U-boat Archive - U-515 - Interrogation Report



	Op-16-Z
	Copy No. 46 of 46.

	NAVY DEPARTMENT
	OFFICE OF THE CHIEF OF NAVAL OPERATIONS
	WASHINGTON

	FINAL REPORT - G/Serial 36

	REPORT ON THE
	INTERROGATION OF SURVIVORS FROM U-515
	SUNK 9 APRIL 1944
	AND
	U-68 SUNK 10 APRIL 1944

	Distribution:
	BAD (9)
	BUORD
	BUSHIPS
	BUSHIPS (Code 515)
	BUSHIPS (Code 815)
	COMINCH (F-21)
	COMINCH (F-4253)
	COMINCH (F-45)
	COMINCH (F-40) (2)
	COMINCH (FX-43)
	COMASWDEVLANT
	COMNAVEU
	DNI (Ottawa)
	G-2 (Col. Sweet)
	Op-16-1 via Op-16-1-F
	Op-16-FA-4
	Op-16-P
	Op-16-1-V
	Op-16-W
	Op-20-C
	Op-23-C
	SONRD (2)
	Lt. Comdr. V. R. Taylor
	C.O., Naval Unit, Tracy, Calif.
	Lt. J. I. Eiband (ComNavNaw, CSDIC, AFHQ)
	Lt. S. R. Hatton (ComNavNaw, CSDIC, AFHQ)
	Lt. J. T. Rugh, Jr. (JICA/ME)
	Lt. (j.g.) R. J. Mullen (4th Fleet)

	17 June 1944

TABLE OF CONTENTS

			Page

CHAPTER	I.	INTRODUCTION	1

	II.	DETAILS OF U-515	4

	III.	GENERAL REMARKS ON U-BOATS	10

	IV.	DESCRIPTION AND SKETCHES OF “HOHENTWIEL” RADAR”	12

	V.	REMARKS ON GERMAN TORPEDOES	14

	VI.	CREW OF U-515	18

	VII.	EARLY HISTORY OF U-515	23

	VIII.	FIRST PATROL OF U-515	25

	IX.	SECOND PATROL OF U-515	27

	X.	THIRD PATROL OF U-515	30

	XI.	FOURTH PATROL OF U-515	34

	XII.	FIFTH PATROL OF U-515	35

	XIII.	SIXTH AND LAST PATROL OF U-515	40

	XIV.	SINKING OF U-515	42

	XV.	HISTORY AND DETAILS OF U-68	47

	XVI.	OTHER U-BOATS	61

	XVII.	BASES	68

ANNEX A		CREW LIST OF U-515 AND U.S. EQUIVALENTS OF GERMAN NAVAL RANKS.

ANNEX B		PARTIAL CREW LIST OF U-68 AND U.S. EQUIVALENTS OF GERMAN NAVAL RANKS.



	CHAPTER I. INTRODUCTION

	U-515 and U-68, both 750-ton U-boats, were sunk on 9 and 10 April 1944, in a coordinated air-surface action. A third U-boat suspected in the vicinity was also attacked, but apparently escaped. The units involved were the U.S.S. GUADALCANAL, U.S.S. PILLSBURY, U.S.S. POPE, U.S.S. CHATELAIN and aircraft of VC-58.

	U-515, commanded by one of Germany’s U-boat aces, Kapitänleutnant Werner Henke, was sunk at 1512 GCT 9 April 1944 at 34.31 N - 19.29 W. She belonged to the series of 750-ton boats numbered U-501 - U-550 built at Deutsche Werft, Finkenwerder, Hamburg. (O.N.I. Note: Of this series of U-boats, 26 are known sunk as of mid May 1944.)

	U-515 was first sighted by VT-24 from U.S.S. GUADALCANAL at 2113 GCT 8 April 1944. At 0027 and 0735 two depth bomb attacks were delivered by VT-23 and VT-31 (or VT-30). Soon thereafter U.S.S. PILLSBURY, POPE and CHATELAIN made contacts and over a period of 3½ hours two hedgehog attacks were made and 82 depth-charges were dropped on the submerged U-boat. Direct hits were scored by the destroyers when U-515 was forced to surface; in addition VT-25 delivered a successful R.P. attack several minutes prior to the sinking.

