U-boat Archive - Sea Search Attack Group Command History






	CHAPTER II

	During the first year of its existence and particularly during the first three months of that period, the First Sea Search Attack Group participated sporadically in anti-submarine warfare. Its aircraft flew 1499.7 hours of patrol and search, sank two submarines, probably destroyed three more.* Forty three sightings were made twenty-two of them by use of MAD** equipment, eighteen by use of ASV equipment, and three visually. The Search is justifiably proud of this record since only a fraction of its time was spent in this work. The credit, of course, is due not so much to the personnel as to the equipment which was far in advance of that being used by other units.

	The search planes were B-18Bs equipped with ASV, MAD and a radar altimeter, the ASV housed in the nose, the MAD housed in a appendage to the tail or "stinger". Personnel of the group were among the first to use the microwave type of ASV, which was incomparably better than the Mark II, then in general use, for submarine search.

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	* Complete report of missions flown shown in Appendix 19-B
	** Magnetic Anomaly Detector


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	This type makes use of a concerted radio beam which, by continuous rotation or oscillation, is made to "scan" the surface of the sea. Objects on the sea then reflect a small portion of the radio waves as the beam passes over them. Reflected waves received in the airplane appear as bright spots or lines on the face of a cathode ray tube. The position of a spot on the tube indicates the distance and direction of a target relative to the airplane. These were the sets made in the Radiation Laboratory at MIT.

	The MAD was an altogether different type of equipment based on the superposition of one magnetic field upon another. It detects large bodies of metal, such as submarines and shipwrecks. Its range depends on the magnetic characteristics of the submarine or other target being sought and extends from approximately 600 feet in the case of a submarine to 15,000 feet on large buildings or shipyards. Since water in the path between airplane and target has no effect upon the range of MAD, submerged submarines may be detected by this equipment (radar, of course, will not do this). The equipment produces trace on a moving tape. During operation any change in the earth's field caused by the presence of a magnetic body will cause an excursion of a recording pen across a moving paper tape, making a permanent record of any signal received. Searching for enemy submarines with MAD is only practical if the position of the submarine is approximately known. This is true since the maximum sweep path of MAD would be approximately 800 feet wide and


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	100 feet deep for an airplane flying at 200 feet. Only approximately 20 square miles per hour could be swept out at an airplane speed of 120 mph. Once a submarine is approximately located by radar or other means and then submerged, the MAD equipment serves to accurately locate and track the submarine.

	A submarine or other magnetic body which is to be detected may be assumed to be a large magnet or "magnetic moment". The field that MAD detects is the super-position of this field on that of the earth. MAD detects any change in the earth's field. This equipment was developed by Columbia University Laboratories under the auspices of NDRC. All airborne tests were conducted in 2nd Search Squadron aircraft.*

	Aircraft range was of course an important matter. All unnecessary equipment was stripped from the planes. Colonel Dolan submitted a recommendation*** for the removal of twenty-nine items weighing in total 973-1/2 lbs in order to be able to install one bomb bay tank.

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	* National Defense Research Committee
	** Much more detailed discussions of ASV and MAD will be found in the chapter on projects.
	*** Appendix 19


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	On July 13, 1942 Lt. Donald L. McKay conducted the first mission during which MAD was actually used in an area where a submarine was known to be located. The object of the mission was to search for a submarine damaged previously by a DB-7. At 1900, position 3849N 7351W, the plane received an indication on the MAD equipment and as the plane circled a fresh oil slick approximately two miles long and fifteen yards wide was noticed. The slick extended from north to south and and was bracketed by aluminum slicks dropped by the aircraft. The submerged object was found to be at the southern extremity of the oil slick, and it was determined by the position of the slicks dropped that the oil slick was moving south at a speed of one knot an hour. The submerged object was believed to be the damaged submarine, and on the forth run the bombardier dropped a depth charge at the beginning of the indication swing of the MAD equipment. There was no visible result, and the pilot was of the opinion that the submarine was traveling at too great a depth to feel the effects of the charge dropped.

	On July 18, 1942, at 1203, with visibility of 3 miles, British Flight Lieutenant Cundy, flying LB-30 AL-596 with special equipment, sighted at twenty-eight miles and ninety degrees to the left, a dark U-boat about 300 feet long with a step conning tower. The position of the U-boat was 3530N 7245W, and it travelled a course of two hundred and twenty degrees at 8 knots. An attack was made directly along course of U-boat from an altitude of three hundred and fifty feet


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	and at a speed of one hundred and eighty-five miles. The U-boat began to dive, but conning tower was still visible at release of depth charges. Four Mk 17 depth charges set for twenty-five feet and spaced at twenty-six feet were dropped as the center of the train was sensed at twenty feet forward of the conning tower. Immediately there appeared a growing oil slick with foam fringe and after three minutes a large air bubble appeared in center of slick. The slick then increased to three hundred feet in diameter, denoting probability of a successful attack.

	Flight Lieutenant Cundy patrolled the area for four hours and twenty-three minutes and no other planes appeared in area during that time.

	During the summer of 1942 the heaviest activity of German sub packs drifted from the Hatteras region to the Gulf region and thence to the Caribbean. On August 15, Colonel Dolan received orders* to detach six crews to the 1st Bomber Command. In six hours seven ASV equipped B-18s were ready to go carrying six complete combat crews** plus maintenance crews, spare parts, and testing equipment. This unit was lead by Colonel Dolan himself. Upon arrival at Miami, they reported immediately to Headquarters, Gulf Sea Frontier. On August 17 they proceeded to Key West from which point they conducted operations until August 23. During this week, they flew 24 missions, had 5 instrument pick-ups of submarines and 3 visual sightings. They made two attacks.

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	* Appendix 20.
	** Roster of these crews appears in Appendix 20.


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	The first attack came on August 21, 1942 at 0505. Airplane #7602 took off from Meacham Field on a sea search flight. The members of the crew were:
	Pilot - Lt. Franklin T.E. Reynolds
	Co-pilot - Lt. William Hafner
	Navigator - Lt. Crowell B. Werner
	Bombardier - Lt. H.B. Wise
	A.S.V. & M.A.D. Radio Operator - Sgt. E.A. Kaszubski

	Airplane #7602 was flying in a southeasterly direction when at 0938 the Radio Operator noticed a signal on the A.S.V. screen at 28 miles, approximately dead ahead. The signal disappeared, and reappeared at 0942, at which time he advised the pilot the A.S.V. showed a target at 19 miles. He continued to direct the pilot by means of A.S.V. until 0948 when a submarine became visible to the pilot, co-pilot and bombardier at a distance of 7 miles. At an altitude of 300 feet, the pilot headed the airplane directly toward the submarine which was fully surfaced and heading in the direction of 100 degrees true at a speed of approximately 8 knots. Dropping to 200 feet altitude at a distance of one mile from the target with a heading of 133 degrees the bombardier was prepared to release bombs. At 0952 the bombardier released two bombs in a train. The run was made on the port stern of the submarine. One depth charge detonated approximately 25 feet off the port side of the submarine abeam of the conning tower, and the second charge detonated approximately 25 feet off the starboard bow of the submarine. These charges were 325 pound Mark IV depth charges with a pressure heading of approximately 320 degrees true; two more such depth charges were dropped in a train at 0953. The first of


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	these detonated at a point approximately 40 feet off the stern. On this run the submarine was visible at a depth of approximately 15 feet. "Direct" over MAD indications were received on both runs.

	Immediately after the first attack, small air bubbles and an oil slick approximately 30 feet wide and 150 feet long appeared in the wake of the submarine. The bomb load of 4 charges having been expended, the pilot climbed to an altitude of 500 feet, constantly circling the oil slick. A very large slick was formed by 0956. At 1007 the plane departed from area in the direction of Key West to refill the bomb bay. At 1012 a radio message was sent to "S 41" Miami giving the position of the attack. The plane received acknowledgement of this message at 1015. At 1025 a message was received from "S 41" ordering airplane #7602 to remain in the area until relieved and advising that a relief plane was being sent. The airplane returned to the area, and at 1118 an ASV signal was picked up at a distance of approximately 8 miles. Descending to 300 feet and heading approximately 210 degrees true, a periscope was sighted at 3 miles moving in the direction of 30 degrees true, at a speed of approximately 2 knots. At approximately 2 miles distant the periscope submerged. The airplane continued on its course at 300 feet altitude and 1122 a strong "off-side" type of signal was received on the MAD equipment, indicating the presence of the submarine to one side of the airplane's course.

	As there were oil slicks astern of the submarine to approximately mark its position, no bronze powder signal smoke or smoke flare was dropped. Circling the area to an altitude of 300 feet, another


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	slightly "offside" MAD signal was received at 1143. Another run over the area netted a further "off-side" signal at 1146, indicating that the airplane had passed within approximately 600 feet of the submarine. Shortly after this, the liaison transmitter was turned on and a message to "S 41" stated that the charges had damaged but had not sunk the submarine. The ship continued to circle the area, maintaining radio communication, and waiting for relief, at approximately 1240 a destroyer, an SC boat and a PC boat were sighted. The airplane was then headed in to comb the area with the MAD equipment and mark the position of the submarine. An area covered by two large and two small oil slicks was first covered with no MAD indication. With a heading of approximately 120 degrees true, the position of the submarine was finally found at 1247 by means of MAD equipment at a point approximately one mile southeast of the center of the four heavy oil slicks in an area containing a small amount of oil forming a poorly defined triangle. A smoke flare was dropped and returning on a heading of approximately 300 degrees true, another smoke flare dropped completing a normal MAD tactical operation and completely bracketing the position of the submarine with smoke flares, the last of which was dropped at 1259. At this point the destroyer was bearing down on the position of the smoke flares, and at approximately 1306 the destroyer and SC boat arrived in position and released a large number of depth charges, forming a pattern over the smoke flares.


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	At this moment the airplane was near the submarine at an altitude of approximately 350 feet. The explosion of the depth charges was distinctly felt by the crew. At 1309 the airplane flew over the position of the depth charge explosions and received a MAD signal indicating that the submarine was in the position of the depth charge explosions. The pilot, navigator and bombardier then observed the surfacing of huge oil bubbles which were rapidly forming a large heavy oil slick. Circling the area, the destroyer was observed to drop more depth charges a few minutes later. At approximately 1324 airplane #7602 left the area, having sighted the relief plane.

	Subsequent information reveals that the PC boat put out a "mouse trap" using contact fuse bombs, some of which detonated, indicating direct hits. Surface observations tended to indicate the submarine was destroyed.

	The depth of the water in the area is charted at 400 fathoms.

	On August 22, 1942 Lt. Robert L. Coleman's patrol, plane #7602, sighted submarine on surface at 0030, position 2340N 8355W, following an ASV instrument pickup at 18 miles. On first run plane was too far to left of sub to deliver attack. Second run was made at 200 feet altitude, 145 miles per hour, at an angle of 90 degrees to course of sub. Three Mark 17 depth charges with 25-foot fuze settings were released in train. Impact of first was 20 feet in front of bow of sub, which had begun dive with stern out, and bow awash. Impact of


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	second and third bombs were on 30-foot spacing on circular course of plane to left. On third run sub bow was upward 35 degrees and vessel was settled by stern. No oil or debris visible in darkness. A fourth run was made but sub was then submerged.

	While these crews were at Meachem Field, the few crews left at Langley were not idle. On August 22 a very interesting engagement took place which made manifest the need for much closer liaison between the army and navy. Conditions were ideal for the direction of surface vessel attack by airborne MAD tracking. Since the two never got together, the action was ineffective.

	At 1330, airplane No. 7563 took off on a MAD demonstration flight. Members of the crew were Lt. Hartbrodt, Pilot; Lt. Rockwood, co-pilot; Sgt. Kantowski, ASV and Radio Operator; and Norman V. Webster, Columbia University MAD research engineer, MAD operator; with Commander Hammond and Lt. Merrill of the U.S.N. as observers.

	At 1441 a depth charge explosion was noted, this having been dropped by a surface vessel. There appeared to be five vessels surrounding an area at approximately Lat. 36 degrees 18' Long. 75 degrees 18'. The plane immediately commenced to search this area with the MAD equipment at a 100-foot altitude. At 1500 the MAD equipment indicated that they had passed to one side of a submerged object, and a bronze powder drift signal was dropped. They then reversed their direction of flight, and at 1503, over approximately


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	the same spot, they again received an "off-side" MAD signal and dropped another bronze powder drift signal. In coming back for a third run over the target they received an "off-side" signal at 1506. No slick was dropped, but a note of the location in respect to the wreck in this area was made, and they continued over the last position of target, but no indication was received on this run, signifying that the target had moved. They returned and searched in the area of the signal picked up at 1506, and, while searching, a patrol vessel dropped a depth charge in this area at 1522. They flew over the area where this depth charge had explode and received no MAD signal. After more searching in the area they received an indication near the position of the depth charge explosion and a drift signal was dropped. They returned to commence to bracket the target with sticks in the normal tactical procedure, but the patrol vessels had moved to the location, and at 1555 they were dropping depth charges in the immediate area of the last two bronze slicks.

