An efficient A.S.V. watch must also be maintained, except that A.S.V. Mark II (metric) must not be used in daylight unless visibility was under three miles, or the aircraft was flying above heavy cloud, or the gear was required for navigational purposes. No restrictions were placed on A.S.V. Mark III (centimetric). To avoid eye fatigue, radar operators should be relieved every forty-five minutes. The optimum altitude for detecting and surprising a U-boat was judged to be 5,000 feet where there was no cloud or where cloud bases were above 5,000. When cloud density was not more than 5/Ioths and below 5,000, aircraft should patrol 500 to 1,000 feet above cloud tops. When clouds were more than 5/Ioths and below 5,000, aircraft should seek concealment by flying as near the cloud base as possible. When a sighting was made, altitude should be lost as quickly as possible in order to be no more than 300 to 500 feet off the deck when three-quarters of a mile to a mile from the target.
The pilot should make the decision as to whether flying an indirect course toward the target was required, either to provide time to get the bomb bay doors open (where aircraft were so equipped) or to avoid an increase of speed that would throw off the bomb intervalometer setting. (Squadron Leader Terence M. Bulloch, cited in chapter 3 for his successes—altogether in his career he would sight 28 U-boats, attack 19, sink 4, and severely damage 3, becoming the most decorated ASW pilot in Coastal—deviated from the rule of fast descent by stalking a sighted boat from cloud cover, and only when positioned to make an attack up or down the boat’s track at an angle of about 20° would he initiate his dive. Bulloch did not fly patrols in May, but spent the month instead testing a new rocket-propelled weapon, to be used in action for the first time on 23 May, at the Aircraft and Armament Experimental Establishment at Boscombe Down.)40
During the final stage of the run-in, aircraft should descend to 50 feet and deliver their attack as nearly as possible along the track of the U-boat, taking their point of aim according to the following data:
(1) The time from the release of a depth charge from 50 feet to detonation at the shallow setting (25 feet) is approximately 5 seconds (2 seconds in the air and 3 in the water).
(2) If the U/Boat is in process of crash-diving, her speed will be approximately 6 knots (10 feet per second). Therefore, if the U/Boat is attacked while some part of the hull is visible, the centre of the stick should be aimed 5 x 10 = 50 feet ahead of the conning tower (or its estimated position) at the time of release.
(If the conning tower is itself in sight, however, at the time of release, it is desirable to make this the aiming point, although theoretically the stick will then fall 50 feet behind it.)
(3) If the U/Boat has dived before the depth charges are released, the stick must be aimed a certain distance ahead of the swirl, the apex of which is made by the foremost end of the conning tower. This distance is, of course, that run by the submarine between its final disappearance and the time of detonation of the depth charges. Assuming that the speed of the U/Boat is 6 knots, the distances are as follows:
Time of Submersion Distance to aim
to release of DC’s ahead of swirl
5 sees. roo ft.
10 sees. 150 ft.
15 sees. 200 ft.
20 sees. 250 ft.
25 sees. 300 ft.
30 sees. 350 ft.
(4) If the periscope only is sighted, the speed of the U/Boat will probably be only about 2 knots, i.e., 3.4 feet per second, hence the stick should be aimed 5 x 3.4 = 17 feet ahead of the periscope at the time of release.
NOTE: An additional allowance must always be made for the underwater travel of the depth charges (40 feet).
If the U-boat had just submerged, the approximate length of its diving swirl (100 feet) could be used as a yardstick for estimating the distance ahead that D/Cs should enter the water. It was unlikely that a D/C attack would be successful, however, if the U-boat had been submerged for more than 30 seconds, in which case baiting tactics might be employed: In these maneuvers, the aircraft set course from the position of the swirl to a distance of at least 30 miles and remained outside that range for not less than 30 minutes; then it returned to the same position, taking advantage of cloud, sun, or weather conditions for concealment, in the expectation that the U-boat would have surfaced again. When a surfaced U-boat used its flak against the aircraft—most boats were then equipped with one 20mm cannon and several machine guns on the bridge—the decision on how to respond rested with the aircraft Captain, but the Tactical Instruction made it clear what was expected of him: “He must remember that the primary reason for his existence is, for the time being, to kill U/Boats and that a U/Boat on the surface presents a much better chance of a kill than one submerged.”