	Sixteen men, including the executive officer and a midshipman, were killed. Henke, the Engineer Officer, the second watch officer, the doctor and forty petty officers and men were rescued. U.S.S. GUADALCANAL landed the prisoners at Norfolk 26 April 1944. After preliminary interrogation seventeen prisoners were further questioned at a U.S. interrogation center.

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	U-515 was the most successful active U-boat of the 10th Flotilla. Henke had been decorated with the Oal Leaves to the Knight’s Cross after claiming the sinking of 28 ships totaling 177,000 tons. This total was divided among the various patrols, as follows:

	1st Patrol: (8 August 1942 - about 20 October 1942)
	10 ships totaling 54,000 tons.

	2nd Patrol: (7 November 1942 - 5/6 January 1943)
	2 ships totaling 29,000 tons.

	3rd Patrol: (About 20 February 1943 - about 23 June 1943)
	12 ships totaling 72,000 tons.

	4th Patrol: (29 August 1943 - 12 September 1943)
	No ships sunk.

	5th Patrol: (1 November 1943 - 16 January 1944)
	3 ships totaling 22,000 tons.

	6th Patrol: (30 March - 9 April 1944)
	No ships sunk.

	Features of interest in this report are:

	(a) Description and drawings of “Hohentwiel” radar set (See Chapter IV).

	(b) Remarks on German torpedoes (See Chapter V).

	(c) Account of the final attack on U-515. This is believed to be as complete a description as has yet been obtained from prisoner sources. (See Chapter XIV).

	- 2 -



	U-68, built at Deschimag, Seebeck, Wesermünde, belonged to the series U-64 to U-68, all of which are now sunk. She was the oldest boat in the 2nd Flotilla and since the spring of 1943 was under the command of Oberleutnant z. S. Albert Lauzemis.

	U-68 was sunk by aircraft from U.S.S. GUADALCANAL at 0634 GCT 10 April 1944 in position 33.31 N. - 18.43 W. Three airplanes delivered an accurate and coordinated attack with rockets and depth-charges which finished off the U-boat in eight minutes.

	Sole survivor of the sinking was a seaman 2 cl. who had made but 2 patrols in U-68. Consequently he was not familiar with the details of her long and active career. He was moderately communicative under interrogation, but not well informed.

	Information concerning U-68 will be found in Chapter XV. It is a compilation of statements made by the sole survivor of U-68 and from British and U.S. held prisoners of war.

	The handling of prisoners aboard U.S.S. GUADALCANAL was outstanding and the work of the interrogation officers at the interrogation center was greatly facilitated by it.






	- 3 -



	CHAPTER II. DETAILS OF U-515

	TONNAGE

	750 tons.

	TYPE

	IX C.

	BUILDING YARD

	Deutsche Werft, Finkenwerder, Hamburg.

	COMMISSIONING DATE

	21 February 1942.

	FLOTILLA

	10th Flotilla, at Lorient.

	F.P.N.

	M-27488.

	CALL LETTERS

	X.A.P.

	INSIGNIA

	A mallet on a white shield.

	COLOR

	Whitish-Gray.

	GREATEST DEPTH

	About 200 meters.

	- 4 -



	DIVING TIME

	35 Seconds to periscope depth.

	BRIDGE STRUCTURE AND ARMOR

	New bridge including Platform II fitted August 1943 at Lorient. Armor plate around forward part of bridge about 16-mm. thick. New structure incorporated so-called “air raid shelter”.

	UPPER DECK GUNS

	(a) On first 3 patrols: One 105-mm. gun forward of conning tower; One single 20-mm. cannon on Platform I; One 37-mm. gun on after deck.

	(b) On 4th patrol: One 37-mm. gun forward of bridge; Two single 20-mm cannons on Platform I; One quadruple 20-mm. mount on Platform II.

	(c) On fifth patrol: One 37-mm. gun forward of bridge; Two twin 20-mm. cannons on Platform I; One twin 20-mm. cannon on Platform II.

