Black May (50 page)

Her American counterpart, carrier U.S.S.
Long Island,
capable of embarking twenty-one aircraft, would not see action in either the Atlantic or the Pacific theaters but spend her career in ferrying, training, and experimental duties. But beginning in 1942, the USN heavily committed funds to the CVE program, and American shipyards began turning out large numbers of improved carrier conversions from merchant hulls, eventually producing 128 by war’s end.
¹¹
British yards produced five. Many of the early U.S. CVEs went to the RN, which made additional modifications, mainly to the avgas fuel systems to prevent vapor explosions, and two of these,
Biter
and
Archer,
were in active service on the Atlantic convoy routes during Black May. Swordfish “L” from
Biter
had earlier, on 25 April, shared in the destruction of U-203 (Kptlt. Hermann Kottmann) along with the destroyer H.M.S.
Pathfinder,
while both ships were with EG5 supporting EG B2, the close screen of Convoy ONS.4. The aircraft’s principal contribution to the kill was two well-placed calcium sea markers, since her two D/Cs
dropped 20 seconds after submergence apparently did not damage the U-boat. On 10 May,
Archer,
with Fourth Escort Group, was supporting EG B6 with Convoy ONS.6.

British naval historian David Hobbs has commented on the relative merits of shore-based and naval-embarked aviation at that period. Most of the flying hours of the former, he points out, were expended in transit to and from their patrol areas rather than in patrol itself. Add to that the fact that significant numbers of shore-based bombers and crews had to be kept in constant rotation on successive legs to and from the convoy, and the economy of carrier aircraft, which were based constantly with the convoy, becomes apparent. Furthermore, Coastal Command aircraft did not always successfully rendezvous with their designated convoys; in 1942, for example, 34 percent of all Coastal sorties were Not Mets. Finally, unlike bombers from afar, the carrier aircraft lent themselves to rapid and flexible tactical use by the escort commander, the attack on U-403 being an apt example.
¹²
The only problem at this date, apart from pilots’ tendency to get lost navigating, was the inadequacy of the Swordfish aircraft in speed and structural strength.

Following the action against this boat, BdU decided that the main body of
Rhein
must be 90 miles behind the fast convoy, with little chance to catch up. Accordingly, it ordered that group, excepting U
-403,
to withdraw from the operation against HX.237 and to move instead against the slower SC.129, which was “considered to offer better chances of success.” The fast convoy would be left to the shadower U-403 and to the six boats of
Drossel
closing from the east.
¹³
The daylight hours of 11 May were quiet, though HF/DF activity increased, and Chavasse sent two destroyers ahead to probe for threats, and two of
Biter
’s aircraft searched the convoy’s perimeter. Later in the day, U-436 (Kptlt. Günther Seibicke) of Group
Drossel
found HX.237 BD 9554 (44°15'W, 27°25'W). Another of
Drossel’
s boats, U
-89
(Kptlt. Dietrich Lohmann), reported the presence of carrier-type aircraft circling overhead—either a confirmation or a first disclosure to BdU that the aircraft that attacked U-403 was carrier-borne.

At 2013, another of
Biters
aircraft, Swordfish “L,” caught
U-436
on
the surface and attacked her with four D/Cs from 150 feet. During the run in, the “Stringhag,” as the frail biplane was called by pilots, took heavy anti-aircraft fire, but the pilot and gunner watched the tracers pass harmlessly between the port upper and lower wings, and the pilot returned fire with his front gun. Following the D/C drop, the pilot climbed to make a return run, but after he got the slow-gaited craft around, the U-boat had disappeared. The pilot dropped a smoke float and resumed patrolling.
¹⁴
At 2100 U
-89
reported the convoy on a new course, 000°, or due north.
¹⁵
Contact was not resumed until daybreak on the 12th, when the surfaced
Drossel
boat U-230 (Kptlt. Paul Sieg-mann) sighted the ship columns in heavy swell astride BD 2826, confirming that the convoy, estimated at 9.5 knots speed, had made an evasive turn to north.
¹⁶
Soon afterwards, U-230 found herself under attack by the first Swordfish to make it off
Biter
s bucking deck that high seas morning, which was the twenty-third birthday of U-230's First Watch Officer (I.W.O.) Herbert A. Werner, a native of the Black Forest region of southern Germany, who was commanding the bridge watch:

This loss had a sobering effect on
Biter,
who decided that antiquated Swordfish should no longer engage in gunfire duels with U-boats, despite their crews’ keenness to do so. Henceforth, the Sword-fish were to attack only with D/Cs when the U-boat was seen to be
diving or had just dived. In other cases the pilot was to keep the U-boat in observation and, if possible, call in surface ship assistance.
Biter
s next attack would include an excellent example of called-in assistance from
Broadway
and the frigate H.M.S.
Lagan.
At 1230, in good weather, visibility 20 miles, Swordfish “B” sighted a wake, then a U-boat distant four miles, proceeding at 12 knots on a course of 060°. At about the same time, the U-boat—it was U
-89
—sighted the aircraft, altered course, and dived. By the time the Swordfish got down to 50 feet and dropped four D/Cs,
U-89
had been under for 30 seconds. The pilot returned to the position, saw no evidence on the surface, dropped a smoke marker, and reported the action by R/T.
Broadway
received the report and closed the position at 24 knots, while the Swordfish returned to
Biter
short of fuel.

At 1301
Broadway
reached the marker and, her asdic dome lowered, obtained a contact bearing 045°, range 1,500 yards. Chavasse decided on a Hedgehog attack, which he delivered just as U
-89
accelerated across his bow. There were no explosions.
Lagan,
in the meantime, had arrived to assist and she now made two unsuccessful Hedgehog attacks of her own. Ten minutes later,
Broadway
regained strong echoes on which to fire a second 24-projectile salvo, with a deflection of 15° right. This time, at 1359, there was a single sharp explosive
CRACK!
that was felt throughout the ship. Twenty seconds later, a second, muffled explosion was heard, and a marker was thrown overside.

Lagan
made two Hedgehog attacks on the position without result, but forty-five minutes after
Broadways
hit on the U-boat’s hull, wreckage appeared on the surface. It consisted of a piece of wood with an electric light switch, two positions for plugs, and the identification
“Schlüssel-M”
(Enigma machine); several pieces of laminated wood varnished on one side and painted white on the other; a woolen jersey with a Nazi emblem; and various other articles of clothing that were not picked up. The single Hedgehog projectile had drilled a fair-size hole. No bodies were seen. They were all entombed below in the Type VIIC iron coffin.
¹⁸
And the burying for that day was not over. Within the same hour as
Broadway
s puncturing hit, another
Drossel
boat was gored; subsequendy it would flail about wounded, call desperately for
help, then die gamely from the last penetrating effects of a weapon never before used at sea. Ironically, U
-89
was on her way to help that boat when death chose her first.

On 10 December 1941, three days after the attack on Pearl Harbor, the U.S. National Defense Research Committee (NDRC), acting on a proposal made to it sometime before by the U.S. Navy, convened a Top Secret meeting of scientists and engineers at Harvard University to consider the feasibility of a low-weight airborne anti-submarine acoustic homing torpedo. The feasibility agreed upon, the participants met again two weeks later to draw up general requirements and assign responsibilities for design and testing. The requirements in sum were that such a homing torpedo should be able to detect, track, and impact a source of underwater noise, such as the twenty-four-kilocycle sound produced by cavitation—the sudden formation and “popping” of the bubbles created by a high-speed marine propeller; be of a size to fit in existing bomb bays or on a 1,000-pound bomb rack; be droppable from 200 to 300 feet from an aircraft in level flight at airspeeds between 120 and 150 knots; be propelled electrically by a lead acid storage battery at 12 knots for five to fifteen minutes; and be able to carry a 100-pound high-explosive charge.

