Japanese anti-submarine warfare: "MAD" Magnetic anomaly detector

[Equinoxe 1978]

I was reading interrogations of Japanese officers after the war and it caught my attention to read that Japan used "Magnetic anomaly detectors", I thought it was something implemented only by the allies...
The interrogation details how it was used, in what aircraft, in what attack patterns , difficulties, etc.
LINK: USSBS: Interrogations of Japanese Officials -- 48/200

but I have a question... think I have never seen or recognized a Japanese MAD unit.

-the American MADs are easy to see, it looks like a long and thick antenna on the tail (like this PBY) but I have never seen such equipment on a Japanese aircraft,

I think I recognize japanese radars, visually they resemble "stickleback" radar antennas, but like I said, I have never seen a Japanese MAD.
Does anyone of you have a photo of such gear?

 

[Shinpachi]

It seems to have been called KMX though I don't know what KMX is short for at the moment.

"KMX is a magnetic detector for aircraft developed by the Japanese Navy. It is also called the Type 3 Mk.1 Detector. While transport ships were being sunk by the U.S. Navy's submarines in the war to destroy commerce line, it was equipped mainly on the Tokai(Q1W) and Type 96 land attacker(G3M) for aerial anti-submarine patrol.

Overview
Development of the KMX began in the fall of 1942 at the Naval Air Engineering Center as a means of detecting submarines from aircraft. From then on, development progressed smoothly and it was formalized in November 1943 (Showa 18)to be put into combat from April 1944 (Showa 19). In particular, the 901-ku at Tateyama Base which was the first unit to be deployed in combat researched the anti-submarine sweep methods to take advantage of the KMX's detection capabilities and also developed anti-submarine sweep methods for each platoon (3 aircraft formation). It was used in actual combat such for establishing the methods.

Though the Japanese Navy did not deploy airborne radar sufficiently and the radar itself lacked reliability due to the limitations of its basic industrial capabilities, KMX detected 15 submarines and destroyed 6 (the results were unconfirmed). KMX's detection ability was reliable to some extent. However, the time when it was actually deployed was just before the Battle of the Mariana Sea and air superiority was being lost in major sea routes and in the waters near Japan. The chances that anti-submarine patrol aircraft could play an active role were limited.

Structure/performance
Because submarines are constructed from magnetic steel, a unique magnetic field is generated around them. KMX is a device that detects changes in this magnetic field using a current-carrying coil. If a coil attached to an aircraft passes through the magnetic field generated by a submarine, an electromotive force will be generated in the coil. Because light and electromagnetic waves at the wavelengths used by regular radar are reflected at the sea surface or absorbed by the sea water due to impedance mismatch, they cannot penetrate deep into the ocean. However, because static magnetic fields are not reflected at the sea surface or absorbed by sea water, it can detect submarines.

However, in order to put KMX into practical use, they needed an amplifier to detect the slight electromotive force from the submarine as well as an electric circuit to eliminate the influence of the Earth's geomagnetic field and a canceller to eliminate the overcurrent noise generated by the aircraft itself. The Earth's magnetic field is several thousand times stronger than the submarine's magnetism and, when the plane's coil changed its angle, it immediately generated a strong electromotive force making KMX impossible to identify the submarine. KMX's effective detection range is not very wide. In terms of performance, if an enemy submarine has a mass of 3,000 tons, the detection range is 160 meters in length and 120 meters in width. If the target was a 1,000 ton class submarine, the length was 120 meters with the width of 90 meters. In the case of the Tokai patrol plane, when a magnetic change was detected, KMX made an alarm sound in the radio crew's receiver and, at the same time, the galvanometer needle turned the switch of warning light on to flash. Furthermore, with a buzzer sound, a signal bomb was automatically dropped to color the sea surface.


Tactics
Due to the narrow detection range, Tokai unit used the following tactics - they flew in formations of three or six planes with each plane apart 200 meters each other. A mark resembling the letter C on an eye chart was placed on the rear of Tokai and, if this mark looked like a continuous circle(?), it meant that the aircraft was maintaining an appropriate distance. This formation flew back and forth crosssing the path of friendly convoys, trying to detect submarines. If the detection was successful, a signal flare was dropped into the sea to color the water surface. The formation moved straight ahead for a while, then turned around to detect the submarine's position again and determine its direction of travel. After determined the target location, all aircraft dropped anti-submarine bombs to sink the target. From March to June 1945, 12 Tokai planes deployed to 951-ku on Jeju Island (Korea) practiced this tactic thoroughly and reported seven guaranteed sinkings in the East China Sea."