	(d) On 6th and last patrol: Two twin 20-mm. cannons on Platform I; One new automatic 37-mm. gun on Platform II.

	AMMUNITION

	(a) 8/9,000 rounds for 20-mm. cannon.

	(b) About 2200 rounds for 37-mm. automatic gun.

	PRESSURE-PROOF AMMUNITION CONTAINERS

	(a) One containing 20-mm. ammunition on the aft part of Platform I.

	- 5 -



	(b) Three on each side of Platform II, the forward 1 on each side containing 20-mm. ammunition, the other 2 on each side 37-mm. ammunition.

	TORPEDO TUBES

	Four forward, two aft.

	TORPEDOES

	Seventeen carried on last patrol. For further details see Chapter V.

	S.B.T. (Submarine Bubble Target)

	Fitted.

	DIESELS

	Two 9-cylinder 2200 horse-power M.A.N. Diesels.

	SUPERCHARGER

	Büchi.

	FUEL OIL

	232 cm. Carried on last patrol. (O.N.I. Note: It is interesting to note that U-801 carried exactly the same amount of fuel oil, 232 cm. On her first patrol. See Final Report G/Serial 33.)

	LUBRICATING OIL

	About three tons.

	- 6 -



	MOTORS/GENERATORS

	Two 500 horse-power Siemens motor generators.

	SWITCHBOARD

	Siemens.

	CONVERTERS

	(a) One 0.3 KVA

	(b) One 1 KVA

	(c) One 6 KVA

	BATTERIES

	Lead-acid type, 62 cells per battery. Capacity when new, 12,000 amp/hrs. Highest charging temperature permitted 45⁰ to 50⁰ C.

	COMPRESSORS

	(a) One Junkers Air Compressor

	(b) One Electric Compressor

	HIGH-PRESSURE AIR

	Sixteen flasks, 2 flasks per bank.

	RADAR

	“Hohentwiel” set fitted. Mattress-type dipole aerial fitted on port side of bridge in place of extensible rod aerial. For details see Chapter IV.

	R.D.B. (Radar Decoy Balloons)

	Carried on 5th and 6th patrols.

	- 7 -



	R.D.S. (Radar Decoy Spar Buoys)

	Not carried.

	G.S.R. (German Search Receiver)

	(a) Wanz G-2

	(b) Borkum

	(c) Naxos

	G.S.R. AERIALS

	(a) Naxos dipole aerial

	(b) Naxos improved “Fliege” aerial, fitted on wooden rod between periscopes. (See Sketch in Chapter III, opposite page 10).

	(c) Fixed basket-type aerial fitted between periscopes.

	D/F GEAR (Direction Finder)

	Standard long-wave Lorenz D/F set.

	TRANSMITTERS

	(a) 200 watt short-wave transmitter

	(b) 150 watt long-wave transmitter

	(c) 40 watt Emergency transmitter

	RECEIVERS

	(a) “Main” Telefunken receiver

	(b) All-wave receiver

	U.K. GEAR (Ultra Kurzwellen - Ultra Short Waves)

	Fitted, but never used. It was stated that the U.K. gear was to be used only upon receipt of special orders.

	- 8 -



	HYDROPHONES

	Multiple unit hydrophones (G.H.G.) fitted. Made by Atlas.

	ECHO Sounder

	Atlas Echo Sounder fitted.

	OXYGEN SUPPLY

	Twelve flasks.

	FRESH WATER DISTILLER

	Made by Siemens. Capacity 15 to 18 liters per hour for drinking purposes; capacity for distilled water for use in batteries about 10 liters per hour.















	- 9 -



	CHAPTER III. GENERAL REMARKS ON U-BOATS

	NEW “FLIEGE” NAXOS G.S.R. AERIAL

	U-515 was fitted with a new type and improved “Fliege” Naxos G.S.R. aerial prior to sailing on her last patrol. One of the radiomen prisoners made a drawing of the aerial which, however, was not drawn to scale. (See Sketch). It was stated that the oscillator in the aerial is a resonant circuit and does not contain a vacuum tube.

