-H.M.S. Hood Reference Materials-
ADM 1-11585: Loss of H.M.S. Hood; Proposed Landing of Naval N.W.B. Equipment from Ships Fitted
Updated 01-Jul-2007

This document is a modern transcription of a portion of Admiralty record ADM 1-11585. The original file is composed mostly of short notes and correspondence. It does not feature an overly detailed text, nor does it contain many technical specifications for the Unrotated Projectile (UP) system used aboard Hood and the other vessels mentioned herein. 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.

This is not the complete document, but only a portion: We've sorted through the myriad of notes and have typed up the most pertinent portion of the texts here.

C.I.N.O. 5491/41
Safety of U.P. Ammunition in relation to present generally accepted Naval Service Standards.

It is fully recognised that the U.P. ammunition does not come up to the accepted standards of safety normally insisted upon for Naval Service.

The acceptance of the U.P. weapons and their associated ammunition has, however, been governed by consideration of high policy.

Active steps have been taken and are being taken as far as possible to improve the standard of safety.

2. A design of shuttered gaine for use with the No. 700 fuze and for the No. 720 fuze if used in the 3 inch U.P. is being pressed on with on P priority. The No. 720 fuze will not be used in the 3" U.P. multiple mounting until the question of prematures in salvo firing has been cleared up.

3. The remarks of the Ordnance Board on the points raised at X and Y will be obtained. C.I.N.O's P.S. is being dealt with separately.

4. D.N.O. fully concurs with C.I.N.O. that the position should be placed on record and, subject to any remarks D.T.S.D. and D.A.A.W. may wish to make it is proposed to submit this paper for the information of the Board.

[signed] W.R. Slayter
DIRECTOR OF NAVAL ORDNANCE
4th July, 1941

Register No. T.S.D. 864/41Minute Sheet No. [1]

With reference to D.T.S.D's 2/7/41 it does not appear to D.N.O. that the report of the Board of Enquiry (N.L. 9821/41) gives rise to the opinion that the U.P. ammunition probably caused the first fire in H.M.S. HOOD.

2. The question of the safety of U.P. ammunition in relation to present generally accepted Naval service standards has been discussed in detail on C.I.N.O. 5491/41. A copy of D.N.O's minute thereon is enclosed for information.

3. The following additional remarks are put forward in amplification of the remarks in C.I.N.O.5491/41.

From the point of view as regards liability to ignition due to cooking off, or penetration of the propelling unit by a hot splinter, there is no great difference between U.P. ammunition generally and Q.F. cartridges, separate or fixed.

It is in the after effect of self ignition of U.P. ammunition generally and N.W.B. in particular, that the increased danger lies.

The behaviour of U.P. ammunition for 2-inch and 3-inch U.P. has been fully reviewed in C.I.N.O. 5491/41.

The position with regard to A.A.D. type B (N.W.B.) ammunition is as follows:-

(i) Self ignition of the propelling unit will result in a directional flame of high intensity over a distance of about 20 feet and lasting for about from 1 to 3 seconds.

(ii) Should the Ready Use Lockers be subjected to sustained heat such as the heat of a cordite fire, there is, apart from the liability of the propelling units to cook off, a risk of the 8 ozs. of C.E. in the bomb component of the N.W.B. detonating.

This liability is considerably greater than with the shell fitted T.N.T. of a fixed Q.F. cartridge due to the fact that the bomb component of the N.W.B. is a thin cased bomb containing C.E.

4. With regard to D.T.S.D's opinion that the N.W.B. equipments should be landed from H.M. Ships, D.N.O. has pointed out in C.I.N.O. 5491/41 that U.P. ammunition generally does not come up to the accepted standards of safety normally insisted on for Naval Service and the acceptance of the A.A.D. type B (N.W.B.) in the first instance and followed later by 2-inch and 3-inch U.P. was governed by considerations of high policy.

The stowage of this ammunition, the balance of which is not required for Ready Use, has to be stowed apart from other magazines and between decks on the deck below the weather, is a constant source of anxiety and for this reason alone, apart from any question of the effectiveness of the N.W.B. equipment in H.M. Ships, D.N.O. would welcome the landing of the A.A.D. type B (N.W.B.) equipments forthwith.

5. D.T.S.D. referred.

N.L. 9821/41 has not been seen by D.N.O. Part N.L. 9821/41 was sent to D.N.O. in error and has been passed to D.O.D. (H) and other staff divisions concerned.

[signed] W.R. Slayter
DIRECTOR OF NAVAL ORDNANCE
12th July, 1941

C.I.N.O. 5491/41 has not yet been seen by D.T.S.D.

2. Whether or not the U.P. ammunition in HOOD contributed to her loss will never be known for certain. The surmise in D.T.S.D's 2.7.41 is based on the report in N.L. 9821/41, on the drawings of the fires prior to HOOD blowing up and on knowledge regarding what explosives were stowed near the scene of the first fires.

3. D.N.O's para 4 supports D.T.S.D's contention that the 7" N.W.B. equipments should be removed because:-

1. They do not effectively contribute to the A.A. defences of the ships in which they are mounted.

2. The potential danger to the ship from the U.P. ammunition.

3. Better close range A.A. guns are becoming available.

4. It is proposed, subject to further remarks by D.N.O. to seek approval to remove the 7" N.W.B's as and when Oerlikon equipments are fitted in capital ships and cruisers in accordance with approved policy.

K.G.V. and P. of W. have already had U.P's removed and 4 or 8 barrel pom poms of B and Y turrets (as originally designed) substituted.

5. Would D.N.O. please append an up to date list of the ships still fitted with 7" N.W.B's?

[signed] CW Longley-Cook
for DIRECTOR OF TRAINING & STAFF DUTIES DIVISION
16/7/41.

Register No. T.S.D. 864/41Minute Sheet No. 2

With reference to D.T.S.D's 16.7.41.

Para. 2. Noted.

Para. 3. Noted.

Para. 4. D.N.O. has nothing to add to his minute of 12.7.41. Concur in action proposed by D.T.S.D.

Para. 5. Appendix I, enclosed, shows the present allocation of 7" U.P. Mk I equipments.

[signed] W.R. Slayter
DIRECTOR OF NAVAL ORDNANCE
31st July, 1941

Submitted for approval to remove 7" Naval Wire Barrage U.P. equipments from H.M. Ships at present equipped, when Oerlikon guns become available to replace them.
[signature illegible]
DIRECTOR OF NAVAL GUNNERY & ANTI-AIRCRAFT WARFARE DIVISION
7.8.41

illegible annotations

Approval noted.

D.N.O. and D.N.C. referred for action to remove 7" U.P's I as Oerlikons are fitted up to the total number approved for each ship.

If considered necessary to promulgate this A. & A. by C.A.F.O. will D.N.O. please take action to do so?

[signature illegible]
DIRECTOR OF NAVAL GUNNERY & ANTI-AIRCRAFT WARFARE DIVISION
17.8.41

Register No. T.S.D. 864/41Minute Sheet No. 3

[Handwriting]
Lockers can be converted for use with 2" U.P. equipment.

Will D.of S. please say to what control storage place they should be sent when first landed. They will then be despatched to firms for conversion or controls can be arranged.

H.S. Pengelly
D.N.O.

[Typed text follows]

Concur in draft C.A.F.O. as amended. Will D. of S. insert the information asked for by D.N.C., and then pass to E.F.O. for publication.

2. Two months have now elapsed since approval was given to remove these equipments.

[signature illegible]
DIRECTOR OF GUNNERY & ANTI-AIRCRAFT WARFARE DIVISION
15.10.41

Noted.

Paragraph 6 has been added.
[signature illegible]
D. of S.
23/10/41

APPENDIX I.
7" U.P. Mark I equipments
Present allocation.

Admiralty Fleet Order
C.A.F.O. 2163.— 7-in., U.P. Mark I Equipments.
Removal from Ships when replaced by Oerlikons
(G/T.S.D./864/41 6-11/1941)

When Oerlikon equipments are mounted in ships at present mounting 7" rocket Mark I (w) equipments, the latter are to be landed.

2. The mountings so landed are to be despatched to the Admiralty, G.M.O., Parkhead, Glasgow.

3. Ammunition for these equipments (A.A.D. Type B) should be returned to the nearest Naval Armament Depot, or officer in charge of Armament Supply.

4. Telephones, change-over switches and other electrical apparatus fitted for operation and control of the mountings should be returned to the nearest Dockyard or Naval Store Depot.

5. Air Look out sights pattern 12951 should be demanded from the nearest Naval Store Depot for each U.P. sight surrendered when these sights have been used in lieu of Air Look out Sights.

6. Ammunition Lockers for 7" Rocket equipments should be sent to N.S.O. (Midland Area), R.N. Store Depot, Shobnall, Burton-on-Trent.