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C.B.  04051 (88)
"U 643"
Interrogation of Survivors
December, 1943
This Report is not to be considered accurate in all respects, having been prepared before complete information was available.  It is therefore not to be taken as historically correct.



          This book is the property of His Majesty's Government.  
          It is intended for the use of the recipients only, and for communication to such Officers under them (not below the rank of Commissioned Officer) who may require to be acquainted with its contents in the course of their duties.  The Officers exercising this power will be held responsible that such information is imparted with due care and caution.  



Attention is called to the penalties attaching to any infraction of the
Official Secrets Acts.
C.B.  04051 (88)
"U 643"
Interrogation of Survivors
December, 1943
  N.I.D. 07754/43.  


          The following report is compiled from information derived from prisoners of war.  The statements made cannot always be verified; they should therefore not be accepted as facts unless they are definitely stated to be confirmed by information from other sources.  


  Introductory Remarks  
      (i)  General;  (ii)  Commanding Officer;  (iii)  Engineer Officer;  (iv)  Other Officers;  (v)  Ratings.    
  Details of "U 643"  
    (i)  Type;  (ii)  Builders;  (iii)  Diesels;  (iv)  Main Motors and Switchboard;  (v)  Batteries;  (vi)  Armament  (a)  Guns,  (b)  Ammunition,  (c)  Torpedoes;  (vii) R.D.B.;  (viii) S.B.T.;  (ix)  G.S.R.;  (x)  Radar;  (xi)  W/T;  (xii)  Camouflage;  (xiii)  Gyro Compass;  (xiv)  Badge;  (xv)  Flotilla.  
  Only Patrol of "U 643"  
      (i)  Departure from Kiel;  (ii)  Patrol in Skagerrak;  (iii) Call at Egersund;  (iv)  Fitting of new G.S.R. Set at Bergen;  (v)  Passage into Atlantic;  (vi)  Operation off Greenland;  (vii)  Failure of the Operation;  (viii)  Operation of "Gruppe Leuthen."    
      (i)  Anniversary Celebration;  (ii)  First Attack;  (iii)  Second attack;  (iv)  Third attack;  (v)  Damage to "U 643."    
  General Remarks  
    (i)  Contact Keeper Buoy;  (ii)  Radar (a) Transmitter, (b) Receiver, (c)  Receiver Circuit, (d)  Cathode Ray Tube, (e) New Mattress Aerial, (f)  Range of Radar;  (iii)  G.S.R.;  (iv)  Anti-Infra-Red Camouflage;  (v)  Acoustic torpedoes;  (vi)  New U-boat Types (a) Torpedo-carrying U-Boats, (b) Midget U-Boats, (c) Four-man U-Boat;  (vii)  Goliath Transmitter;  (viii)  Listening-in to British Broadcasts;  (ix)  Security Training;  (x)  Training of U-Boat Officers;  (xi)  U-Boat Losses;  (xii)  Protective Grease for Guns;  (xiii)  Second Japanese Submarine to visit France;  (xiv)  Extensible Diesel Intake Trunking;  (xv)  K.F.R.G. Electrode Minesweeping Gear;  (xvi)  Dönitz.  
    (i)  Libau;  (ii)  Kiel;  (iii)  Swinemünde;  (iv)  Trondheim;  (v)  Berlin.  
Appendix "A."  Early History of "U 643"  
Appendix "B."  "U 643":  Tests of Lubricating Oil  
Appendix "C."  Ship's Company of "U 643"  
      (i)  Survivors;  (ii)  Casualties;  (iii)  Total crew.    
  (C51136)                                                                                                                             B*2  


8th OCTOBER, 1963.
  (i)  General  
          "U 643," a 500-ton U-Boat commanded by Kapitänleutnant Hans Speidel, was sunk on the afternoon of 8th October, 1943, by Liberator T of 120 Squadron, in approximate position 56° 18' N., 026° 30' W.  Eighteen prisoners, including the Commanding Officer, the Engineer Officer and the Medical Officer survived, being quickly picked up by H.M, ships "Oribi" and "Orwell."  The total complement of the U-Boat was 48.  
          "U 643" was exactly one year old on the day sue was sunk, having been commissioned on 8th October, 1942.  She was however, only on her first patrol, having sailed from Kiel on 26th August, 1943 and had no successes whatsoever to her credit.  Her working-up period had been prolonged to 10 months because of various mechanical defects and accidents.  
          Special features of this report are further information on:  
                  (a)  Fu.Bo.  (Section V.)  
                  (b)  Radar.  (Section V.)  
  (ii)  Commanding Officer  
          The Commanding Officer of "U 643" was Kapitänleutnant Hans Speidel, aged 26, of the 1936 term.  His service career was a varied one.  Before the war he was serving in the "Emden" and visited numerous Japanese ports in her.  He then transferred to the Fleet Air Arm and was later seconded to the German Air Force, in which he became an Oberleutnant and won the Iron Cross, First Class in silver.  He stated that he had taken part in the first air attacks against England, and that he had also flown in Russia, participating in a number of attacks on Moscow.  He then rejoined the Navy sometime in 1941 and entered the U-Boat Arm, attending the U-Boat School at Gdynia for five months.  He then made four patrols as First Lieutenant under Kapitänleutnant Guggenberger in "U 81" in the Mediterranean.  Next he carried out the U-Boat Commanding Officer's Course, upon completion of which he was given command of "U 643."  He joiner her at the Blohm & Voss Yards in Hamburg in mid-1942.  
          Speidel is the perfect Nazi or, in the words of the Welfare Officer who met him, "a complete swine."  He boasts that he wears the Golden Hitler Youth Badge, and his behavior is insolent and arrogant.  He speaks good English, having spent two years in England as a student.  His chief concern in his U-Boat seems to have been security, which he drilled into his men ad nauseam.  Unfortunately he had further opportunity of doing so during the transfer of the prisoners after disembarkation in the United Kingdom.  It was said that he slept 24 hours a day while on patrol.  He was hated and feared by all on board.  
  (iii)  Engineer Officer  
          The other surviving officer was Leutnant (Ing.) Karl August Kennepohl, aged 21, of the 1939 term.  Little was learned of his early career except that he had served in minesweepers in 1940.  He was extremely security-conscious, but pleasant and well-mannered.  
  (iv)  Other Officers  
          Leutnant zur See Ulrich Settgast, the First Lieutenant, and Leutnant zur See Hans Gneisse, the Second Lieutenant, did not survive.  The Medical Officer, Assistenzarzt Siegfried Hoffmann was not interrogated, being protected personnel.  Ratings reported that he kept regular watch on the G.S.R. in spite of his status.  
  (v)  Ratings  
          The surviving ratings were security-conscious, tough and fluent liars.  They did not forget their captain's oft-repeated instructions on behavior as prisoners of war.  Their morale was high, as is usually the case with crews that have just left Germany.  The officers were cordially hated by all the ratings.  Nearly all the survivors were making their first patrol in a U-Boat.  Their average age was 20-1/2 years.  
  (C51136)                                                                                                                              B*2  


