1
REPORT ON INTERROGATION OF SURVIVORS FROM "U 444" A 500-TON
	U-BOAT, SUNK AT 0015 ZONE TIME ON 11th MARCH, 1943
	________________
	I.  INTRODUCTORY REMARKS
	Only four rating survivors were picked up when "U 444," a 500-ton U-Boat, was sunk by H.M.S. "Harvester" and F.F.S. "Aconit" at 0015 Zone Time on 11th March, 1943, in approximate position 51° 14' N., 29° 18' W.
	"U 444's" Captain, Oberleutnant zur See Joseph ("Sepp") Langfeld, and his officers are missing.  The total complement is believed to have numbered about forty-five men.  The four rating prisoners were not unduly security-conscious, but in each case their experience was limited.
	"U 444" belonged to the 3rd U-Boat Flotilla, and a main feature of this report is information concerning this flotilla and its base and U-Boat shelters at La Pallice.
	In order to present a complete picture of La Pallice, information obtained from survivors of another 3rd Flotilla U-Boat, "U 432," sunk on the same day as "U 444," has also been included in this report.
	Information regarding new types of German torpedoes, obtained from survivors of "U 444," has been incorporated in the report of the sinking of "U 432" (C.B. 04051 (64) ).
	Equivalents of German and Royal Naval ranks used in this report are:
	Kapitän zur See Captain. Fregattenkapitän Senior Commander. Korvettenkapitän Junior Commander Kapitänleutnant Lieutenant-Commander. Oberleutnant zur See Lieutenant. Leutnant zur See Sub-Lieutenant. Oberfähnrich sur See Senior Midshipman. Fähnrich zur See Junior Midshipman
	(Ing.) after a rank denotes Engineer Officer, as
	Kapitänleutnant (Ing.) Lieutenant-Commander (E).
	II.  DETAILS OF "U 444"
	(i)  Displacement
	500-tons.
	(ii)  Type
	VII C.
	(iii)  Building Yard
	Schichau, Danzig.
	(iv)  Armament
	Guns.  One 88 mm. (3,46 in.) forward, for which 250 rounds were carried.  One 20 mm. (.79 in.) on bridge.  Four 12.7 mm.  (.5 in.) machine-guns as close range defence weapons.  Two Type M.P. 34 machine pistols.
	Torpedoes.  Fourteen carried.  Stowed as follows:
	Four electric torpedoes in tubes forward.
	Four electric torpedoes in bilges forward.
	Two electric torpedoes suspended from slings in bow compartment.
	One electric torpedo on after torpedo compartment floor plates.
	One in tube aft.
	Two air torpedoes in upper deck containers aft.
	Torpedo Tubes.  Four forward, one aft.  Tubes were modified to enable new types of torpedoes to be fired; these were, however, not embarked,  (See C.B. 04051 (64) ).
	Torpedo Pistols.  Four-whiskered, Type G. VIIH (impact).
	(v)  Diesels
	Description.  Two 6-cylinder, 4 stroke with supercharger, manufactured by Germania Werft and thought to be similar to those in H.M.S. "Graph."
	(vi)  Main Motors and Electrical Supply
	Main Motors.  A.E.G.  Maximum rating, 280 r.p.m.  720 amps., 220 volts for 1/2 hour.  Double commutator type with commutator at either end.  Watertight up to shaft level; above that spray proof.  Journal bearings; micrometers no longer fitted.
	(N.I.D. Note.  This possibly indicated shortage of tool-making capacity.)
	(C49259)                                                                                                                    B**

 

	2
	Cooling.  Cooling air is cooled by water coolers supplied either from the Diesel circulating or electrically driven pumps.
	Revolutions.  Submerged:
	60 r.p.m.   Dead slow. 100 r.p.m.   Slow. 165 r.p.m.   Half speed. 200 r.p.m.   Three-fifths speed. 238 r.p.m.   Three-quarter speed. 245 r.p.m.   Full speed. 250-280 r.p.m. Emergency speed, depending on state of batteries.
	Diesel-electric cruising speed:
	240 r.p.m. on Diesel side; 140 r.p.m. on motor side only.
	Switches.  A.E.G. contactors with three breaks in parallel.
	Main supply Cables.  Six in parallel, jute served rubber covered (approximately 3 mm. thickness of good quality rubber), each 75 mm. squared cross section copper, to the positive and negative of each main motor.
	Copper strip on back of switch panel.
	W/T Suppression.  2 by 3 micro-Farad condensers across each commutator.
	Batteries.  Lead. Acid.  Type M L.A. 800 made by Hagen of Westphalia.  Two units each of 62 cells, each unit being of 8,600 amps./hr. capacity.  Maximum discharge rate 1,440 amps.  Life estimated as three years.
	W/T Supply.  Taken from batteries through motor generator sets.  Six-volt accumulator for supply to emergency transmitter (Not sender).
	Electric Welding.  By discontinuing port motor and running it as motor generator set.  So arranged would supply maximum of 120 amps. at 68 volts.
	(vii)  G.S.R.
	Fitted with G.S.R. Metox Type R.600; an early type with a wavelength from 90 to 250 cms.  It had no improvements compared with types described in previous C.B.s  According to a Telegraphist all U-Boats in the 3rd Flotilla, to which "U 444" belonged, were fitted with Metox Type R.600.
	W/T operators were said to be critical of the primitive manner in which D/F bearings were obtained by holding two iron bars on one side of the aerial.  (N.I.D. Note.  See C.B. 04051 (60).  Section II (vi).)  This method was considered slow and it gave aircraft plenty of time to get into attacking position.
	(viii)  W/T Equipment
	"U 444" carried standard W/T equipment.
	R/T portable set removed at final adjustments.
	Underwater telegraphy set used only near own coast.
	(ix)  Hydrophones
	(a)  K.D.B., trainable and fitted near the bows.
	(b)  G.H.G., multi-unit type:  fitted.
	(x)  S.B.T.
	Fitted in electric motor room by Deutsche Werke, Kiel.
	(xi)  Depth Gauges
	Three fitted; reading to 82 ft.  (25 metres), 658 ft. (200 metres) and 984 ft. (300 metres) respectively.
	(xii)  Sounding Gear
	"Elektrolote":  Carried.  Echo-sounder:  fitted.
	(xiii)  R.D.F.
	Not fitted.
	(xiv)  Scuttling Charges
	Three scuttling charges were supplied and placed in the following positions:
	One by the cooling-water inlet for the electric motors; one in the control room by the main bilge pump sea inlet; one forward alongside the torpedo tubes.
	(xv)  Conning-tower Badges
	During working-up a man with his tongue sticking out; the idea of the Engineer Officer.  For operations; a buck chamois.

