The Sinking of the U-550

The German submarine U-550 was a member of the Kriegsmarine 10th U-boat Flotilla. She was a long-range Type IXC/40 U-boat constructed by Deutsche Werft shipbuilding company of Hamburg. Built for World War II service, the U-550 was commissioned on 28 July 1943 and placed under the command of Kapitänleutnant Klaus Hänert.

U-550, drawing


On April 15th, 1944 convoy CU-21 consisting of 28 merchant ships left New York City bound for Great Britain.

Convoy CU-21 was accompanied by Escort Division 21.5, consisting of Coast Guard-manned destroyer escorts (DE) USS Poole (the flag ship), USS Kirkpatrick, USS Harveson, USS Peterson, USS Joyce, and was reinforced by one Navy DE the USS Gandy.


On the morning of April 16th, approximately seventy-five miles south of Nantucket Island, the U-550 located convoy CU-21. One of the largest tankers in the world, the T-3 tanker SS Pan Pennsylvania carrying 140,000 barrels of 80 octane gasoline, was a member of this convoy.

08:05, the U-550 torpedoed the SS Pan Pennsylvania. The torpedo hit the tanker on the port side (left), slightly aft of amid ships, at the #8 tank. Three Destroyer Escorts, the Joyce, Peterson, and Gandy. immediately began searching for the U-boat .

SS Pan-Pennsylvania
SS Pan-Pennsylvania

08:45, the Peterson made a sound contact and proceeded to attack, dropping six depth charges in a shallow pattern with negative results.

Gandy (DE-764)
Gandy (DE-764)


09:01, Joyce was ordered, with assistance from the Peterson, to pick up survivors from the Pan Pennsylvania. Gandy screened the two DE’s.

Fifty-six survivors were rescued from the tanker from a total ships complement of eighty-one.


09:50, Joyce acquired a sound contact at a 100 foot depth, with no way (stopped), fired thirteen Mark 9 depth charges set for depths of fifty to one hundred and fifty feet. Two charges failed to launch.

Depth Charge Attack
Depth Charge Attack

09:58, U-550 broached bow first astern of the Joyce. Joyce, Peterson, and Gandy fired with all guns that could bear while the U-boat crew attempted to man their guns.


10:02, The Gandy rammed the U-550 thirty feet from the stern of the sub, with all her guns still firing.

Peterson fired two shallow depth charges from her starboard “K” guns.

Pan Pennsylvania was inadvertently set on fire by ricocheting shell.


10:03, U-550 surrendered.

10:05, The submarine crew was ordered to abandon ship.  An explosion was heard in the submarine, evidently a scuttling charge.

10:30, U-550 sank stern first.

10:45, Joyce picked up twelve survivors and one body (four officers, eight men, and one dead) while the Peterson screened.

The Pan Pennsylvania continued to drift.

01:15/17 Turned over, burning, 100′ of bow showing with 10′ above surface.

12:57/17 In an attempt to sink the Pan Pennsylvania the USS Sagamore, USCGC General Greene, USS Hazel, USS SC-1338, USS Rescue, and USCGC Harriett Lane commence firing on her.

12:04/18 General Green stands off as planes bomb tanker.

A burial at sea was performed on the Joyce for deceased German submariner.
From the Coast Guard web site:

Photo provided by captain Robert Wilcox, USCG (Ret.), the Joyce’s commanding officer during her battle with the U-550. Captain Wilcox wrote the following description on the back of the photo:

“Funeral services on board USS Joyce (DE-319) in North Atlantic Ocean, 18 April 1944, for ex-German Navy Machinist Wanz who died aboard Joyce from wounds received in fire fight between U-550 and USS Joyce, Gandy and Peterson on 16 April 1944.

May 6th: Machinists Mate Gunther Heder died in Newport hospital, and buried in Rhode Island Historical Cemetery Newport #1.

Photo courtesy of John Stanford
Photo courtesy of John Stanford

Information compiled by Mark Munro & Steve Jackson