          The following are the British equivalents of ranks mentioned in this report:  
Korvettenkapitän Lieutenant-Commander.
Kapitänleutnant Lieutenant.
Oberleutnant zur See Sub-Lieutenant.
Leutnant zur See Junior Sub-Lieutenant.
Oberfähnrich zur See Midshipman.
Fähnrich zur See Junior Midshipman.
Seekadett Cadet.
Marinestabsarzt Surgeon Lieutenant.
Marineoberassistenzarzt Surgeon Lieutenant (Junior).
          The suffix "(Ing.)" after a rank in place of "zur See" denotes Engineer Officer.  The suffix "der Reserve" denotes a Reserve Officer.  
  Type 500 tons, VII C.
  Displacement Blohm und Voss, Hamburg.
  Builders 6 cylinder G.W.
Speeds and Fuel Consumption (according to a document, removed from a prisoner from "U 643")
Diesel-electric procedure.    
Fuel consumption
Diesel revs.
Main Motor revs.
L.F. (Slow)
240 r.p.m.
155 r.p.m.
H.F. (Half)
285 r.p.m.
195 r.p.m.
2 x H.F. (Three fifths)
330 r.p.m.
215 r.p.m.
A.F. (Four fifths)
360 r.p.m.
240 r.p.m.
        (N.I.D. Note.  Consumption in "U 353," a 500-ton U-Boat, at slow speed on Diesel-electric, was given as 1.7 tons/day in C.B. 04051 (53), page 12.)
  Main Motors and Switchboard. A.E.G.
  Batteries M.L.A. 1000.  The battery compartment had been painted with a special anti-acid paint.  This proved unsatisfactory, not being acid-proof.
            (a)  Guns One quadruple 20 mm. (0.79 in.) mounting on the lower bandstand.  Two twin 20 mm, guns on the upper bandstand.  Twenty rounds per magazine.  Four M.G. 15's with drum feed on the bridge.  No gun forward.
            (b)  Ammunition Two special slides for conveyance of ammunition from the bridge to the lower bandstand had been built by ship's staff.
            (c)  Torpedoes Twelve carried, of which four were "Curly" (F.A.T.), stated to be electric and the remainder normal air and electric.  No acoustic torpedoes were carried, there were none available in Kiel.  Upper deck torpedo containers had been removed.
      (N.I.D. Note.  No further information or confirmation on torpedoes could be obtained, as no torpedo rating survived.)
  R.D.B. Ninety balloons carried in three boxes.  Operated only by the Captain and the Engineer Officer.
  S.B.T. Fitted.  Prisoners believed that the charge carried was a new type.  It was described as a white cartridge with holes in the top.
  G.S.R. "Wanz" type fitted at Bergen in early September, 1943, replacing the original Metox 600A.  Wave band stated to be from 120 cm. to 180 cm.  Basket aerial.
  Radar Fitted.  Extensible combination Radar G.S.R. aerial.
  W/T Normal equipment.  No "Mein" receiver was carried.
  Camouflage Anti-infra-red camouflage paint, appearing grey in colour in normal light, was applied to the bridge structure at the building yards.  It was tested at Kiel with a special "telescope," at night, by a patrol-boat which passed alongside.  The paint was stated to have suffered severely from the heavy seas, and much rust was already in evidence.
  Gyro Compass Fitted with a new type of cooling system silent in its operation.
  Badge The "Olympic Rings" of Commanding Officers of the 1936 term.
  Flotilla 5th Flotilla, Kiel.  Due to join 1st Flotilla, Brest.


