the information available and is therefore liable to lead to the neglect of information which may make the difference between hitting and missing the enemy.
(iii) If required in the fore control it must also be necessary in the after control, which means still more equipment and personnel for fire control.
(iv) It is most undesirable to increase the congestion already existing in control positions and D.C.Ts.
(v) There is a great deal of evidence from practice firings to show that the plot distracts the control officer’s attention from the target, from rate keeping and the control of fire generally. In action is must be anticipated that he will have no time to devote to a plot except to the detriment of his other duties.
33. The trial of a control officer’s plot arose because the value of the TS. Plot in assisting with more complicated range spotting rules was not fully appreciated. Experience now shows that the control officer’s plot is not only unnecessary but may be a danger, and it is desired that this trial should now cease.
34. While on this subject it is once again emphasized that while the spotting plot in the T.S. is particularly helpful in applying automatic corrections, the plot operator in a well-trained control team will often be in a better position that the control officer to appreciate the hitting gun range on which to base the next group.
36. The Commander-in-Chief, Home Fleet, expresses the following opinion on this subject:-
“In cruisers, it is considered that the application of spotting corrections from a T.S. spotting plot is necessary, and the advantages obtainable from a proper use of this plot are already evident.
Simplicity is considered to be an important requirement in the design of the plot.
In capital ships a form of plot has also been found advantageous, but has been situated in the control position
In modern capital ships it would seem preferable to conform to the arrangement in cruisers.”
PART 1. – GENERAL REVIEW – ADDITIONAL OBSERVERS 11
Additional Observers
36. Various outlying positions have been tried for stationing additional spotter observers, and in peace practices the majority have achieved their object. It is probably, however, that in action only suitably equipped gunnery positions will be satisfactory, if all doubt as to the target to spot on is to be removed. This would rule out the crow’s nest and other positions not fitted with bearing indicators.
37. It is, therefore, considered that outlying spotter observers should only be stationed in the after control and one of the turrets.
Communications for Control and Spotting Officers
Control officers
38. The opinion has been expressed by several ships that the control officer’s telephone should be fitted with a switch to enable him to talk on either the spotting or the rate group. This is concurred in, and arrangements are being made for new construction and ships being refitted to be fitted accordingly. Other ships should do this from their own resources demanding gear as necessary from the dockyards.
Spotter Observers
39. Spotting lamps fitted by ship’s staff have generally proved satisfactory and approval has been given for this arrangement to be adopted in all capital ships and cruisers.
40. The suggestion of one ship to fit the lamps in the control officer’s binoculars is not liked in view of the resulting interference and complication. The ideal is considered to be a self evident lamp box containing two “over’ red lamps and to “short” green lamps for each observing position situated near the control officer, and near the T.S. spotting plot. Corresponding pushes are fitted in each observing position and these are used as follows:-
One “short” push pressed .. Some shots seen short.
One “over” push pressed .. Some shots seen over.
Both over or short push pressed Whole salvo seen “over” or “short”.
One short and one over push .. Straddle observed.
pressed
To simplify wiring and to obviate the danger of a stale report being acted on the lamps should only burn while the push is being pressed.
T.S. Control of Inclination
41. Results have been inconclusive and in many of the reports it is not clear that this method has been given a serious trial. No doubt circumstances have been against the investigation, but there appears to be a considerable body of opinion which deprecates the
12 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
idea of adjusting enemy settings on information collected in the T.S. without previous reference to the rate officer aloft, whatever the conditions.
42. Although there is much to be said for this point of view, indifferent rate keeping in spite of better equipment points to faulty methods, and it is concluded that the T.S. is one place where there is scope for improvement.
43. It is not intended that the control officer (or the rate officer beside him) should be deprived of his authority in this respect, but it is essential that available information in the T.S. should be quickly and intelligently co-ordinated, and reliable deductions put into effect with the least delay. The control can be kept informed during the process through the rate group telephone, and by the same means can prevent an obvious and serious error.
44. In order to carry out a complete investigation of this method it might be necessary to station the principal rate officer in the T.S. with inclination observers in the control positions.
45. It is desired that special attention should be given to improved methods of rate keeping throughout the year and investigations on the lines of the foregoing paragraphs are to be continued.
Estimating the Inclination of British and Foreign Warships
46. The Commander-in-Chief, China, makes the following interesting observation:-
“It is most noticeable on the China station that it is far more difficult to estimate the inclination of modern foreign warships than of their British contemporaries. Whereas the British ships have upperworks with vertical edges and large areas of fat surface in the fore and aft line or athwartships, the foreigners, who have clearly considered the matter carefully, are seldom seen with anything but a curved surface, and very broken up vertical lines. In additions, such devices as placing the masts out of the centre line have been observed.”
This question is receiving consideration in the design of new ships but in existing ships it is not clear that anything can be done other than the improvisation which were made use of in the war, such as snaking the rigging and breaking the funnel line by the addition of strips of painted canvas.
Inclinating on the Towing Ship
47. Where tried this has been reported on favourably, except in one or two cases when exceptional yawing of the H.S.B.P.T. occurred. Under these conditions inclinating on the target would probably have been no less misleading, and the realistic practice for observers and inclinometers would appear to outweigh any disadvantages.
PART 1. – GENERAL REVIEW – DIRECT SPOTTING 13
Direct Spotting
48. It has been suggested that judging by straddles by the number of short shots in line is a dangerous practice with multi-gun salvos. This is not concurred in.
Though not infallible shorts are often the only guide, as explained in C.B.3026, page 142, and this aid to spotting must be taken into account.
Position of Splashes on a Representative Target
49. The Commander-in-Chief, Mediterranean, reports:-
“The Rear-Admiral Commanding, Third Cruiser Squadron, refers to the necessity of keeping splashes aft on a representative fast moving target in order to ensure hits amidships. It is important that this should be stressed and always aimed at in Centurion firings as there is a natural and correct tendency to keep splashes ahead in target firings in order to facilitate spotting.”
