The Secret WWII Tactic that Tricked U-boats to Surface

the intent of this video was to review the anti-submarine Gambit tactics Allied aircraft would adopt in hunting U-boats during World War II we will also listen to the Sona buoy sound differences of a submerged and surface submarine at the end we will walk through a case study where Gambit tactics were adopted to claim a U-Boat kill this is a part 15 video in the channels bombers vs submarines Battle of the Atlantic series early anti-submarine Warfare techniques were based on combat Lessons Learned or on-the-job training as discussed in this 1983 Office of the Air Force 863-page vol 1 document titled the Army Air Forces in World War II each attack was studied by bomber command with the view to develop an effective anti-submarine tactical Doctrine combat Lessons Learned include don't pay too much attention to oil slicks shark fins can be mistaken for periscope Lakes use cloud cover as a method of concealment during attacks approach a U-Boat down the moon path when attacking at night lastly if the U-boats emerge prior to the execution of a depth bomb attack the attacking plane should adopt baiting or Gambit tactics the plane will leave the area for a certain amount of time in orbit then return hoping the submarine has surfaced which will lead to an attack as discussed in previous videos once a submarine spots an aircraft it will usually dive operational combat data indicates that after 15 seconds of submergence aircraft deployed depth bombs are not effective this premise is based on operational data as shown in this chart from a Declassified 1946 Office of the chief of Naval operations report titled anti-submarine warfare in World War II of the 150 attacks on U-boats During the period from January through July 1943 none of the U-boats were sunk or damaged if the attack occurred while the U-boats degree of submergence exceeded 15 seconds in a Gambit or baiting maneuver the attacking plane retires from the submarines area and waits for the submarine to surface there are two types of Gambit tactics depending on if the patrolling aircraft is equipped with Sona buoys or not if the aircraft does not have Sona buoys then the aircraft will Mark the Spot of submergence as discussed in this Declassified January 1945 United States Navy document titled United States Fleet anti-submarine and escort of Convoy instructions the aircraft should employ Gambit tactics to bait the submarine to the surface if an attack was delivered orbit the area for 15 minutes looking for signs of damaged or sunky boats prior to starting the Gambit tactics and calculating the submarine's position assume an underwater speed of six knots for the first 10 minutes and three knots after the first 10 minutes Gambit tactics are described on this page from an April 1945 air staff intelligence historical division document titled the anti-submarine command drop a marker on the u-boat's last known location withdraw 30 miles from this marker orbit for 30 minutes to one hour depending on the plane's fuel supply return and search the contact area for a service view boat it is difficult to estimate the damage inflicted on an attack U-Boat see the Channel's part 8 series video for information on indications that a U-Boat has sunk this chart outlines the square sonobui pattern to be adopted and tactics to follow in a Gambit search for sonobui sensor equipped aircraft sonubui sensors have omnidirectional hydrophones which will transmit the underwater sounds to the aircraft range of the sonobi signals to the aircraft is 5 to 10 miles if the aircraft is at an altitude of 300 feet and 30 to 40 miles if the aircraft is at an altitude of 5000 feet usage of sauna boys is covered in the Channel's Part 12 video the aircraft will drop a center sonobui at the submarine's last known location the aircraft will drop four more Sona buoys in a four by four mile pattern as shown in this diagram the aircraft will Square orbit the area maintaining each flight leg equal to four times the visual range of a surface submarine this chart outlines the distances for an effective visual search for unlimited visual conditions and flying at 5000 feet the effective visibility of a surface submarine equates to 23 miles this implies the Gambit orbit Square distance leg would equate to 92 miles the Gambit orbit distance leg will need to be reduced since the son of bui's Maximum transmission distance equated to 40 miles when traveling at an altitude of 5000 feet the Sona buoy operator would listen to the Sona buoys and instruct the pilot where to attack the U-Boat if he hears indications that the submarine has surfaced anti-submarine command adopted tools to assist in training aircraft crew members in sonobua usage this image from a January 1945 chief of Naval operations and Bureau of Aeronautics Naval Aviation bulletin describes a sonobui training aid the aid includes records of sound Sony buoy operators would likely experience during combat operations let's listen to the sounds of the Gambit module you should be able to distinguish the sounds of a submarine on the surface from the sounds of a submarine which is submerged in a gambler or baiting maneuver your plane will fly out of the area and wait for the sub to come up then you must be able to tell by listening when the sub is on the surface there is usually a change in the character of the signal received you may still continue to hear propeller beats but you may also begin to hear the Roar of the diesel engine in the following examples the sounds from a submerged submarine will be compared with the sounds from a surface submarine first of death feed three knots range 500 yards [Music] and now the same sub on the surface speed approximately 7 knots range 800 yards foreign first at Periscope depth speed for knots range 300 yards in the course of the example the sub Blows Its tanks surfaces and proceeds away from the buoy at a speed of 7 knots please [Applause] [Applause] [Music] foreign and is preparing to change over to diesel [Music] [Music] the sub is now on diesels and proceeding away from the buoys range 500 yards [Music] [Applause] [Music] [Applause] thank you the success of the Gambit or baking maneuver depends upon your ability to interpret the sounds you hear over the Expendable buoys your buoy may not be close enough to the sub to pick up sounds such as the blowing of Tanks but you should be able to distinguish the sounds of a sub's diesels from its electric motors the squeaking sounds heard after the submarine surface were caused by hand operations of valves controlling the ballast tanks let's take a look at a case study of a successful usage of Gambit tactics from a December 1942 anti-submarine command monthly intelligence report on December 17 1942 a pby spotted a U-Boat from an altitude of 2000 feet with unlimited visibility and Scattered clouds note that sonobui sensors and the mark 24 homing torpedo were not available in 1942 a submarine wake was observed 10 miles ahead the U-Boat died by the time the pby arrived a smoke marker was dropped the plane climbed through the clouds to an altitude of 3500 feet after 30 minutes the plane returned to observe awake it flew to the nearest cloud and headed towards the direction of the Wake the U-Boat was still on the surface two miles away the pby dropped two Mark 29th and a single Mark 17 depth bomb while the U-Boat deck was Awash the explosions were estimated to be within the lethal range the crew took pictures of the U-Boat while under attack photo one shows a sub's position a few seconds before the depth bombs are released the conning Tower is visible and the decks are Awash the pby is at an altitude of 40 feet photo 2 was taken 210 seconds after the depth bombs explosions the sub is rising out of the water a residual air bubble is still visible the U-boats angle is 45 degrees up with the bow and conning Tower exposed the depth bombs residual dark sea patch is in the image photo 3 was taken 25 seconds after photo 2 the conning Tower is in the same relative position to the residual air bubbles this implies a loss of propeller power there is a large volume of air lost just aft of the conning Tower and at the stern the sub is settling Stern low about one minute after photo 3 was taken the sub sank without forward motion and emitting air bubbles by holding back the kill stores and applying Gambit tactics the pby was in a much more favorable attack position for a surface attack if you've enjoyed this video please consider liking commenting and or subscribing to the Channel World War II U.S bombers

Channel: WWII US Bombers

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Length: 11min 32sec (692 seconds)

Published: Fri Jun 16 2023