	During the short period between U-515’s departure and sinking no radar transmissions had been picked up on this aerial, although several transmissions were intercepted while the standard “finger” Naxos aerial was in use.

	The “Fliege” Naxos aerial may be mounted either in the D/F loop or between the periscopes, at the option of the U-boat’s commander.

	EARLY TYPE “FLIEGE” NAXOS G.S.R. AERIAL

	When a radioman prisoner was shown the drawing of the “Fliege” Naxos aerial as illustrated in Final Report G/Serial 32, he pointed out that in his opinion the “aluminum rings” were not really rings but a continuous spiral which did not extend beyond the knife edge of the detector. He thought that the extent of this spiral could be adjusted to fit the wave length for which it was desired to set the aerial. He stated that the dipole is 7½ mm. in diameter and 15 mm. long. He does not believe that there is a permanent D.C. biasing voltage on the detector.

	- 10 -



	“ROTTERDAM” RADAR SET

	A radioman stated that copies of radar sets taken from British aircraft are now being used by the G.A.F. It was believed that experiments are being conducted as to its suitability for U-boats.

	GOLIATH TRANSMITTER

	The radioman stated that aboard U-515 the Goliath radio transmitter was listened to only if messages had been missed during the daytime.

	TYPE IX C U-BOATS

	The Engineer officer reported that no more U-boats of the IX C type are being built now.

	U-BOAT PRESSURE HULLS THICKENED

	The Engineer officer believed that in the future the pressure hulls of U-boats will be thickened to withstand either greater depth or closer depth-charge attacks.

	WALTERBOATS

	The building program of Walterboats has been abandoned according to U-515’s Engineer officer. The lack of rare metals required to withstand the extreme temperatures generated in internal combustion turbines was cited as the main reason. This prisoner was also convinced that up to now German scientists have failed to solve the problem of an underwater craft with relatively high submerged speed and endurance.

	- 11 -



	CHAPTER IV.

	DESCRIPTION AND SKETCHES OF “HOHENTWIEL” RADAR

	Prior to sailing on her 6th and last patrol, U-515 was equipped with the new “Hohentwiel” radar set, the first U-boat to be so fitted at Lorient. The “Hohentwiel” U-boat radar set has been adapted from the G.A.F. radar of the same name, and the set built into U-515 still incorporated some of the features which are more specifically suitable for aircraft. For example, a switch for altitudes over or under 3,000 meters was built-in as was a motor driven remote control tuning circuit. The sketches, opposite page, illustrate the entire installation and are self-explanatory. (Radar sketches: General Installation, Radar Transmitter, Radar Receiver)

	The mattress aerial is 10 cm. Wide at its base, narrowing to 4 cm. At the top. This construction permits search for aircraft in a more advantageous manner than if the aerial had parallel sides. Although this set embodies a number of improvements over the old type of U-boat radar, particularly the fact that it is controlled from the radio room rather than from the control room, it is still very cumbersome and inconvenient. For example, when the operator whishes to rotate the mattress aerial he has to send word up to the conning tower so that men on the bridge will get out of the way. Furthermore there is no automatic locking device which aligns the aerial correctly above its housing before it is hydraulically lowered. During an experimental search with this gear in the Bay of Biscay on U-515’s last patrol the aerial was not accurately lined up with the housing when it was lowered and as a result was

	- 12 -



	so badly damaged that the set was unusable for the balance of the patrol.

	“Hohentwiel” radar is built by Lorenz in Berlin. Later models of “Hohentwiel”, of which a prisoner has seen an example, no longer incorporate any of the G.A.F. features. The X-gear shown on Plate III is eliminated in later models. The aerial also is to be redesigned. When undergoing training at Ghent, Belgium, for “Hohentwiel” radar operation, he saw mattress aerials with 2 rows of 4, 6 and even 8 dipoles, but otherwise identical with the one on U-515. The antenna on U-515 could be rotated through 360 degrees. This was done rather slowly but continuously after due notice to the bridge watch as stated above. Wave length on the “Hohentwiel” was believed to be variable anywhere within a length from 30 to 80 cm. Normally, however, the wave length used is 50 cm.