The point was made that a U-boat’s bridge made a very unstable gun platform in any kind of sea and particularly if the sea was beam-on, and that even a large aircraft properly handled and using its forward guns presented a fleeting, dangerous, and difficult target. Aircraft Captains should therefore press home their attacks against enemy fire, preferably from dead ahead, “making full use of the front guns to kill the U/Boat’s gun crews or at least to keep their heads down.” (The U-boats, for their part, were instructed when under attack to keep the aircraft on a stern bearing in order to present a small target—though, ironically, this helped the aircraft to drop a D/C straddle up track—and to use all available flak and machine gun fire simultaneously. When the aircraft began its final run in, the U-boat should initiate evasive maneuvers at maximum speed using full helm. In cases where a strong cross-wind was blowing, the U-boat’s avoiding action should be to windward in order to take advantage of the aircraft’s drift sideways.)
Aircraft carrying six or fewer D/Cs on hunting patrols or sweeps, such as Derange, should drop the whole load in one stick; aircraft carrying more than six should drop sticks of six. Aircraft on convoy or other escort duty should drop sticks of four, leaving D/Cs for a possible second attack; this rule could be altered at the Captain’s discretion, for example when nearing his PLE or while returning to base. After carrying out an attack on a diving boat by day, the aircraft must drop a marker on or beside the swirl. By night the position must be marked by flame floats, usually two dropped at the same time as the D/Cs.
For purposes of assessment and so that every possible lesson could be learned from each attack, a complete and detailed record, for example, of the exact time lapse between submersion of a U-boat and the release of D/Cs, should be kept by members of the crew. “The story should be complete to the smallest detail and even facts which may appear irrelevant should be included.” Within twenty-four hours a connected account should be written down and read by the crew.41
Not all of these rules were observed to the letter, as will be seen in the after-action reports that follow. Some pilots, following Terence Bulloch’s example, fudged the rules and had unorthodox successes. But in the main, Coastal’s tactical doctrine proved out not only in the Bay but also in the convoy routes. The mole, it turned out, had a lot to fear from the crow. At 2055 GMT on 30 April (all times that follow are GMT), L/L Wellington “N” of 172 Sqdn. lifted off from Chivenor in Devon, bound southwest to the Derange ribbon, where the cloud was 4/Ioths to 7/Ioths with bases at 2,000 feet, the sea moderate to rough, the air bumpy, and visibility 2–4 miles. At 0007 on 1 May, Pilot Flight Sergeant Peter W. Phillips was patrolling in the ribbon at 1,200 feet on course 168° when he obtained an S/E contact (Special Equipment, a code word for A.S.V. Mark III 10cm radar) bearing Green (starboard) 45°, range 6'½ miles. Phillips dived on the surfaced U-boat, which was proceeding inbound on a course of 132° at seven knots, and, after reach-ing 550 feet three-quarters of a mile from the target, he “struck” (switched on) the Leigh Light. The run-in was made on the U-boat’s port bow at 8o° to track, while the Navigator, Sergeant H. A. Bate, fired about forty rounds from the front gun before it jammed, and at 0100 Phillips released six Mark XI Torpex D/Cs set to shallow depth and spaced 50 feet apart from a height of 75 feet. All were seen by the re
ar gunner to explode with blue flashes, two to port and four to starboard; Nos. 2 and 3 were thought to have been very close to the U-boat’s hull.
During the aircraft’s pass over the target a shudder was felt underneath, though no gun fire was observed. (An hour after the attack it was found that the hydraulic system had been damaged; not known until landing was that the port tire had been punctured.) Phillips made a 180° turn to port and, four minutes later, flew back over the attack position, which was marked by flame floats. Except for a patch of foam and bubbles, nothing could be seen, not even a diving swirl. After twelve more minutes in the vicinity, Phillips resumed patrol. At 0452 he and his five-man crew landed at the nearest base, Predannack in Cornwall. As they did so, the port landing gear collapsed, and the aircraft swung off the runway and slammed into a Nissen hut. Beyond scratches, the crew were not injured. The base Medical Officer pronounced them “very lucky.”42
The U-boat they had attacked, U-415 (Oblt.z.S. Kurt Neide), returning from her first war cruise, was also very lucky. Damaged by Phillips’s D/Cs, she would be attacked twice more before the day was out. At 1136 she was visually sighted on the surface in visibility 15 miles, at 4435'N, 10°37'W, by Sunderland “M” of Royal Australian Air Force (RAAF) No. 461 Sqdn., flying on Derange. Bearing Green 30° at a range of 5–6 miles, the U-boat was estimated at 6 knots on a course of 100°. Seeing the aircraft approach, U—415 dived. Pilot Flight Lieutenant E. C. “Bertie” Smith, DFC, put the flying boat into a dive and attacked the swirl 18 seconds after submergence from the U-boat’s port beam, dropping four Mark XI D/Cs set shallow and spaced 200 feet apart from a height of 50–75 feet. The D/Cs straddled the U-boat’s line of advance 70–100 feet ahead of the apex of the swirl. No debris appeared, however. Smith took his aircraft off on baiting procedures and returned in cloud 29 minutes later, but again saw no evidence of damage where his sea marker had disappeared in rough seas.
