Contact Us   |    Join   |    Donate


In the January Submarine Review, Phoenix discussed the World War II U.S. experience with steam-driven torpedoes, the Mk 14s and 23s, and with the electric-powered Mk 18s. But, one other type of submarine-launched electric torpedo, the Mk 27 “CUTIE” should have also been discussed to understand WW II experience with “electrics.”

Although only a few CUTIEs were used by u.s. submarines in WW II, their success was so exceptional that they should not be forgotten. They were a small torpedo with a small warhead, slow, and with passive acoustic homing. Understandably with today’s very fast, big warhead torpedoes — and consequent high. self noise — a passive acoustic homing capability in a torpedo is pretty much ruled out. Further, the u.s. has placed primary emphasis on having submarine torpedoes for anti-submarine use, and against enemy submarines which are relatively quiet compared to the loud, surface ship targets of WW II, and against which a passive acoustic torpedo could be truly effective. Thus the lessons learned from the use of the CUTIE against Japanese warships are rarely appreciated.

The history of the u.s. Mk 27 torpedo began with a recognition in 1943 that the Germans were using a terminal homing torpedo called the GNAT -the German Naval Acoustical Torpedo. It was a torpedo that guided itself to contact with the target by the noise generated by a ship’s propellers. Earlier, the U.S. Intelligence community became aware of German work on passive acoustic torpedoes. Hence, a torpedo project was initiated in 1940 with the passive homing system work centered at Bell Labs and the Harvard Underwater Sound Laboratory. With engineering development then assigned to Western Electric and G.E., a socalled “Mine Mk 24” with the code name of “FIDO” was put in production and 10,000 units were ordered. But this number of units was radically reduced when it became evident that it would be a highly effective weapon. The Mine Mk 24 (“mine” being a misnomer for security reasons, to not alert the enemy to this new torpedo) made its debut in 1943 for use primarily with air craft. FIDO accounted for 31 U-boats sunk and 15 damaged from the 142 attacks made against U-boats during World War II.

In approximately the same time frame, Westinghouse adapted the Mine Mk 24 for submarine use and called this anti-escort torpedo the Mk 27 or “CUTIE.” (See illustration.) This passive acoustic small torpedo, weighed 120 pounds, was 19 inches in diameter and 90 inches long, had a 95 pound warhead of HBX, made 12 knots and ran 5000 yards. It didn’t see service in u.s. submarines until late in 1944 in the Pacific theater. Whereas only seven CUTIEs were fired by a total of three submarines, there were 4 hits recorded — an impressive record of success. Actually there were 106 Mk 27 Mod 0 torpedoes fir ed by other platforms as well as submarines during WW II with 33 hits resulting in 24 ships being sunk and 9 ships damaged. A single torpedo thus tended to achieve the same results against escorts as a salvo of larger non-homing torpedoes.


Significantly, the Mk 27 CUTIE was quietly launched from a torpedo tube by starting it while still in the tube and letting it swim out taking 8 to 10 seconds to clear the tube. The noisy ejection of the conventional torpedo was thus eliminated.

One other passive acoustic torpedo, the Mk 28, appeared in the Fleet before the end of WW II. It was a full-size, 21-inch diameter, 21-foot long electric torpedo of 20 knots speed, 4,000 yards range and with a 600 pound warhead — and could be submarine launched. There were 14 of these Mk 2Bs fired during the War with only 4 hits resulting. This was probably due to inadequate training in its tactical use.

As for the firing of CUTIEs by the three submarines, as noted in Clay Blair’s Silent Victory, their use was initiated by Carter Bennet in SEA OWL.

On the first patrol of SEA OWL in November of 1944, in the shallow waters of the Yellow Sea, Bennet gave a CUTIE its first submarine test. A small patrol craft was the target. SEA OWL was taken down to 150 feet — a safe depth which would prevent the CUTIE from homing on SEA OWL — and one Mk 27 torpedo was fired. A hit resulted and SEA OWL was surfaced to check the effectiveness of the torpedo. Bennet found the patrol craft in a sinking condition — making this attack, in Bennet’s judgement, “an unqualified success.” On his second firing of a CUTIE, again from 150 feet deep and again at a small patrol craft, there was again a convincing explosion and SEA OWL was surfaced, to find the vessel not badly damaged but dead in the water. The patrol craft was then finished off with a Mk 18 torpedo. Soon afterward, Bennet tried two more CUTIEs against what he believed to be a destroyer coming out of Nagasaki. Nothing happened — perhaps because the destroyer was making too much speed or because the destroyer spotted the torpedoes. But the latter reason was less likely than the former since the early models of the Mk 27 appeared useless against a target going more than 8 1/2 knots.

On April 9, 1945, George Street in TIRANTE, after attacking a small convoy and sinking a 5,500 ton transport loaded with troops, was put under depth charge attack by several escorts. Street then fired one CUTIE, heard a loud explosion overhead with breaking up noises, but never knew the ultimate result of this attack. Nor was this escort listed as sunk — but perhaps it was too small for the official records.

On July 1, 1945, Frank Lynch in HADDO attack~d a 4-ship convoy off Inchon, Korea — in a dense fog and in only 65 feet of water. Two freighters were sunk and two damaged in Lynch’s 8torpedo attack. The fog lifted and an escort, a frigate, was sighted charging at HADDO. At flank speed, HADDO fled for deeper water being chased by two escorts. Staying on the surface seemed fatal so HADDO was dived in 80 feet of water. Two CUT!Es were released — hoping that they wouldn’t hook back on HADDO. One torpedo hit Coastal Defense Vessel No. 72, an 800-ton frigate, which blew up and sank. The other escort broke off his attack to rescue survivors.

In effect, the CUTIE with its passive acoustic homing feature proved to be a useful anti-escort torpedo, particularly for submarine use in shallow waters. Its swim-out feature was non-alerting to searching surface escorts. And its successful use in extreme situations, as a last-ditch submarine defensive measure, might have encouraged greater emphasis on this kind of weapon for future submarine operations.

R. C. Gillette

Naval Submarine League

© 2022 Naval Submarine League