AIRCRAFT SPOTTING
Accuracy of Fall of Shot for Range
50. A collective analysis showing the average error in yards of aircraft fall of shot reports for all day firings is shown below. The mean errors for 1938 show little change compared with 1937, although a larger proportion of firings were witnessed by acting observers and observers’ mates.
Mean Error of Signalled Reports
| Mean Range | KK |
100 |
200 |
300 |
400 |
500 |
600 |
700 |
800 |
900 |
1,000 or over |
10,000 yards |
73 |
49 |
83 |
99 |
119 |
137* |
132* |
151* |
260* |
- |
- |
12,000 yards |
57 |
46 |
76 |
117 |
103 |
126 |
130 |
130 |
180 |
140* |
252* |
14,000 yards |
70 |
56 |
53 |
99 |
119 |
137 |
170 |
183* |
214* |
170* |
728* |
16,000 yards |
56 |
75 |
113 |
128 |
122 |
182 |
177 |
136 |
141 |
196 |
244 |
18,000 yards |
37 |
41 |
59 |
142 |
124 |
113* |
354* |
195* |
216* |
133* |
- |
20,000 yards or over |
71 |
69 |
75 |
74 |
192* |
182* |
350* |
- |
270* |
- |
427* |
All ranges- |
|||||||||||
1938 |
52 |
59 |
76 |
108 |
124 |
153 |
176 |
176 |
180 |
188 |
277 |
1937 |
57 |
52 |
69 |
85 |
117 |
149 |
170 |
186 |
192 |
167 |
206 |
1936 |
68 |
72 |
81 |
101 |
137 |
178 |
190 |
257 |
194 |
229 |
252 |
Number of observations |
|||||||||||
(1938) |
1,106 |
1,016 |
1,115 |
799 |
556 |
310 |
271 |
144 |
160 |
50 |
70 |
14 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
Aircraft Inclination Reports
51. The mean error of aircraft reports of target course in all firings was 10.2º, based on 203 observations
Accuracy of Fall of Shot for Line
52. The mean error of aircraft reports of fall of shot for line was 95 yards, based on 151 observations.
Aircraft Spotting by Pilots
53. In the Mediterranean and China Fleets spotting has on occasions been carried out by the pilot in the absence of the observer, and a midshipman or rating trained to transmit enemy course reports. Results are reported to have been encouraging, and it has been recommended that pilots should be trained and prepared to spot.
54. While in a single ship action spotting by the pilot might be feasible in the absence of fighter opposition it would be out of the question in a fleet action. Training is also a difficult for the machine cannot be flown to give both pilot and observer a view, and the latter at present gets insufficient practice.
55. In the circumstances it is not desired to lay down any policy for spotting by pilots nor to fit permanent circuits and keys in aircraft for the purpose.
Aircraft Spotting Communications
56. In action it must be expected that continuous and reliable aircraft spotting will be the exception rather than the rule and the utmost efficiency in communications is, therefore, required to ensure that it will not be ineffective from this cause.
It follows that experienced telegraphists who will be available for all practices should be employed on the aircraft spotting wave and particularly at the set
57. The speed and accuracy of tuning in spotting aircraft, particularly on H/F waves, is still far from satisfactory. Efficiency in tuning is specially important when relief aircraft are taking over and when shifting wave to avoid jamming.
To assist tuning, crystal wave-metres G.L. are now being supplied to all carriers for calibrating the portable wave-metres for use in the aircraft.
PART 1. – GENERAL REVIEW – AIRCRAFT SPOTTING 15
Provision of a Vertical Scale in Target Practices
58. The Commander-in-Chief, China, reports:-
“No satisfactory method of providing a vertical scale for aircraft spotting has yet been evolved on the China Station. High masts, 80 ft. and 60 ft., have been stepped in the B.P.T.s and H.S.B.PT. respectively. These heights represent the average heights of the foretops and funnels of Japanese cruisers, but the problem of providing a suitable mark for the top of the masts has not been solved. A flag is unsuitable because a flag large enough to be clearly seen at 18,000 yards when full extended is, in practice, only fully extended in wind conditions unsuitable for towing targets.
Bamboo topmasts have been constructed. These make a satisfactory mark from the point of view of the observer, but in spite of every effort to cut down weight, they are too heavy and the small beam of the targets makes efficient staying impossible. A case occurred in which mast and top-mast carried away, bringing down part of the lattice and making the target unmanageable, with the result that it went ashore, and this has resulted in extreme reluctance to use the topmasts at all. It is, however, intended to continue trials:-
(i) using a high mast either end of the target, with flags of appropriate size at the masthead and spread on stays joining them;
(ii) using a sail with boom and gaff at the masthead. A device of this kind, which sets itself according to the wind was seen on a Japanese high-speed target.”
59. These methods might be tried on other stations where difficulty is being experienced. Reports as to their success or otherwise will be welcome.
SPOTTING RULES
60. The reports on spotting rules forwarded in accordance with Admiralty Message 2340/23/9/38 were unanimous in recommending that the spotting rules should be standardised as soon as possible, but detailed proposals for achieving this differed considerably.
61. While some suggested that the 1938 trial rules should be retained unaltered and others stated that the introduction of the zig-zag was too complicated and unnecessary, there was a welcome tendency in all reports to regard the zig-zag groups as a useful adjunct rather than the main basis of the rules, and to emphasise, on the other hand, the importance of good rate keeping.
16 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
62. The Commander-in-Chief, Home Fleet, states:-
“My general views on this subject are as follows:-
(a) In the interests of training and efficiency it is essential now to standardise the spotting rules for a term of years.
(b) The 1938 rules are in the main satisfactory.