	- 13 -

CHAPTER V. REMARKS ON GERMAN TORPEDOES

U-515 carried a total of 17 torpedoes on her sixth and last patrol, distributed as follows:

Location	Number	Type	Pistols

Bow tube #1	1	T-3	Pi-2

Bow tube #2	1	T-3	Pi-2

Bow tube #3	1	T-1 FAT I	Pi-1

Bow tube #4	1	T-1 FAT I	Pi-1

Stern tube #5	1	(One
		(or two
Stern tube #6	1	(T-5's

On bow plates	2	T-3	Pi-2

Under bow plates	4	(1) T-3	Pi-2
		(3) T-1 FAT I	Pi-1

On stern plates	3	(1) T-3a FAT II	Pi-2
		(Other 2 unknown)

Upper deck containers	2	T-1	Pi-1
	_____
Total	17

On her previous patrol U-515 had a total of 15 torpedoes aboard, distributed as follows:

Location	Number	Type	Pistols

Bow tube #1	1	T-3	Pi-2

Bow tube #2	1	T-3	Pi-2

Bow tube #3	1	T-1 FAT I	Pi-1

Bow tube #4	1	T-3	Pi-2

Stern tube #5	1	T-5	Pi-4a

- 14 -

Location	Number	Type	Pistols
Stern tube #6	1	T-3	Pi-2

On bow plates	2	T-3	Pi-2

Under bow plates	4	(2) T-3	Pi-2
		(3) T-1	Pi-1
		(1) T-1 FAT I	Pi-1

On stern plates	3	(1) T-5	Pi-4a
		(2) T-3	Pi-2
	_____
Total	15

PISTOLS

Before leaving on her fifth patrol, U-515 was required, for an unknown reason, to turn in her Pi-3 Pistols (combination impact-magnetic firing pistols fitted to air-driven torpedoes) for Pi-1 pistols to be used with T-1’s and FAT-I’s.

The Pi-4a, fitted to T-5, was said to be a combination inertia-magnetic firing pistol.

TYPES OF WARHEADS

K-a: Old T-1 warhead fitted with Pi-1 impact firing;

K-b: Old T--2 warhead fitted with Pi-2 impact firing;

K-c: New T-3 warhead fitted with Pi-2 impact-magnetic firing;

K-d: New T-1 warhead fitted with Pi-3 impact-magnetic firing.

(Note: K is abbreviation for “Kopf”.)

(a) Prisoner does not believe that T-5 circles.

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	(b) The SS setting may be used for a non-acoustic run, as a “Fangschuss”, a term used to signify a torpedo fired to sink a ship which has been disabled by a previous torpedo.

	(c) The torpedoman’s mate believes that T-5 can be countered by means of depth-charges.

	(d) Unlike the testing of the magnetic-firing Pi-2 pistol on board the U-boat, the testing of Pi-4a (and of other pistols used with T-5) is done only at the service stations.

	(e) On 1 occasion, U-515 kept a T-5 in a flooded tube for almost 30 hours.

	(f) U-515 carried 2 cans (containing 25 liters in each) of E.T.42 which is to oil the propeller shaft not only of T-5 but also of all electric torpedoes.

	(g) On U-515’s fifth patrol. 1 T-5 was fired against a DD; range about 1,000 meters; depth-setting between 4 and 5 meters; fired at periscope depth from stern tube; U-515 dived immediately after firing, not as a safety measure against the T-5 but because of an impending attack.

	(h) The voltage of the battery in T-5, after being charged, was said to be between 85 and 90.

	(i) According to the torpedoman’s mate, the hydrophones are being used, in conjunction with the firing of T-5’s, up to a limited U-boat depth. He added that 25 meters was the maximum depth at which a U-boat fired all types of torpedoes.

	(j) The mate expressed his opinion that some T-5’s were not acoustically but rather magnetically steered, adding that noisemakers

	- 16 -



	were entirely useless. He had heard of the rudders of T-5 going hard over when metal was held in front of the nose. (O.N.I. Note: Prisoner was not confused between the rudder throw at the “Spatz” test and the throw caused by the presence of a piece of metal.)