 

	3
	III.  SECOND AND LAST PATROL OF "U 444"
	(i)  "U 444" commences her Second Patrol
	At 1200, on 1st March, 1943, "U 444" left La Pallice on her second and last patrol.  Unaccompanied by any other U-Boat, she received Sperrbrecher escort until night fell.  She passed between Ile de Ré and Ile d'Oléron.  Course for the next six days varied between 275° and 280°.  "U 444" followed no regular diving routine and submerged on occasion by day and by night.  Her G.S.R. was in operation and she dived six times in all when aircraft contacts were made.  When on the surface she invariably used Diesel-Electric propulsion.
	(ii)  "U 444" ordered to join a Patrol Sweep
	On about 7th March, 1943, "U 444" was ordered by signal from Admiral U-Boats to take up position in a patrol sweep, to intercept an approaching convoy.  She proceeded due west, at six knots on Diesel-electric.  The sea was calm and she was able to maintain her speed.
	(iii)  "U 444" sights an Independently Routed Ship
	On the night of 7th-8th March, the shadow of a fast independently routed ship was sighted.  "U 444" turned to a course of 060° to pursue.  For 2-1/2 hours she followed the ship at full speed, attaining a speed of 18 knots.  "U 444" could not, however, close sufficiently to attack, and the chase was finally abandoned.  She then resumed her westerly course and proceeded at 8-9 knots to regain her position in the sweep.
	(iv)  "U 444's" Patrol Sweep
	The name of this patrol sweep was not disclosed, but it was said originally to have consisted of about 19 or 20 U-Boats.  On 8th March, however, 8 or 9 U-Boats, not including "U 444," were detached to intercept another convoy.
	On 9th March, "U 444" and the 10 or 11 U-Boats remaining in her sweep, were ordered to alter course slightly to southward to intercept the first convoy.
	(v)  The Convoy Sighted
	At 1304, 10th March, a U-Boat commanded by Kapitänleutnant Hunger made a first sighting signal.  At 1559, "U 444" herself reported that she had the convoy in sight.  She then took up position ahead of the convoy.  Shortly afterwards Oberleutnant zur See Trojer's U-Boat reached the convoy and later a fourth U-Boat, whose identity was unknown.
	Hunger was described as a poor "contact keeper" for he failed to send sufficient signals.  Although not entitled to act as "contact-keeper" herself, "U 444" found it necessary to supplement such signals as were sent with others of her own.
	(N.I.D. Note.  The convoy intercepted by this patrol sweep was H.X. 228 escorted by H.M. Ships "Harvester" (S.O.), "Escapade," "Garland," O.R.P. "Burza," "Narcissus," and F.F.S. "Roselys,"  "Aconit" and "Rénoncule."  U.S.S. "Bogue," escorted by U.S.S. "Belknap" and U.S.S. "Badger" joined at 1345, 6th March.  H/F D/F bearings were reported on 9th March at considerable distances, in a general northerly direction.
	The first indication of U-Boat activity close to the convoy, at 0232Z/10th March, was obtained by "Escapade," in position 49° 55' N., 33° 17' W., by H/F D/F bearing 031°, and again by "Harvester" at 0740 10th March, on a bearing of 060°.
	At 1238Z/10th March, "Bogue's" aircraft attacked a U-Boat on the port beam of the convoy.
	Depth-charges jammed, however, and the aircraft crashed on landing.  The carrier and her escort then left the convoy.
	As a result of this sighting "Escapade" was stationed on the port beam of the convoy during daylight.  No further H/F D/F reports were received on that day.
	At 2024 Zone time on 10th March (dusk), escorts in N.E.6 "Rénoncule" and three stragglers 20 miles on the port beam were rejoining.  When escorts were assuming their right stations, three ships were torpedoed.  "Harvester" ran down the columns to the rear where one of the ships was sinking.
	It was intended to carry out operation "Observant" round the position of the wreck.  On the first leg an asdic contact was obtained and classified as a submarine.  This was attacked with a 14-charge pattern and it was considered a very accurate attack.  The shock of the depth-charges put the gyro-compass out of order, and on running in to carry out a hedgehog attack it was considered that it would be advisable to use this weapon with magnetic compass and the attack was abandoned; no further contact was obtained.  S.S. "Orange Leaf" was near by picking up survivors and "Aconit" was ordered to stand by her.  "Harvester" then steamed on a course of about 230° with the intention of turning after some six miles in the hope that the U-Boat, if undamaged, and thinking there were no escorts around, would surface and be picked up on R.D.F.  Just after having turned back in the convoy's course another asdic contact was obtained and this was attacked with a 14-charge pattern, but there was no evidence and the contact was not so definite as the first one.  Course was then set to rejoin the convoy at a speed of 22 knots.)
	(C49259)                                                                                                                    B* 2

 