	During the action they made attempts to establish communication with the patrol vessels by means of Grimes light, but without success. Their signals were not answered.

	As the patrol vessels were in the area of the last slicks they dropped, they could no longer continue the MAD search. They then tried to communicate with the patrol vessels by means of the airplane's


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	liaison transmitter and receiver adjusted to 3000 K.C. Unanswered calls were made between 1340 and 1347. At 1345 they observed further depth charges exploding at a point 0.5 miles northeast of the position of the last bronze powder slicks, or at a position approximately two and one-half miles northeast of the wreck that has its masts and funnel protruding from the water at Lat. 36 degrees 15'; Long. 75 degrees 20'.

	At this point airplane #7563 left the scene of action and returned to Langley Field.

	On September 1, 1942, a killer search was started by Lt. George N. Diddison at position 3602N 7455W when he observed a slick, received several MAD signals, and saw a floating object resembling a boiler and something that appeared to be the outline of a submarine. Pictures taken by Captain Leo J. Foster showed a large floating slick and floating object made up of segments joined together to form a cylinder. A surface ship was furnished by the Norfolk Naval Operating Base to pick up the floating object, but a thick fog, with zero visibility, prevented their finding it. Lt. Robert W. Lehti received a strong ASV-MAD signal on September 2nd, but he could not identify the object because of the fog. Lt. Robert E. Easterling reported several MAD signals on September 3rd and noted a garbage slick at 3603N 7455W. Lt. Robert L. Coleman also received similar signals. The patrol of September 4th reported negative results and the search was discontinued on September 7th because the weather closed in.


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	In September the group was called upon to send eight crews to the British West Indies. Colonel Dolan took eight crews (B-18s) and two transports*. This unit was based at Trinidad from September 22 through October 16, during which period Sea Search planes and crews engaged in 78 killer searches and 8 patrol missions; they made six sightings and three attacks.

	The first attack was made on October 1, 1942 by Lt. Lehti and the following crew: Co-pilot Lt. Hafner, Navigator Lt. Cothran, Bombardier Lt. Wilson, and Radar Operator Hericsina. A submarine sank a freighter in the mouth of the Orinoco River, and a continuous killer search was ordered out by the 1st Sea Search Attack Group in that area. At 2007 the ASV operator reported a target on the radar screen at 12 miles. As they approached it the pilot let down to 300 feet at 125 mph, bomb doors open, and the ASV operator called out the signals until the bombardier saw the submarine. He dropped two 325-lb. depth charges as the aircraft passed over the stern, heading 45 degrees to course. There was no moon, but the crew could see the hatches open, lights below, and men scrambling over the hatchway as the submarine began to submerge. The interphone was not working and the bombardier could not tell the pilot to turn quickly enough to make another attack. Lt. Lehti, on learning of the submarine's presence, circled for about 45 minutes, and, as the ASV Operator no longer

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	* List of personnel involved appears in Appendix 21.


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	received signals, he went to shore to get a navigation fix and returned immediately to the area. The ASV Operator picked up a signal at 8 miles and led the aircraft to the vessel. The bombardier recognized the submarine at one-quarter mile and dropped the remaining two charges. This attack was made to the port side across the stern at 45 degrees to the course of the submarine. Estimated one hit with the submarine submerging immediately.

	The second attack was made on October 2nd by Lt. Reynolds and the following crew: Co-pilot Lt. Hickman, Navigator Lt. Friszie, Bombardier Lt. Thiele, and Radar Operator Neiss. At 0500 the ASV Operator picked up a signal at 16 miles and directed the pilot to the target until the bombardier sighted the conning tower and deck barely awash of a U-boat in position 9°5'N 60°20'W. The submarine was going about six knots in a direction bearing 170°. The airplane attacked at 200 feet directly from the stern. The bombardier dropped three depth charges, two 325-lb. and one 650-lb., while the conning tower was still visible. Lt. Reynolds circled immediately and attacked again from the starboard side directly across the conning tower, and the bombardier dropped his fourth depth charge, weighing 325 pounds, estimating another direct hit. Lt. Reynolds continued circling, and the submarine was seen sinking on its side. After it was no longer visible on the surface, a round swell appeared and lasted for about 30 minutes. Lt. Reynolds sighted survivors in a life raft at 0730, and they were later picked up by P.C. boats.


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	The bombardier claimed destruction of the U-boat by means of the depth charges, basing his claims on the fact that the submarine was on it's side when sinking.

	The third attack occurred on October 13th. The freighter Wildwood reported that a submarine attempted an attack but failed, and the 1st Sea Search Attack Group immediately started a killer search. Lt. Riddison took off at 1715 with the following crew: Co-pilot Lt. Burghoff, Navigator Lt. Harnon, Bombardier Lt. Tressel, and Radar Operator Robinson.

	At 1910 the Radar operator picked up a signal at 14 miles and directed the pilot to the target. The bombardier sighted a submarine at 300 yards 45° starboard of the aircraft. On turning to attack the bombardier lost sight of the submarine so the pilot headed to shore to get a navigation fix.

	At 2137 the ASV Operator picked up a signal at 12 miles 35 to the port. The aircraft sighted the submarine on the surface 300 yards to the port at position 8° 32' N 59° 34' W. The submarine was not moving. The aircraft made a 180° turn and at 2145 passed over the submarine and the bombardier released a 650-lb. depth charge across the beam. The result was not observed, but the bombardier believed he overshot. The whole submarine was visible when attacked, but it had submerged when the plane returned after circling.

	These three attacks were made on moonless nights.


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	The A.S.V. equipment on the eight ships ordered to Trinidad was ground checked on September 18, and found to be in good operating condition. The ships were loaded with a collection of testing equipment and spare parts considered adequate for three weeks of active operations. A.S.V. personnel consisted of six maintenance men and eight operators.

	Only seven of the ships of Sea Search organization were available for missions, since #7507 did not arrive until October 30, and #7575 went out of service on October 2, due to a broken landing gear. However, a considerable load was put on the testing facilities and supplies by the fact that, shortly after arrival, six B-18B's were delivered to the 9th Bomb Group. These came completely bare of testing equipment and spare parts, so that the Search was called upon to help them in operations. Later, six ships of the 40th Squadron, all non-operative, were put in Search hands for servicing. Finally, in response to a request from the navy, Search maintenance restored to service 517A* equipment on one of their PBM flying boats based at Port of Spain.

	These unanticipated demands so overworked testing facilities and drew down stocks of spares, that on September 27, a wire was sent requesting facilities for setting up a ground station, and followed

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	* Type of Search Radar manufactured by Westinghouse.


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	on September 29th by a wire asking for standard groups of replacement parts and tubes. These arrived October 6. Meantime, it being apparent that several weeks would elapse before #7575 could be placed in service, the 517A installation was taken from it and set up as a ground station. Thus by October 6th the maintenance situation was well in hand and remained so for the rest of the stay at Trinidad.

	Upon departure the Search left with the 9th Bomber Group all of the testing equipment and spare parts which had been brought or shipped so that for the time being they were in a position to maintain the ships they then had. Furthermore, a number of discussions were held with officers from the 9th Bomber Group and the 6th Fighter Command relative to the maintenance problems on 517A sets and they were left with a clear understanding of what is needed in the way of practices and facilities.

	This detached service made it quite apparent that a considerable supply, both in quantity and variety, of spare parts was essential to the operating units along with an adequate number of maintenance men. It was concluded that one maintenance man* per plane was not too many, although they should be worked as a group, and not assigned to a particular plane.

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	* Not the radar operator. These are two distinct jobs. It has become standard practice to send one operator and one mechanic with each radar equipped plane.


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	As a result of the abundance of experimental work carried on by Sea-Search and as an outgrowth of its combat experience, General Arnold requested that certain tests be performed at Key West to demonstrate to Army-Anti-Submarine and Navy personnel, the effectiveness of the tactics evolved by the Search Group. The report of these exercises contains so much of Sea Search tactical doctrine that it is bound into the narrative of this history rather than being set aside as an appendix. A perusal of this report will equip the reader with a knowledge of Sea Search tactical doctrine and of the conclusions finally arrived at as a result of the many projects dealing with Anti-Submarine warfare. The report begins on the next page.


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	June 7, 1943
	HEADQUARTERS
	1ST SEA SEARCH ATTACK GROUP "H"
	LANGLEY FIELD, VIRGINIA

	REPORT OF SEA SEARCH EXERCISES AT KEY WEST

	1. OBJECT:

	To further field test Sea Search Antisubmarine Warfare devices under simulated combat conditions, and to determine the practicability of tactics which have been evolved for use of these devices on a live submarine.

	2. INTRODUCTION:

	a. The tests were requested in a letter from the Commanding General, Army Air Forces, through the Office of Assistant Chief of Air Staff, dated April 30, 1943, Subject "Submarine Tests at Key West." The tests were started on May 17, 1943, and were completed on May 26, 1943.
	b. For simplification, this report is divided into the following three sections:

	SECTION I

	MAD MARK VI TACTICS: This includes preliminary MAD range and signature tests conducted on the submarine. Results of tactical MAD search missions using B-18's with MABs are discussed; also results of MAD missions using B-24's both with and without the Odograph.

	SECTION II

	LOW ALTITUDE OPTICAL BOMBSIGHT: This includes discussion of tests in stick droppings using the N-3A bombsight and the Gremlin Mark II bombsight.

	Section I - MAD MARK VI TACTICS

	1. DESCRIPTION:
	a. Mark VI Double Wing-Tip MAD.
	b. Retro bombs and Rails.
	c. Retro Flares.
	d. O-Type MABS.
	e. Sonic Radio Buoy.
	f. Radio Altimeter.
	g. Marker Slicks.
	h. Odograph.

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	I N D E X, Contd.

	2. CONCLUSIONS.

	3. RECOMMENDATIONS.

	4. DISCUSSION:
	a. The submarine.
	b. MAD signature and range tests.
	c. Proposed MAD tactics.
	d. MAD tactical searches with B-18's.
	e. MAD tactical searches with B-24's.
	f. Table of Missions.
	g. Maintenance and operations.
	(1) Tentative service requirements of Mark VI MAD.
	(2) Effect of B-18 and B-24D electrical systems on MAD.
	(3) Double O-Type MABS.
	(4) Magnetic Compensation Requirements of B-18 & B24D Airplanes.
	(5) Slick Dropper.
	(6) Electrical retro bomb and retro flare releasing system - B-18 airplanes.
	(7) Radar and communications.
	h. Detailed results of MAD tactics.

