U-boat Archive - U-490 - Analysis of Attacks

UNITED STATES FLEET

HEADQUARTERS OF THE COMMANDER IN CHIEF

NAVY DEPARTMENT

WASHINGTON 25, D. C.

FF1/A16-3(17)

Serial: 02908 22 August 1944

CONFIDENTIAL

From:	Commander in Chief, United States Fleet.
To :	Commander in Chief, U.S. Atlantic Fleet.

Subject:	Anti-Submarine Joint Action by USS FROST, USS HUSE, USS INCH, and USS CROATAN Aircraft
	On 11-12 June, 1944.

Enclosure:	(A) Analysis of Subject Action.

1. Enclosure (A) is forwarded for information.

F. S. LOW,

Assistant Chief of Staff.

Copy to:

CinCPac	ComCaribSeaFron
ComTHIRDFleet	ComPaSeaFron
ComFIFTHFleet	ComWesSeaFron
ComSEVENTHFleet	Co.AlSeaFron
ComFOURTHFleet	ComHawSeaFron
ComEIGHTHFleet	CO U.S. NavTraCen Miami
ComTWELFTHFleet	DE Shakedown Group Bermuda
ComAirLant	LantASWUnit Norfolk
ComAirPac	Naval War College
ComDesLant	FltSoundScol San Diego
ComDesPac	CO WesCoSoundScol San Diego
COTCPac	ComCortDiv 13 (USS FROST)
ComEastSeaFron	CO USS FROST (DE-144)
ComGulfSeaFron	CO USS HUSE (DE-145)
	CO USS INCH (DE-146)



	CONFIDENTIAL Incident No. 6391 (A) (B) and (C)

	ANALYSIS OF COORDINATED ANTI-SUBMARINE ACTION
	BT USS FROST, USS HUSE, USS INCH AND
	USS CROATAN AIRCRAFT

	Employment………….Offensive A/S Operations
	Time………………….0802 GCT 11 June to 0110 GCT 12 June 1944
	Position………………43-47N/40-08W
	Depth of water……….2700 fathoms
	Weather Conditions….Overcast; Visibility varying from 5-15 miles;
	Sea Force 2, direction not stated;
	Wind Force 2, direction not stated
	Sonar conditions……..Good
	Contact first made by...HF/DF
	Range…………………Estimated within 50 miles
	Number of attacks……7 HH; 14 DC; 4 Creeping Attacks; Gunfire

	1. BRIEF NARRATIVE.

	(a) While searching for a submarine known to be in the area, an enemy HF transmission was heard at 0136, 11 June. The transmission was fixed by CominCh within 50 miles of a position 40 miles west of the Task Group. Three ships of the group obtained accurate ground wave bearings and course was shaped to intercept. At 0600 a 4 plane search was launched but at 0745 the weather had so deteriorated that the aircraft were recalled. As CROATAN turned into the wind to conduct landing operations, FROST made sonar contact at a range of 650 yards. The contact was within 10 miles of the estimated position of the submarine. CROATAN made an emergency turn away. HUSE was designated to assist. HUSE and FROST then streamed FXR gear and proceeded to attack.

	(b) At 0805 FROST fired a hedgehog pattern which resulted in three hedgehog detonations followed by two muffled explosions two minutes later. HUSE made sonar contact at 0818 and planned to make a hedgehog attack. However, acting on information obtained from the FROST that the submarine was probably deep, a full depth charge pattern set at 400 feet was ordered. Four charges failed to leave the track due to a failure of the release gear. During the attack, HUSE experienced considerable interference from her FXR gear and retrieved it.

	(c) As contact was not regained at 0822, OBSERVANT was started and resulted in FROST regaining contact at 0851. At 0859 FROST fired a hedgehog pattern followed by a full depth charge pattern set at 400 feet. A fathometer reading of 270 feet was obtained on this run.. OBSERVANT was begun again at 0925. Momentary contacts were made at 1000 and 1023. At 1106 FROST regained contact and attacked with a 16-charge depth charge pattern set deep. Air bubbles rising to the surface followed this attack. At 1115, CROATAN aircraft

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	Enclosure (A)
	To CominCh conf. ser. 02908
	Dated 22 August 1944



	began dropping sono-buoys. Both ships stopped engines shortly thereafter to permit the aircraft to listen on the sono-buoy receivers. Good indications were received on one buoy but the ships did not regain sonar contact. 1213 OBSERVANT was started and resulted in HUSE regaining contact at 1227. A hedgehog pattern was fired without result. Contact was regained and at 1247 a creeping attack was made with HUSE acting as assisting ship. Large air bubbles resulted from this attack. FROST regained contact at 1255 and attacked with full depth charge set at 500 feet. An oil slick and air bubbles were then observed. At 1307 ComCortDiv 13 directed HUSE to lay a very deep pattern in the area where bubbles were observed to be rising. 1313 FROST made an attack. (It is not clear if this was a hedgehog or a depth charge attack.)