	4
	Prisoners said that "U 444" was not concerned in this early attack, nor had been depth-charged.  Langfeld, they added, was intent on sinking only large ships and he therefore missed a number of firing chances at smaller targets.  He spent some time trying to maneuvre "U 444" into the middle of the convoy without success.  At 1015, 11th March, when "U 444" was surfaced, Langfeld sighted a satisfactory ship ahead.  So engrossed was he in the preparations for achieving his first success that he had eyes for nothing but his target.  The suspense also affected the bridge look-outs who turned from their sectors to watch the course of events.  It thus came about that a destroyer approaching from astern was first sighted when he was a mere 500 yards distant.
	IV.  SINKING OF "U 444"
	As soon as the destroyer was seen all thought of attack was abandoned.  The look-outs tumbled down into the Control Room followed by Langfeld shouting "Alarm ! Alarm !"  The U-boat at once crash dived.  A prisoner said that he then turned to a P.O. telegraphist and said "Herr Funkmaat !  You might just as well make your will !"  The P.O. telegraphist remarked:  "Look at the old man, he is in a terrible state of nerves !"
	(N.I.D. Note.  At about 1001 "Harvester" was again in contact with the convoy.  At 0115 on 11th March in position 51° 14' N., 29° 18' W. a second attack developed, apparently synchronised from either beam, two ships being torpedoed.  As "Harvester" was taking up station on the starboard beam, an R.D.F. echo was obtained on about Green 60, 1,000 yards.  Course was altered towards and very soon a white wake and shape of a conning-tower were seen.  The U-Boat could not have been more than 300 or 400 yards away when she dived and a 14-charge pattern was dropped in the swirl by eye.)
	The first depth-charges fell when "U 444" had reached a depth of approximately 120 feet and was still diving.  Prisoners said that all the charges exploded above the U-Boat and this saved her from immediate destruction.  Damage, however, was severe.  The lighting failed and an inrush of water, which could only be plugged with the greatest difficulty, entering the forward W.C.  Water was also entering aft owing to a leak in the cooling system in the motor compartment.  The motor switch-board caught fire and flames could only be got under control with CO2 equipment.  The bilge pumps were damaged and a large variety of instruments smashed.
	Survivors said that the morale of many of the men at this time was deplorable, and that senior as well as junior ratings were trembling and weeping with fear.  Diehl, the Second Lieutenant, left his post in the bow compartment and came rushing into the Control Room, tears streaming down his face, and said:  "The depth gauge in the forward compartment is smashed."  A boatswain's mate, named Seehausen, who had nine previous patrols to his credit, lost all self control.
	As "U 444" was bow-heavy the crew was ordered aft, but it was then judged that there was little chance of saving the U-Boat and the order was given to surface.  Prisoners said that on breaking surface "U 444" proceeded on Diesels for five to ten minutes.  Destroyers were bearing down on them, however, and as it was obvious that they could not escape being rammed the order to abandon ship was given.
	According to a P.O. telegraphist, the wireless transmitter was still in order, although the receiver was wrecked.  He managed to make a signal reporting their sinking condition before he left the U-Boat.
	(N.I.D. Note.  After dropping her depth-charges, "Harvester" had carried out a sweep with asdics and R.D.F., and in a very short while R.D.F. echoes had obtained a bearing about Red 70, 1,200 yards.  Course was altered towards and speed increased, the the U-Boat was sighted on the surface.  Fire was opened with 4.7 in. and Oerlikons and speed increased with  intention of ramming.  The U-Boat was taking violent evasive action, and on two occasions attempts to ram resulted in the U-Boat, caught in the beam of the 10 in. signal projectors, passing down "Harvester's" side about 20 yards away.  Eventually, when the U-Boat tried to cross "Harvester's" bows from starboard to port, she was fully illuminated in the light of the signal projectors and, at a speed of about 27 knots, she was rammed abaft the conning-tower.  Men were already climbing out of the conning-tower and jumping into the sea before the actual impact.  The ram was at about an angle of 90° and the shock severe.  The U-Boat scraped down "Harvester's" bottom and came to rest entangled under the stern.
	In "Harvester" flooding had started in the forward compartment and all water-tight doors and hatches had been closed.  Efforts were made to get rid of the U-Boat by working the engines, but she remained firm under "Harvester's" stern, bumping and scraping in the movements of the sea.  There were Germans in the water, shouting for help.  The U-Boat appeared to be lying on her side, sticking out she from under the stern, and "Harvester" went ahead.  The U-Boat appeared to be sticking out of the water at an angle of about 40° and well down, right up to the conning-tower.  Just before getting clear one survivor was picked up.  There was no time to pick up any others although there were many in the water.  Very shortly afterwards a loud underwater explosion was heard which so damaged "Harvester's" port engine that it was put out of action.  After some three or four minutes, firing was seen fine on the port quarter, "Aconit" was known to be close by R.D.F.
	"Aconit" reported that at 0135 Zone time on 11th March, she sighted "Harvester" stopped, bearing 110°, range 550 yards, and altered course to avoid.  A minute later she sighted a U-Boat proceeding at slow speed, bearing Red 70°, range 300 yards, inclination 110 right.  Wheel was put hard over to port in order to ram, at the same time fire was opened with Oerlikon, the target being illuminated with searchlight.  At 0137 Zone time "Aconit" rammed the U-Boat amidships, and in passing over her five depth-charges were dropped set to shallow.  Speed at the time of ramming was 180 revs., which was reduced to 115 revs. as the result of ramming.  Immediately after ramming, shouts of "Hilfe !" were heard and four Germans were picked up.)