	MAD MARK VI TACTICS

	1. DESCRIPTION: The equipment used in this series of tests consists of the following major units:
	a. MARK VI DOUBLE WING-TIP MAD:
	This equipment comprises two complete magnetic detectors, each having an approximate range of 600 feet on medium sized submarines. Each equipment is supplied with a tape recorder which keeps a record of MAD activities in chronological order. These recorders are also used to indicate whether the airplane had passed to the right or left of a submarine. A coil mounted in the ceiling of the forward section of the B-18 shall serve as a checking means to equalize the sensitivity of the two mad units.
	With the exception of a different detector time constant and a difference in weight, the Mark VI MAD equipment is very similar to the older Mark IV equipment. The front of panel operation is the same.
	b. RETRO BOMBS AND RAILS:
	Each B-18 airplane is equipped with six retro rails under each wing. These rails normally carry twelve 60-pound Mark 20 contact bombs. For practice purposes, however, the rails will be equipped with attachments

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	Sect. I - MAD Mark VI Tactics, Cont'd.

	that permit the use of subcaliber ammunition. The system operates on the 28 V system of the airplane.
	The twelve bombs may be fired in a ripple of two sticks of six. The retro bombs are fired backward at a speed of 135 miles per hour. A suitable timer delay is provided in order that they may strike the water at the point of release. The rails are set at an angle to spread the bombs in a pattern approximately 120 feet wide at 100-foot altitude. The retro bomb control box, which is located in the bombardier's compartment, contains a time delay control which should be set to delay the second ripple .5 second. The full caliber retro bombs are equipped with a hydrostatic fuse whereby they will not fire on contact until they have reached a depth of approximately 18 feet. At a 100-foot altitude, an error of 10 miles per hour in ground speed would cause an error of approximately 35 feet in the striking position of the bombs.
	c. RETRO FLARES:
	In the rear gunner's hatch of each equipped B-18 is a retro flare tube which may be fired manually or automatically by means of the MABs unit. This tube is readily reloadable from the inside of the airplane. The retro flares consist of Mark V float lights equipped with rocket motors. The burning time of those flares is from 15 to 18 minutes. The retro flare tube is set at an angle of 9 degrees from the horizontal in order that the projectiles will not strike the tail wheel. Retro flares are designed to counteract a ground speed of 135 miles per hour. Cross winds will cause a deflection of the retro flares. In winds the error may be appreciable. At an altitude of 100 feet and for every ten miles of cross wind, the flare will strike the water approximately 35 feet in error on the downwind side.
	d. O-TYPE MABS:
	The O-type MABS is an electronic device that automatically fires retro bombs on the crest of the negative or positive magnetic poles of a submarine. One shall be used for each single Mark VI installation. The unit is designed in such a manner that it will not fire on normal maneuver noise or on ordinary signals from geological deposits, the bomb and flare switches should however be turned off during sharp maneuvers. A three-hold control is provided in order that the unit will not fire unless a signal exceeding a predetermined amplitude is received. In normal tracking procedure this value (for bombing) may usually be determined by means of the right-left indications during the first two passes from stern to bow over a submarine. Since the maximum of a submarine's magnetic field occurs ahead and astern of the submarine and may be of different magnitudes, it is essential that the unit fire on the first magnetic crest when approaching the submarine from astern. This magnetic pole may be either positive or negative. A polarity switch is provided on the MABS units that selects

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	d. O-type MABS, Cont'd.

	the proper polarity. The retro bombs are therefore automatically fired on the stern magnetic pole. A time delay is provided in order that the retro bombs will be released directly over the submarine.
	These MABS units are mounted one atop the other on the bombsight mounting. They are normally operated by the bombardier.
	e. SONIC RADIO BUOY:
	Each MAD equipped airplane carries eight sonic radio buoys and a receiving set. Sonic buoys are stored near the rear gunner's hatch in the B-18 airplanes. The receiver is mounted in the bombardier's compartment. The output of the receiver is connected to the R-1 position of the interphone system in such a manner that the command receiver is automatically disconnected when the sonic buoy receiver is turned on and connected when the sonic buoy receiver is turned off.
	Sonic buoys should not be launched at an altitude of less than 150 feet, and the correct launching altitude may be determined by the equivalent in feet of the airspeed of the plane provided this airspeed is in excess of 150 mph.
	f. RADIO ALTIMETER:
	The absolute altimeter permits the pilot to determine accurately his altitude up to 400 feet. The instrument may be set for any desired altitude within this range. For this purpose three lights are provided. An amber light burns when the altitude is within 10 feet of that desired. An increase in altitude will cause a green light to burn. A decrease in altitude will cause a red light to burn. For the tactics herein described the indicating system shall be set for a 100-foot altitude.
	g. MARKER SLICKS:
	T-1 green flourescein slicks in Wilsonite plastic containers, which have a papier-mache outer covering, were used in most of the MAD missions. These slicks are approximately 1400 cc. and are dropped by means of an automatic slick dropper.
	h. ODOGRAPH:
	The Odograph is a device which automatically plots the ground course of an airplane. The track through the air mass is automatically plotted by means of a gyro stabilized fluxgate compass, which determines the direction of flight, and a true airspeed meter, which indicates the speed of the plane. The wind's direction and velocity are manually set into the Odograph, and the resulting plot shows the actual track of the airplane over the ground with an average error of 3 per cent.

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	43.


	2. CONCLUSIONS:
	a. That the MAD retro tactics tested at Key West with the submarine S-15 are reliable and effective and that these tactics should be employed in antisubmarine warfare.
	b. That the same tactics and techniques can be applied to B-24 airplanes if suitable equipped and that such action should be taken with the least possible delay.
	c. That the minimum search width of Mark VI MAD varied from 450 to 550 feet when the plane was at 100-foot altitude and the S-15 submarine was at 100-foot depth.
	d. That the Odograph, in its present model, because of its sensitivity to error in wind setting and to change in wind, did not seem satisfactory for directing MAD tactics. Slicks and flares on the sea are the only dependable governing elements.
	e. That sono buoys and sono buoy receivers, green flourescein slicks and automatic slick droppers along with Mark V retro flares are necessary accessories in flying MAD search patterns.

	3. RECOMMENDATIONS:
	It is recommended that:
	a. Action be taken to equip additional antisubmarine aircraft on active patrol with MAD retro bombing apparatus and related accessories as quickly as possible.
	b. The the Odograph be discarded as a means of tracking a MAD search pattern, but that it be used as an aid to long range navigation.
	c. Further training of combat crews and development of tracking and attack tactics be continued.

	4. DISCUSSION:
	a. THE SUBMARINE - S-15:
	(1) Construction: 3/8-inch boiler plate construction. 231 feet long; 21 feet wide at widest point; 875 tons surfaced; 1050 tons submerged. From bow to stern, the compartments are the torpedo room, the battery room, the control room, the engine room, and the motor room. The conning tower is over the control room. It is double hulled except at the torpedo room and the motor room. Ballast and fuel tanks lie between the hulls.
	Speeds: Crash diving time 1 minute 40 seconds at 7 knots. Dives to 100 feet in 2 minutes thereafter at 6 knots. Normal submerged speed is 3-4 knots. Turning speed submerged - 180 degrees 5 minutes;


	44.


	4. DISCUSSION:
	a. THE SUBMARINE - S-15:
	(1) Speeds: Cont's 90 degrees - 3 minutes; 45 degrees - 1-1/2 minutes.
	(2) Magnetic History: Recommissioned two years ago at Philadelphia. It has been based at Canal Zone ever since, never going more than 1,000 miles from there. It gets wiped once a month. It was last wiped on May 1st. Its induced moment in cgs units is about 7 x 107 longitudinally, 2 x 107 athwartships, and 5 x 106 vertically, and its permanent longitudinal moment is less that 2 x 107 according to preliminary estimates by the Airborne Instruments Laboratory based on results of tests which follow. It is presumed that the permanent moment in hard steel German U-boats is about equal to the induced, so this submarine presents minimal signatures.
	(3) The Area: The exercises were run during the day in an area off Key West, Florida, eight miles by 5 miles, within which the depth of water varied from 100 to 140 fathoms with a sandy bottom. The night time exercises were run in an area sixteen miles by five miles in the same vicinity. The S-15 was accompanied by an Eagle Boat which during the day stayed about two miles to the North. The relative location of the escort and the submarine were unknown to the crews.
	b. MAD SIGNATURE AND RANGE TESTS:
	(1) MAD Signature Tests:
	(a) RB-18B No. 37-470 on May 17 made 48 passes at 200 feet altitude and 125 mph airspeed: Twelve with the S-15 headed in each of the directions N, S, E, and W. On each submarine heading the plane crossed three times N, three times S, three times E, and three times W. The first of each three passes was over the conning tower. The angle from vertical to the base of the conning tower was measured on each offside pass by the drift meter, so the deviation from the desired 200 feet could be computed.




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45.

(b) B-24D No. 41-23684 on May 17th made 16 passes at 200 feet altitude and 190 mph airspeed over the conning tower. Four passes were made with the S-15 headed in each of the four directions N, S, E, and W. On each direction of the S-15 the plane flew once N, once S, once E, and once W.

(2) MAD Range Tests:

RB-18B No. 37-538, on May 17th and RB-18B No. 37-470 on May 18th made 12 runs with S-15 heading E. At 400, 500, 600 feet altitude the planes made passes N, S, E, and W on each heading of the S-15.

(3) Results:

The Airborne Instrument Laboratory estimated from the results that the moments of the S-15 are approximately as follows:

Induced longitudinal 7 x 10 to the 7th cgs units

Induced athwartships 2 x 10 to the 7th cgs units

Induced vertical 5 x 10 to the 6th cgs units

Permanent longitudinal less than 10 to the 7th cgs units. Therefore the S-15 has practically no permanent moment. It was flashed on May 1st and her commander says that frequently he is told she does not need flashing when he takes her in for monthly flashing job. It is thought that the hard steel German U-boats have permanent moments about as large as the induced moments, which should make a German U-boat no harder to track on an E or W course than the S-15 could be tracked on a N or S course.

The noise level in the area was 1/2 to 3/4 gamma. The minimum recognizable signal was 2 gammas.

Following are typical signals in gammas for a plane flying 200 feet over the surfaced S-15, which are the same as for a plane at 100 feet and the S-15 at 100 feet depth. In all cases the signal is the larger of the two wing tip signals.

Submarine Heading	Plane Heading	Over Conning Tower	Over Point 200 ft. From Conning Tower
N or S	N or S	30 (Gammas)	15 (Gammas)
N or S	E or W	20	10
E or W	N or S	10	4
E or W	E or W	7	3

Following are the typical signals at 400 and 500 feet flying directly over the conning tower:

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46.

Submarine Heading	Plane Heading	Signal at 400 Feet Altitude	Signal at 500 Feet Altitude
N or S	N or S	10 (Gammas)	2-3 (Gammas)
N or S	E or W	4	1
E or W	N or S	1-2	1
E or W	E or W	1-2	1

The above information shows that for a plane at 100 feet altitude and the S-15 at 100 feet depth, the minimum search width varies from 450-550 feet, depending on the heading of the S-15 regardless of the heading of the plane.

If hard steel German submarines have a permanent longitudinal moment about equal to the induced longitudinal moment, the above signals would be at least double in most headings, and ranges and search widths would be about 25 per cent larger.

c. PROPOSED SEARCHING TACTICS:

Attacks on enemy submarines are designated as Class A when the attack has been made on a surfaced submarine; Class B when the submarine has crash dived but has been submerged 30 seconds or less; and Class C when the submarine has been submerged for a longer period.

MAD equipment should be used for searching only in case a recent contact has been established or if surface evidence of a submarine exists. It is generally impracticable to use MAD to sweep large areas unless a number of MAD equipped airplanes are used. Experience has shown that, when a large MAD signal is received in shallow water during a wide area search, it is probable that the airplane has flown over a wreck.

Since submarines generally do not remain submerged any more than is considered necessary to avoid detection, it is obvious that the best chance for establishing a contact is for a patrolling air-plane to fly at the established altitude for a radar or visual search. Having made a Class A or B contact, the MAD and MABS equipment serves to locate, track, and release bombs on the submerged submarine.

When contact is made either by radar or visually, the airplane should proceed to the target as directly as possible, as the radar or visual contact may be lost while flying to the submarine. Both the navigator and radar operator must supply the pilot with information for a timed run. The following detailed procedure should be used.

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	47.


	The radar operator informs the pilot and navigator of a contact. If the contact is visual, the radar operator shall be instructed to pick up the target by radar in order to determine the range. The pilot shall head toward the target with direction from the radar operator if directions are necessary.
	The MAD radar operator calls out the distance of the submarine every full mile; for instance, "Target, 9 miles, "Target, 8 miles," etc.
	On each cue word, "Target", the navigator starts his stop watch, resetting it on each new range as given by the radar operator. This is important since the target may disappear and the shortest range value is likely to be the most accurate.
	The navigator shall have on the navigating table an aircraft plotting board on which the magnetic direction and velocity of the wind shall have been plotted. From the indicated airspeed, he may then accurately estimate the ground speed and drift. In the event of a disappearing contact the navigator shall instruct the pilot as to the proper magnetic heading to fly; and, when the airplane arrives over the computed point of submergence, the navigator shall call "Slick" into the interphone. The pilot shall release two slicks or a Mark V float light at this call of s"Slick". A timed run from a distance of seven or eight miles should be accurate within ten seconds. During the tracking procedure the navigator shall plot the position of the flares dropped and note them with right or left data as supplied by the MAD operator.
	The MAD operator shall have the MAD equipment in proper adjustment at all times during a patrol flight. During an action he shall determine the magnetic characteristics of the submarine being attacked and shall supply information on polarity and amplitude upon request by the bombardier.
	The radio operator shall at the first cue word of "Target" turn the radio transmitter on and place the key in the down position in order that a continuous tome will be transmitted. This tone shall be continued until the submarine is detected, tracked, and bombed, and then a report of the attack and the position shall be transmitted. If the object sighted by radar is not a submarine, the steady signal will be turned off as quickly as possible and a negative report transmitted. This procedure is recommended for three reasons:
	(1) Intermittent operation of the radio transmitter on B-18 airplanes interferes with the operation of MAD equipment.
	(2) The long, steady tone supplies a cue to shore stations that an action is underway, and an RDF may be taken.

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	48.


	(3) The operator would not normally have the airplane's position at the beginning of an action, and the navigator would be too busy during the preliminary part of an action to supply the radio operator with accurate information. The Radar-MAD operator may turn the transmitter on in the event a radio operator is not carried.
	The engineer, who is normally stationed in the rear of the B-18 airplane, shall wear his headset at all times during a patrol. He shall make sure that the slick dropper is loaded and the retro flare tube is in position and loaded. He shall see that four sonic buoys are ready for launching, making a note of the order of the colors that denote the frequencies of the sonic buoys. During an action he shall reload the retro flares tube and slick dropper as quickly as possible after they are operated.
	On a preliminary signal from the pilot to prepare to drop sonic buoys, he shall quickly remove any retro flare, raise the retro flare tube, and launch the sonic buoys on instructions from the pilot. The cue word for dropping the buoys shall be "Drop." The sonic buoys shall be dropped in the following order: Red, Green, Blue, Yellow.
	On the cue word, "Target", the bombardier shall open the bomb bay, turn on the sonic buoy receiver, and then prepare for a Class A attack with a train of two Mark 17 Depth Charges spaced 85 feet, since only two Mark 17's can be carried with a load of full caliber mousetrap bombs. Otherwise a stick of four Mark 17 Depth Charges would be dropped, spaced 60 feet apart. The Gremlin low altitude bombsight, or equivalent, shall be used. If the submarine submerges to the extent that a Class A attack is not possible, or if the Class A attack is unsuccessful, MAD Class C attack shall be commenced immediately at an altitude of 100 feet. As the plane approaches the point of disappearance, the bombardier and MAD operator shall watch for a signal on the MAD meters; and, if this signal should come before or after the navigator calls "Slick" into the interphone system, they shall give the cue, "Flare", and fire a retro flare on the crest of the first swing of the MAD meters. The MABS will automatically fire if set properly. The bombardier and MAD operator should, however, be prepared to fire manually. If no signal is received, a trapping procedure is commenced. If a signal is received, the point of contact shall have been marked with a retro flare, and the cloverleaf tracking procedure shall ensue. If contact is lost on the second leaf, the trapping circle shall be commenced. These procedures are later herein described.
	The co-pilot during a tactical operation shall concentrate on the proceedings and assist the pilot as much as possible to avoid a mistake in flying the patterns. He shall also, at the Pilot's discretion, see that all members of the crew are at their proper stations and that the retro flare, MABS, and sonic buoy equipment are ready for action at all times during the flight. He shall also keep the compass properly set to enable the pilot to fly the required headings.

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	49.


	The pilot shall be in command of the entire operation, and therefore he must be thoroughly familiar with the whole procedure. He must make absolutely sure that every member of the crew thoroughly understands his job. If he fails to receive proper instructions during an operation, or if some member of the crew fails to do his part, a costly error may result. One mistake can spoil an entire operation. In flying the trapping circle the pilot shall drop slicks of float lights every 45 degrees and as often thereafter as is necessary to properly mark the circular course. The pilot is provided with a push button for this purpose. In smooth water Mark V float lights are desirable. The slick dropper shall be loaded by the engineer with the proper choice of markers immediately after take off in accordance with the pilot's directions. In flying the trapping circle, the pilot shall, if no contact has been made after the first 20 minutes, order the engineer to drop sonic buoys. These shall be dropped every 90 degrees on a 2-1/2 mile circle in line with the center of the original circle and the four cardinal points of the compass.
	If a stronger signal is heard from one sonic buoy than the other, the new trapping circle shall be started using this sonic buoy as the center.

	CLOVER LEAF PATTERN
	Each clover leaf pattern allows two runs down the submarine's course and two runs at right angles to his course. Each turn of this pattern os270 degrees to the left. These turns shall be executed as quickly as possible. The altitude shall be as near 100 feet as possible. The first two runs should establish the course of the submarine. The point of successive contact will probably advance between 200 and 600 feet per minute, corresponding to submarine speeds of from 2 knots to 6 knots. A ground speed of 120 mph is recommended, and the time delays in the retro flare and the retro bomb release circuits should be adjusted for this speed. The MAD operator shall during the first four passes over the submarine determine the polarity of the stern magnetic signal when running up the course of the submarine.
	The clover leaf pattern shall be flown a sufficient number of times to mark accurately the course and determine the polarity of the field at the stern of the submarine in order that the pilot may fly directly over the submarine on an effective bombing run. One pattern consisting of four passes may be sufficient if the flares line up well. It is advantageous to commence up course type runs as quickly as possible. This will allow full use of the left-right properties of the MAD equipment.
	The accuracy of the tracking depends on the skill of the pilot, co-pilot, and navigator in flying the pattern properly at a ground speed of 120 mph and upon the bombardier in setting the O-type MABS units to fire at the proper instant.

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	50.


	The bombing run is made when a sufficient number of passes have been made over the submarine and good MAD indications have been secured. This having been done, a reasonably straight row of flares should be visible. The bombing run is then made up the line of flares which indicates the course of the submarine. The bombardier shall have set the thresholds of the MABS units to a point where a signal of the proper polarity and 75 per cent as large as the largest of those received in tracking will trigger the retro bombs. The bombs will not therefore be triggered unless the bombing run is made directly over the submarine, and when the signals from both wing tips are approximately equal. On the bombing run a flare should always be released, as the first bombing run may be offside, and another run may be necessary. The MAD operator should note whether the airplane passed to the right or left of the target and so inform the pilot and navigator in order that correction may be made on the following bombing run.

	THE TRAPPING CIRCLE

	The trapping circle is normally established by flying in a straight line past the computed point of submergence for a period of 21 seconds after the word slick has been called on the interphone by the navigator. The navigator times this run and informs the pilot when the 21 seconds have elapsed, whereupon the pilot drops a slick or a smoke flare by means of his slick dropper release button. The radius of the trapping circle is thus established, and the pilot turns to the left and flies in this circle, dropping slicks or flares every 45 degrees and as often thereafter as is necessary to mark the contour of the circle. If it is necessary to drop sonic buoys, the pilot, co-pilot, navigator, and bombardier may turn their interphone switches to the R-1 position and listen to the sonic buoy receiver while the bombardier tunes from sonic buoy to sonic buoy. If the submarine is moving within the range of a buoy, its sounds should be heard and a new trapping circle shall be established, as previously outlined. When the submarine attempts to leave this second circle, its speed will probably be reduced, and there is a very high probability that it will be detected by the MAD equipment when trying to escape from the circle. It will be noted that, when contact is established by means of the trapping circle, the heading of the submarine is approximately known, since it is escaping from the trapping circle in a known direction which may be assumed to be on a line bearing from the center of the circle through the point of contact.
	The Clover Leaf Pattern is commenced in accordance with Figure 3, as soon as a MAD contact is established on the trapping circle.
	d. MAD TACTICS WITH B-18's AT KEY WEST:
	(1) The B-18's accomplished 21 MAD tactical missions at Key West. The flights involved the carrying out of full scale tactics

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	51.


	in detecting, tracking, and attacking the submarine by the use of Radar, Mark VI MAD (Mark VI MABS in the missions flown with B-18 37-470 and 37-538), sono buoys, green flourescein slicks, Mark V retro flares, and subcaliber Mark I retro bombs.
	(1) Procedure in flying the missions was as follows:
	(a) The S-15 slowly circled on the surface at seven knots. Upon seeing the plane making an attack run, it crash dived without reduction of speed in one minute and forty seconds, continued for two minutes at six knots, at which time it was 100 feet, and thereafter proceeded at four knots, performing evasive tactics. The submarine remained submerged for one hour and a quarter, while the plane carried out searching tactics.
	(b) The plane picked up the submarine on its radar from a patrol altitude of 1500 feet and a distance of ten to fifteen miles. It homed on the submarine, making full use of cloud cover and sun, planning to cross the point of submergence at about 100 feet altitude. In the event that the pip on the radar screen disappeared, the navigator and radar operator were prepared to make a timed run to the point of submergence, unless the submarine had already been seen visually. An attempt was made to fly in along the course of the submarine so that the ensuing clover leaf tracking procedure would be oriented properly with respect to the course of the submarine.
	(c) Upon crossing the presumed point of submergence, the plane dropped a slick, and, if a MAD signal were received, a retro flare would also be ejected.
	(d) In cases where a MAD signal was received, the plane executed a 270 degree clover leaf turn to the left, aiming to cross the course of the submarine some distance in front of the first retro flare. 270-degree clover leaf turns were continued in this manner until two had been made without MAD contact, or until six to eight flares had been dropped so that a bombing run was possible.
	(e) In the event that no MAD contact was received upon crossing the presumed point of submergence, or in the event that two 270-degree clover leaves had been executed without MAD contact, the plane would follow a trapping circle procedure. A trapping circle one and one half miles in diameter, which may be flown in one minute and forty seconds, was laid down about the point of the last contact as marked by slick or retro flare. This trapping circle wa small enough to prevent the submarine from passing through the search width of the Mark VI MAD apparatus, namely, 500 to 700 feet, provided it was not going more than 4 about 4 knots, the normal speed of the submarine after having been at escape depth for some time. The contour of this circle was marked by four or more green flourescein slicks so that it might be flown accurately.

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	52.


	(f) The trapping circle was flown for twenty minutes unless another MAD contact was received. At the end of the twenty minutes, sono buoys were dropped from 150 feet at the North, South, East and West points on the outer edge of the circle. These buoys were at the same or at four different frequencies and were listened to in succession. Two slicks were dropped with the sonobuoys so that they might be found again. If propeller and engine noises were heard on one or more of the sono buoys, the plane continued to fly the same trapping circle for ten minutes more, paying particular attention to the vicinity of the active buoy. If no MAD contact was received on the original trapping circle in this time, a new trapping circle was established around the loudest sono buoy. The same tactics were followed around this circle as around the previous circle.
	(g) When a contact was received on the trapping circle, a retro flare was expelled, and a 270 degree to the left clover leaf tracking procedure was begun again.
	(h) When six to eight retro flares had been dropped, marking the course of the submarine accurately, a 360 degree turn to the left was executed, and the plane made a bombing run down the line of the last few flares, paying particular attention to the left and right indication. If the indication was too much to the left or right, no bombs were dropped, but another flare was expelled and another bombing run made. When a satisfactory bombing run was being made the retro bombs were expelled in two ripples of six bombs each, automatically or manually, upon the peak of the MAD signal.
	(i) In the event that the submarine heard concussions on the hull, it expelled a yellow or black smoke flare, noted the time of the concussion carefully and notified the escort vessel sonically the escort vessel in turn radioing the information to the plane.
	e. MAD TACTICAL SEARCHES WITH B-24'S:
	Four MAD missions were accomplished in the B-24D. Since this plane was not equipped with either retro flare tubes or retro bomb rails, flourescein slicks and smoke flares were used instead. The tactics used were the same as those performed by the B-18's except that the B-24D is capable of making three or four clover leaf patterns after losing contact rather than the two as in the case of the B-18.

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53.

f. TABLE OF MISSIONS:

Table I

Resume of MAD Tactics, RB-18B

21		Tactical problems were run over submarine.
11		Resulted in hits on the submarine; all attacks were successful.
5		Failed because of improper tactical procedure by the crew.
4		Failed because of breakdown of MAD equipment or related circuits in flight.
1		Failed because of a premature dive of the submarine before the problem began.

Resume of MAD Tactics, B-24D
4		Tactical problems were run over submarine.
2		Were successful trackings.
2		Failed because the Odograph was being used instead of slicks.

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54.

Table II

Detailed Results of RB-18B MAD Tactics

				No. Bombs Dropped
Date	Run No.	Number of Trackings*	Successful Attacks	Improper Tactics by Crew	Equipment Failure	Submarine Error
May 18	1	1			MAD
	2	0				Premature Dive
	3	0			MAD

May 19	1	1		1
	2	2	1
	3	0			MAD
	4	3	1
	5	2		1

May 20	1	3	1
	2	1	1
	3	1	1
	4	1	1
	5	1		1

May 21	1	2			MAD
	2	2	1
	3	1	1

May 24	1	2	1
	2	1	1
	3	2		1
	4	2	1
	5	2		1

Total	21		11	5	4	1

Whenever bombs were dropped, the submarine reported hits.

* 0 Indicates no MAD contact on first cross

1 Indicates one clover leaf procedure

2 Indicates two clover leaf procedures separated by a trapping circle

3 Indicates three clover leaf procedures separated by trapping circles.

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55.