U-415 had received a severe shaking but was still intact.43 At 1727 she was sighted for a third time, in position 44°13'N, 10°23'W, by Derange aircraft Whitley “E” of 612 Sqdn. The sea had moderated to a slight swell and visibility was still 15 miles. The U-boat was bearing 180°, distant 5 miles, at a fast speed, 15 knots, on course 090°. Pilot Flight Sergeant Norman Earnshaw descended from 3,000 feet, intending to attack from the U-boat’s port quarter at 20° to track. As he began his run in at about 150 knots, U-415 opened fire with 20mm cannon and light machine guns. Earnshaw’s release from 90 feet of six Mark XI D/Cs, set to shallow, spaced 200 feet apart, exploded 200 feet to starboard of the target, as the U-boat took hard evasive action in a tight turn.
Kicking rudder, Earnshaw set up for a second attack. Meanwhile, U-415 dived. In the second attack, made from the U-boat’s port beam at 90° to track, two D/Cs were released from 70 feet and exploded 28 seconds after submergence 300 feet ahead of the swirl. This time oil was seen. Earnshaw patrolled the scene for 40 minutes, then set course for base at Davidstow Moor in Cornwall.44 Further shaken, U-415 limped on to her base at Brest. At BdU, Donitz and Godt were relieved to learn of her safe arrival. Their war diary recorded: “U-415 was bombed three times … Despite much damage she was still able to dive.”45 The good luck that carried U-415 through May Day would stay with her until 14 July 1944, when she struck an RAF mine and sank in the Brest approaches.
Two other attacks in the Bay were made on 1 May: At 0825, Halifax “C” of 502 Sqdn. dropped six D/Cs on a surfaced boat, and at 1015, Hampden “L” of 1404 Sqdn. released six on a surfaced boat. Initial contact was made by eye in each case. Return fire was not observed from either boat before it dived. There were no visible results from the attacks. Three daylight attacks on surfaced boats were made the next day, 2 May: by Sunderland “R” of 10 Sqdn. at 0810; by Hudson “W” of 269 Sqdn. at 1437; and by Whitley “G” of 612 Sqdn. at 1531. In the first and third attacks initial contact was by eye; in the second it was obtained by S/E. None of the boats was reported to have fought back.
The first kill in May was made at dusk that day by Flight Lieutenant “Bertie” Smith and his ten-man Australian crew in the same Sunderland “M” they had flown the day before (which deserves mention only because it should be noted that air crews frequently switched aircraft from day to day within a squadron). Smith was trolling in the Derange ribbon at 2,500 feet in the base of 6/Ioths cloud. Visibility was 10–12 miles. The darkening sea below was rough in 26-knot winds from 010°. At 1917, eyeballs sighted a U-boat on the surface bearing Red (port) 45°, range 10 miles. Smith estimated it to be traveling at 10–12 knots on an outbound course of 270°. He pushed forward his four engine throttles and climbed into cloud, where he turned to make his approach. At four miles from the target he dove from the cloud. On sighting the flying boat, the U-boat responded with flak and machinegun fire, and when Smith was down to 300 feet and ½ mile distant, the U-boat abruptly altered course to port. Smith was able to complete his run-in from the U-boat’s port beam at 90° to track, while RAF gunner Sergeant R. MacDonald swept the deck with fire from the bow turret. Just before release from an altitude of 50–70 feet, the U-boat gunners were seen scrambling for the conning tower hatch.