  (i)  Departure from Kiel  
          "U 643" finally sailed from Kiel on her first patrol in Thursday, 26th August, 1943, well over 10 months after her commissioning.  She had two minesweepers as escort and was in company with three other U-Boats, of which one was a minelayer of unestablished tonnage, one a 740-tonner, under command of an officer named Bender (N.I.D. Note.  "U 841" under Kapitänleutnant Bender, was sunk on 17th October, 1943, by H.M.S. "Byard" in 59° N., 31° W.), and one was a 500-ton boat.  This group sailed to Kristiansand S., where it lay over one night, and then proceeded to Haugesund.  
  (ii)  Patrol in Skagerrak  
          "U 643" was then ordered to patrol the Skagerrak for two or three days with two of the other boats.  The reason for this patrol was, one prisoner suggested, to prevent Danish ships from escaping to Sweden.  
  (iii)  Call at Egersund  
          On 2nd September, 1943, at the conclusion of the Skagerrak patrol, "U 643,"  proceeded with the other two U-Boats to Egersund, where they lay over one night.  Next day the U-Boats proceeded to Bergen.  
  (iv)  Fitting of new G.S.R. Set at Bergen  
          "U 643" entered Bergen on 3rd September, 1943, for a stay of 11 days.  The purpose of this call was the installation of the new "Wanz" G.S.R. set, which "U 643" received after the other U-Boats had been fitted and had sailed.  A test of the lubricating oil was made on the 10th.  (See Appendix 'B.')  Fuel was taken and provisions embarked for a patrol of 10 weeks.  
  (v)  Passage into Atlantic  
          "U 643" sailed from Bergen on 14th September, 1943, in company with three U-Boats, one of which was stated to be "U 378," commanded by an officer named Lauterbach.  Escort was furnished only to the entrance of the fjord.  Course was shaped through the Rosengarten, in the vicinity of which a destroyer attack was successfully evaded by diving to 100 metres (328 ft.).  Procedure during this period was to submerged by day and to recharge batteries for only about three hours at night, from 2300 to 0200.  
  (vi)  Operation off Greenland  
          After about 10 days in the Atlantic, "U 643" proceeded to an operational area off Greenland and joined a group of about 20 U-Boats forming "Gruppe Rossbach."  The group was spread southwards from the tip of Greenland, its duty being to intercept an approaching east-bound convoy estimated at 72 ships.  The U-Boats were spread 15 miles apart.  "U 643" being the southernmost boat.  The next position was occupied by the U-Boat commanded by Hunger, and other boats in the group were "U 378," under Lauterbach, "U 336," under Baltz, "U 645," under Ferro, "U 273,." under Oberleutnant Engel, and the U-Boats commanded by Finke, Hungershausen and Boddenberg.  
          At about this time "U 643" suffered damage to her periscope and her quadruple 20 mm. in seas of force 7 or 8.  The shields of the quadruple mounting were completely torn away and other external fittings were bent and twisted.  The ammunition slides from the bridge were both washed overboard.  Water entered the packing of the mirror of the main periscope and flooded it.  Speidel reported these defects to Control and was ordered to return to base unless he could effect repairs.  
          Temporary repairs were undertaken.  At one time, "U 643" lay helpless on the surface for two and a half hours while the welding equipment was brought up through the conning-tower hatch in order to clear away the wreckage of the shields and refit the pedestal and other parts of the quadruple mounting.  Another time "U 643" surfaced in the early evening and fitted a cap over the periscope housing to support the periscope from the inside.  During this time "U 643" dared not risk a pressure greater than that of 14 metres depth.  Control then gave Speidel his choice of remaining at sea or returning to base, and Speidel elected to continue his patrol.  
  (vii)  Failure of the Operation  
          The operation against the convoy nevertheless failed.  The U-Boat commanded by Hunger, next in line north of "U 643" developed battery trouble and was recalled to base.  Whilst returning on the morning of 7th October, she passed "U 643" and about 20 nm further south she sighted an aircraft and a destroyer of the convoy escort.  Hunger, however, failed to report this sighting to Control until nightfall.  He was answered by a sharp signal blaming him for causing the loss of an opportunity for "Gruppe Rossbach" to attack the convoy.  
          Next morning, 8th October, "U 643" was searching for the convoy in her old position at the southern end of the line.  Another U-Boat of the group, stated to have been "U 378" under Lauterbach, developed trouble and was returning to base.  As she was proceeding southwards not far from "U 643" the latter heard her signal to Control that she had sighted two destroyers and an aircraft and heard Control order her to attack.  Within a few minutes "U 643" heard a loud explosion, saw a flash in the distance and heard the signal reporting that t destroyer had been sunk.  
          (N.I.D. Note.  O.R.P. "Orkan" was torpedoes and sunk at 0610 on 8th October, 1943, in position 56° 30' N., 26° 25' W.  She formed part of the 10th E.G., who was acting as a support group in the vicinity of Convoy S.C.143.)  
  (C51136)                                                                                                                              B**  


          Shortly afterwards "U 643" herself picked up a G.S.R. contact on an aircraft.  She engaged on the surface and was sunk before she could report the probable presence of the convoy to the rest of her group.  Prisoners were convinced that the convoy got through unmolested about 30 miles south of the nearest U-Boat in the line.  
  (viii)  Operation of "Gruppe Leuthen"  
          Prisoners from "U 643" professed to know some details of an operation against a Murmansk convoy in the Denmark Straits by "Gruppe Leuthen" shortly before the "Rossbach" operation.  "Gruppe Leuthen" was said to have been disbanding while "U 643" was in the "Rossbach" line, and some of the U-Boats joined the new group after being refuelled.  "Leuthen" was said to have sunk 10 destroyers and a high tonnage of merchant shipping of the convoy.  The U-Boat commanded by Hepp is said to have sunk one destroyer and four ships, totaling 19,000 tons, and then to have been sunk herself.  Other U-Boats in the pack were those commanded by Kruschka, Epp, Forstner, Scheibe and Otto.  The last-named suffered heavy damage to his boat and was himself severely wounded.  This group of experienced U-Boat commanders was said to have carried acoustic torpedoes only.  Control was stated to have made a signal to them saying that they were the pioneers of the latest weapon and that everything depended on them.  
          (N.I.D. Note.  This may be a very inaccurate and garbled reference to Convoys O.N.202 and O.N.S.18.)  
  (i)  Anniversary Celebration  
          "U 643" began the day of 8th October, 1943, confidently and with high hopes.  It was her anniversary and at 0800 Kapitänleutnant Speidel ordered one minute for silent reflection on the U-Boat's commissioning a year ago and for renewing high resolve.  He then announced that they would mark the occasion by performing some deed worthy of the day.  
  (ii)  First Attack  
          Accordingly when "U 643" obtained a G.S.R. contact on an aircraft shortly after 1300, the Captain did not dive, but ordered the guns to be manned.  There was plenty of time, and all was in readiness when the aircraft approached.  Fire was opened immediately and prevented the aircraft from making an accurate attack so that her depth-charges did no damage.  
          (N.I.D. Note.  At about 1313 on 8th October, 1943, Liberator Z/86 sighted a U-Boat, Green 30°, distant seven miles, and attacked from 020° Red quarter with two Mark XI depth-charges.  Evasive action by the U-Boat prevented the use of the bombsight and the depth-charges entered the water 60 ft. ahead of the bows.  Flak from the U-Boat was ineffective.)  
  (iii)  Second Attack  
          Suddenly there appeared directly astern of the first aircraft a second Liberator running in at high speed to attack.  The U-Boat's gunners shifted their sights to this new target and gave it all they had.  As a result the aircraft's depth-charges fell wide of their mark and inflicted no damage.  
          (N.I.D. Note.  At 1312 on 8th October, 1943, Liberator T/120, on passage to escort S.C. 143, flying on track 166 at 1,800 ft. obtained an S/E contact and made visual sighting simultaneously on a U-Boat on the surface bearing Red 15°, distant eight miles, in position 56° 18' N., 26° 30' W. course 80°, speed 12 knots.  The U-Boat was of the 500-ton type and only four men were noticed on the bridge.  The aircraft climbed into cloud and made a direct approach from approximately four miles, experiencing heavy flak from the U-Boat which made the continuation of direct approach unhealthy.  The aircraft too violent evasive action and attempted to make a head-on attack, but because of the evasive tactics of the U-Boat, the attack was finally delivered from Green 100°.  Four Mark XI Torpex depth-charges, set to shallow depth, spaced 60 ft., were released from 100 ft. while the U-Boat was on the surface.  The depth-charges were seen to overshoot, No. 1 exploding 200 feet ahead of the U-Boat in line with her course.  The U-Boat appeared to be undamaged and the aircraft's pilot prepared for a second attack.)  
  (iv)  Third Attack  
          (N.I.D. Note.  Liberator T/120 attacked a second time from Green 100°, releasing from 30 ft. four Mark XI Torpex depth-charges, same setting as before, upon the still surfaced U-Boat.  The charges were seen to straddle the U-Boat, No. 1 falling to starboard and Nos. 2, 3 and 4 to port.  No. 1 depth-charge exploded below the U-Boat and the remainder exploded on the port side.  The U-Boat then slowed down and the aircraft made a front gun attack from the bows.  No opposition was encountered on this run, so the aircraft circled the U-Boat, which by this time had come to a standstill and was down by the bows with the crew on the bridge preparing to abandon in dinghies.  At this juncture they hoisted the German flag.  90 minutes after the second attack the U-Boat was seen to explode forward of the bridge structure and to sink immediately by the bows.  The grey explosion plume rose to a height of 150 ft., and survivors were seen being thrown into the water with many being killed.  A large oil patch, 300 yards across, was then visible with scattered wreckage.  
          Meanwhile the aircraft had been homing escort vessels, three of which arrived on the scene 20 minutes after the explosion, and picked up 18 survivors.)  