(c) In formulating the final rules the aim should be simplification and standardisation, with a view to reducing the different sets of rules to a minimum. Alterations to the 1938 rules should only be made with these ends in view.”
63. The Rear-Admiral Commanding the 1st Cruiser Squadron in the following paragraphs expresses a view which is held by a great many experienced officers:-
“(i) My views are that it is most essential not only that spotting rules should be standardised as soon as possible but, more important still, that the rules should be made as simple as possible.
(ii) It is hardly an unfair criticism to say that in the last ten or fifteen years, every time that the Gunnery results over a period have not shown improvement, some squadron or other has suggested a new form of spotting rules in the hopes of getting better hitting results.
(iii) It would not appear that the many changes in the spotting rules have had much effect on the hitting results. On the other hand, the frequent changes in the rules have undoubtedly caused uncertainty in the minds of control officers and have certainly tended to distract the latter’s attention from the real problem which has to be solved if good hitting results are to be obtained, i.e.:-
“Keeping the inclination of the enemy correctly.”
(iv) This is the crux of the whole question of hitting the enemy, and no amount of “trending” or any other form of spotting rule will produce good hitting results if the rate keeping is bad.
(v) There is no getting away from the fact that in spite of improvement in material we have made very little if any improvement in inclination results from 1918 to the present day. This points to faulty methods.
(vi) I believe that we would get improvement if we were to simplify the spotting rules and concentrate our main effort on rate keeping.”
The underlying principle he emphasises must form the basis of any method of controlling gunfire, but in recent years it has been in danger of being forgotten in the search for “ideal” spotting rules.
PART 1. – GENERAL REVIEW – SPOTTING RULES 17
64. The result of the last three years investigations, as revealed by practices and reports from sea, may be summed up briefly as follows:-
(i) The value of the zig-zag group for verifying range and rate is established.
(ii) Normal day action rapid groups are better than rapid salvos, which in the past have allowed “the guns to run away with the control”.
(iii) There is little or no advantage in a separate set of rules for aircraft observation which at best will probably be only intermittent. Minor adjustments in direct rules are all that is required to enable advantage to be taken of “reliable” distance reports.
(iv) Complicated refinements such as the reverse ladder have no particular merit.
(v) There is no apparent reason why the same basic rules should not be suitable with minor adjustments for all low angle armaments.
65. These conclusions were confirmed at a meeting between Fleet and Admiralty officers, and the “Standard Spotting Rules” given in Appendix I of this book were drawn up to embody these principles, and to include the majority of the details recommended from sea.
66. These rules only differ from the 1938 trial rules where changes were necessary to achieve the standardisation and simplicity, which it is considered will outweigh any theoretical disadvantages in their details.
Appendices II and III contain the extracts from the Standard rules which are applicable to destroyers, escort vessels, secondary armaments, etc., and omit, for example, all references to aircraft observation.
It is intended that these rules which have also been issued in Admiralty Letter M/T.S.D.320/38/G, dated 5.1.39, and in C.A.F.O. 353/39 should remain in force for a number of years.
THROW-OFF FIRINGS
Reporting Fall of Shot
67. In a simultaneous throw-off firing using simulated aircraft spotting, the observers of the two firing ships were exchanged and carried out the duties of rake-officer and W/T operator. This proved most satisfactory in reducing lag and eliminating errors, and is recommended for trial.
18 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
Marking Fall of Shot
68. The use of two rakes (C.B. 3001/38, page 12, para. 48) has been favourably reported on on all occasions of their use, and this method of marking is now recommended for general adoption.
Aircraft Observation
69. In one or two cruiser throw-off firings aircraft have attempted to spot the fall of shot for range.
In the absence of a scale their reports can only be most erratic and the practice afforded to the observer is too unrealistic to be of any value. When aircraft are employed in throw-off firings it is desired that their activities should be limited to estimating range and bearing, and reporting course and speed.
RANGEFINDING. (C.B. 3001/38, page 13.)
Initial Ranges for Opening Fire
70. The general opinion is that circumstances permitting and under good rangetaking conditions, a reliable rangefinder cut should be awaited before opening fire, but this delay need not be prolonged by waiting for the plot to develop. When ranging is difficult, fire will probably have to be opened with an estimated range based on the horizon method.
71. In the reports, intervals of 30 seconds to one minute are referred to as the permissible delay for a rangefinder range. In practice the analysis charts show that the average interval between the first plotted range and the first salvo is between one and two minutes for capital ships and 8-in. cruisers, and about one minute for 6-in. cruisers.
72. It is apparent, therefore, that such delays do not appear unduly long, but no specified interval can be laid down. The Captain must decide according to the circumstances how long fire may be withheld, bearing in mind the improved accuracy to be expected by not hurrying the first salvo.
Tuning to Rangefinders
73. Initial tuning to rangefinders is not always accurate and frequent opportunities of re-tuning both before opening fire and while finding line are not taken advantage of. Again, during the course of a firing, opportunities of applying a previously determined straddle correction to the mean rangefinder range when spotting is difficult have often been lost.
PART 1. – GENERAL REVIEW – RANGEFINDING 19
74. Plot spotting should enable much fuller use to be made of a good rangefinder plot during an action and, as has been suggested by one ship, should permit the range to be re-tuned during the firing of a deflection group without upsetting the control.
Stereoscopic Rangefinder Trials
75. Although the results of the rangefinder trials at Fort Cumberland since the war were conclusively regarded as being in favour of the coincidence rangefinder to the exclusion of the stereoscopic, a scrutiny of the reports shows that under certain conditions of poor visibility the latter may have the advantage.
76. It is also known that some progressive foreign navies still favour the stereoscopic rangefinder, and it is not beyond the bounds of possibility that developments in the construction of these foreign rangefinders have advanced quicker than our own, resulting in an instrument which is superior to those used in the trials.
77. It has, therefore, been decided to purchase three of the latest foreign stereo-rangefinders and arrange a further series of comparative trials at Fort Cumberland.
Apart from putting the stereo principle to another searching test the trial will provide the first opportunity we have ever had of comparing the optical and constructional qualities of up-to-date foreign rangefinders with our own.
Application of Target Travel Corrections
78. Where used, the rule “always apply” the change in range correction has proved satisfactory and has not upset the control by the distortion of spotting corrections. On the other hand, reports criticise the correctness of this rule on theoretical grounds, and mention occasions such as re-assessing the inclination to remove a large error the wrong side of 90º when the application of the change of range correction may confuse the control.
Such confusion has so far not yet occurred, and the occasions on which confusion may arise, particularly with plot spotting in the T.S., are considered sufficiently rare to retain the new rule “always apply”.
79. In ships not fitted with A.F.C. Tables where the range correction can only be computed approximately on a Dreyer calculator, it is doubtful if the lag and complications of drill justify the invariable application of the change in the correction. When the change is large an arbitrary spotting correction will probably serve the purpose as well as the approximation of the calculator. See C.B. 3026, page 56, para. 31; C.B. 3001/1914-36, page 34.
20 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
80. Changes in the deflection, however, according to reports, cannot be treated in the same way, since it will be too difficult to prevent their duplicating the line spotting corrections on frequent occasions.
While this view is concurred in, it is desired to emphasize the accuracy with which the modern fire control table is capable of holding the target for line once the correct deflection has been found. Close co-operation between the rate officer and spotting officer on the question of applying the deflection correction when adjusting the settings should result in the fullest use of the deflection mechanism and a reduction of the line spotting corrections required. This applies particularly at fine inclinations when alterations of course are easily seen and the new inclination is easy to judge.
Enemy’s Speed
81. It frequently occurs that an adjustment to enemy’s speed setting is not made when it drops on an alteration of course, and at best a long delay occurs after re-setting the inclination. The speed across plot operator should be informed when the enemy is reported altering course so that he may anticipate a change in speed, and be in a better position to appreciate the significance of variation in his plot. For large alterations an arbitrary adjustment in speed should be made without awaiting confirmation from the speed across plot.
Spreads
82. These remain about the same as last year and the remarks in C.B. 3001/38, page 44, para. 28, again apply.
83. In addition it is thought that there may be a tendency to attempt too high a rate of fire for the standard of drill achieved. The erratic fall and spreads of B and C salvos indicate that the firing of groups is at times being hurried. It is considered important that maximum output should be worked up to progressively while preserving accuracy.
84. It has been suggested that the overall spread, particularly of multi-gun salvos, is not representative of the hitting power of salvos since about 75 per cent. of the shots fall in a zone about two-thirds of the overall spread in length and centred on the M.P.I. This distribution of shots generally follows the normal law of errors, and deductions from the analysis must take into account that the distribution about the M.P.I. is indicative of potential hitting power, while overall spreads give a measure of the standard of drill, particularly pointer following and ramming, at the guns.
85. The present method of assessing the actual rate of hitting is considered satisfactory, and it is not desired further to complicate analyses by introducing a table of the mean difference of all rounds from the M.P.I.
PART 1. – GENERAL REVIEW – RANGEFINDING 21
Warmer Correction
86. C.A.F.O. 2741/38 recently issued on this subject is reproduced below:-
“The ruling given in C.B. 3026, page 64, para 69, and the instructions issued in C.B.3001/34, page 28, para. 18, have been under review, and it is now clear from the evidence available from experimental firings, which is supported by the results of practices, that with certain types of guns the chances of obtaining hits with opening broadsides will be increased by the application of a warmer correction.
2. It has, therefore, been decided that the following corrections are to be used with full and reduced charges:-
Gun Warmer Correction.
8-in., B.L., Mark VIII .. .. + 300 yards.
6-in. B.L., Mark XXIII .. .. + 200 yards.
4.7-in. Q.F., Mark VIII .. .. + 200 yards.
Warmer corrections for other marks and calibres of guns are not to be used.
3. These corrections are considered the most suitable for full charges at normal opening ranges, but they cannot be regarded as ideal for all conditions, since:-
(a) The warmer effect is purely an M.V. effect which will vary with the range and charge in use.
(b) The difference in M.V. between the “warmer” and subsequent rounds may vary between wide limits and does not appear to be systematic.
(c) The effect is generally only present for the first round from a cold gun.
(d) While generally negative, the sign of the warmer effect on M.V. and range may vary in isolated cases.
For simplicity, however, it is necessary to adopt a standard correction for the respective guns affected.
4. From the foregoing it will be seen that opening broadsides from cold guns are unreliable from the control point of view, whether a warmer correction has been applied or not.”
87. Remarks on the suitability of this correction from experience in practices should be included in the annual reports.
Analysis Chart of Range – Scale
88. Where the scale of the analysis chart differs from that of the range plot on the table the former should be used in preparing the analysis, and a note inserted at the top stating the scale of the table plot.
22 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
Cant of Trunnion Error. (C.B. 3001/36, page 90.)
89. The limitations of the method of correcting for canted trunnions, described in C.B. 3001/36, page 90, have been disclosed in practice firings during the year, and proposals have been put forward for additional equipment to enable this correction to be applied more accurately and with less lag.
These proposals will be fully met by the cross-levelling gear which will go into production shortly, and in the meantime temporary additions to fire control equipment cannot be contemplated.
90. It is recommended that either the method described in C.B. 3001/36 should continue to be used or, as suggested by one ship, that the layer and trainer should be taught to fire with the top of the vertical cross-wire above the point of aim as far as conditions permit.
When conditions are beyond these artifices fire must be withheld on a large turn.
USE OF LONG RANGE A.A. ARMAMENTS FOR LOW ANGLE FIRE (G.13)
By Day
91. The Commander-in-Chief, Home Fleet’s views on this problem are summarised in the following paragraphs:-
“(a) In any future war the long range A.A. ammunition will need to be preserved, so far as possible, for its primary purpose.
(b) The threat of a torpedo attack at short range by night, is nevertheless, so considerable that the A.A. armament must be used to defeat the attack. Its use in short range night actions should therefore be practised.
(c) By day the tactical necessity for using the long range A.A. armament for low angle fire is far less and its use in such circumstances will lead to an ineffective expenditure of valuable ammunition.
(d) In the present circumstances in the home Fleet the training of the long range A.A. armament in low angle fire by day can only be undertaken to the detriment of training in more important functions. The development of the use of this armament, for this purpose, should therefore be discontinued in the Home Fleet and low angle day practices should no longer be carried out.”
92. The Commander-in-Chief, Mediterranean, is in full agreement with these views, but the Commanders-in-Chief on other stations, where changes in personnel and conflicting commitments interfere less with training, have not expressed opinions against the development of L.A. fire by day from the long range A.A. armament.
PART 1. – GENERAL REVIEW – USE OF LONG RANGE A.A. ARMAMENTS FOR LOW ANGLE FIRE 23
93. Another recent authoritative opinion on this problem was to the effect that “it is necessary to be prepared to make use of this armament against L.A. targets.”
94. While training difficulties at the present time are fully appreciated, it is doubtful if these alone should control the policy, for, when expansion is complete, and in war, they should largely disappear. On the other hand, the vital factor is considered to be the quantity of ammunition carried, which is specially emphasized by the Commander-in-Chief, Home Fleet.
95. After weighing up all these considerations it has been decided that the problem of using the long range A.A. armament in anti-ship action by day should not b pursued for the present.
By Night
96. Opinion is unanimous that the long range A.A. armament should be used for low angle fire as opportunities occur in night action is spite of limitations discussed in C.B.3001/38, page 23, paras. 109 to 112, which incidentally make no mention of defence by this armament against night aircraft attacks.
97. The annual gunnery reports from sea take into account all three possible functions of this armament at night, and extracts from those of the Commanders-in-Chief, Mediterranean and China, are reproduced below.
Commander-in-Chief, Mediterranean:-
(i) It is considered very desirable that both the H.A. Control Systems and the Star Shell Control Arrangements should be fully manned at night, in view of the probability of night air attacks. If this is done the change-over from Star Shell to H.A. Control System (and so to using the H.A. armament for L.A. fire) presents little difficulty and can be very rapidly carried out. The Fire Buzzers and Telephones merely have to be switched over in the H.A.C.Ss.
(ii) The best arrangements that can at present be made for using H.A.C.S. for surface fire involve the use of a Dumaresq and Vickers clock. In order to compete with greater efficiency against fast targets, it is thought that certain slight modifications to the tables will proved advantageous. These modifications to the H.A.C.S.III have been proposed by Warspite and will be forwarded.
(iii) Although only two guns are normally required for Star Shell, it is not considered that one H.A. battery should ever be used fro Star Shell and surface fire simultaneously from different guns. The reasons for this are, firstly, because confusion is likely to arise and secondly, because four-gun salvos are considered necessary for fire to be effective.
24 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
The organisation recommended is:-
(a) Existing Ships with not more than Four single or Two Twin H.A. Mountings Each Side.- All guns to be able to use either Star Shell, H.A. firing, or surface firing by night, but no two of these methods ever to be used simultaneously.
Ammunition for surface firing to be stowed in separate lockers. If ready-use supply is expended, time taken for replenishment must be accepted.
(b) Future Capital Ships with more tan Two Twin H.A. Mountings, or H.A./L.A. Mountings Each Side.- Reserve two mountings for Star Shell only. All the remainder to be ready to engage surface or A.A. targets. Whether the Star Shell firing from two mountings can be continued while engaging surface targets with the remainder must be a matter for trial. Separation of the Star Shell and H.A. Fire Buzzers would be necessary, which would complicate existing fire control gear.”
Report by Suffolk forwarded by the Commander-in-Chief, China:-
(i) In Suffolk, blast from the main armament should not interfere with the 4-in. armament.
(ii) With the existing system the 4-in. guns can follow either the director or the star shell Evershed, but can be in communication only with the H.A.C.P. or the Star Shell control, i.e. when the telephone switch is put to “star shell” the H.A.C.P. cannot speak direct to the guns, but the star shell officer can.
(iii) The 4-in. Control Officer in the director is in touch with the H.A.C.P. under both conditions. With this system both mountings of the battery must be either in Star Shell Control from the Fore Control or in control from the H.A. director and H.A.C.P. for A.A. or L.A. fire. When in Star Shell Control one mounting could be sued for L.A. fire in local control, but this is not recommended as the primary system.
(iv) It is considered that the 4-in. armament on the disengaged side should be prepared to engage a target and that this could be done be re-arrangement of the telephone system so that each mounting separately can be switched to Star Shell Control. Additional communication would also be required between the 4-in. Control Officer and the Star Shell Control Officer.
(v) The organisation would then be:-
(a) Before the “Alarm” – All 4-in. armament on Star Shell control both sides.
PART 1. – GENERAL REVIEW – NIGHT FIGHTING 25
(b) Main armament committed on one side – The 4-in. control officer on the disengaged side stands by for L.A. fire with one mounting star shell control.
(c) Satisfactory illumination of the main armament target – The 4-in. on that side can be split to allow one mounting to be employed for L.A. fire at the main armament target.
(vi) Since at night the 4-in. armament may be required for either star shell, low angle, or anti-aircraft fire, and for anti-aircraft or low-angle fire by day, it is considered that the ready-use stowage of ammunition per gun should be increased.