Four Mark XII D/Cs straddled the boat just aft of the tower, after which the boat described a tight circle, apparently out of control, then came to a gradual stop with a bad list to port. A large volume of brown vapor blew out from its stern and a white vapor plume rose about three feet from its port quarter. Then a heavy flow of oil was observed pouring from its port side. Meanwhile, Smith was making a climbing turn to 500 feet to set up a second attack, which he delivered at 75 feet with four D/Cs released from the target’s starboard bow at 15° to track, again straddling the tower. The now gravely wounded boat settled by its stern. The oil patch spread to 300 yards in diameter. Some fifteen crewmen were seen jumping into the water, where they waved frantically at the aircraft. Then, at 1940, the U-boat’s stern sank beneath the waves; its bow followed, reappearing twice briefly at an angle of 30°. The victim was U—465 (Kptlt. Heinz Wolf, 28 years old, from Emmerich/Rhein), on her third war patrol. Smith and crew remained in the area for 30 minutes, then, having reached PLE, returned with their victory photographs to base at Pembroke Dock in South Wales.46
Two daylight attacks were made on 3 May against boats sighted on the surface in the Derange ribbon: by Sunderland “S” of 461 Sqdn., at 1044, and by Whitley “R” of 10 Sqdn. O.T.U. In the first instance, the initial contact was made by eye and four D/Cs were released 22 seconds after the U-boat had submerged. In the second, the contact was also made by eye, and five D/Cs (one having hung up) were released while the boat was still on the surface. There were no visible results in either case. On the next day, 4 May, Halifax “S” of 58 Sqdn. was on morning patrol, having lifted off at 0555 for the Derange area, where the seas were very rough under 7/Ioths-8/Ioths cloud, visibility 8–10 miles. At 1740, the crew made the visual sighting of a creamy wake, bearing Green 90°, which led to a surfaced U-boat, outbound from base at 6–8 knots on a course of 270°, distant 4–5 miles.
Pilot Flying Officer John M. Hartley turned to starboard, lost height rapidly, and approached out of the sun. At 1,400 yards the U-boat opened fire with what Hartley thought was an impressive amount of armament: “heavy guns” from the afterdeck, followed at 1,200 yards by “cannon at the front of the bridge,” and later by cannon on the forward deck and two pairs of machine guns on a stepped gun platform in front of the conning tower. He could see about fifteen of the boat’s crew, most of them manning the cannons and guns, but two men in black uniform and another in a white sweater, all wearing peaked caps, standing on the deck at the port side of the tower. Hartley ordered answering fire against the pugnacious boat, which scattered some of the men manning cannon and machine guns, the rest maintaining heavy and light flak.
By evasive action Hartley managed to prevent his four-engine Halifax from being hit by that fusillade, and at a quarter of a mile from target, he leveled out to release six Mark XI D/Cs from the U-boat�
�s port quarter at an angle of 60°-70° to track. The navigator firing the front gun saw one man on deck hit and fall overboard. Altitude at the time of release was a relatively high 200–400 feet. The rear gunner reported that the D/Cs straddled aft of the conning tower, two on the port quarter and four on the starboard beam. In addition, the gunner had fired 500 rounds at the tower and hull as the aircraft passed. But the U-boat submerged thirty seconds after the Halifax, turning back, caught sight of it again, and no damage was visible, only the usual D/C scum. Baiting procedure was followed, Hartley returning at 0910, but the marker could not be found. With PLE reached at 1000, the Halifax returned to base, landing at 1258. Subsequent assessment by NHB/MOD has identified the boat as U-/90, which suffered “slight damage,” nothing to prevent her continuing on Feindfahrt.47
Three more attacks in the Bay were made later in the day: by Halifax “A” of 502 Sqdn. at 1920, by Catalina “J” of 202 Sqdn. at 2110, and by L/L Wellington “P” of 407 Sqdn. at 2309. In the first, initial contact was made by eye and six D/Cs were released on a surfaced U-boat. In the second, contact was also made by eye and five D/Cs (one hanging up) were dropped 37 seconds after submergence. In the third, contact was obtained by S/E and six D/Cs were dropped 10 seconds after submergence. No results were evident, but minor damage was done to U-405 (Korv. Kapt. Rolf-Heinrich Hopmann) by the Halifax, and the target of the Catalina was later assessed to be U-6oo (Kptlt. Bernard Zurmühlen).48
Three daylight attacks were made on 7 May in the Derange area, the first two on diving boats by Wing Commander Wilfrid E. Oulton of 58 Sqdn. At 0656, just after dawn (Oulton forbade his crew to eat breakfast prior to a morning flight because it put “spots,” not U-boats, before the eyes), Oulton sighted a U-boat’s wake from the cockpit of Halifax “S,” dived on the target, and dropped six D/Cs over its swirl 10–15 seconds after the U-boat’s submergence. And at 1015, Oulton dived on another U-boat’s wake and released three D/Cs on the submerging boat while its conning tower was still visible. The first attack yielded no visible results. The second, now known to have been against the outbound U-214, badly wounded her Commander, Kptlt. Rup-precht Stock, and forced the boat back to her base at Brest. Oulton’s aircraft received machine-gun hits during the run in.49
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