Bell Laboratories, a division of the Western Electric Company, and the Harvard Underwater Sound Laboratory (HUSL) agreed to pursue independent but cooperative and information-sharing development of the general design. The General Electric Company would design the propulsion and servo motors (and it may also have developed parts or all of the hydrostatic depth-control system). A lightweight 48-volt, shock-resistant, lead-acid storage battery was developed by the Electric Storage Battery Company.
¹⁹
HUSL measured the “self noise” made by the torpedo’s own propeller and solved the problem of allowing for it; though this was not the problem it might have been, owing to the participation of the David Taylor Model Basin at the Washington Navy Yard. There, Dr. Karl Schoenherr, after discussing prop noise for twenty minutes with Bell Labs visitors, whipped out a large piece of paper and drew a propeller design freehand. “Here is your prop,” he
said, presenting the sketch of a propeller with a 14¾-inch diameter and a 12-inch pitch. When the Bell Labs people protested that these were hardly the precision specifications they required, Schoenherr had a draftsman make a more exact, scaled, dimensional drawing and, after lunch, presented that instead. Not only did the design well serve the prototype acoustic torpedo then under construction, it was not improved upon until five years after the war was over.

The sometimes improvisational character of the torpedo’s development was further demonstrated when, for the midsection casings of the torpedo body, Western Electric and Bell Labs engineers turned to a bathtub manufacturer “whose most precise measuring instrument appeared to be a wooden yardstick”; but the company made and shipped interchangeable sections that were remarkably free of defects.
²⁰
In the end, the only significant difference between the Bell Labs and Harvard configurations of the torpedo were the type and placement of the sound-receiving hydrophones. In the Bell Labs model, Rochelle salt crystal hydrophones were arranged symmetrically around the circumference of the torpedo midsection. In the Harvard model, magnetostriction hydrophones were mounted on the nose section. While there was no meaningful difference in the performance of the two systems, it was decided by the NDRC to go with the Bell model, since the nose section containing the 92-pound warhead of HBX—1 Torpex high explosive and Mark 142 impact fuse in the forward 14½ inches of the weapon could then be handled independently and, in operations, be attached just before the torpedo was mounted on an aircraft. The four acoustic sensors, left, right, up, and down, homed to the noisemaking target by
body shadow.
The hydrophone on the right side, for example, did not hear the noise to the left, or port side, which was shadowed by the torpedo’s body, hence the torpedo’s guidance system turned the torpedo to port. The up and down sensors acted in the same way along the depth axis.
²¹

Prototypes of the torpedo were tested by both boat launches and aircraft drops to measure and verify performance characteristics. The principal testing was done at Solomon’s Island on the deepwater Patuxent River in Maryland and at Key West, Florida. At the latter site a
USN submarine with a protective cage built around its propellers served as a target for air-launched homing torpedoes loaded with plaster instead of explosive. After the first three of six torpedoes banged into the propeller cage repeatedly until they broke themselves apart, the Captain in command of the exercise called a halt to the testing, reminded everyone present of his secrecy oath, and advised USN personnel involved to stay out of submarines!
²²

With testing completed, the design was frozen in October 1942, and production under sole contract was awarded to the Western Electric Company. The first production model was delivered to the USN in March 1943, a remarkable fifteen months since conception. It measured 19 inches in diameter, 84 inches in length, and weighed 683 pounds. Its maximum speed underwater was 12 knots, more than adequate to overhaul a U-boat at its best submerged speed. In fact, its operating characteristics were very close to those first proposed in December 1941. Since the midsection hydrophones had maximum sensitivity in a direction at right angles to the sound source, it was not expected that the Bell model chosen, having reached its preset depth, would head directly, nose-first, at the target, even if dropped along the submerged U-boat’s track. As a USN operations research study reported in August 1946: