F.d.U./B.d.U.'S War Log

16 - 31 January 1940

PG30256

	Date Position, Wind, Weather   and Sea State, Illumination, Events Time Air Pressure, Moonlight etc.
	Group Headquarters West     16.1           U 44 reports passage from the sea area west of the Channel that she has sunk 3 steamers, including the Dutch S.S. "Arendskork".  She has started on her passage south, as her position is known.         17.1           U 30 entered port.  She sank a patrol vessel type Agatha on her way out and scored a hit on "Barham".  The minelay off Liverpool went off well and according to plan.  It required a lot of dash, thought, ability and determination.  It was carried out in shallow water strongly patrolled.  By the 16th 3 mined areas had been declared off the port.             On the day of his return the Commanding Officer had the satisfaction of knowing that the whole of Liverpool harbor had been temporarily closed because of mines.                          U 31 sailed for her operations area according to Operations Order No. 20, after completing trial runs off Heligoland.                     A conference was held in Wilhelmshaven with representatives of the Torpedo Experimental Command because of renewed unexplained torpedo failures.  The main matter under discussion was the suspicion held by B.d.U. for some time now that MZ could fail to fire, even if shot under.  There have been repeated cases of shots fired at close range with good firing data which have not brought results and the reasons have been obscure even to the Torpedo Inspectorate (U 470).  These cases have increased particularly recently (U 24, U 15, U 20, U 59, U 60).   The Director of the Torpedo Experimental Command reports that U 20's shots cannot be explained.  Even if the speed had been wrongly estimated, at least one shot should have hit.  The only possible explanation for the failure of the 3 torpedoes to fire would be the fact that the size of the ship had been very much over estimated.  The Commanding Officer of the boat denies this possibility.  I have reached the following conclusions with regard to these and similar failures!             All the Torpedo Experimental Command's analyses of shots are possible for the particular case under consideration and possibly correct in some cases.  But I cannot believe that, with a whole series of failures of this kind, there are other reasons in every case.  I am convinced that there is a connection between all these so-called unexplained shots and there is a common cause for their failure which has not yet been discovered.  Up to now I have believed that in many cases boats have fired past, due to misinterpretation of the firing data or aiming mistakes. In individual cases I have sent the boat for further training. But now, with these failures of shots fired under the most simple conditions by a series of the best-trained Commanding Officers and torpedomen, I cannot accept this explanation any longer.  Some of these C.O.'s have undergone 2 years of training in peacetime and all of them, when reexamined, were found to have good or very good skill in firing.             From now on, I shall regard all such shots at closest range, where a detailed examination of the circumstances and the firing data exclude the possibility of a miss, and which so far have been regarded as unexplained, as failures of the firing unit.  It has happened again and again in these cases that the Torpedo Inspectorate
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	Date Position, Wind, Weather   and Sea State, Illumination, Events Time Air Pressure, Moonlight etc.
	has held the view that the boats have missed or made incorrect observations, only because the reason for the possible failure was not known and could not therefore be made to apply and that afterwards their view was turned out to be incorrect.  See, for instance, premature detonations, detonations half-way through the run, firing under with impact firing.             The attitude to be adopted to this problem is therefore, other unknown causes of failures are possible.  Otherwise we shall never get anywhere.           18.1           There is still uncertainty about the actual possibilities of supplying in Spain and a practical experiment is therefore necessary.  U 44, at present off the west coast of Spain, can be used for this; she can then operate together with boats which are sailing up to 14 days after her.  Supply has therefore been ordered for 25/26 in Cadiz.         19.1           Nothing to report.         20.1           Ice is beginning to have a direct effect on plans for operations.  Firing and diving training in the Baltic will have to be suspended for the present.  There is a choice between delaying the operation of several boats with new C.O.'s until the cold spell is over or sending them on to operations before they have completed the scheduled working up and firing practice periods.  As they are all officers whom I believe already capable of handling difficult situations, I have decided to send them on to operations immediately. They will first of all go to operations areas where comparatively little patrol is to be expected.  As soon as possible all boats will be transferred from the Baltic to the North Sea.         21.1           U 34 reported that she had carried out her minelaying operation off Falmouth.  She has managed it very quickly.                   Further sinkings indicate the presence of U 44 off the northwest coast of Spain.  Several U-boat warnings show that the enemy is taking action.                   The Director of the Torpedo Inspectorate telephoned me today.  Trial shots have been made against T 123, which did not fire, and magnetic measurements have been made on torpedoes in store, with the result that the Torpedo Inspectorate considers the possibility of torpedoes not firing is proven.                   The fact that its main weapon, the torpedo, has to a large extent proved useless in operation has been the greatest difficulty with which the U-boat Arm has had to contend with since the beginning of the war and it has had a most serious effect on results.  At least 25% of all shots fired have been torpedo failures.  According to statistics covering all shots up to 6.1., 40.9% of unsuccessful shots were torpedo failures.     1) In August 1939, before the boats left port during the emergency period, a conference held in the Torpedo
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	Date Position, Wind, Weather   and Sea State, Illumination, Events Time Air Pressure, Moonlight etc.