  (v)  Damage to "U 643"  
          Liberator T/120's second attack was well placed and the damage done to "U 643" was comprehensive and fatal.  The U-Boat was thrown violently into the air.  Lights went out and instruments were wrecked.  Diving tanks No. 3 and 5 were torn open and one of the batteries and the main switch were put out of action.  Water was entering the battery compartment.  The quadruple 20 mm. mounting was torn out of its bed and washed overboard, taking one rating with it.  The U-Boat was heavily down by the bows and was slowly sinking.  Confusion seems to have reigned in the U-Boat.  The Captain was below and the First Lieutenant was on the bridge.  The latter gave the order to dive and the men on the bridge began to go below.  The order was canceled from below by the Engineer Officer, who said diving was impossible because of the damage and lack of air pressure.  His intention was to keep the U-Boat afloat as long as possible.  Futile efforts were then made to pass ammunition and life-jackets up to the bridge.  Meanwhile the men below heard her being hit by the aircraft's guns.  Then the Captain seized the German war flag, went up to the bridge and hoisted it defiantly, while the men, completely disorganized, tried to take cover and clear away the dinghies.  
          Although there was ample time for the men to inflate life-belts, assemble their gear and even to rescue some bottles of brandy, no further defensive action was taken by the U-Boat and no further signal was made to Control, who had only been informed that they were being attacked.  A scuttling charge was passed up the conning-tower, but it was never used, for suddenly a terrific blast shook the boat as the batteries exploded.  Most of the men still below were killed, and those on deck were either also killed or thrown into the water.  "U 643" sank at once by the bows.  
  (i)  Contact Keeper Buoy  
          A prisoner described a new buoy, stated to have undergone trials in the Baltic and intended to be used by U-Boats to indicate the position of convoys.  It is termed "Fühlungshalterboje" and is familiarly known as "Fu.Bo."  
          The buoy is about 1 metre (3.38 ft.) high and 40 cm. (15.7 in.) in diameter.  It is dropped by the U-Boat when she first sights a convoy.  Half hour or an hour later, it bursts open and ignites a floating flare of various pre-set colours.  About five different colours, red, green, yellow, etc. are said to be used, each colour having a different meaning relating to the convoy's movements.  
          Before dropping the buoy, the U-Boat makes a signal warning other U-Boats to watch for it.  A second signal is made after the buoy has been dropped, giving its position relative to the convoy.  
  (ii)  Radar  
          The surviving telegraphist of "U 643" gave the following description of the latest German U-Boat Radar equipment:  
          Transmitter and receiver are two entirely separate units.  The transmitter is built into the "S" shaft (so called because it was meant to accommodate the "S" equipment, the German asdic which was later abandoned).  The receiver is situated in the control room.  The recess in the bridge fairing, which formerly took the extensible W/T aerial, has been enlarged to take the Radar aerial.  This change is obvious when seen from the air.  
  Transmitter The transmitter comprises two distinct parts (upper and lower).  The upper part is divided horizontally into two sections.  The top section (German description:  part "X") includes a small transmitter/receiver with miniature cathode ray tube in the top left-hand corner, both serving for the correct turning of the main transmitter.
    The lower section ("Z") contains the calibrating part ("Messkette").
    The lower part ("T") of the transmitter comprises three horizontal sub-sections (from top to bottom):
    (1)  Modulator ("TS" Steuerstufe).
    (2)  Mains unit ("TN" Netzstufe).
    (3)  A power oscillator ("TU" Ultrastufe) with two transmitter valves, type TS6.
    Wavelength of transmission was give as 80 cm.  Prisoner mentioned the anode voltage of 8,000 v. and cathode 2 v.
  Receiver The receiver also comprises two distinct parts (upper and lower).  The upper part is sub-divided vertically.  The left section (in German referred to as "OB" Beobachrungsteil) is the indicator unit with the cathode ray tube.  The right section is the mains unit ("NE" Netzteil).  The lower part ("R") of the receiver comprises three horizontal sub-sections (from top to bottom):
      (1)  Instrument board ("RI" Instrumentteil) showing grid voltage (220 v., anode voltage (8 kv.) grid bias (minus 2,000 v.), miliameter (showing about 7 ma).  There is a fifth window for another instrument, but prisoner had never seen it installed on any set.
      (2)  L/F section ("RN" Niederfrequenzteil).
      (3)  H/F section ("RH" Hochfrequenzteil).


  Receiver Circuit The incoming signals (375 Mc.) enter an oscillator circuit with one valve, type PH.4671.  The amplifier stage which follows contains three valves, type RV.12P.2000, then there are two more oscillator circuits, the first with one valve, type PH.4671, the second with three valves, type RV.12P.2000.  The last stage is the rectifier stage containing one valve, type S.R.F.G.5.  The type RV.12P.2000 valves are of minute size (like an acorn) and have no special socket, the connections being soldered.  The coupling between stages is alleged to be inductive.  The pulse recurrence frequency used is 500 cycles.
  Cathode Ray Tube The cathode ray tube was of normal design with Wehnelt cylinder.  Prisoner stated that the tube contained two complete sets of all vital parts, so that by switching over on the tube socket, the tube can still be used after the first set has a breakdown.  The cathode is indirectly heated (voltage 4 v.) and an auxiliary anode voltage of minus 1,450 v. is applied.  The voltage on the deflecting plates is plus 1.500 v.
  New Mattress Aerial This consists of squares of wire mesh, the sides being 20 cm. (8 in.).  Protruding from the mattress are eight dipoles 20 cm. long with short reflectors on the top.  The upper four dipoles are the transmitter aerials, the lower four are the receiver aerials.  The back of the mattress carries a figure-8 aerial, which can be used to obtain bearings in conjunction with the G.S.R.
  Range of Radar Prisoner estimated the range of German destroyer Radar as 40-50 km. (22-27 miles) and that of U-Boats as 7 km. (3.8 miles) under favorable weather conditions.  He thought that U-Boats using Radar could be detected by other craft at a greater range than their own Radar was effective.  Prisoner would have liked to dispense with Radar in U-Boats all together, and have it replaced by a G.S.R. set three times the size of the present one.
  (iii)  G.S.R.  
          The new type G.S.R. which "U 643" carried operates on the wave band of 120-180 cms., but it is capable of picking up higher harmonics and thus transmissions on the wave length of 60 cms. would appear on the 120 cm. scale.  Prisoner had heard of trials carried out with some new sets which had three interchangeable coils or coil-condenser combinations.  These new G.S.R. sets were alleged to operate on three wave bands, i.e. 60-120, 120-180 and 180-220 cms.  
  Signals Referring to Radar and G.S.R.  
          Prisoner (Telegraphist from "U 643"), stated that all signals referring to improvements, changes and new equipment of Radar and G.S.R. were prefixed with the code word "BASTLER."  
  (iv)  Anti-Infra-Red Camouflage  
          A prisoner states that every U-Boat leaving Kiel on patrol is tested with infra-red rays.  "U 643" was tested as follows:  "U 643" lay at the Tirpitz Mole.  The Commanding Officer inquired at the ST. LOUIS depôt when the testing could take place.  The reply was that it could be done at once.  It was already dark.  A patrol boat about 10 metres (33 ft.) long approached and lay alongside.  The Commander then asked how long the process would take and was informed that it was already finished, and was satisfactory.  
          The anti-ray paint used is supplied ready mixed from the dockyard and its ingredients are unknown to the crew.  It is grey-black in colour.  
  (v)  Acoustic Torpedoes  
          A W/T rating from "U 643" states that the latest acoustic torpedoes are called "Zaunkönig."  He heard the name when he intercepted a signal from Control to a U-Boat operating in "Gruppe Leuthen," thought to be the first pack equipped with them.  The signal conveyed congratulations on
the first destroyer sunk by a 'Zaunkönig.' "
          Another prisoner thought that the acoustic torpedo would not be sued in large numbers until the "new torpedo" is in service.  This is a torpedo with electric propulsion which will eventually be used with an acoustic head.  
          Trials with new torpedoes were being carried out at Hel in the spring of 1943 in conjunction with Heinkel 111 aircraft.  


  (vi)  New U-Boat Types  
  Torpedo-carrying U-Boats A prisoner said that he had seen at Swinemünde a new U-Boat type of 600 tons with an extraordinarily broad deck covering the external tanks.  There was a torpedo store room between the Control Room and the Petty Officers' mess (see C.B. 04051 (80), Section vi (b), page 4).
  Midget U-Boats A prisoner reports seeing a two-man U-Boat at Hel.  The length visible above water was about 8 metres (26 ft.), and the conning-tower was large enough for one man.  The U-Boat was towed out of harbour and then proceeded under her own power, much exhaust being visible.  (See C.B. 04051 (68), page 12)
(c)   4-man U-Boat A prisoner had heard of trials of a 4-man U-Boat at Hel.  This U-boat has only one propulsion unit, and the fuel was stated to be contained in bottles.  (See C.B. 04051 (84), Section V (vi).)
          (N.I.D. Note.  Experimental work, believed to be connected with midget U-Boats, had already been reported at Hel.)  
  (vii)  Goliath Transmitter  
          A prisoner from "U 135" stated that the new giant transmitter called "Goliath" is probably at Norddeich, though he is not certain.  It has a maximum power of 1000 kw., but is not working on full power.  Its special feature is that it is the first long-wave station whose frequency can be altered.  
  (viii)  Listening-in to British Broadcasts  
          A U-Boat officer said that he and other officers frequently listened to the British radio when at sea.  Their favorite time for doing this was immediately after coming off the first watch.  
          Listening-in at base in Lorient was infrequent and considered daring because of the willingness of some officers to gain credit by reporting such incidents.  
  (ix)  Security Training  
          It was stated that every U-Boat carried a book of instructions and warnings on behavior as a prisoner of war.  Passages from this book were read daily to the crew of "U 643" until she was through the Rosengarten.  
  (x)  Training of U-Boat Officers  
          Several officers agreed that training of new officer personnel in the German Navy today is completely inadequate.  One Commanding Officer said that his First Officer was completely incompetent.  The practice of sending prospective Commanding Officers out on operational patrols for training has been abandoned, and their only experience is that gained during the tactical exercises.  
  (xi)  U-Boat Losses  
          (a)  An officer, who was last at the base on 3rd August, 1943, stated that of 20 U-Boats in the 9th Flotilla at Lorient, 10 were sunk within two months.  
          (b)  An officer stated that in August, 1943, great difficulties were cause by the loss of so many supply U-Boats.  Many operational boats had now to carry out supply duties.  
  (xii)  Protective Grease for Guns  
          A prisoner stated that the grease for protecting U-Boat guns from damage during submersion is a greyish-black grease of animal origin with the reference number Z.D.N.26.  It is supplied in tins.  
  (xiii)  Second Japanese Submarine to visit France  
          A second Japanese submarine visited Lorient in summer 1943.  Prisoner had heard rumors that she was sunk on her return voyage.  They confirmed the sinking of the first one near Singapore some months ago.  
          (N.I.D. Note.  The arrival of a Japanese submarine at Lorient in summer, 1943, is confirmed, but nothing is known of her subsequent sinking.)  
  (xiv)  Extensible Diesel Intake Trunking  
          A prisoner had heard of recent trials in Kiel of U-Boats fitted with an extensible intake trunking.  The purpose of this innovation was to enable a U-Boat to proceed on Diesel propulsion at periscope depth, with consequent increased speed.  It was thought that this might be practicable, particularly in darkness.  