It is also suggested that the supply arrangements form the magazine should comprise two hoists for each side, one of which each side at night be reserved for the supply of star shell.”
98. The Commander-in-Chief, Home Fleet, does not suggest any detailed procedure to be followed, but states that the employment of the long range A.A. armament for low-angle purposes at night should be definitely limited to short range action on the “disengaged” side.
99. Until detailed reports of practices by the 1st Battle Squadron and 1st Cruiser Squadron are received there is insufficient information available to formulate a definite policy, and the situation remains substantially as set out in C.B. 3001/38, page 23, paras. 109 to 112. The guiding principle should be to ensure that star shell and A.A. fire will not be interfered with by the requirements for L.A. fire, but the organisation should permit of efficient L.A. fire when the opportunity occurs, particularly when conditions are unsuitable for star shell. It is also clear that it is unsound to divide the fire of one battery of four guns between either star shell, H.A., or surface firing.
100. Modifications to communications and to ready-use stowage of ammunition on a standard basis for all ships will be considered as soon as requirements are clearer. Ships must, therefore, temporarily adjust communications as far as they can from their own resources to suit the organisation adopted.
NIGHT FIGHTING
Alarm Procedure
101. The new procedure of reporting “ON” when on the bearing ordered and “TARGET” when the enemy can actually be seen in the sights has now had a thorough trial and has been favourably reported on by all Commander-in-Chief.
102. A modification suggested is that the director should not report “target” until the guns are “ready,” particularly with a fast training D.C.T. and comparatively slow training armament.
26 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
It is considered that this contingency can be dealt with by internal organisation if found necessary, but in well-drilled ships no difficulties should arise, and in any ship the turrets should be on by director by the time the bridge can act on the report “target.”
103. It has been decided that the new procedure is to be adopted and the Appendix to C.B. 3026 will be amended accordingly.
104. Opening fire with training by Evershed and laying on the horizon has been found difficult to investigate in peace practices for safety reasons, particularly in ships without D.C.Ts. All recent opinions expressed on the subject are in agreement with C.B. 3026, page 132, para. 81. Under the circumstances, therefore, it is considered that “firing by Evershed” should be regarded as an emergency measure for use only in a last resort in action.
Estimating the Range at Night
105. More attention has been given to practising the estimation of range in all night exercises with, it is reported, beneficial results, but there is still scope for greater accuracy in the opening range in night firings.
In night exercises on bright moonlight nights the general tendency to under-estimate the range on sighting, which may be as much as 7 or 8 miles, was conspicuous.
106. The drill in the transmitting station described in C.B. 3001/38, page 20, para. 88, has proved satisfactory, and it is proposed to include this in the appropriate section in the Firing Manual.
107. It is considered most important that great attention should continue to be paid to these two aspects of training for opening fire at night.
Night Throw Off Firings
108. The use of a searchlight by the target ship to indicate the target line was tried in one practice to investigate the possibility of spotting full gun salvos by direct observation from the firing ship under these conditions.
It has been assumed that overs would not be seen, that straddles in the beam would appear white and shorts would appear black against the beam, but it was found that no reliance whatever could be placed on these assumptions and that spotting was further confused by ricochets from shorts appearing in the beam.
The use of full gun salvos in this type of practice for the purpose of exercising night spotters is considered a waste of ammunition and is not recommended.
PART 1. – GENERAL REVIEW – NIGHT FIGHTING 27
109. This practice emphasised the necessity of deciding the direction of throw-off to suit the relative position of the S/L and control in order to avid interference with the direct observation of splashes.
Rangefinder Control
110. The Commander-in-Chief, Mediterranean, reports:-
“In general the method of control by rangefinders, if cuts are obtained, supported by the fall of shot observed, is considered to be sound. The T.S. officer should have no hesitation in informing the control officer immediately if the range plot develops, and obtaining his approval to tune to the rangefinders even in fire has already been opened.
Where the rangefinder, director and control positions are separated, as in capital ship secondary armaments without D.C.Ts., the danger of the rangefinder picking up the wrong target, if several are present, is too great to allow full rangefinder control to be accepted.”
111. The Rear-Admiral Commanding, 3rd Cruiser Squadron remarks:-
“There seems no reason to alter the policy at present in force in the Third Cruiser Squadron, viz., that rangefinder control should be the primary method at night when in company, spotting corrections only being applied if a ship’s own fall of shot can be distinguished for certain.”
112. These views are concurred in, and it is desired to stress that no opportunity of tuning to a R/F range before hitting is established should be missed.
Use of Illuminants
Searchlights
113. Ships in company at night should bear in mind the following objection to sweeping ahead which has been mentioned by the Rear-Admiral Commanding, 3rd Cruiser Squadron:-
“The sweep forward by the sighting ship for further targets is very liable to blank the line of sight to the original target to such an extent that laying, spotting and rangetaking are impracticable.”
This might necessitate using the after control, if manned, while the sweep is in progress.
28 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
Indirect Illumination
114. Night practices carried out during the year have shown that indirect illumination provided by a well controlled searchlight can be effective at short and medium ranges, but at longer ranges spotting and rangefinding difficulties are likely to be experienced.
115. The procedure which will ensure that the attacking ship opens fire immediately the illuminating ship exposes a searchlight has not yet been evolved, even in the comparatively simple conditions of peace practices. In war it is difficult to envisage any procedure which will not involve communication between the two ships with the consequent danger of disclosing their presence.
116. It seems probably therefore that opportunities for the use of indirect illumination in night action will be limited to an unengaged ship seizing a chance of developing effective fire against an enemy already illuminated and engaged. This would be the situation if the illuminating ship were forced to open fire in self defence on account of delay in the attacking ship.