	(d) 1317 aircraft laid another sono-buoy pattern and HUSE and FROST withdrew from the area. Engines were stopped at 1324 to permit listening on the sono-buoys. “Muffled booming sounds were heard on the aircraft and FROST’s sono-buoy receivers.” Neither FROST nor HUSE was able to obtain sonar contact. At 1413 OBSERVANT was started resulting in the HUSE obtaining sound contact 12 minutes later. A full depth charge pattern was fired without result.

	(e) 1445 OBSERVANT was again begun. At 1505 aircraft reported a strong indication on a sono-buoy which lead to FROST regaining contact. This contact was attacked by a full pattern of depth charges. FROST also made a hedgehog attack at 1526. HUSE followed with a hedgehog pattern at 1535. OBSERVANT was started at 1537 and at 1548 engines were stopped to listen on the sono-buoys. Indications were received on one sono-buoy and sonar contact followed. FROST attacked with a combined hedgehog and depth charge pattern at 1615. OBSERVANT was started at 1620 and resulted in FROST regaining contact at 1647. She fired a hedgehog pattern at 1655 with negative results. OBSERVANT was begun at 1700 resulting immediately in regained contact. 1711 a creeping attack was made with FROST acting as assisting ship. Another creeping attack was made at 1727 with FROST again acting as assisting ship. Contact was then lost and at 1755 OBSERVANT was begun.

	(f) At 1937 INCH joined the search . 1940 all three ships made sonar contact. FROST attacked with full depth charge pattern at 2005. HUSE was then ordered to rejoin CROATAN.

	(g) 2016 INCH who had obtained the sonar contact from FROST attacked with full depth charge pattern. 2142 a creeping attack was made with FROST acting as assisting ship. On this attack, a 30-charge pattern was dropped. Contact was regained and at 2235 FROST obtained a fathometer reading of 600 feet. Contact was then lost and at 2247 OBSERVANT was begun resulting in FROST regaining contact at 2256. A full 13-charge pattern followed at 2300.

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	Enclosure (A)
	To CominCh conf. ser. 02908
	Dated 22 August 1944

(h) The Task Group Commander now decided that if the submarine were given an opportunity, she would attempt to surface and escape shortly after dark. To encourage this move, SNOWDEN was directed to a position about 5 miles south of the estimated position of the submarine while FROST and INCH were directed to employ gambit tactics, retiring at decreasing speed to a position to the northward. The submarine obliged and surfaced between FROST and SNOWDEN at 0027. FROST and SNOWDEN made radar contact and at 0041 INCH and FROST illuminated it with starshell and searchlight and opened fire with all batteries. Just as the first starshells were fired the submarine was seen to signal “SOS please take our crew.” 0059 SNOWDEN reported seeing the submarine sinking stern first with the bow up at an angle of 450. Soon after FROST and INCH began recovering survivors while SNOWDEN screened. 0110 a large underwater explosion was heard and at 0135 all three ships rejoined CROATAN.

4. ANALYSIS OF ATTACKS

(a) Resume of attacks.

Time	Ship	Type Attack	Number Charges	Depth Settings	Lost Contact Range	Remarks

0805	FROST	HH	24	-	220 yds	Three underwater explosions followed by two muffeled explosions two minutes later

0821	HUSE	DC	9	350 to 450 ft	200 "	4 charges failed to release from tracks. Report states deep pattern dropped on information secured from FROST taht sub was deep.

0859	FROST	HH	24	350 to 450 ft	800 "	Fathometer reading of 270 ft obtained.
		DC	13

1106	FROST	DC	16	500 to 600 ft	550 "	Large air bubble observed after this attack.

1233	HUSE	HH	24	-	300 "

1247	FROST	Cr.	18	500 to 600 ft	-	Creeping attack. HUSE assisting FROST. 2 large air bubbles seen followed by more air bubbles and oil slick.