	Trials Department during which the doubts expressed by B.d.U. with regard to the proper functioning of the pistol were dismissed as unfounded by Rear Admiral Wehr, Director of Torpedo Trials Department. 2) On 14.9 U 29 reported by radio that 2 torpedoes had fired prematurely after covering the safety distance.  The Torpedo Inspectorate first wished to make out that the U-boats had made an error in position of 30-60 miles.   I would not accept this explanation.  The Torpedo Inspectorate then recommended setting the pistol 2 zones lower, in order to lessen its sensitivity.  This meant that they would not be certain to fire against merchant ships under 3,000 BRT if shot under and such ships would therefore have to be attacked with impact firing.  An order was accordingly given to the U-boats by B.d.U. on 14.9. 3) Failures were not eliminated however.  Further premature detonations were reported.(U 27 reported that the explosion caused slight damage to the boat).  Until the cause was discovered, the Torpedo Inspectorate arranged for the torpedoes to be fitted with an "A" setting of the switch, which made it possible to cut out electric firing. 4) After the "A" setting of the switch had been fitted, B.d.U. ordered on 2.10 that only impact shots were to be fired.  This meant that for the present the danger of premature detonation was eliminated.  The step was taken for the sake of safety of the boats, until such time as the cause of premature detonation was discovered. 5) At the beginning of October the Torpedo Inspectorate stated that the cause of premature detonation in the G7e had been traced to a bad cable lay-out.  The cables had now been laid differently and the G7e could once more be fired under.  In the case of the G7a mechanical disturbances were causing premature detonation and the G7a could therefore still not be fired under until the question was finally cleared up.   I expressed doubts on these different explanations for premature detonations, but as the Director of the Torpedo Inspectorate assured me that the G7e was now safe, I decided to try and I released the G7e for firing under with "MZ". 6) On 18.10 U 46 reported a premature detonation of a G7e in an attack on a convoy.  It was therefore established beyond question that the pistol was not safe in the G7e despite the adaptation made.  I again ordered impact firing only also for the G7e, with electric firing cut out (switch setting "A").   We were thus back where we were in 1914/18.  But I had to make this difficult decision to abandon the much-vaunted, much-discussed magnetic firing in order to avoid losing boats, directly or indirectly, through our own weapons and in the interests of U-boat successes. 7) On 20.10 the Director of the Torpedo Inspectorate informed me by telephone that he had discovered that day that the torpedo (G7a and G7e) was keeping a depth 2 meters below
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	Date Position, Wind, Weather   and Sea State, Illumination, Events Time Air Pressure, Moonlight etc.
	that indicated.  Numerous reports from boats, stating that the torpedoes had failed to fire with impact firing units despite good firing data, also indicated that the torpedoes were running deeper than their setting and therefore passing under the target.  I therefore ordered on 20.10 that torpedoes with impact firing were to be set at a maximum depth of 4 meters.  At the suggestion of the Torpedo Inspectorate, I ordered further that torpedoes with impact firing were to be set at 2 meters or less than the draft of the target.  But in order to avoid surface breaking and consequent cold running the minimum depth setting had to be fixed at 3 meters, and 4 meters in an Atlantic swell.  This meant that torpedoes could not be fires at targets with a draft of less than 5 or 6 meters, e.g. destroyers could not be attacked. 8) On 23.10 a conference was held in Wilhelmshaven between B.d.U., Director of Torpedo Inspectorate and Director of Torpedo Trials Department and Torpedo Experimental Command, in which the following points were confirmed:   a) variations in depth considerably greater than hitherto assumed were to be expected. b) that the cause of premature detonation had not yet been established. c) at B.d.U.'s request, it was agreed that at least the explosion at the end of the run which had also frequently occurred, should be eliminated in the near future. It was thus established that the effective functioning of the torpedo was very limited indeed:   with impact firing, danger of passing under with "MZ" shot, danger of premature detonation. 9) On 5.11 a new (adapted) pistol was brought out and it was hoped that, by stabilization of the needle, it would be proof against premature detonation.  The pistol was designated Pi(A-B).  With this pistol use of magnetic firing was again permitted.  Depth was to be set at draft of target plus 1 meter.  All our hopes were now centered on this pistol and further reports received of failures of the present pistol seemed less important. 10) U 28 and U 49 were the first boats to sail with Pi(A-B), on 8.11 and 9.11 respectively.  On 19.11 U 49 reported one G7a premature detonator after the safety distance had been covered, one G7e probably failed to fire, 2 G7a detonated after covering 2000 meters.  This was a bitter disappointment and our best hopes were dashed in one blow.  Apparently there was no improvement on previous conditions.  Further reports followed from other boats of premature detonations and failures to fire. 11) Some of the specialists in the Torpedo Inspectorate suggested that the pistols should be set 2 zones below the setting shown in the chart in order to reduce sensitivity and so avoid premature detonation.  The depth setting should be the same as the draft of the target and
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	Date Position, Wind, Weather   and Sea State, Illumination, Events Time Air Pressure, Moonlight etc.