The courses on which MAD bombing runs were made were:
(1)	170°	(4)	30°	(7)	150°	(10)	180°
(2)	180°	(5)	180°	(8)	40°	(11)	0°
(3)	150°	(6)	130°	(9)	0°

Detailed Results of B-24D MAD Tactics

Date	Flight No.	No. Trackings	No. Successful Trackings	Unsuccessful on Account of Dependence on Odograph
May 18	1	1		1
May 19	1	1		1
May 20	1	2	1
May 21	1	3	1

TOTAL	4		2	2

This B-24D was not equipped with retro flare of retro bombs and only one wing tip MAD installation was working.

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	56.


	g. MAINTENANCE AND OPERATION:
	(1) Tentative Service Requirements on Mark VI MAD:
	The six MAD Mark VI dual installations on B-18 airplanes #37470, 37538, 38590, 37561, 39021, and 37593 were made at Langley Field. First production MAD units were employed. The cable installations were made during April and May, 1943, by Langley Field Sub-Depot Engineering electricians and sheet metal men under the direction of Lt. Erickson of Wright Field. Since these were the first installations, many small errors were made in the cabling details which included cold solder joints and poorly insulated plug connections. As there are cable junctions in the wings in these installations, failures at these points in the field were very difficult to locate and repair. The elimination of such junctions or better workmanship in their installation is the obvious solution. Extremely close supervision of all phases of each installation is necessary. A one week course should cover cabling, plug wiring, soldering, and junction box wiring. The prospective supervisors should actually perform the type of work required until they are thoroughly competent to direct, test, and judge the workmanship of electricians and sheet metal workers in connection with MAD installation work. Airborne Instruments Laboratory should be able to supply a suitable instructor.
	A comparatively high rate of failure was experienced with the A and B units of first production. The troubles were largely due to defects in assembly. The units have now been shaken down to the point that they are giving reliable service. Two sets of A and B units of newest manufacture were flown to Boca Chica Field, from Mineola, and installed on #37470 on May 17th. These units have given no trouble whatever to date.
	Approximately 190 man hours, civilian and military, were required to service the MAD and MABS equipment for a period of seven days.
	The estimated requirements for servicing a squadron of MAD and MABS equipped airplanes flying daily missions are as follows:
	(a) Personnel:
	1. MAD officer thoroughly trained in MAD field work.
	2. NDRC civilian MAD engineer with field experience until suitable Army personnel are trained.
	3. Six MAD trained enlisted men with at least two months' MAD field experience.

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	57.


	(b) Equipment:
	1. One complete set of spare MAD A, B, and C and head units, cables, and racks for a ground set-up.
	2. Four extra heads.
	3. One complete set testing equipment as specified for Mark IV MAD.
	4. Complete spare small parts for groups of six, twelve, and eighteen airplanes. This shall be completed on the basis of requirements after a larger series of tests than were possible at Key West. These tests are being carried on at Langley Field.
	An outline of the service troubles encountered on the Key West operations are listed below:
	(a) Magnetometer Heads:
	1. Loose rear end bolts on birds.
	2. Side bearing nuts on heads loosening.
	3. Belts loosening and bearings cut due to excess vibration caused by running up motors on ground and shock from landings with flat tires.
	4. Scored bearing races and balls. Three ball bearing races had to be returned by lathe.
	5. Front shock mounts gradually tended to fail and the back lord mounts, to break.
	6. One head was destroyed because of a landing with a flat tire.
	(b) A, B, and C unit failures:
	1. One burned out motor generator due to failure of bakelite insulation in "c" unit female plug section.
	2. Three "A" unit partial failures due to defective 12SL7 and 6K5 tubes.
	3. One 6L6 tube in "B" unit developed a heater to cathode short circuit.
	Since the larger part of the trouble encountered has been in the heads, it is recommended that a removable bird be designed in order that the heads may be placed on the wing tips only at the times MAD missions are flown. With this precaution, a satisfactory head life may be expected. A head that is easily removable from the bird would perhaps be a satisfactory alternative. However, it is recommended that ultimately a new head be designed which will withstand severe shocks and vibrations.

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	58.


	The use of heavier rubber shock mounts, or the present style mounts constructed in such a manner that they could be easily replaced would be a temporary solution to the problem.
	(2) Effect of B-18 and B-24D electrical systems on MAD:
	The 14V voltage regulator employed in B-18 airplanes is of the vibrating type. It is extremely unreliable because the contacts frequently stick or fail to make contact even though the regulators are serviced in accord with recommended practice. When these contacts suddenly stick or open after having been stuck, a magnetic field builds up or collapses with resultant interference to MAD equipment. Two remedies are possible. The easiest one is to replace the regulators with a carbon pile type which gives extremely smooth control. As there were available no 14V type carbon pile regulators to our knowledge, a 28V type was converted at Boca Chica Field and used with complete success. Data on this regulator is attached. The most satisfactory method of correcting the effects of varying magnetic fields on the MAD equipment seems to be the elimination of magnetic loop circuits in the electrical wiring of the B-18 airplane. A complete two wire system with the negative 14V and 28V leads grounded at one point only should completely eliminate this type of MAD trouble. The present adverse effect on the airplane compass caused by the proximity of 28V leads to the compass would also be eliminated.
	The ideal combination would be carbon pile regulators on both the 14V and 28V system in addition to a complete two wire system. This modification would result in fewer MAD failures and false MAD signals and would at the same time save many 14V generators and 12V batteries which have failed in large numbers due to the defective operation of the 14V regulators.
	The B-24D, if equipped with MAB, should also be equipped with carbon pile 28V regulators. These may be installed very quickly since they may be plugged in in place of the General Electric silver finger type generally employed. A two wire system, while entailing more complication in the B-24D airplane, is advisable.
	(3) Double O Type MABS:
	During the maneuvers at Key West, it was found that the single O-type MABS unit connected to one Mark VI unit does not give complete automatic retro flare release during tracking procedures. Unless the threshold is closely set and the bombing run altitude is exactly correct, the single O unit, the detector approximately 100 feet further away on the opposite wing tip is likely to pick up no signal above the noise level. In this event, the retro flares must be released manually.

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	59.


	A solution to this problem is possible with the use of a T-type MABS unit or two O boxes. Since the O-type MABS is in production and has been tested, its use in pairs is recommended for both B-18 and B-24 airplanes. Experience has indicated the necessity of the double O box installation or an equivalent set of apparatus.
	With two O units arranged with retro flare release contacts in parallel and retro bomb release contact in series, and arrangement is secured that gives in effect a "yes-no" circuit, range control, and threshold control. Coupled with the use of two tape recorders to indicate direction, nearly all the advantages of the T-type MABS are secured.
	With one Mark VI set of O-type MABS out of commission, single unit operation is possible since the units may be rendered entirely independent of each other by means of one switch. Detection, tracking, and bombing may thus be carried on with only one unit in operation with somewhat less probability of contact and with less accuracy in bombing runs than is possible with two units.
	Two O-type units mount vertically on the bombsight mount in the bombardier's compartment of the B-18 airplane. Two units may be mounted atop the rack type double Mark VI MAD assembly of the type used in B-24D #123684.
	(4) Magnetic Compensation Requirements of B-18 and B-24 Airplanes:
	Magnetic compensation was found to be unnecessary on the B-18 airplanes equipped with Mark VI equipment. The noise encountered due to maneuvers during the tactics flown was on the order of 3 gammas with straight noise of approximately 1/2 gamma. This is not considered objectionable if proper precautions are taken in turning off the bomb and flare release switches of the O-type MABS during the steep turns used in the clover leaf tracking procedure.
	The Mark VI equipment on B-24D #123684 gave 7 gamma noise on clover leaf maneuvers with 1/2 gamma noise on level flight. Magnetic compensation is desirable in the B-24 installations, although not perhaps absolutely necessary if a skilled operator is employed.
	(5) Slick Dropper:
	With proper servicing the slick droppers were found to operate in a satisfactory manner in the B-18 airplanes. Due to the high salt content in the air at Boca Chica, the slick dropper electrical relay release contact corroded rapidly. By operating the dropper mechanism several times before a flight and making any contact adjustments

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	60.


	necessary, the possibility of failure is minimized. During the first few days of the tests at Boca Chica, the newly installed slick droppers gave trouble due to the fact that a suitable service routine has not been set up. The records show that this trouble was overcome by proper servicing.
	The operation of the slick dropper in the B-24D #123684 was not satisfactory with the rear hatch open since no. 5 slick would blow upward out of its compartment and break in the airplane. After this shortcoming was discovered, the No. 5, or rear position, was not used. In future installations, a wind shield would be installed at the forward underneath side of the doppler outside the airplane. Tests are being carried out to determine if this windshield will correct the difficulty.
	Approximately 18 man hours were consumed during a period of seven days in adjusting and servicing eight slick droppers.
	(6) Electrical Retro Bomb and Retro Flare Releasing System in B-18 Airplanes:
	During the first four days of the tests at Key West, difficulty was experienced with both retro bomb and retro flare firing circuits. It was possible to fire only approximately 50 per cent of the retro bombs and occasional retro flare misfires occurred.
	The wiring of the circuits with the exception of one airplane checked properly, and firing of one or two retro bombs at a time could be accomplished on the ground using any combination of rails. The misfires continued until the system was changed from 14V operation to 28V operation. After the change only one retro bomb failed to fire, and this was due to a broken connection in the retro bomb connecting plug. While the retro bomb and retro flare firing arrangement was designed to operate on the 14V airplane system, it is evident that the resistively and voltage drop in the wiring to the rails are too great when all of the bombs are fired in two closely spaced ripples. A larger wire size or a higher voltage was needed. The 28 volt connection was the quickest solution, and the reliability of the firing system may now be considered to be completely satisfactory. All six of the B-18 airplanes used in the tests are now changed over for 28 volt operation. The reliability of the retro flare firing circuit was also improved by the change, no misfires having occurred when using a firing voltage of 28 volts.
	The time delay relay in the retro flare and retro bomb control box will give a maximum delay of approximately 0.1 second with all of the hold coil series resistance in the circuit. This delay is not sufficient, as it is felt that t delay of 0.3 seconds to 0.5 seconds would permit more range error in releasing the bombs. It is therefore recommended that mechanical delay type relay be used instead of the present electrical relay installed at this time.

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61.

(7) Radar and Communications:

The labor used in maintaining the radar, communications, and radio sonic buoy equipment employed during the tests was approximately as follows:

	Man Hours
	Daily Checks	Repairs	Total
Radar	50	79	129
Communications	96	14	110
Sonic Buoy	21	0	21

Radar testing and repair was done by four radar mechanics. A table showing radar performance and maintenance time for each airplane follows as well as a list of repairs made.

7561	Replaced magnetron and returned.
7561	Transmitter defective because of burned out transformer. Replaced transformer.
8590	Equipment ban on ground check after airplane had ground looped on take-off. Replaced two fuses (MIT).
7470	Transmitter defective. Rewound transformer (MIT).
3708	Refitted wobble joint connection in transmission line and returned.
3684	Found wires in cable reversed and wobble joint not properly fitted. New cables had just been installed by Langley Sub-Depot. This work done by personnel of Boca Raton Field.

MIT radar sets required the most maintenance. SCR-717A operated perfectly after some initial trouble in one installation was corrected.

Communications checks were made daily by the radar operators. A list of repairs made follows. In only two of these cases did communications failure cause difficulty in tests.

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62.

Communications Repairs

3679	Command transmitter reported out. Off frequency.
7561	Command set and interphone out. Replaced dynamotor fuse.
7561	Radio operator's interphone out. Repaired bad station box.
7464	Command set reported out. Antenna switching relay contacts adjusted.
8590	Co-pilot's headset disconnector cord repaired.
7538	Co-pilot's headset replaced.
684	Replaced trailing wire replaced.
7593	Liaison set out. Replaced UT-4C modulator tube.

Radio sonic buoy equipment was checked daily by the radar operators. No repairs were necessary.

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63.

RADAR PERFORMANCE DURING TESTS AT KEY WEST

May 16 through May 27, 1943.