 

	5
	Thus of the total complement of "U 444" only five ratings, one of whom later died, were taken prisoners.  Those who were saved could give little information as to the fate of the officers, except that the Engineer Officer was one of the first to leave the U-Boat and that he may possibly have shot himself in the water.  Langfeld is believed to have been killed by gunfire on the bridge.
	(N.I.D. Note.  C.B. 04051(64) will contain further information on the attack on Convoy H.X.228, and describe the sinking of "U 431" and the loss of the "Harvester.")
	V.  GENERAL REMARKS ON U-BOATS
	(i)  Experimental Fuel
	A stoker said that he had heard of a new fuel, looking like glycerine, which was some sort of low explosive and gave very little exhaust.  This was being tried out experimentally in a U-Boat with Diesels and no electrical drive.  He mentions Maybach as the makers of these engines.  Trials had taken place at both Danzig and Kiel.  A speed of 28 knots was claimed.  He also spoke of the Deutsche Werke, Kiel, having experimented with this fuel in E-Boats.
	(N.I.D. Note.  No confirmation of this information has been received and it is considered improbable.)
	(ii)  Submerging after G.S.R. Contact
	U-Boats dive after a G.S.R. contact at the discretion of the Officer of the Watch.  Dives are generally not more than half an hour in good visibility and about three-quarters of an hour in bad visibility.
	Personnel trained at Le Tonquet are warned that British aircraft will switch off their R.D.F. after getting a contact and will make a dead-reckoning approach.  U-Boat personnel are therefore warned that if they get a clear contact which suddenly disappears, they are to regard it as highly dangerous.
	They are also instructed that British aircrews, after switching off their R.D.F.will make a dead reckoning approach and then switch on again, having lowered the power of the transmission in the hope of deluding the G.S.R. operator into the belief that the aircraft is flying away, or is flying parallel with the U-Boat.
	A prisoner said that G.S.R. operators do not claim to estimate range accurately, but that there is now a system of reporting Strength 1, 2, 3, 4, or 5 G.S.R. contact to the Officer of the Watch.  The bridge watch are then expected to intensify their look-out.
	An aircraft giving a Strength 2 or Strength 3 contact is reckoned as just coming over the horizon, whereas Strength 4 or 5 is regarded as highly dangerous, with the aircraft within attacking range.  In such circumstances a U-Boat will normally dive.
	It is not customary to increase speed or alter course after a dive following a G.S.R. contact.
	If an aircraft is so close that an attack is imminent and the U-Boat has no time to dive safely, orders are to remain surfaced and engage the aircraft.
	(iii)  G.S.R. near a Convoy
	A telegraphist maintained that G.S.R. is intensely operated in the vicinity of a convoy when the U-Boat is hear enough to be able to make an attack.  Reliance is not solely placed on the bridge watch.  The prisoner asserted that only an hour to an hour and a half before "U 444" was actually sunk, he picked up a contact on, he believed, wavelength 134 cm., which he presumed was the destroyer which sank them, or another destroyer.  He had previously picked up the same contact earlier in the night.
	He also alleged that the G.S.R. aerial and cable jammed while the crew were hauling it clear, in order to close the hatch, added five seconds to their diving time and was a contributory cause of their being sunk.
	(iv)  G.S.R. and Submerged Passage through Bay of Biscay
	On "U 444's" first patrol the G.S.R. became useless during the U-Boat's return to base through the Bay of Biscay.  Consequently they submerged, even at night, as they felt that they had no means of detecting aircraft first in view if British A.S.V.  The G.S.R. was faulty owing to a broken part, for which there was no spare.
	(v)  Special Explosive Charge for G.S.R.
	It is believed that a demolition charge can be fitted to the G.S.R. in the event of capture seeming likely.
	(vi)  G.S.R. Training
	A Telegraphist said that "U 444's" W/T personnel left on their first patrol with only elementary knowledge of G.S.R., having been given merely a short lecture explaining its operation.  Prior to the second patrol the prisoner was sent to Le Touquet for a short course.  The course was 35 strong and included C.P.O. Telegraphists who were to be detailed to instruct the personnel of each flotilla.
	(C49259)                                                                                                                    B**3

 

	6
	(vii)  New Type German Asdic
	A prisoner claimed to have seen a new short-range S-Gear (German asdic) made by Siemens.  It has dial adjustment in two settings:  80-300 and 300-1,000 metres.  Frequency of the note used is 800 cycles per second.
	It was alleged that this S-Gear was on trial in a few U-Boats, one of which was lost by betraying its position through its use.
	Trials are now being made with short-range inaudible S-Gear.
	(viii)  W/T Routine
	Homing Signals.  A Telegraphist said that "contact-keepers," when in the immediate vicinity of a convoy, transmitted "Viktor-Viktor" from the 20th to the 25th and the 50th to the 55th minute past the hour.  The prisoner claimed this wa a system newly introduced in January, 1943.
	When homing signals are sent, frequencies are different for the following periods:  0800-1200, 1200-1400, 1400-1800 (?).  1800 (?)-2200, 2200-0800.  The prisoner said he did not know the wavelength of these signals, but said that they were always made on low frequency.
	(ix)  Aircraft Reports by U-Boats
	A Telegraphist said that U-Boats report the presence, arrival, and departure of aircraft escorting a convoy, and that all U-Boats report the presence of aircraft in or near the Atlantic "Gap."  This is irrespective of whether they are "contact-keeper" or not.  He added that this report may be delayed owing to the U-Boat being compelled to dive and to avoid the aircraft, but that the reason for diving would be reported to Admiral U-Boats on surfacing.
	(x)  Detection by Aircraft
	A prisoner claimed that when off the coast of Ireland on her first patrol "U 444" regularly expected aircraft attacks punctually between 1400 and 1430, especially the latter time.  These aircraft arrived with remarkable punctuality.
	(xi)  Lichtenstein Apparatus A/C Aerials
	A prisoner from the blockade-runner "Germania" (see C.B. 04051 (59) ) said that the Lichtenstein apparatus, used as A.S.V., by German aircraft (the Ju.99 was specifically mentioned), enables the wavelength to be changed in the air, the object being to give surface forces the impression that they are being A.S.V.'d by a destroyer, so that the look-out is concentrated on expected surface forces.  In the meantime the aircraft changes to airborne wavelength and thereby obtains surprise.
	This is done by altering the effective length of the aerials by means of a sliding "muff," which insulates a portion of the aerial, leaving a shorter length available for immediate use.
	The prisoner also claimed that the technique of reducing volume as the aircraft approached the target, with the object of giving any possible Search Receiver Operator the impression that the contact was flying away, is already being used.
	(xii)  1,600-ton U-Boats.
	A prisoner claimed that 1,600-ton U-Boats are all supply U-Boats and none have torpedo tubes.  He had seen two at Kiel; work on the deck was still proceeding.  He believed that special torpedo containers were fitted over the saddle tanks and to each side of the conning tower.
	(N.I.D. Note.  Boats of about 1,600 tons, which are probably minelayers and probably have torpedo armament, are believed to exist.)
	(xiii)  1,200-ton U-Boats
	A prisoner claimed to have seen a 1,200-ton U-Boat commanded by Kapitänleutnant Lüth at Danzig in the autumn of 1942.
	Armament.  One 105 mm. (4.4 in.) gun forward; one 20 mm. (.79 in.) gun on conning-tower platform; one 37 mm. (1.46 in.) aft.  It was stated that 27 torpedoes were carried.
	Another prisoner said that 1,200-ton U-Boats were really of 1,600-ton surface displacement; 1,200-ton U-Boats had M.A.N. Diesels and not G.W. Diesels, which were gradually going out of use.
	(xiv)  Minelaying U-Boats
	Larger type minelaying U-Boats were said by one prisoner to have six mine shafts forward and six on each side of the conning-tower above the saddle tanks.
	(xv)  Daimler-Benz Engines in U-Boats
	It was alleged that trials have recently been made with a U-Boat fitted with Daimler-Benz engines.

 

	7
	(xvi)  Bilge Pumps
	Present type bilge pumps will work against a head of 393 ft. (120 m.) maximum, but at that depth they cannot eject fast enough to cope with a leak as thick as a man's thumb.  A new type is being developed which will make it possible to get rid of water against much greater heads, thus enabling U-Boats to dive deeper.
	(N.I.D. Note.  Leutnant zur See Danckworth, sole survivor of "U 224," said that he thought the new type pump would eject against a head of 492 ft. (150 m.).)
	(xvii) Diving Depths
	A stoker said that the maximum diving depth of a U-Boat was at the discretion of her captain and varied from U-Boat to U-Boat according to the depth at which weeping became excessive.  This occurred at 492 ft. (150 m) in "U 444," but a more normal figure was 780 ft. (240 m.).  He had heard of U-Boats which could submerge as deep as 982 ft. (300 m.).
	(xviii)  Exercise Dives
	According to one prisoner, it was customary for "U 444" to dive to about 200 ft. every day when on patrol.  This dive was an exercise one, and generally took place in the early morning.
	(xix)  Duration Submerged
	The longest period "U 444" remained submerged was for 12 to 14 hours on one occasion in the Bay of Biscay.  Air was cleansed by potash cartridges.  Prisoners had never heard of lithium hydrogen being used for this purpose.
	(xx)  Wiping of U-Boats
	Wiping of U-Boats takes place in the Kiel Canal Lock, cables being looped across the lock itself, so that a U-Boat can pass over them.  A high frequency alternating current is used.
	(xxi)  Action Stations
	A telegraphist said that he was kept at his action station for 24 hours before the sinking of "U 444."  He added that, if necessary, he might have had to remain closed up an indefinite time without relief.  On such occasions the men were given caffeine tablets, which were powerful enough to keep them awake for 48 hours at a stretch.
	(xxii)  Colour of Paint on Inside of U-Boat Bridges
	The insides of U-Boat bridges are painted green to allow for maximum relief of strain on the eyes of look-outs.
	(xxiii)  Substitution of Extra Fuel Tanks for Upper Deck Torpedo Containers
	A prisoner claimed that extra fuel tanks have replaced upper deck torpedo containers in some 500-tonners and that he had actually seen a U-Boat so fitted at Kiel.
	(xxiv)  Cessation of 500-ton U-Boat Building
	A stoker claimed that Germany is giving up the construction of 500-ton U-Boats and will not replace those sunk.  Emphasis is to be on 740 and 1,200-ton U-Boats, "which can almost take the place of a small cruiser."  The prisoner added that it had now been realized that the ship's company must be more comfortable to withstand the hardships of the longer cruises now contemplated.
	(N.I.D. Note.  This may be correct as a forecast, but the proportion of 500-ton U-Boats building has not changed at present.)
	(xxv)  Admiral Dönitz
	It was said that Admiral Dönitz had made a point of inspecting each U-Boat Division Training Class at the commencement of instruction.
	(xxvi)  U-Boat Losses
	A prisoner said that, of the total losses of German U-Boats, 20 percent had been caused by the stupidity or ignorance of the crews and not by enemy action.
	(xxvii)  Damage to U-Boat Bases in Occupied France
	A prisoner said that, when he was in La Pallice between the 12th and 13th February, 1943, a 500-ton U-Boat docked alongside "U 444."  This U-Boat was described as a "guest" U-Boat from Brest.  He added that the presence of a Brest-based U-Boat in La Pallice was most likely due to bombardment, and that either further repairs had been rendered impossible at Brest or that the U-Boat had been damaged there during raids.
	(xxviii)  Personnel
	A prisoner said that, when he was in La Pallice in February, 1943, he had heard of a recent order of Admiral Dönitz that the entire German Navy was to be combed for men fit to serve in U-Boats.  This was to include Supply Assistants and Writers.  He thought that the big surface units would not be affected before the smaller craft, especially Minesweeping Flotillas, which had already been thoroughly combed through and possibly reduced in numbers.
	(C49259)                                                                                                                    B**4

 