	the torpedo thus brought closer to the ship so that the firing field would be effective even at the reduced pistol sensitivity.  I was against this and the Director of the Torpedo Inspectorate and the remaining specialists agreed with me. 12) Small alterations to the pistol (insulation of the copper cap, smoothing a thrust collar) did not bring any improvement.  Every now and then premature detonations seemed to become fewer for a time and firing under was adhered to, because firing with impact firing units would again have meant many failures due to passing under.   13) Report of shots, in which the pistol failed to fire, despite certain firing data, became more and more numerous.  The Torpedo Inspectorate believed that the pistol could not fail to fire if shot under and refused to accept any idea that failures could be caused by this section of the pistol.  I had all shots, which the commanding officers believed to be failures to fire examined by the Torpedo Inspectorate.  They thought that these must be due to misses or be regarded as unexplained.  I can no longer accept this explanation. in view of the large number of reports of shots failing to fire with certain firing data.  I consider that in many cases the failure of the pistol to fire is proven and I made this quite clear in a conference with Torpedo Experimental Command on 19.1 (see War Log of 17.1). 14) Experimental firing at T 123 afterwards showed that in fact several pistols failed to fire when shot under.  The Torpedo Inspectorate now admits the possibility of failures to fire and issued the following instructions, to be passed on to the boats, on 21.1:   1. For targets under 4,000 BRT, destroyers and surfaced S/M's, depth setting 4 meters. 2. The pistol may fail to fire against targets under 1,000 BRT. 3. For all other targets, depth setting draft plus 1 meter, even in bad weather. The results remain to be seen. 15) In addition to the negative results of trial firing at T 123, recent magnetic measurements of the body of the torpedo and the battery compartment have shown that these exercise an irregular, unstable magnetic effect on the pistol and may cause a strengthening (premature detonators) or a weakening (firing failures) of the magnetic unit. The torpedoes in store are to be demagnetized.  The Torpedo Inspectorate doubts if this will be successful.  The causes of the failures have therefore by no means been mastered. 16) The Commanding Officers' and crews' confidence in the torpedo is very much shaken.  Again and again the boats have tried, in the face of strong enemy activity, to fire their torpedoes under the best possible conditions and often when they have made a daring attack they have been
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	Date Position, Wind, Weather   and Sea State, Illumination, Events Time Air Pressure, Moonlight etc.
	rewarded with failures and even danger to themselves.  At least 300,000 tons, which might have been sunk, can be reckoned lost through torpedo failures.  I think it is certain, for instance, that U 47 Lieut.(s.g.) Prein's shot at the London class cruiser was a premature detonator.  It is very bitter for Commanding Officers and the executive control to find that the U-boat Arm cannot achieve the success expected of it, in spite of a thorough peacetime training, because of torpedo failures. I will continue to do all I can to keep up the fighting spirits of the U-boats in the face of all the setbacks.  We must continue to fire torpedoes in order to discover the causes of the defects and remove them.  But commanding officers and crews will only gradually regain full confidence in the torpedo if lasting technical improvements can be made.        22.1         U 32 entered port.She carried out her minelaying operation and also sank a steamer of 800-1,000 tons in the North Sea.             The Commanding Officer's explanation of why he thought the minelay could not be carried out in the Clyde is not convincing.  He pressed a long way forward and turned back when he was in the midst of anti-S/M forces and only a few miles from the position in which he was to lay the mines, although he himself did not think he had been detected.  He did not make another attempt on another day.  The operation was a difficult one - too difficult for this C.O.  I shall arrange for another boat to carry it out.         23.1           U 34 and U 44 each reported a convoy in her operations area.  At the moment there are so few boats in operations area - 2 off the coast of Portugal and 2 south of Ireland - that it will be a matter of great luck if these few boats, which are spread over a wide area, succeed in working together.  But the attempt must be made.