							Man Hours Maintenance
Plane Number:	Type of Radar:	No. Flights using Radar:	No. Flights Satisfactory:	Total Hrs. Flown:	Hrs. Operated on flights:	Hrs. Operated On Ground:	Routine Checks:	Repair
8590	MIT	4	4	6:10	5:00	3:10	5:10	1:30
7470	MIT	7	7	12:30	10:15	3:10	3:00	25:00
7593	MIT	1	1	1:45	1:30	2:50	12:25	---
7538	MIT	3	3	4:30	3:00	2:20	6:45	---
7561	MIT	3	1	11:30	4:05	4:50	1:00	13:45
7464	517-C	3	3	5:00	4:15	3:20	6:55	---
8587	517-C	RADAR NOT USED
7465	517-C	RADAR NOT USED
3708	517-C	2	1	3:55	2:50	3:00	3:15	6:00
3684	717-A	5	5	9:00	6:45	8:00	5:25	33:00*
3679	717-A	4	4	4:20	2:35	3:00	6:15	---
9021	NO RADAR
TOTAL		32	93%	58:00	40:15	33:40	50:10	79:15
AVERAGE (per airplane)				6:29	4:28	3:44	5:34	15:51

* All one maintenance job made necessary by faulty installation of new cables at Langley Field.

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	64.


	g. DETAILED FLIGHT RESULTS OF MAD TACTICS
	(1) FLIGHTS OF MAY 18, 1943:
	(a) RB-18B #37-561
	Take-off: 1400
	Pilot: Captain Herrick.
	The plane received Radar contact at 18 miles, ran in over the spot where the submarine had submerges and received a MAD contact on the first cross. Upon getting no further MAD contact, they adopted a trapping circle. The submarine then surfaced for an unknown reason and then submerged again. Another short run-in was made, and another MAD contact developed. Not receiving any further MAD contacts, a trapping circle was again established which was continued without success. The submarine surfaced outside the trapping circle. The reasons for this failure were malfunctioning of the voltage regulator and generator supplying power to the MAD.
	(b) RB-18B #38-590
	Take-off: 1505.
	Pilot: Lt. LeVan.
	The plane arrived at the sanctuary to find the S-15 submerged. Contact was made with the escort, and the submarine was brought to the surface, but it submerged again almost immediately, staying down for about 25 minutes. Apparently the submarine mistook a PBY in the area for the RB-18B. The submarine finally was again surfaced on request, but it again submerged prematurely. However, the plane made a run on the spot where the submarine had been last seen and dropped a slick where the submarine was thought to have been last seen. No MAD indication was received. A trapping circle was established around the slick. A MAD indication was thought to have been received at one point on the trapping circle, and a retro flare was dropped manually. A clover leaf procedure was then followed. No further indications were received.
	(c) RB-18B #37-470.
	Take-off: 1630.
	Pilot: Captain Herrick.
	The plane had a front tire blow out on take-off and was unable to proceed.

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	65.


	(d) RB-18B #37-561
	Take-off: 1725.
	Pilot: Lt. Biddison.
	A visual sighting was made, and the plane ran in to the presumed point of submergence, dropping a flare although it received no MAD signal. It then adopted a trapping circle. They thought they received a MAD signal at a point on the trapping circle. They dropped a flare and a slick and went into a clover leaf procedure, but received no further MAD contacts. The sono buoy was also dropped near the point where the MAD contact was thought to have been received. However, no propeller noise was heard, merely microphonic and water noises. On this flight the 12-volt voltage regulator was irregular, producing noise in the MAD; the interphone system was bad, and the slick dropper was inoperative so that it is not surprising that contact was not established.
	(e) B-24D #41-23684.
	Take-off: 1755.
	Pilot: Lt. Easterling.
	This flight was intended to determine the usefulness of MAD in a B-24D. One of the aids to the procedure is the Odograph which it is hoped will be useful in marking down the track of the plane. B-24D #23684 which is used in this test is not equipped with retro flare firing tubes or retro bombs. Slicks are used in lieu of retro flares, and the bombing can only be simulated. Otherwise the procedure is the same as with the RB-18B. The B-24D made a run in from 11 miles after radar contact and crossed the point of submergence of the submarine two minutes after the submarine had submerged. This run was timed from six miles away when the Radar pip disappeared. A MAD signal was received on the first pass and two more MAD contacts were developed in the ensuing clover leaf pattern. However, the submarine was lost at this point. No slicks were used in this procedure since it was hoped that the Odograph would enable the plane to stay on the proper pattern. However, the contact was lost as the Odograph drifted off due to change or mistake in wind. It would seem that retro flares or slicks are necessary to keep the plane from straying away from a contact. It is expected that future tactics will involve the dropping of slicks. The right wing tip MAD was rather noisy and signals were hard to recognize.
	(2) FLIGHTS OF MAY 19, 1943:
	In these tests the submarine was to dive upon sighting the plane, preserving normal speed conditions, namely, seven knots for one minute and forty seconds, six knots for the next two minutes at the end of which time it was to be at 100 feet and then three to four knots

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	66.


	thereafter. A northerly or southerly course was to be followed, but the plane crews did not know this. Each plane had only one hour to track and attack the submarine with subcaliber retro bombs which were loaded with shotgun shells for recognition. The firing pins on these shells are specially wrapped with Scotch tape to prevent firing on the surface of the water.
	(a) RB-18B #37-470.
	Take-off: 1145.
	Pilot: Captain McKay.
	The submarine was picked up by the Radar at the range of four miles and 1000 feet. When the plane passed over, the submarine was still visible, and a Class A depth charge attack could have been made. A MAD signal was, of course, received at this first pass, which was 1000 feet. A retro flare was dropped automatically by the MABS. A clover leaf tracking procedure was followed. On the first three clover leaves no further MAD indications were received, but the clover leaf tracking procedure was continued, and in all about a dozen MAD indications were received. These appeared to lie on two lines perpendicular to each other which was so confusing that no bombing run was made. It is suspected that there may have been another submarine in the vicinity. The submarine eventually surfaced along the northern line of retro flares.
	Since the next plane had not arrived on the scene, the submarine was requested to submerge again, and the plane made another Radar run very similar to the first. A MAD indication was received on the first pass, and six petals of a clover leaf tracking procedure were laid down, but no further signals were received. Therefore, six 3-1/2 minute trapping circles were executed around the retro flare and slick marking the first signal. The submarine apparently managed to get through the trapping circle but she was discovered when she pushed up her periscope momentarily and then dived again. A clover leaf tracking procedure was followed with four or five retro flares being dropped, and then a bombing run was made with six bombs being released. The remaining six, which were supposed to drop 3/10ths of a second later, or about 55 feet farther along, were not released because apparently the 12-volt system was too overloaded to do the work. The bombs were dropped at 1410, and the submarine surfaced at 1420. The submarine reported hearing a concussion at 1410, the submarine then being at about periscope depth because of some operating trouble. The plane was on course 170 degrees during the bombing run.
	Sono buoys were dropped during the first tracking procedure but gave only water noises. They were apparently dropped somewhat prematurely.

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	67.


	(b) RB-18B #37-538.
	Take-off: 1345.
	Pilot: Lt. Haffner.
	The submarine was seen visually at a distance of seven to eight miles and began to submerge when the plane was about one-half mile away. Its conning tower was still visible as the plane passed over. The MAD apparatus apparently was out of commission at this time, because it gave no indication of the visible submarine directly below. A two-mile trapping circle was thrown around the point of submergence. About 20 minutes after the tactics were commenced, two sonobuoys were dropped north and south. Loud propeller noises were heard from the southern buoy and at the beginning, faintly from the northern buoy. The trapping circles were continued until sixteen in all had been made. At that time the submarine surfaced south of the southern sono buoy.
	This flight is interesting because it illustrates the usefulness of sono buoys.
	(c) RB-18B #37-561.
	Take-off: 1500.
	Pilot: Lt. Biddison.
	The radar was inoperative so that a run was made in from a visual sighting fast enough so that a Class A attack would have been possible. MAD indication was obtained on the first pass and on the first and second leaves of the clover leaf tracking procedure, but no indications were received on the last two leaves. A trapping circle was thrown around the three retro flares. Eventually an indication was received on the edge of the trapping circle, and a clover leaf tracking procedure was again carried out, but the submarine was again lost before a bombing run could be made; thereupon, a second trapping circle was laid about the last flare dropped. The submarine was again contacted and its course marked by five or six retro flares released manually as a clover leaf procedure was followed. Two bombing runs were made. No bombs were dropped on the first run because of a somewhat low ground speed. On the second run the retro bombs were manually released,only six firing, the second six not being released because of the overloaded 12-volt system. The submarine reported hearing one concussion at 1555 and two more concussions a minute or two later. There were two explanations of the second two concussions: the bombs may have exploded on the bottom, which at this point is more than 100 fathoms; or the hits were simultaneous but reported on unsynchronized watches. The slick dropper was out completely, and neither retro flares nor retro bombs are dropped automatically in this plane. The bombing run was made on course 180 degrees.

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	68.


	(d) RB-18B #37-593.
	Take-off: 1625.
	Pilot: Lt. McGehee.
	The submarine was seen visually at ten miles, the Radar being able only to pick up the escort. When the plane passed over the submarine, a Class A attack would have been possible. MAD contact was received at the first pass at an altitude of 100 feet. Two other MAD contacts were received on the next two clover leaves, but the submarine was then lost. The plane continued to do additional clover leaves for five minutes and then took up a trapping circle about the last retro flare which it held for twenty minutes at which time two sono buoys were dropped. On the northern sono buoy, shaft and motor noises were heard. Thereupon a trapping circle was laid about the sono buoy. However, it was hard to set up this trapping circle because slicks had not been dropped to mark the spot. Clover leaves were also flown around this northern sono buoy. This submarine surfaced outside the trapping circle and clover leaf patterns. This flight illustrated the fact that it it probably unwise to adopt a trapping circle around an active sono buoy when the problem is restricted to such a short period. It would have been better to stay on the original trapping circle for ten or fifteen minutes longer, paying close attention to the area near the active sono buoy. On this flight some trouble was had with retro flares not firing.
	(e) B-24D #41-23684.
	Take-off: 1745.
	Pilot: Lt. Easterling.
	This flight was intended to test the possibility of tracking with MAD in a B-24D airplane. This plane is not equipped with retro flare or retro bomb tubes. The course would have to be marked by means of slicks or smoke lights and by using the Odograph. The MAD equipment on only one wing tip was working properly. The submarine was seen visually about ten miles away and had been submerged for about 22 seconds when the plane passed over. A MAD signal was received at an altitude of about 200 feet on this pass. A slick and a smoke light were dropped to mark the point of this contact and a clover leaf procedure was started which resulted in no more contacts. This crew relied almost entirely on the use of the Odograph to plot their course, which was apparently unreliable because the wind changed speed and direction, making the Odograph trace drift off. It seems unlikely that the Odograph is dependable enough (because of the importance of wind) to do MAD tracking which must be done on the basis of flares or slicks on the sea itself. The Odograph in MAD tactics might bring back a fairly reliable record of exactly which courses

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	69.


	have been followed, although very accurate winds must be put in even for this purpose.
	(3) FLIGHTS OF MAY 20, 1943:
	For these exercises the submarine skipper had been instructed to use evasive tactics at will finishing each set of maneuvers on a north or south heading. This procedure was unknown to the airplane crews.
	(a) RB-18B #37-470.
	Take-off: 1140.
	Pilot: Captain McKay.
	Since the Radar was out, a visual run-in was made from about five miles. The plane passed over the submarine while the conning tower was still visible. A clover leaf tracking procedure was followed which produced three contacts on which retro flares were automatically expelled. The submarine was then lost, and a one minute and forty second trapping circle wa set up, marked at the north, south, east, and west points by slicks. On the seventh turn around the circle a MAD contact was again received and clover leaf procedure followed, but contact was again lost after several leaves. Thereupon, a one minute and 35 second trapping circle was set up and the submarine was again contacted on the fourth turn about the circle. The clover leaf tracking procedure was then successfully followed and several bombing runs were made until the proper left and right indication was received. The retro bombs were manually fired at 1300. All even bombs held up and one odd bomb held up. However, the submarine skipper reported a hit. The escort vessel reported that the submarine had been hit once. One interesting thing about this run is that the attack run was made while the submarine was heading on course 150 degrees. The submarine log shows:
	Dived on course, 350° at 1215.
	Steadied on course, 180° at 1229.
	Steadied on course, 150° at 1242.
	Surfaced at 1324.
	(b) RB-18B #37-538.
	Take-off: 1305.
	Pilot: Captain Herrick.
	This plane was proceeding away from the area at an altitude of 200 feet to commence its exercises when the submarine suddenly began to submerge 2-1/2 miles away. The plane immediately turned and made its first pass about a minute after submarine had disappeared, a slight swirl being the only thing visible. A MAD contact was received upon the first pass at an altitude of 100 feet. A clover leaf procedure was followed and about ten contacts were

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	70.