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Enclosure (A)

To CominCh conf. ser. 02908

Dated 22 August 1944

1255	FROST	DC	13	-	-	No ASW form or recorder trace received for this attack.

1259	HUSE	DC	12	350 to 450 ft	200 yds	1 K-Gun failed to fire.

1307	HUSE	DC	13	250 to 350 ft	-	No sonar contact. Pattern laid over area where bubbles were observed.

1313	FROST	DC	13	350 to 450 ft	300 "	---

1428	HUSE	DC	13	450 to 550 ft	500 "

1507	FROST	DC	13	350 to 450 ft	350 "

1526	FROST	HH	24	-	350 "

1535	HUSE	HH	24	-	450 "

1615	FROST	HH	24	-
		DC	131	350 to 450 ft	450 "

1655	FROST	HH	24	-	480 "

1711	HUSE	Cr.	13	500 to 600 ft	-	HUSE attacking, FROST assisting.

1727	HUSE	Cr.	11	500 to 600 ft	-	Only 11 charges fired due to fouling of K-Gun

2005	FROST	DC	13	500 to 600 ft	250 "

2016	INCH	DC	13	500 to 600 ft	400 "	INCH coached onto contact by FROST.

2142	INCH	Cr.		500 to 600 ft	-	INCH attacking and HUSE assisting ship.
		DC	30

2300	FROST	DC	13	500 to 600 ft	350 "

(b) While these attacks were generally well conducted, the use of hedgehogs and depth charges in the same run and the employment of hedgehogs on a submarine believed to be deep are not in accordance with doctrine.

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Enclosure (A)

To CominCh conf. ser. 02908

Dated 22 August 1944



	(c) In his forwarding endorsement, ComCortDiv 13 stated,

	“Much interference was experienced in the sonar gear from FXR gear. When an escort was forward of the beam of the escort which had contact, the interference was pronounced and completely drowned out both the transmission and echo. It was necessary to stop the interfering escorts to eliminate this interference. In view of this experience the following FXR doctrine has been established.

	“FXR gear will be streamed at such times as it is felt necessary to afford protection to the escorts. After contact is gained and one attack is made the attacking ship will inform other escorts as to probable depth of sub. If sub is deep FXR gear will be recovered. If sub is medium or shallow FXR gear will be kept streamed until such time as sub increases depth.

	“It is believed that a deep submarine is not in a position to attack with torpedoes, consequently FXR gear is not needed. With the shallow or medium submarine, a torpedo attack can be expected.

	“It is realized that the submarine may and can change its depth from deep to shallow or medium during an operation. When the submarine varies its depth as above, escorts are then dependent upon standard evasive tactics to avoid being hit by the acoustic torpedo. This disadvantage must be accepted in order that the best sonar conditions be available to the attacking escort.”

	The above quoted doctrine is premised on accurate knowledge of the depth of the U-boat and if such information were available, it is considered that the doctrine would be sound. Since, at the present stage of development, the depth determination is by estimate, the application of this doctrine introduces the possibility of lack of immunity from an acoustic torpedo.

	5. The following information obtained from PW’s cannot be accepted as fact and is presented as a matter of interest only:

	“Immediately following the first attack, U-490 submerged to a depth stated to have been between 240 and 260 meters and remained there during the attack. In all survivors counted a total of 189 depth charges which were directed at them during the following 17 hours. All the charges exploded well above the boat, which was practically undamaged. She proceeded at silent running speed (Schleichfahrt) and, during each run in of an attacking vessel, swerved sharply to port or starboard without changing speed.

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	Enclosure (A)
	To CominCh conf. ser. 02908
	Dated 22 August 1944



	“In addition to the usual two-beat pinging, depth charge detonations and screw noises, some survivors stated that they heard noises resembling those made by a buzz saw and also what they believed to be the impact fragments of depth charges exploding about them.

	“When the air began to get foul, although there was no water or chlorine gas in the boat, the captain concluded that it would be impossible to remain submerged until darkness the next night, and therefore gave orders to surface and abandon ship, so that the entire complement could be saved. All hands left the U-boat and took to the water with rubber boats or life vests and were picked up by the Task Force.”
















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	Enclosure (A)
	To CominCh conf. ser. 02908
	Dated 22 August 1944