117. From this it follows that a shadowing ship, which will normally be a cruiser or destroyer of inferior armament to the opponent being shadowed, should only be relied upon for indirect illumination after the action has already been commenced by the attacker.
The distraction to be anticipated by the illuminating ship opening the attack may be considerable, but unless her fire is likely to be effective it is question whether it will justify the risk of her destruction before her consorts fire becomes effective.
118. To sum up, the element of surprise which might e attained by initial indirect illumination appears to be impossible to achieve in action, but practice with indirect illumination will be of value in preparation for the other occasions when it will be practicable. To provide realism, the illuminating ship should also engage the target.
119. The following are some of the experiences in night practices using indirect illumination:-
(i) Only splashes near the target can be spotted with certainty.
(ii) Rangetakers in particular have great difficulty unless the searchlight is accurately controlled.
(iii) Own searchlights and/or star shell must be instantly ready to augment the illumination and must be used without hesitation as required.
PART 1. – GENERAL REVIEW – NIGHT FIGHTING 29
(iv) Flank marking reports from the illuminating ship can be made with accuracy and little delay, and arrangements should be made for using them.
(v) Estimated range is more inaccurate than normally in night practices at ranges at which indirect illumination may be used but no delay for a rangefinder range can be accepted. The Commander-in-Chief, Mediterranean remarks:-
“A cruiser with a short loading interval should not hesitate to open fire at night with an estimated range. This applies also to the secondary armament of capital ships, but for the main armament a reasonable delay for a R/F range or the hitting range of the secondary armament is acceptable.”
This view is concurred in.
(vi) The silhouetting effect of destroyers’ searchlights is insufficient unsupported by other illuminants for opening fire except at short range.
120. Further information on the use of indirect illumination and opinions on the points raised in the foregoing paragraphs should be included in annual reports.
Aircraft Flares
121. Weather conditions interfered on several occasions with the use of aircraft flares in night practices. On those practices which were successful the Commander-in-Chief, Mediterranean, remarks:-
“The 3rd Cruiser Squadron report that in a night full calibre Centurion firing with flare illumination it was apparent that although sufficient illumination was provided for laying and spotting of shorts, ranging was not possible.
The use of aircraft flares outside the range of normal illuminants places the user in a position of great tactical advantage, provided the enemy is not similarly equipped. The difficulty of ranging can be overcome to some extent by ranging on the flares themselves. This has been found to be practicable, and although only approximate ranges of the target can be obtained the results are more accurate than those obtained by estimation.
The First Battle Squadron, reporting on this subject state that illumination was most effective and excellent range plots were obtained. The position relative to the target for dropping the flares has not yet been fully established, but trial has shown that one flare burning from 2,500 down to 1,000 feet over or slightly on the disengaged side of the target will provide sufficient illumination for ranging and direct spotting up to 8,000 yards. The frequency and position of dropping the flares in order to maintain one in this position will depend on the
30 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
relative wind. Experience to date indicates that it will generally be impossible for aircraft to spot the fall of shot with flare illumination.
The above reports are conflicting so far as ranging is concerned; it appears, however, that good ranging is possible provided the flares are dropped in the correct position.”
122. The firings by the 3rd Cruiser Squadron indicated that bolder initial range corrections than those provided for by the spotting rules may be required when opening fire with an estimated range at the limit of range up to which flares may be effective. This should be borne in mind, but care should be exercised in the use of large “up” corrections owing to the difficulty in spotting overs at night.
Use of Star Shell to show up Movements of an Enemy burning a Searchlight
123. A special trial carried out on the China Station confirms previous experience that a well directed searchlight will probably conceal the movements of a small ship, but that, if a good star shell illumination is maintained ahead and astern as well as behind the enemy, the chances of observing inclination from one or other of the control positions during momentary faulty training of the searchlight are increased. It was considered probable that enough of a large ship would be shown up by good star shell illumination to enable an alteration of course to be observed, but this requires confirmation.
124. The Commander-in-Chief, China, remarks that the use of a searchlight to conceal movements, unless exposed for short intervals only, is likely to be a most dangerous procedure as it will provide an aiming and a ranging mark which may well prove fatal.
Night Spotting
125. One report refers to confusion being caused by ricochets from a salvo out for line falling in the beam of the searchlight and being spotted as the true fall of shot. It is considered that attention to an accurately worked time of flight hooter should help in overcoming this difficulty.
Aircraft Spotting at Night
126. From such further experience as has been gained it seems probably that aircraft reports at night will be unreliable and may be most misleading.
INTRODUCTION OF NEW GUNNERY RATES
127. Details of the new organisation of gunnery non-substantive rates referred to in C.B. 3001/37, page 11, para. 11, were published in A.F.O. 1678/38. The reasons for the new rates, together with the arrangements for the transfer from the old to the new rates, were circulated to all ships in Admiralty Letter N.2901/38 of 16th June, 1938.
128. Although the official date of the transfer to the new rates was the 15th February, 1939, it must be appreciated that it will be some years before the number of officers and men borne in all ships is adjusted to the revised complements. This is due to the training limitations of the Gunnery Schools.
129. In the meantime, Commanding Officers can assist considerably by employing men as far as possible at duties they will be required to perform in the new rate to which they have been transferred, or for which they have been earmarked.
130. Importance is attached to the remarks in Admiralty Letter N.2901/38 of 16th June, 1938, concerning:-
(a) The notation in the Gunnery History Sheet (S.1245) of the action stations held by ratings.
(b) The avoidance of local draftings for the sole purpose of adjusting the complements of ships to that allowed with the new non-substantive rates.
POINTS ON WHICH INFORMATION IS REQUIRED WHEN OBTAINABLE FROM NORMAL PRACTICES
G.1. The working of the control team organisation (paras. 20 to 31 and C.B.3001/8, pages 9 to 11).