	received, retro flares being fired both manually and by MABS. At 1403 a bombing run was made, six bombs being dropped, the delay circuit not firing the second string of six. The submarine reported a concussion in the torpedo room at this time. The submarine was reported on course 30 degrees on the bombing run, and the plane was going on course 19 degrees on its bombing run. The S-15 log shows:
	Dived on course, 000° at 1335.
	Changed to course, 30° at 1358.
	Surfaced at 1421.
	(c) RB-18B #38-590.
	Take-off: 1420.
	Pilot: Lt. LeVan.
	A Radar run-in from seven miles and 500 feet was made. The submarine had been submerged for about 30 seconds as the plane passed over. A MAD signal was received on the first pass at an altitude of 100 feet, a retro flare being released manually. A clover leaf procedure was begun and successive MAD contacts were received with retro flares being dropped each time. Careful notice was paid to left and right indications on each pass. When enough flares had been dropped to mark a bombing run, the run was made and the bombardier manually released the six odd bombs, only five of which fell. This was at 1453. According to the submarine log a concussion was heard in the torpedo room at 1457, the discrepancy being due probably to difference in watches. The submarine threw up a black smoke bomb. The plane continued to track the submarine by throwing a trapping circle around the bombing point, upon which the submarine was eventually indicated again. A clover leaf tracking procedure was set up and about seven successive contacts followed, marked by manually released retro flares. A bombing run was again made, the six even bombs being dropped. A hit was reported by the release of a black smoke bomb. The submarine log, as reported, showed course 180 degrees. The first bombing run was at 180 degrees, the second, at 130 degrees, as reported.
	(d) RB-18B #37-561.
	Take-off: 1555.
	Pilot: Lt. Biddison.
	The Radar set sensitivity was down. The submarine was seen visually at eight miles away and crossed at 100 feet on the first pass while its decks were still awash. The submarine skipper tried to get away at high speed, running in a generally easterly course in this case. At 1623 he submerged on course 160 degrees at seven knots and changed 4 minutes later to a course 160 degrees at seven knots and changed 4 minutes later to a course 60 degrees still at seven knots. He held this course and speed for 19 minutes

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	71.


	minutes at which time he changed his course to 30 degrees and six knots. Eight minutes later he changed his course to 330 degrees at four knots. Thirteen minutes after that at 1724 he surfaced. The plane made no MAD contacts after the first cross, although they did three clover leaves. They laid down a trapping circle and after six times around the trapping circle dropped sono buoys north and south. On the northern buoy microphonics and propeller noises were heard at first, but the propeller noises faded away quickly. They continued on their trapping circle for the rest of the problem. If our regular tactics of dropping four sono buoys had been followed, the submarine would have without a doubt been picked up on the easterly sono buoy and might have been trapped within a circle thrown around the buoy. Nothing was heard from the southern sono buoy. The S-15 may have gone through the trapping circle while the plane climbed to 500 feet to drop the buoys. It was later learned from the New London Sound Laboratories that 150 feet is high enough in a B-18. The S-15 might have been picked up at this altitude.
	(c) B-24D #41-23684.
	Take-off: 1745.
	Pilot: Lt. Easterling.
	A radar run-in was made from 16 miles at 1500 feet, and the submarine was crossed with its decks still awash. The plane made this successful run-in due to good use of cloud cover and flying down sun. The left wing tip installation was completely out of order. The plane followed the regular Sea Search tactics of using trapping circles and clover leaves, but, of course, was hindered by not having any retro flare tubes, being forced to resort entirely to slicks and smoke flares. A clover leaf procedure was followed after the MAD contact on the initial run-in and seven contacts were made over a period of about 15 minutes. Then a two mile trapping circle marked with slicks and smoke flares was instituted and held for 10 to 15 minutes. Eventually a contact was received on the circle and the submarine was held through successive contacts for about twenty minutes by a clover leaf procedure. The submarine was still under control when it surfaced. The Odograph provided a clear picture of the action, although a wind change caused it to drift somewhat. However, it is doubtful whether this procedure could have been followed successfully without using slicks and flares. The S-15's log was as follows:
	Dived on course, 80° at 1805.
	Changed to course, 200° at 1814.
	Changed to course, 000° at (no record)
	Surfaced on course, 000° at 1905.

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	72.


	(4) FLIGHTS OF MAY 21, 1943: (procedure same as May 19th)
	(a) RB-18B #38-590.
	Take-off: 1410.
	Pilot: Lt. LeVan.
	The MAD on the left wing went out as did the radio. The plane, therefore, landed in 25 minutes without proceeding with the problem.
	(b) RB-18B #37-561.
	Take-off: 1136.
	Pilot: Lt. Biddison.
	A Radar run-in was made from 5 miles and altitude of 500 feet and a Class A attack would have been possible, on the first pass. A MAD indication was received on this pass at an altitude of 100 feet. Successive MAD contacts were made as clover leaves were executed, but although three bombing runs were attempted the right and left indications never seemed to be quite good enough to drop bombs. It was discovered after the plane had returned that the right wing tip installation had been gradually going out. Eventually the submarine was lost, and a trapping circle procedure was followed, the submarine eventually being picked up again. A clover leaf procedure was followed with four or five contacts and a bombing run set up. As in the previous case, left and right indications never seemed proper to drop bombs. The tactical procedure was very good. All retro flares on this plane are released manually by the bombardier. The S-15's log was not secured, but the navigator's plot showed a 180 degree course during the first tracking and about 150 degrees on the second tracking.
	(c) RB-18B #37-470.
	Take-off: 1500.
	Pilot: Captain McKay.
	A radar run-in was made from six miles and 1500 feet. A timed run was made on the submarine although it was not entirely necessary since the swirl was still visible from about 1-1/2 miles where the pip disappeared. The submarine had been submerged about 40 seconds when the plane passed over. A MAD contact was received on the first pass. The crew took into account that the swirl coasted off to the left indicating a probable right turn. Three indications were received on the first clover leaf procedure, and the plane executed five more petals after losing contact. It then set up a 1 minute 40 second trapping circle and got a MAD contact on the eastern edge of the circle after 1-1/2 turns. It was 12 minutes from the time of the last MAD contact to the time the trapping circle was assumed. The plane made four petals of a clover leaf, getting four

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	73.


	contacts in a row and then made a bombing run, but the MABS failed to release the bombs. They then made a second bombing run dropping two strings of six bombs manually, spaced with a 3/10th second delay between strings. The submarine sent up a black smoke signal indicating a hit. The submarine's log is not available, but the navigator's plot indicates he submerged about 135 degrees, circled around to the right, passing to the north of his submergence point, then turned east and eventually southeast. The bombing run was made on course 150 degrees.
	(d) RB-18B #37-538.
	Take-off: 1305.
	Pilot: Captain Herrick.
	This crew did not have enough time to run through their problem because of a transfer of passengers from the submarine to the escort vessel so they returned. They were scheduled to take off again at 1630, but hydraulic trouble prevented the flight.
	(e) RB-18B #37-561.
	Take-off: 1739.
	Pilot: Lt. Biddison.
	The Radar was not operating, but the submarine was sighted visually seven to eight miles away, and a run-in was made while the decks were still awash. A MAD signal was received on the first pass, and a clover leaf tracking procedure was followed. They made one bombing run, dropping 12 retro bombs in two sticks of six, spaced 3/10ths of a second apart. The submarine reported two hits. This whole tracking and attack procedure lasted only 15 minutes. The plane then made another 180 degree turn, got a MAD indication, and then adopted a trapping circle for demonstration purposes. At one point on the trapping circle a false indication was received which became apparent after two clover leaves. The trapping circle was again adopted, and eventually another MAD contact was received. They had three contacts on the ensuing clover leaf procedure, but the search was then abandoned because the retro flare tubes began to misfire. The crew made the observation that the Mark V retro flare does not light quickly enough namely two three minutes after striking the water, to allow a very fast tracking procedure to be made. The bombing run was made on course 40 degrees. Later the S-15 appeared to be on course 000 degrees.
	(f) B-24D #41-23684.
	Take-off: 1845.
	Pilot: Lt. Easterling.

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	74.


	A Radar run-in was made from ten miles and 1200 feet altitude. The submarine was still surfaced as the plane passed over due to the fact that the plane chose to approach in the sun. This crew kept an altitude of 100 feet to 150 feet on turns and dropped to 50 feet on the straight away. One MAD contact was received on the first clover leaf, but no further ones were received on the next three to four clover leaves. They then set up a 1 minute 40 second trapping circle and after five turns mad a contact on the circle. They followed a clover leaf procedure for three leaves, but received no contact so that they adopted a new trapping circle which they went around ten to fifteen times. They then dropped sonobuoys from 500 feet altitude to the north and to the south. The northern buoy was listened to for two turns before the bombardier realized that a buoy had been dropped to the south. He then listened to the southern buoy and heard rapid propeller noises dying away. The plane was about to set up a trapping circle around the southern sono buoy when the submarine suddenly surfaced, since the time was up, a short distance south of the southern sono buoy. They would almost certainly have picked up the submarine had they had time to follow a trapping circle around the southern sono buoy. As before, only one wing tip installation was operating on this plane, and they were forced to use slicks instead of retro flares, not having any retro flare installation. The interesting points in this experiment are the much larger speed at which a B-24D airplane can regain contact and the fact that sonobuoys apparently are extremely useful in regaining contact. The Odograph trace gives a good picture of the complete exercises. It was reset only once because of a wind change. The S-15 submerged on course 270 degrees, then apparently turned left, adopting course 90 degrees, and then took and kept course 180 degrees. This is a guess based on the Odograph trace.
	(5) FLIGHTS OF MAY 24, 1943:
	(a) RB-18B #37-470.
	Take-off: 0905.
	Pilot: Lt. McGehee.
	A run-in was made from seven to eight miles from 300 feet altitude with a Radar signal which gradually faded out. The submarine was first seen visually at a distance of about four miles, and only the periscope was visible as the plane passed over at 100 feet. A MAD contact was, of course, received as the plane passed over, and a clover leaf tracking procedure was followed, on which three more contacts were received. Contact was, however, lost and a one minute thirty second trapping circle was laid down around the last contact. On the eighth round of this circle MAD contact was received on the north edge. A clover leaf procedure was again followed, and after five leaves

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	75.


	with five MAD contacts, a bombing run was made, dropping bombs automatically by the MABS. Eleven bombs fell in two strings. The inboard bomb on the left wing held up due to bad connection. The bomb run was made at 0957, and the submarine released a yellow smoke bomb indicating a hit. Later, the captain of the submarine reported having heard two concussions. The S-15's log showed:
	Submerged to 100' depth 6.5 knots 0931.
	Steadied to course 000° at 3.6 knots 0930.
	The navigator reported the bombing run was made a 340 degrees.
	(b) RB-18B #37-538.
	Take-off: 1105.
	Pilot: Captain Herrick.
	A visual run-in was made from eight miles. As the plane passed over at 100 feet, the point of submergence, the swirl was still visible. A MAD contact was received on the first pass, and a clover leaf procedure was followed, getting seven to eight more MAD contacts. Bombing runs were then made, the first two or three being intended merely to drop flares. On the next four bombing runs the MABS failed to give automatic release so that another bombing run was made, and the bombs were dropped manually. The first run-in was made at 1125 and bombs were dropped at 1156 on a southwest course. The number one bomb on the right wing and the number six bomb on the left wing hung up. The submarine reported hearing one concussion in the torpedo room and another concussion in the motor room at that time. The S-15 log showed:
	Submerged to 100 feet 6 knots 1118.
	Course 180° 3.6 knots 1119.
	Surfaced 1210.
	The bombing run was reported as 172 degrees.
	(c) RB-18B #37-561.
	Take-off: 1220.
	Pilot: Lt. Coleman.
	The submarine was first seen visually at a distance of about ten miles, and the decks were still awash as the plane passed over at 100 feet altitude. The bombardier inadvertently released all the bombs manually at this point. The submarine reported a slight concussion was heard in the torpedo room at this time. After

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	76.


	the first MAD signal was received on the first pass, a clover leaf procedure was followed during which three successive further MAD signals were received. Instead of making a fourth clover leaf, the pilot made a 180 degree turn, and came back up the track of the submarine. No MAD contact was received on this pass, so a trapping circle was laid down. About ten minutes later sono buoys were thrown out at the north and south points of the circle. On the northern buoy very faint engine and propeller noises were heard and strong engine and propeller noises were heard on the southern buoy. The trapping circle was continued for ten minutes longer. The submarine later surfaced southeast, outside the trapping circle. The reason that it got out is probably that the slick dropper was not working so that it was impossible to throw out slicks to mark the circle. The S-15's log is as follows:
	Submerged to 100 feet 6.5 knots 1302.
	Course 180° 3.5 knots 1305.
	Surfaced 1406.
	(d) RB-18B #38-590.
	Take-off: 1405.
	Pilot: Lt. LeVan.
	A Radar signal was received at a distance of six and a half miles and an altitude of 400 feet. However, the submarine had already been seen visually at a distance of nine miles. As the plane passed over at an altitude of 100 feet, the decks of the submarine were still awash. A MAD contact was received, but a slick was dropped instead of a retro flare for fear of hitting the submarine. A clover leaf procedure was instituted. A MAD signal was received on the first leaf but the retro flare did not fire. Two or three more clover leaves were flown, but no further contacts were made. Therefore, a one minute forty second trapping circle was laid down around the point of submergence. After circling for seven minutes, a contact was made and a retro flare fired at the northern edge of the trapping circle. In the ensuing clover leaf tracking procedure, five contacts were made and retro flares fired. A bombing run was made, but the indication was too much to the right so that no bombs were dropped. Another bombing run was then made and the bombs were released manually, the second bomb on the right wing hanging up. Bombs were dropped at 1456. The submarine reported two concussions in the torpedo room one concussion in the motor room, and one concussion in the battery room at that time. These may not have been independent hits, however. The log of the S-15 showed:

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	77.