  (xv)  K.F.R.G. Electrode Minesweeping Gear  
          A U-Boat officer with considerable previous experience in minesweepers stated that about a year ago in the K.F.R.G. ("Kabelfernräumgerät") electrode minesweeping gear, the electric cables were spread by otters from which the electrodes were streamed astern.  The otters could be set to hold the electrodes either on the surface or at a per-determined depth.  The current strength used was about 2,000 ampères.  In the early days of this sweep, D.C. was employed but later the current was reversed with a frequency of about 12 times per minute.  
  (xvi)  Dönitz  
          The First Lieutenant of "U 523," who was last ashore in early August. 1943, stated that Dönitz is still B.d.U., and that all U-Boat Commanders still report to him after each patrol, or, on rare occasions when he is not available, to his Chief of Staff, Rear-Admiral Godt.  
  (i)  Libau  
          Libau has become the base of the 25th U-Boat Flotilla (Torpedo Firing Flotilla) formerly based on Gdynia.  
  (ii)  Kiel  
          (a)  Pressure Dock.  Prisoners said that this dock lay in October, 1942, in the Schwentine River Estuary at Kiel, between Howaldt's Werft and the Deutsche Werke.  They had no knowledge of any intention to remove it from that position, but said that as it was a floating dock, it would be possible to tow it through the Kiel Canal without undue difficulty, although it was very broad.  
          The dock was described as a floating cylinder of steel and concrete about 110 meters (360 ft.) long and with an internal diameter of 10-15 meters (32-49 ft.).  The walls were 2-3 metres (6.5-10 ft.) thick.  Prisoners were of the opinion that it would accommodate 750-ton U-Boats, and probable even 1,200-tonners, but that it would not accommodate a supply U-Boat.  Prisoners added that it was the only one of its kind on Kiel, and, as far as they knew, the only one of its kind in Germany.  
          Every new U-Boat has to undergo a trial in this dock, the trial taking about half a day.  Once the boat is in dock, most of the crew leaves her, and only the Engineer Officer and about eight senior engine room ratings remain on board.  The prisoners from "U 643" and the rest of the crew spent the time testing escape apparatus in a tank in another part of the yard.  Prisoners could give no details about how the test was carried out, but presumed the pressure was applied by the use of compressed air.  They thought that a pressure equivalent to a depth of 90 metres (295 ft.) could probably be applied.  (N.I.D. Note.  This pressure dock was first reported as having been moved about mid-August, 1943.  On 17th September, 1943, photographic reconnaissance located it in position N.E. of Rendsburg, off Borgdstedter Enge island).  
          (b)  A group of U-Boats, usually four, leaves Kiel every Tuesday and Thursday morning at 08.00.  (N.I.D. Note.  It is clear that this rate of outflow is not consistently maintained or there would be an average of 36 new operational boats each month which is too high.)  
          (c)  Bomb damage at the Howaldt Yards includes a direct hit on the works stores.  The U-Boat depôt ship was also slightly damaged but is still habitable.  
          (d)  The Howaldt Yard is expected to cease building U-Boats within a year and to change over to building tanks.  (N.I.D. Note.  There is no confirmation of this and it is thought to be unlikely.)  
  (iii)  Swinemünde  
          A prisoner stated that a great many workshops and boats had been moved from Stettin to Swinemünde, which has never been bombed.  
  (iv)  Trondheim  
          (a)  The whole dockyard has been destroyed.  
          (b)  The Senior Officer of the 13th Flotilla is Korvettenkapitän Rolf Rüggeberg.  (N.I.D. Note.  This officer of of the 1926 term, was formerly Naval Attaché in Madrid, and is known to have commanded a U-Boat.  
          (a) is considered to be exaggerated.)  
  (v)  Berlin  
          Korvettenkapitän Liebe and Kapitänleutnant Kuppisch have been appointed to the O.K.M. (Admiralty, Berlin).  


Early History of "U 643"
          (i)  "U 643" was commissioned on 8th October, 1942.  She left Hamburg a few days later and arrived in Kiel on 13th October.  
          (ii)  U.A.K. trials and part of the U.A.G. trials were carried out at Kiel.  U 643 then proceeded via Sassnitz and Rönne to Danzig.  She was held up in Sassnitz four of five days because of enemy minelaying operations.  
          (iii)  U.A.G. trials were completed at Danzig in a fortnight's time.  
          (iv)  T.E.K. trials were held at Gydnia in early December, 1942.  
          (v)  Pre-tactical exercises and Agru-Front trials were conducted at Hal late December, 1942, to early January, 1943.  "U 643" proceeded to Danzig to celebrate Christmas.  On 1st January, 1943, she was :Seewachboot" for one night, with half the crew replaced by trainees.  These men, being inexperienced, damaged the Junkers and electric compressors.  "U 643" proceeded to Danzig for repairs on 3rd January.  
          (vi)  Repairs and battery charging at Holm Yard, Danzig began in early January, 1943, and lasted until 28th March, 1943.  
                  (a)  A new Radar aerial was fitted to the bridge.  
                  (b)  Explosion of both batteries occurred on 5th January, when sparks from the acetylene flame cutter, which was being used to make alterations on the bridge for the aerial, fell into a ventilating shaft filled with gas from newly charged batteries (Knallgas).  An entirely new set of batteries had to be installed.  
                  (c)  Flaking of the protective paint on the bulkheads of the batter compartment because of careless application necessitated the complete removal of the new batteries immediately after the laborious job of installation had been completed.  
          "U 643" left the Holm Yard on 28th March, 1943.  
          (vii)  Second Agru-Front trials were held at Hel during April 1943.  These were interrupted by two more short periods in dock at Danzig for various repairs, including adjustment of a propeller shaft.  
          (viii)  Torpedo firing followed at Libau for a nine-day period in early May.  The 25th Flotilla have just been transferred there from Gdynia.  
          (ix)  Tactical exercises were held at Gdynia in mid-May.  
          (x)  Silent running tests were made off Rönne in late May.  
          (xi)  Anti-aircraft gunnery trials were made at Swinemünde in early June.  They lasted several days.  "U 643" was also wiped at this time.  
          (xii)  Final adjustments began at the Howaldt Yard, Kiel on 5th of 6th June, 1943.  Repairs were made to the port propeller shaft which was defective.  The new bridge structure, with the quadruple 20 mm. mounting on the lower bandstand and the two twin 20 mm. mountings on the upper bandstand, was fitted at this time.  
          (xiii)  Second silent running trials were made off Sonderburg in late July, 1943, chiefly for the purpose of testing the repairs to the propeller shaft.  
          (xiv)  Second anti-aircraft gunnery trials were held at Seinemünde in early August, 1943.  
          (xv)  Fitting out for patrol began at Kiel-Wik about 10th or 12th August, 1943.  Actual departure was then again delayed by an order from Control forbidding all U-Boats to sail until further orders.  "U 643" was then ordered to be alongside the "ST. LOUIS," where her Metox 600A G.S.R. set was unshipped, to be replaced by the new "Wanz" set, later fitted in Bergen.  
"U 643":  Tests of Lubricating Oil
(Document obtained from Obermaschinist R. Schulz.)
German Naval Arsenal, Bergen Bergen:  11.9.43.
Chemical Laboratory Tests Nos. 824/825.
  Type of lubricating oil. Z.d.M.7.
Ship or unit "U 643."
Previous use Port and starboard engine lubricating tank.
Samples taken 10.9.43. (Tested 10.9.43.)
          Data of analysis:  
Test 824.
Test 825.
1. Appearance Opaque Opaque
2. Colour, according to Ostwald 10 10
3. Mechanical pollution 0.27 per cent 0.14 per cent
4. Water content 0 per cent 0 per cent
5. Specific gravity at 20°C. 0.914 0.914
6. Viscosity at 20°C. 54.8E 55.3E
  Viscosity at 50°C. 8.6E 8.8E
  Viscosity at 100°C. 2.10E 2.12E
7. Flash point. 208°C. 207°C.
8. Neutralisation index 0.34 0.28
9. Oil dilution Traces. Traces.
10. Residue at 500°C. 0.5 per cent. 0.5 per cent.
11. Emulsivity with distilled water Emulsifies. Emulsifies.
  Emulsivity with sea water Emulsifies. Emulsifies.
Verdict:  Both oils may continue to be used.
                                                                                                                   Dr. LEBOK  


