PRELIMINARY  REPORT  ON  INTERROGATION  OF  SURVIVORS  FROM  U.643,  A 500-TON  U-BOAT,  SUNK  ON  8th  OCTOBER,  1943.
     
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  INTRODUCTORY  REMARKS.  
     
          U.643, a 500-ton U-boat under command of Kapitänleutnant Hans SPEIDEL, was sunk on the afternoon of 8th October, 1943 in approximate position 560 14' N., 0260 55' W., by Liberator T of 120 Squadron, assisted by Liberator Z of 86 Squadron.  
     
          Eighteen prisoners, including the Commanding Officer, the Engineer Officer and the Surgeon-Lieutenant survived the sinking, being picked up by destroyers.  
     
          U.643 was exactly one year old on the day she was sunk, having been commissioned on 8th October, 1942.  She was only on her first patrol, however, having sailed from Kiel on 26th August.  Her working up period had been prolonged to 10 months because of various mechanical defects and accidents.  
     
          Features of the final report are expected to be further information on:  
     
          (i)  Fu. B.O.  
          (ii)  G.S.R.  
          (iii)  Infra-red paint.  
          (iv)  Convoy battle of end September early October.  
     
          Unfortunately no torpedo rating survived.  
     
  DETAILS  OF  U.643.  
     
 
(i) Type: 500 tons, VII C.
     
(ii) Builders: Blom and Voss, Hamburg.
     
(iii) Diesels: G.W.
     
(iv) Electric Motors: A.E.C.
     
(v) Armament: Guns:  One quadruple 20 mm. (.79 in.) mounting
 
     
 
 

 

 
 
 
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    on lower bandstand.
    Two single 20 mm. guns on upper bandstand.
    Four M.G. 15's with drum feed on bridge.
    No guns forward.
     
    Torpedoes:  12 carried of which four "Curly", stated to be electric, and the remainder standard T.2 and T.3.
    No acoustic torpedoes carried, there being none available in Kiel.  They are known under the name of "Zaunkönig".
    Upper deck torpedo containers removed.
     
(vi) R.D.B. Ninety balloons carried in three boxes.
     
(vii) S.B.T.: Fitted.  New type of charge carried, described as a white cartridge with holes on the top.
     
(viii) G.S.R.: "Wanz" type fitted at Bergen in early September.  Basket aerial.
     
(ix) Radar: Fitted.  Extensible aerial.
     
(x) W/T: No "Mein" receiver.
     
(xi) Camouflage: Anti-infra-red camouflage paint applied to bridge structure at the building yards, which appeared as a grey colour in normal light.  Thought to have been partly washed off by heavy seas during patrol.  Tested at Kiel with special telescope, at night.
     
(xii) Compass Gyro: Fitted with a new type of cooling system silent in its operation.
     
(xiii) Flotilla: Due to join 1st Flotilla, Brest.
     
(xiv) Contact Keeper Buoy: A prisoner described a new buoy to be used by U-boats to indicate the position of convoys.
 
 
 
 

 

 
 

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    They are called "Fuhlungshalterbojen" and are familiarly known as "Fu.B.O."
            The buoy is about one metre high and 40 cms. in diameter.  It is dropped by the U-boat when she first sights a convoy.  The U-boat dives, leaving the buoy on the surface.  Half an hour later the buoy explodes, sending off a combination of green, red and yellow stars.  Five different combinations of these are said to have different meanings relative to the convoy's movements.
            Before dropping the buoy the U-boat sends out a signal warning other U-boats to watch for it.  A second signal is sent out after the buoy has been dropped, giving its position relative to the convoy.  The prisoner believes that the buoy has been used only in trials in the Baltic so far.
 
     
  FIRST AND LAST PATROL.  
     
  (i)  Departure.  
     
          U.643 sailed from Kiel on her first patrol on Thursday, 26th August, 1943, at 0800.  She had a minesweeper escort and was in company with four other U-boats, namely one 1,200 or 1,600 ton minelayer, one 740-tonner, and two 500 tonners.  Her departure was postponed from beginning August by a special order from DÖNITZ forbidding all U-boats to put to sea until such time as he considered it safe for them to proceed.  U.643 proceeded to Kristiansand S. and spent one night and one day there.  
     
  (ii)  Patrol in Skagerrak.  
     
          U.643's first assignment was to patrol the Skagerrak in order to prevent Danish ships from escaping to England.  This she did for two or three days, in company with all of the group which she left Kiel except the minelayer.  
     
  (iii)  Call at Maugesund and Kgersund.  
     
          Upon completion of the Skagerrak patrol, U.643 proceeded to  
 
 
 
 

 

 
 

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  Hugesund where she lay over one night.  She then proceeded to Egersund where she also lay over one night.  From there course was shaped for Bergen.  
     
  (iv)  New G.S.R. at Bergen.  
     
          U.643 arrived at Bergen on 3rd September, 1943.  Here she was fitted with a new "Wanz" G.S.R. set.  She also refueled.  
     
  (v)  Passage into Atlantic.  
     
          U.643 sailed from Bergen on Tuesday, 14th September, 1943 in company with four other U-boats from the base there.  One of these was U.378, under the command of an officer named LAUTENBACH.  She experienced a destroyer attack in the vicinity of the Rosengarten, but escaped by diving to 100 meters.  Procedure during this period was to submerge by day and to recharge batteries only at night for about three hours.  
     
  (vi)  Operation off Greenland.  
     
          After about ten days in the Atlantic, U.643, still with U-LAUTERBACH, proceeded to an operational area off Greenland, and joined a line of about 20 U-boats, spaced 15 miles apart, forming "Gruppe Rossbach".  This group was to operate against an approaching convoy estimated at 72 ships.  U.643 was the southernmost boat in the line.  The next U-boat to the north was commanded by an officer named HUNGER.  This boat was recalled to base, and during passage back on the morning of 7th October sighted an aircraft and a destroyer about 20 miles south of U.643.  HUNGER failed to report this sighting until nightfall.  He was reprimanded by Control for causing the complete failure of the operation against the convoy by this loss of time.  The next day U.643 picked up a G.S.R. contact on an aircraft, engaged on the surface, and was sunk.  This meant that the convoy passed between 30 and 40 miles south of the nearest U-boat and escaped.  
     
  SINKING.  
     
  (N.I.D. Note:  paragraphs (i), (ii) and (iii) are from the reports of the aircraft concerned).  
     
  (i)  First Attack.  
     
          At 1313 on 8th October, 1943, Liberator Z of 86 Squadron sighted  
 
 
 
 

 

 
 

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  U.643 on the surface in approximate position 560 14' N., 0260 55' W., bearing green 30, distance seven miles.  She attacked with two Mark XI D/C.s in the face of ineffective flak from the U-boat, which took evasive action.  The D/C.s struck the water 60 feet ahead of the enemy's bows and lifted the U-boat out of the water.  One man was seen in the water and 20 on deck wearing life-jackets.  The German war flag was hoisted on the bridge.  
     
  (ii)  Second and Third Attacks.  
     
          Immediately afterwards Liberator T/ 120, which had also been circling overhead, made two attacks in quick succession, each with four Mark XI D/C.s.  Three of the first four overshot, but the second four straddled the U-boat just ahead of the bridge structure.  The U-boat was lifted out of the water and lost way; having sent up intense flak until the last attack.  
     
  (iii)  Sinking.  
     
          Aircraft continued to circle overhead, and some little time later the U-boat was seen to explode with a grey plume 150 feet high.  Fifteen to twenty men were observed in dinghies.  These were picked up by destroyers at 1514.  
     
  (iv)  Fatal Damage to U.643.  
     
          The sequence of events in the U-boat herself at the sinking is not yet clear.  There was water entry and diving tanks were damaged.  The final incident was the explosion of the batteries which killed some men and drove others out of the boat and sank her.  There was no need for scuttling charges.  Diving was impossible at the end, as only 30 kg. of air pressure remained.  
     
  EARLY HISTORY OF U.643.  
     
  (i)  Commissioned 8th October 1943.  Left Hamburg for Kiel a day or two later.  
     
  (ii)  U.A.K. and part of U.A.G. at Kiel.  
     
 
(iii)  To Danzig, via Rönne to finish U.A.G.
 
 
 
  (iv)  T.E.K. at Gdynia, December 1942.  
     
     

 

 
 

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  (v)  Pre tactical trials (Vertaktische) and Agrufront at Hela, late December 1942 to early January 1943.  Port propeller shaft found to be knocking, and all compressors put out of order by green trainees.  
     
  (vi)  Refit at Holm Werft, Danzig, early January to 28th March 1943.  
     
          (a)  New Radar aerial fitted.  During alterations to the bridge fairing for this new aerial, sparks from the acetylene flame cutters fell into a ventilating shaft filled with gas from newly charged batteries.  
     
          (b)  Explosion of the batteries resulted, and a complete new set had to be fitted.  THe date of the explosion was 5th January 1943.  
     
          (c)  Flaking of the protective paint on the new batteries necessitated their removal and repainting.  
     
          (d)  Compressors and propeller shaft were repaired.  
     
  (vii)  Second Agrufront and tactical exercises at Hela, April 1943.  
     
  (viii)  Torpedo firing at Libau, early May 1943.  
     
  (ix)  Silent running tests off Rönne, end May 1943.  
     
  (x)  A/A gunnery trials and degaussing at Swinemünde, early June 1943.  
     
  (xi)  Final adjustments at Howaldt Yard, Kiel, beginning about 8th June 1943.  Further repairs made to port propeller shaft.  
     
  (xii)  Second silent running trials off Sonderburg to test propeller shaft, late July, 1943.  
     
  (xiii)  Second A/A gunnery trials at Swinemünde early August, 1943.  
     
  (xiv)  Provisioning at Kiel-Wik beginning about 10th or 12th August, 1943.  
     
     
     
 
 
 
 

 

 

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