	Submerged to 100 feet at 6.0 knots 1436.
	Course 000° 3.6 knots 1438.
	Surfaced 1508.
	(e) RB-18B #37-470.
	Take-off: 1530.
	Pilot: Lt. Rockwood.
	The Radar was out. The submarine was sighted visually at a distance of twelve miles from 1000 feet. As the plane passed over the conning tower was still visible. Clover leaf tracking procedure, lasting sixteen minutes, was followed. Six MAD contacts were made and retro flares were fired. At this time the submarine, it was later learned, changed course from south to north with 180 degree right turn. Contact was lost, and after three more clover leaves, a trapping circle was laid down around the last contact. The submarine came up on a northern heading at the edge of the circle, just as another signal was received. The crew refrained from making a bombing run during the first clover leaf tracking procedure because they mistakenly thought that the submarine would surface after being hit, and they wished to use the whole hour and fifteen minutes allowed for tracking practice. The Log of the S-15 showed:
	Submerged 100 feet 6.0 knots 1551.
	Course 180° 3.5 knots 1552.
	Course 000° 3.5 knots 1605.
	Surfaced 1624.
	(f) B-4D #41-23684.
	Take-off: 1005.
	Pilot: Lt. Easterling.
	This flight was unable to do its problem because of confusion in the area due to the presence of other planes.

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	78.


	SECTION II

	IDENTIFICATION

	During the course of the Key West exercises, some tests were conducted using both the searchlight and the forward firing rocket flare. The tests of this equipment were not successful largely because of the brilliant moonlight during the period of May 17th to 26th and intermittent thunderstorms. Furthermore, the rocket tube proved to be unsafe for firing due to the flashback in the bombardier's compartment; and, after a few trials, these tests were discontinued. However, enough was accomplished so that interesting data could be supplied by the observers on the S-15, and a consensus of opinion indicates the following:
	The chief advantage of the searchlight lies in the fact that the collision course may be set by the radar operator and all preparations made for an accurate bombing attack before identification is necessary. The light having both vertical and azimuth controls is operated by the bombardier and is not turned on until just prior to the bomb release point. A few seconds are sufficient for identification, and the light can then be turned off and the bombing runs completed in the darkness. Observations made from a friendly submarine have indicated that the light does not have sufficient candle power to blind the crew of the submarine, and it is felt by some observers that, if the light remains on for 10 or more seconds, an enemy submarine gun crew would have a fair chance of attacking the aircraft with gun fire. As is obvious, the searchlight furnishes direct illumination of the target while the rocket flare is fired beyond the target and therefore illuminates the target in silhouette. Observations indicate that the approaching aircraft cannot be seen by the submarine crew as long as the aircraft is on the target side of the submarine. In other words, assuming that the rocket flare has properly identified the submarine, the aircraft can complete its bombing run with the target definitely silhouetted throughout and without having antiaircraft fire directed at the approaching aircraft, however, once the plane has passed over the submarine the situation is reversed and the plane becomes silhouetted against the light of the rocket flare and, in the opinion of many observers, becomes an excellent target for antiaircraft fire from the

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	79.


	submarine. It is believed, however, that this opinion be discounted somewhat because it is based on the assumption that the actual bombing attack would have been unsuccessful. In any event it is recommended that the attacking aircraft should employ evasive tactics as soon as the bombs have been released. Furthermore, during the bombing run on a surfaced enemy submarine, machine gun fire should be directed from the aircraft upon all personnel exposed on the deck or the conning tower of the submarine.
	As a matter of fact, disregarding all opinions to the contrary, reports and records from the combat areas show little evidence of successful antiaircraft attacks by submarines even in broad daylight, so it appears very doubtful that either the searchlight or the rocket flare would unduly expose the aircraft to counter attack. Moreover, the searchlight should not at any time be used as an instrument of search. Its sole purpose is to identify the target, and two or three seconds' illumination is sufficient for that purpose. The actual search should be normal radar procedure, and the bombing approach should be directed by the radar operator so that the time the searchlight is turned on, the position of the target has been anticipated, and it will be immediately illuminated by the searchlight.
	Comparisons between the rocket flare and the searchlight seem to favor the searchlight because its period of illumination can be definitely controlled by the bombardier, and its angle and direction can also be controlled.
	The rocket flare is only effective when the target lies directly in the reflected beam on the water, between the rocket and the approaching aircraft. This situation cannot be controlled, and in the event of a strong cross wind, the rocket flare may drift away from the target, causing its track to be lost entirely.
	Further modification of the searchlight is being accomplished, and tests will continue in order to develop the best possible tactics and technique for using this equipment in antisubmarine warfare. A new forward firing rocket tube is being installed, and tests of this means of target identification will be continued at Langley Field.

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	80.


	SECTION III

	LOW ALTITUDE OPTICAL BOMBSIGHT

	1. DESCRIPTION OF THE EQUIPMENT:
	a. The Gremlin Sight:
	This sight consists of a large reticule in the rear and a line in front to determine the dropping angle. The reticule is illuminated and the line is luminescent. The sight may be turned in azimuth on its base, and the vertical is indicated by an illuminated spirit level. It is set for bombing at 300 feet altitude. The ground speed may be set in by adjusting the position of the front line. The sight is calibrated to drop the first bomb 150 feet short. It consists of simple parts which could be machined quickly.
	b. The N-3A Sight:
	The N-3A gun sight has a collaminated beam optical system with a red reticule suitable for night work. There is no parallax difficulty, since the optical system projects the reticule on the target. It has been mounted on the base of a Norden Bombsight including the P.D.I. controls. There is a spirit level on the sight to determine the vertical. The dropping angle is adjusted by turning a dial which changes the angle of the A-1 reflector. The whole combination is mounted on the Norden stabilizer with P.D.I. indication to pilot.
	c. Drift Marker Bronze Slicks:
	Drift marker bronze slicks were dropped. They had been previously determined to have a very unstable trajectory with a differential trail over Mark 17 depth charges of 60 to 100 feet. The bomb bay shackles were loaded with shock cord to release immediately under the three pound weight of the slicks. In dropping the bombardiers took account of the trail characteristics, but the ballistic instability of the bombs made the dropping difficult.

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81.

2. CONCLUSIONS:

With full consideration for the known discrepancies of the bronze slicks as simulated Mark 17 depth charges, it is felt that the exercises at Key West demonstrated satisfactorily the effectiveness of 60-foot spacing of bombs for class A attacks. Furthermore, both the N-3A and the Gremlin Bombsights proved to be very satisfactory for low altitude bombing with the results slightly in favor of the Gremlin. While these results are not conclusive, they are of considerable value since they represent the first tests conducted by the 1st Sea Search Attack Group using a live, moving submarine as a target, and the number of estimated kills is most encouraging.

3. RECOMMENDATIONS:

This headquarters recommends that the N-3A sight be used in all antisubmarine aircraft equipped with the Norden stabilizer and that the Gremlin sight be installed in aircraft not so equipped.

4. DISCUSSION:

As the S-15 proceeded at about ten knots on the surface on its way to the problem area, a B-24 crossed it three times at an altitude of 300 feet at 185-200 mph airspeed, dropping five drift marker slicks spaced 60 feet to simulate a string of five Mark 17 depth charges. The bombardier did not take into account underwater travel but did consider the heavy trail characteristics of these slicks. On each flight, one pass was to be a beam run, another 30° off the submarine's forward track, and the last, 30° off the submarine's backward track.

(a) Flight Reports (Measurements from Photographs (P) or Observations from submarine (O):

(1) May 18th:

B-24D #41-23679.

Pilot: Captain Zinn.

Gremlin Sight.

Wind: 12 knots. 130°

Run	Airspeed	Altitude	True Heading		Results (Nearest Bomb)
1	175	300	90°	Beam	Miss. 65' far side (P)
2	175	300	220°	30° Stern	Probable kill 10' far side (P)
3	175	300	35°	40° Bow	Kill. Straddle. (P,O)

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82.

(2) May 19th:

B-24D #41-23679.

Pilot: Captain Zinn.

N-3A Sight.

The sight had been damaged and was out of calibration by 5 degrees. No useful results.

(3) May 20th:

B-24D #41-23679.

Pilot: Captain Zinn.

N-3A Sight.

Wind: 8 knots. 120°

Run	Airspeed	Altitude	True Heading		Results (Nearest Bomb)
1	175	300	96°	70° Stern	Miss. 150 feet short (P)
2	172	300	195°	20° Stern	Kill. Center straddle (P)
3	175	300	320°	10° Bow	Kill. Center straddle (P)

(4) May 21st:

B-24D #41-23679.

Pilot: Captain Zinn.

Gremlin Sight.

Wind: 5-8 knots. 120°.

Flight #1:

Run	Airspeed	Altitude		Results (Nearest Bomb)
1	185	300	30° Bow	Damage. 50 fet to port (P)
2	180	300	40° Stern.	Kill. Bow Straddle (P)
3	180	300	75° Bow.	Kill. Straddle (P)
4	180	300	Beam.	KIll Straddle (Observed from plane)

Flight #2:

B-24D #41-23708.

Pilot: Lt. Rockwood.

N-3A Sight.

Run	Airspeed	Altitude		Results (Nearest Bomb)
1	175	300	80° Stern.	Kill. Straddle behind C.T. (P)
2	175	300	10° Stern.	Kill. Middle Straddle (P)
3	175	300	60° Bow.	Miss. Ahead of Bow (O)

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83.

b. Synopsis:

Sight	Runs	Kills	Probable Kill	Damage	Miss
Gremlin	7	4	1	1	1
N-3A	6	4	0	0	2

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84.

The First Sea Search Attack Group had, in the course of its combat operations, won recognition for a number of meritorious individual achievements. War Department General Orders Nos. 11, 35, 36* had directed the awarding of Air Medals to nineteen Search flyers. On 23 June 1943, Major General B.M. Giles and Colonel E.E. Aldrin landed at Langley Field to review the group and award these medals.

Those receiving air medals were:

Major Francis B. Carlson

Major Leo J. Foster, Jr.,

Captain Robert L. Coleman

Captain Frederick A.V. Hartbrodt

Captain Robert W. Lehti

Captain Franklin T.E. Reynolds

Captain John F. Scanlan

Captain John F. Zinn

1st Lt. Junior M. Barney

1st Lt. Travis M. Boykin

1st Lt. Ned B. Estes

1st Lt. Clarence L. Harmon, Jr.

1st Lt. Alvin E. McGehee

1st Lt. James E. Pope

1st Lt. Crowell B. Werner

2nd Lt. Robert E. Tressel

2nd Lt. Charles V. Wilson

M/Sgt. Edward M. Lemons

T/Sgt. Edward A. Kaszubski

Those receiving Oak Leaf Clusters were:

Major Francis B. Carlson

Captain John F. Zinn

1st Lt. Junior M. Barney

1st Lt. Ned B. Estes

1st Lt. Clarence L. Harmon, Jr.

1st Lt. Crowell B. Werner

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* Appendix 22 contains these orders citing the reasons for each award.

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Click this text to view photographs of the presentation of the above awards by General Giles


	85.


	On March 13, 1943 and June 7, 1943 the group issued orders* authorizing the American Theatre Ribbon for 172 officers and men.










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	* Appendix 23.

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