Nominal Roll of "U 643"
          (i)  Survivors:  
English Equivalent.
Speidel, Hans Harold Kapitänleutnant Lieutenant 20.5.17
Kennepohl, Karl August Leutnant (Ing.) Junior Sub-Lieutenant (E) 22.5.22
Hofmann, Dr. Siegfried Marineassistenzarzt Surgeon Sub-Lieutenant 27. 3.15
Schulz, Rudolf Obermaschinist Chief Stoker and Chief E.R.A., 1st or 2nd Class.   8. 3.15
Brand, Heinz Maschinenmaat Leading Stoker and E.R.A. 5th Class   8. 2.21
Hellmanns, Josef Maschinenmaat Leading Stoker and E.R.A. 5th Class   4. 4.20
Winkel, Josef Matrosenobergefreiter Able Seaman 26.12.23
Pauliick, Rudolf Matrosenobergefreiter Able Seaman   3. 6.21
Zimmermann, Eugen Matrosenobergefreiter Able Seaman   8. 4.20
Zückner, Willi Matrosenobergefreiter Able Seaman 21. 1.23
Hochmuth, Gerhard Matrosengefreiter Able Seaman 22. 8.25
Mathony, Heinz Matrosengefreiter Able Seaman 15. 9.25
Reichow, Ernst Matrosengefreiter Able Seaman 23. 9.22
Gräser, Heinz Maschinengefreiter Stoker, 1st Class 20. 6.24
Holleck, Alfons Maschinengefreiter Stoker, 1st Class   9.11.22
Kölbl, Gerhard Maschinengefreiter Stoker, 1st Class   7. 4.23
Kühne, Kurt Maschinengefreiter Stoker, 1st Class 22.12.22
Strickner, Pail Funkgefreiter Telegraphist 24. 1.23
Officers . .
Chief and Petty Officers . .
Men . .
          (ii)  Casualties:  
English Equivalent.
Settgast, Leutnant zur See Junior Sub-Lieutenant.
Gneisse, Leutnant zur See Junior Sub-Lieutenant.
Giese, Obermaschinist Chief Stoker and Chief E.R.A., 1st or 2nd Class.
Degener, Obersteuermann C.P.O. (Navigation).
Holz, Bootsmannsmaat Leading Seaman.
Heggermann, Bootsmannsmaat Leading Seaman.
Gundlach, Bootsmannsmaat Leading Seaman.
Tuchel, Maschinenmaat Leading Stoker and E.R.A., 5th Class.
Bonzeik, Maschinenmaat Leading Stoker and E.R.A., 5th Class.
Dittberner, Maschinenmaat Leading Stoker and E.R.A., 5th Class.
Peuckert, Maschinenmaat Leading Stoker and E.R.A., 5th Class.
Krecji, Funkmaat Leading Telegraphist.
Becker, Funkmaat Leading Telegraphist.
Coppan, Funkmaat Leading Telegraphist.
Graupner, Matrosenobergefreiter Able Seaman.
Fritsche, Maschinenobergefreiter Stoker, 1st Class.
Görlitz Maschinenobergefreiter Stoker, 1st Class.
Günther, Funkobergefreiter Telegraphist.
Göthel, Mechanikerobergefreiter Able Seaman (S.T.).
Albani, Mechanikergefreiter Able Seaman (S.T.).
Kapesser, Mechanikergefreiter Able Seaman (S.T.).
Matzigkeit, Matrosengefreiter Able Seaman.
Zentner, Walter, Matrosengefreiter Able Seaman.
Buhlert, Maschinengefreiter Stoker, 1st Class.
Pätzold, Maschinengefreiter Stoker, 1st Class.
Kessler, Maschinengefreiter Stoker, 1st Class.
Michel, Maschinengefreiter Stoker, 1st Class.
Arlt, Maschinengefreiter Stoker, 1st Class.
Dolze, Maschinengefreiter Stoker, 1st Class.
Gödl, Maschinengefreiter Stoker, 1st Class.
Officers . .
Chief and Petty Officers . .
Men . .
          (iii)  Total Crew:  
Officers . .
Chief and Petty Officers . .
Men . .
  (C51136)   500    1/44  



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