	8
	(xxix)  Passage of Straits of Gibraltar
	A prisoner alleged that some U-Boats had reached the Mediterranean from the Atlantic by passing through the Straits of Gibraltar under the cover of Spanish merchant ships, by arrangement with the Spanish authorities.
	(N.I.D. Note.  There is no confirmation of this.)
	(xxx)  Raiders and U-Boats
	It was the opinion of prisoners that no more raiders would be sent to sea now that Germany had sufficient U-Boats.  Raiders were considered uneconomical in comparison with a large type U-Boat.
	(xxxi)  27th U-Boat Flotilla
	This Flotilla at Pillau, carries out tactical exercises in the Baltic.  Newly commissioned boats about to carry out tactical exercises join this Flotilla temporarily.  The convoys assembled for target purposes for these exercises were under the control of a merchant navy Commodore.  The attacking U-Boats are under the orders of a Captain (S) who sails in the Senior U-Boat.
	(xxxii)  Diving Time
	A prisoner said that an A/A/ twin gun platform added abaft the bridge of more recent 500-ton U-Boats adds between five and eight seconds to the U-Boat's best diving time.  Owing to its shape, the additional platform was a very dangerous place in rough weather.
	(N.I.D. Note.  The addition of an A/A gun platform abaft the conning-tower is confirmed.)
	(xxxiii)  Electric Torpedoes
	A prisoner said that the only modification to electric torpedoes he knew was that since G7H pistils had been fitted, water resistance had been increased in comparison with earlier types.  The brushes on the electric motors had been reset to maintain 30 knots and consequently the range of the torpedo had been reduced.
	(N.I.D. Note.  The G7H impact pistol had been in general use since 1941.  See also C.A.F.O. 659/43.)
	(xxxiv)  Distilled Water and Sulphuric Acid for U-Boats
	The necessity of topping up batteries with distilled water varies according to the operational area of a U-Boat.  It was said that the level in the batteries goes down about 1 mm. daily in the Mediterranean and correspondingly less in the North Atlantic, where a U-Boat will not have to top up her batteries until her return to base, unless the patrol lasts more then sixty days.
	About 100 gallons of distilled water are carried by each U-Boat.  The water is carried in light metal, square-shaped, containers, which are stowed near the electric motors.  To add 30 mm. yo each of the 62 cells of each battery, approximately 50 gallons of distilled water are required.
	It was said that the distilled water content in each cell must not fall below the level of the plates and when topped up should reach 60 mm. above the plates.
	U-Boats expect to lose 20 mm. monthly in the process of drawing off gas which forms whenever the batteries are charged.
	A very superficial test of the distilled water is occasionally carried out by taste or by litmus paper.
	Sulphuric acid is not carried in U-Boats in extra containers, all necessary filling being done at base.  For small batteries the mixture is one part H2SO4 to eighteen parts distilled water, and in the U-Boat batteries one part to twenty parts distilled water.
	Water for the French bases is distilled at Paris.
	In Norway there is a small plant at Bergen, and both Gdynia and Pillau have their own plants.
	Distilled water for La Pallice comes by rail from Paris in 12-gallon carboys.  These are stowed in Pen No. 7 of the shelters.  They are dealt with by French dockyard workers under the supervision of a German Petty officer.  There are always about 150 to 200 carboys in the shelter and access is easy, no signature being required.
	Normally not more than one or two carboys (10-20 gallons) of sulphuric acid would be kept in stock.  That used for auxiliary batteries is only handled by the electrical section of the yard personnel, because the batteries are taken to the workshop for topping up, and the electrical personnel are mostly German, as they have constantly to board U-Boats.
	VI.  SURFACE SHIPS
	(i)  "Graf Zeppelin"
	A prisoner claimed that he knew one of the dock engineers who had been working on the aircraft carrier "Graf Zeppelin" at Kiel.  During the early part of "U 444's" trials his friend took him over the carrier.  The flight deck was being relaid one deck lower, to improve stability, and he was tool that the carrier was to be rebuilt according to Japanese design with funnels below the flight deck.
	(N.I.D. Note.  This might be true, but it seems unlikely at this stage.  The report is also not supported by photographic evidence.  See also C.B. 04051(62), Section VI.)
	The "Graf Zeppelin" was to have had seven main water-tight compartments, each sub-divided.  She is now to have more.
	It is planned to build in her engines and funnel aft.

 

	9
	She originally took a maximum of sixty planes on board, and it is now hoped that she will carry from seventy-two to eighty.
	The prisoner could give no accurate information as to the types of aircraft to be carried, but he had heard rumours that these were to be Me.109T's and Stuka T's.  Some of the ship's company have already been drafted to her.  The prisoner thought that the carrier would finally be ready early in 1944.
	(ii)  "Gneisenau"
	The same prisoner said that he had also been shown over "Gneisenau."  He remembered clearly that his engineer friend told him that the ship was to be lengthened by 78 ft.
	He was told that "Gneisenau" would not be ready for sea until the end of 1943, owing to the bomb damage done to her in a night raid on Kiel in March, 1942.  She was to have six 15-in. guns fitted in place of her nine 11 in. guns.  There were to be two twin 15 in. turrets forward and one 15 in. turret aft.
	(N.I.D. Note.  This statement corroborated similar statements which appeared in C.B.s 04051(51), page 24 and 04051(55), page 20.  Air photographs confirm that the entire ship's main armament is completely removed.)
	(iii)  E-Boat "S.37"
	Said to have been lost in October, 1940, by mine.  The body of Senior Midshipman Heinz Schlösser, belonging to this boat, was washed ashore on the Danish coast.
	VII.  BASES, TRAINING ESTABLISHMENTS, ETC.
	FRANCE
	(i)  La Pallice
	(N.I.D. Note.  This section also contains information obtained from prisoners from "U 432," sunk on 3rd March, 1943.  Both "U 444" and "U 432" were based on La Pallice and it was considered that a more complete picture could be given if the statements of survivors from the two U-Boats were combined in one report.)
	(A) SHELTERS AND DOCKYARD INSTALLATIONS
	(a)  Berthing Capacity (Original Shelter)
	The U-Boat shelter at La Pallice, situated at the eastern end of the Basin, consists of seven pens.  (See Plan "C," shaded portion north-east corner of Bassin.)
	Pens Nos. I and II (No. I being the northernmost pen) are wet docks, the remaining five are dry docks.
	Each of the two wet docks can hold three U-Boats, two beam to beam and a third interposed between them.
	It has been seen, when a large number of U-Boats were at the Base, that as many as four U-Boats have lain together in one wet dock.  In that case the two outer U-Boats lay slanting with their sterns across the dock pier heads, projecting, to a certain extent, outside the shelter.
	(N.I.D. Note.  This has never been seen in air photographs.)
	Three 500-ton U-Boats can, however be comfortably accommodated and van be reprovisioned, loaded with torpedoes and refuelled in any one wet pen.  Then three U-Boats are in a wet pen together, the bows of the centre U-Boat are approximately level with the conning-towers of the other two, while her conning-tower is just forward of the sterns of the two others.
	One 1,200-ton U-Boat can be berthed in any of the seven pens, and a 1,600-ton Italian U-Boat was reported by prisoners as docked in a dry pen early in 1943.
	The seven completed ones can hold a maximum of eleven U-Boats, in which case six would be 500-ton U-Boats in the two wet docks.
	All the pens as high enough to enable periscopes to be unshipped within them.
	(b)  Dimensions and Thicknesses
	Overall length (along the line of the pens)   522 ft. Overall width   433 ft. Length of pens   317 ft. Width of double pens above W.L. 66 ft.         Do. below W.L. 56 ft. Width of single pens above W.L. 46 ft.         Do. below W.L. 36 ft. Height of building above H.W.L. overall 56 ft.         Do. internal 44 ft. Thickness of concrete Roof 11ft. 5 in.         Do. Outside walls 8 ft. 3 in. Thicknesses of partitions are in following three sizes. 4 ft. 11 in., 6 ft. a in., 4 ft. 1 in. Thickness of foundations Outside walls 18 ft.         Do. Partitions 13 ft. 1 in. and 16 ft.                 (According to the thicknesses of the walls built on top of them.)

 

	10
	It will be seen that over half the length of the shelter is taken up by the pens.  East of them, and within the shelter, runs a passage from north to south, wide enough for lorries to pass back and forth.
	There is an entrance door at either end of the passage and a smaller door on the north side of the shelter leading into the main electrical power house.  (See "U" Plan "C.")
	(c)  Southern Extension
	Work is being carried out on the construction of three new pens adjoining the south side of the shelter.  It is intended to remove the ground west of these pens, making the Basin a rectangle.  The old wall on the north side of the ground now being excavated is a strong quay wall and will probably be retained.  The new block contains three pens, Nos. VIII, IX and X, of which VII and IX are dry docks and X is a wet dock containing 2-3 U-Boats.  Thus this extension when completed, will hold five additional U-Boats, bringing the total capacity at La Pallice shelter to 16 U-Boats.
	One prisoner said that the three new pens are definitely for 1,200-ton U-Boats and possibly for two 1,200-ton U-Boats, since he thought that the building of three new pens for three U-Boats only would be a waste of time.
	Should two 1,200 ton U-Boats line in a pen together, one would probably be a little abaft the other.
	It was generally thought by prisoners that the concrete roof over the three new pens, which is now complete (April, 1943), it three metres thicker than the old shelter roof; the later is to be built up to the same level.
	It has not been thought necessary to strengthen the main shelter structure for this addition, since the outer walls are already three to four metres thick, and far stronger than is necessary to support the present roof.
	The wall between the old and new shelters is the old stone wall of the quay and will be removed when the new pens are completed.
	The interior of the shelters is not very noisy, there being only the hum of machines and occasional hammering to be heard.
	(d)  Workshops.  (See Plan "A" and Plan "D.")
	On the east side of the central passage-way and occupying the remaining length of the shelter, are the workshops.  These are built on the old quay level and consist of two storeys.  They can be numbered 1-7 from North to South, since they continue the line of the seven pens.
	Each workshop section consists of two storeys.  The upper storey is about half the height of the lower.  There are ordinary doors, possibly in a line, through the middle of the upper storey walls.  At the end of each upper storey workshop is a small storehouse for miscellaneous material.
	The two storeys of the workshops stand on the east side of the central passage, and, having no doors on the west side, the interior of the workshops is to a certain extent visible from the central passage, so that men standing in the passage can talk or shout to men standing in the workshops.
	No. VII Workshop
	The guard room is on the ground floor.
	The radio repair shop is on the first floor.  In the radio repair shop, a prisoner said that he saw about twelve men working.
	No. VI Workshop
	The ground floor of No. VI workshop is the torpedo room.  There are no doors leading out of it into neighbouring workshops.  About twenty men work on the ground floor of No. VI workshop.  On the first floor is the shop for the torpedo tubes and the "Feuerleit" (Fire Control) workshop; about twenty men are employed here.  At the back of the first floor a small wooden stairway leading to the Leather Working Shop and Carpenters' Shop, were in all ten men are employed (some French) and one girl.
	No. V Workshop
	The ground floor is the machine shop, possibly about twenty-five men work in here.
	No. IV Workshop
	On the ground floor is the welding plant.  About ten men are employed.  There is an opening (no door) into the machine shop of the fifth workshop.  The periscope workshop is probably on the first floor of No. IV workshop.
	No. III workshop, No. II workshop - see Plan "A" for layout.
	No. I Workshop
	No. I workshop contains the electric power plant (see Plan A2 and "U" Plan "C").  This is an isolated block containing two U-Boat Diesel engines and two transformers.  High up on the north wall of this block are some small openings, like windows, probably connected with ventilation of the Diesel engines.  This block containing the electric power supply is probably cut off by a wall from the rest of No. I workshop.  Normally current is carried overland by masts from and E.N.E. direction to the auxiliary electric power station (See "A" Plan "C").  It passes through this station and continues underground into the shelter electric power station, or passes through transformers in the auxiliary power station.