G.2. Any difficulties encountered with the standard spotting rules due tot eh absence of a plot in the control position (para. 33).
G.3. The stationing of additional observers (paras. 36 and 37).
G.4. Communications for control and spotting officers (paras. 38 to 40).
G.5. Centralised control of inclination in the T.S. (paras. 45 to 49).
32 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
G.6. Difficulties experienced due to the invariable application of changes in the range travel correction, and whether the line correction can be more frequently applied than is normally done at present (paras. 82 to 84).
G.7. Warmer corrections (paras. 90 and 91).
G.8. The use of long-range A.A. guns for low-angle fire at night (paras. 100 to 104).
G.9. Indirect illumination (paras. 118 to 124).
G.10. The use of aircraft flares for illuminating targets at night (paras. 125 and 126).
G.11. The relative advantages of G.M.S. and G.I.C. concentration in the large scale fleet firing (para.20).
PART II. – SECT. A. – BATTLESHIPS AND BATTLE CRUISERS 33
PART II
_______
ANTI-SHIP GUNNERY
_______
SECTION A. – BATTLESHIPS AND BATTLE CRUISERS
1. The following tables show the results obtained in full calibre practices of which reports have been received by the end of 1938. The figures in brackets indicate the results obtained during 1937.
CONCENTRATION OF FIRE
Master Ship Control (G.M.S.)
| Target and Number of Practices | Mean Range |
Full Gun Salvos per Min |
Output, per cent. |
Spread |
Hits per Gun/Min |
Direct – D.
Aircraft – A |
15-inch Pair Ship |
||||||
145 ft. B.P.T. 1 |
16,000 |
1.44 |
77.3 |
539 |
.144 |
D |
6-inch with 15-inch M.A.C. Pair Ship |
||||||
Centurion 1 |
9,300 |
2.25 |
98 |
384 |
.114 |
D |
Individual Ship Control (G.I.C.) |
||||||
15-inch Pair Ship |
||||||
Throw-off 1 |
24,000 |
1.75 |
100 |
- |
.036 |
A (simulated) |
6-inch with 15-inch M.A.C. Pair Ship |
||||||
Centurion 1 |
10,400 |
2.08 |
96.2 |
252 |
.305 |
D |
34 C.B. 3001(39).- PROGRESS IN NAVAL GUNNERY, 1939 EDITION
SINGLE SHIP PRACTICES
2. Day
| Target and Number of Practices | Mean Range |
Full Gun Salvos per Min |
Output, per cent. |
Spread |
Hits per Gun/Min |
Direct – D.
Aircraft – A |
16-inch |
||||||
145 ft. B.P.T. 3 |
17,300 |
1.85 |
99 |
296 |
.092 |
D |
145 ft. B.P.T. 3 |
18,300
(17,700)
|
1.64
(1.60)
|
82.6
(94.4)
|
418
(276)
|
.124
(.057)
|
A |
H.S.B.P.T. 4 |
16,000 |
1.88 |
95.9 |
328 |
.087 |
D |
H.S.B.P.T. 1 |
19,400
(16,000)
|
1.60
(1.95)
|
87
(93.4)
|
178
(326)
|
.155
(.390)
|
A |
6-inch with 16-inch M.A.C. |
||||||
Centurion 2 |
15,600 |
2.13 |
100. |
197(3) |
-152 |
A |
15-inch |
||||||
145 ft. B.P.T. 3 |
15,000
(14,000)
|
2.01
(2.02)
|
90.6
(91.9)
|
246
(253)
|
.165
(.220)
|
D |
145 ft. B.P.T. 2 |
11,200 |
1.92 |
86.3 |
227 |
.152 |
A |
H.S.B.P.T. 4 |
14,200
(13,400)
|
1.92
(2.07)
|
93.5
(88.6)
|
190
(258)
|
.088
(.110)
|
D |
H.S.B.P.T. 12 |
15.300
(14,400)
|
1.90
(1.90)
|
89.9
(88.5)
|
226
(182)
|
.139
(.126)
|
A |
Throw-off 3 |
15,900
(14,000)
|
1.90
(1.91)
|
87.9 |
- |
.073
(.064)
|
D |
Throw-off 4 |
16,500
(15,700)
|
1.71
(1.86)
|
- |
- |
.035
(.073)
|
A (simulated) |
6-inch with 15-inch M.A.C. |
||||||
Centurion 6 |
10,200 |
2.48 |
100 |
171 |
.078 |
D |
3. Night
| Target and Number of Practices | Mean Range |
Full Gun Salvos per Min |
Output, per cent. |
Spread |
Hits per Gun/Min |
Average interval challenge to 1st salvo (seconds) |
16-inch |
No practices | |||||
| 15-inch | ||||||
145 ft. B.P.T. 3 |
3,000
(3,100)
|
1.07
(2.38)
|
94
(100)
|
412
(195)
|
.636
(.459)
|
33 |
6-inch with 15-inch M.A.C. |
||||||
Centurion 2 |
7,500 |
2.51 |
94 |
272 |
.153 |
37 and 190 |
PART II. – SECT. A. – BATTLESHIPS AND BATTLE CRUISERS 35
RANGEFINDING
4.
Armament. |
Error |
Average Error of 1st Salvo. |
Percentage of 1st Salvos to Straddle |
Mean Range |
Average Time Ranging before Open Fire (seconds). |
|
At Open Fire. |
At Cease Fire. |
|||||
16-inch |
546
(90)
|
470
(275)
|
370
(190)
|
23
(90)
|
17,500
(15,400)
|
82 |
6-inch with 15-inch M.A.C. |
225
(317)
|
100
(107)
|
450
(250)
|
0
(16.7)
|
15,600
(13,200)
|
80 |
15-inch |
334
(380)
|
257
(220)
|
500
(480)
|
21.9
(20)
|
14,700
(14,200)
|
|