 

	11
	Should the shelter electric power station be out of use, the shelter can be supplied from the auxiliary power station.
	In part of the No. I Workshop, near the central passage, (see Plan "A") is the electric switch gear.  This was only being built in mid-February, 1943.  Should this be destroyed, the auxiliary power station can act as electric switch centre for the whole shelter.
	U-Boats while in dock get their lighting from the shelter source.
	(e)  Cranes  (See Plan "D.")
	All the pens are the same height.  The electric crane servicing each pen runs between the walls of that pen from the western end right back over the central passage, and is available as far as about half way through the workshops.
	The cranes are used for torpedo servicing and periscope lifting.
	There is no transverse crane running north and south.
	The new Diesel engines which were built into "U 432" in La Pallice were fitted with the help of a huge crane outside in the harbour.  The work was definitely not done in the shelter.
	(f)  The Pens
	The dry pens are all of the same width and length, i.e., about 12 metres across and about 95 metres long (long enough to allow five metres' space between a U-Boat's bows and the rear wall and 15 to 20 metres between the stern and the western end of the wall).
	The wet pens are about 18 metres broad.
	Nos. I and II pens are wet.
	A prisoner said that he saw drop doors being fixed in the dry pens and noted that they were too wide to fall below the level of the wet pen piers.  The construction of doors for the wet pens had barely begun (mid-February, 1943), but he thought that the same would apply in the case of the wet pens and that also the rise and fall of the basin water-level would allow a certain gap beneath the dropped doors.
	The dry pens are fitted with metal caissons which can be placed into position by flooding.  Each dry pen has alternative positions for the slots to take the caissons.  A prisoner suggested that the alternative positions for the slots in the dry pen piers are perhaps explained by the fact that the caissons were placed in the inner slots for a 500-ton U-Boat.  This may therefore point to the outer slots being used for a bigger U-Boat.  The cement block upon which the caisson rests would make no difference as the underpart of a U-Boat is, of course, curved.
	Two prisoners said that they had seen ordinary double lock doors (of the swing back type) used in the dry docks, and are of the opinion that if two doors are placed at the end of each dry dock, either they must be of small dimensions, or consist of one ordinary door and one caisson.  At night, with no drop doors fitted in the dry pens, it is possible to see work going on inside with binoculars from the western end of the basin.
	One prisoner said that since mid-February, 1943, when there appeared to have been a sabotage scare in the shelter, a search-light sweeps the basin and the shelter front about every five minutes.  This search-light was alleged to stand near the S.W. corner of the basin.  Other prisoners said that they had neither heard nor seen anything of the search-light.
	The pens are divided underwater by solid walls 4.50 metres thick, upon which are built the upper walls which support the roof of the shelter.  The ends of these walls are square.
	Rising from the centre of the broad lower walls are narrower walls of two metres in width which support the roof.  The upper walls being narrower than those upon which they are standing, it is possible for workmen to walk along the small platform left by the wide surface of the lower wall.
	The lower wall also projects out beyond the top wall, enabling one to follow the platform round into the next pen.  (See Plan "E.")
	In the upper wall are several openings, the westernmost opening being smaller than the remainder.  Through these openings one can look across the whole line of pens.  The openings are about two to three metres apart.
	Referring to Plan "E," opening number two contains a small rotary pump, which works the mechanism inside the thick lower wall, for pumping out the leakage water which seeps in when the pen os "dry."
	In opening number three stands a second larger pump - used for pumping the main water out of the pen when the caisson has been sunk into place.  This latter pump takes two to three hours to empty the pen.
	(g)  Dry Docking and the Caissons.
	It was believed by prisoners that a U-Boat could only be dry-docked at high tide.  The water level within the basin falls and rises about 1.50 to 2.00 metres.
	(N.I.D. Note.  The shelters being in a locked basin this sounds incredible.  It must be supposed that the main locks are damaged and allow the water level in the basin to fluctuate.  The effect of the low tide on the dry-docking procedure would be (a) to prevent the caisson from floating enough to be maneuverable and (b) to prevent a U-Boat from clearing with her keel the cement block upon which the caisson rests.  This cement block is about 3.00 metres in depth.)
	A prisoner said that about 1.50 metres projected above the dry pen floor and about 1.50 metres was embedded in the ground.

 

	12
	He inferred that the U-Boat keel would not clear the 1.50 metre cement block for the following reason:  The permanent blocks used for dry-docking a U-Boat stand about 1 metre high.  The water level of the dock must be lowered 2.0 to 2.5 metres by pumping, in order to enable the keel to rest on the blocks.
	At low tide the U-Boat keel is already near the blocks and the cement block is 50 cm. higher than they are, making it impossible for the U-Boat to clear the cement.
	The buoyancy of the lock door is so arranged that the door only rises about 40-50 cm. from its sunken position to its floating position, and if the basin water level is low tide level, this will not take place.
	When the caissons of the pens are not in position, they are moored near the end of the lower wall of the pen.  When a U-Boat had been brought into the pen and it is desired to close the caisson, workmen climb to the top of the caisson, which is then maneuvered into its correct position over the slots into which it must sink.  The workmen standing on top of the caisson, protected from falling by railings, operate valves on the top of the caisson and these flood and sink it on to the concrete block, the specially shaped keys fitting into the slots.  The pen is then pumped dry and the water is drained from the caisson through a drain on the inner side.  A 500-ton U-Boat would then be about 1.0 metre below the level of the pier.
	In order to raise and remove a caisson, the dry pen is flooded.  The pen gradually fills and so raises the caisson about 30-40 cm., the height needed for swinging it free of the slots.
	The keys on either side of the caisson are so made that the key enters the slot from the inner side on one end of the caisson and from the outer side on the other end, so that it is easily removed, once it is floating, by a strong twisting moment.  When floating, about 3.0-3.50 metres of the caisson are above water level.  When a U-Boat has been dry-docked, the upper drop door is lowered to meet the caisson.  Work is then carried on inside the pen by electric-light.
	(h)  Entrance Doors to Shelters from Land
	The Main North Door Entrance
	The main north door is about six metres broad and six metres hi