KMX - Wikipedia

ja.wikipedia.org

 

[ThomasP]

Hey Equinoxe 1978,

As far as I know, there were no visible pieces of the Japanese MAD equipment external to the fuselage. The Type 3 Model 1 MAD (KMX) detector coil was contained in the rear fuselage of the carrying aircraft. Apparently the Japanese figured out a way to use the equipment effectively without putting the detector coil in a boom/stinger or towed pod. The USN rated it as effective as its US counterparts. The following image is from the "Intelligence Targets Japan" series of reports:

 

[wrenchedmyspanner]

Hey Equinoxe 1978,

As far as I know, there were no visible pieces of the Japanese MAD equipment external to the fuselage. The Type 3 Model 1 MAD (KMX) detector coil was contained in the rear fuselage of the carrying aircraft. Apparently the Japanese figured out a way to use the equipment effectively without putting the detector coil in a boom/stinger or towed pod. The USN rated it as effective as its US counterparts. The following image is from the "Intelligence Targets Japan" series of reports:

View attachment 743708

I continue to marvel at the kinds of stuff I learn from this forum. Keep up the great work!

 

[Equinoxe 1978]

It seems to have been called KMX though I don't know what KMX is short for at the moment.

"KMX is a magnetic detector for aircraft developed by the Japanese Navy. It is also called the Type 3 Mk.1 Detector. While transport ships were being sunk by the U.S. Navy's submarines in the war to destroy commerce line, it was equipped mainly on the Tokai(Q1W) and Type 96 land attacker(G3M) for aerial anti-submarine patrol.

Overview
Development of the KMX began in the fall of 1942 at the Naval Air Engineering Center as a means of detecting submarines from aircraft. From then on, development progressed smoothly and it was formalized in November 1943 (Showa 18)to be put into combat from April 1944 (Showa 19). In particular, the 901-ku at Tateyama Base which was the first unit to be deployed in combat researched the anti-submarine sweep methods to take advantage of the KMX's detection capabilities and also developed anti-submarine sweep methods for each platoon (3 aircraft formation). It was used in actual combat such for establishing the methods.

Though the Japanese Navy did not deploy airborne radar sufficiently and the radar itself lacked reliability due to the limitations of its basic industrial capabilities, KMX detected 15 submarines and destroyed 6 (the results were unconfirmed). KMX's detection ability was reliable to some extent. However, the time when it was actually deployed was just before the Battle of the Mariana Sea and air superiority was being lost in major sea routes and in the waters near Japan. The chances that anti-submarine patrol aircraft could play an active role were limited.

Structure/performance
Because submarines are constructed from magnetic steel, a unique magnetic field is generated around them. KMX is a device that detects changes in this magnetic field using a current-carrying coil. If a coil attached to an aircraft passes through the magnetic field generated by a submarine, an electromotive force will be generated in the coil. Because light and electromagnetic waves at the wavelengths used by regular radar are reflected at the sea surface or absorbed by the sea water due to impedance mismatch, they cannot penetrate deep into the ocean. However, because static magnetic fields are not reflected at the sea surface or absorbed by sea water, it can detect submarines.

However, in order to put KMX into practical use, they needed an amplifier to detect the slight electromotive force from the submarine as well as an electric circuit to eliminate the influence of the Earth's geomagnetic field and a canceller to eliminate the overcurrent noise generated by the aircraft itself. The Earth's magnetic field is several thousand times stronger than the submarine's magnetism and, when the plane's coil changed its angle, it immediately generated a strong electromotive force making KMX impossible to identify the submarine. KMX's effective detection range is not very wide. In terms of performance, if an enemy submarine has a mass of 3,000 tons, the detection range is 160 meters in length and 120 meters in width. If the target was a 1,000 ton class submarine, the length was 120 meters with the width of 90 meters. In the case of the Tokai patrol plane, when a magnetic change was detected, KMX made an alarm sound in the radio crew's receiver and, at the same time, the galvanometer needle turned the switch of warning light on to flash. Furthermore, with a buzzer sound, a signal bomb was automatically dropped to color the sea surface.


Tactics
Due to the narrow detection range, Tokai unit used the following tactics - they flew in formations of three or six planes with each plane apart 200 meters each other. A mark resembling the letter C on an eye chart was placed on the rear of Tokai and, if this mark looked like a continuous circle(?), it meant that the aircraft was maintaining an appropriate distance. This formation flew back and forth crosssing the path of friendly convoys, trying to detect submarines. If the detection was successful, a signal flare was dropped into the sea to color the water surface. The formation moved straight ahead for a while, then turned around to detect the submarine's position again and determine its direction of travel. After determined the target location, all aircraft dropped anti-submarine bombs to sink the target. From March to June 1945, 12 Tokai planes deployed to 951-ku on Jeju Island (Korea) practiced this tactic thoroughly and reported seven guaranteed sinkings in the East China Sea."

KMX - Wikipedia

ja.wikipedia.org

Thank you very much for the information Shinpachi

-An extra question, you talked about "a signal bomb" and I have seen these images (including the one exposed in ThomasP's answer) where you can see that "bomb", what was it exactly? a flare, a smoke bomb, ink in water?

I suspect it was smoke, I think I remember seen a movie or short depicting a Japanese plane launching a smoke bomb to mark the position of a submarine for surface units, maybe is that...

NOTE: I found it
View: https://youtu.be/nnlKl6KrnU4?feature=shared&t=579

 

[Shinpachi]

No docs tell whether it was smoke or color dye. Wikipedia says it was like dye.

Source: 航空技術の全貌・下巻(1955)

 

[Shinpachi]

The flying boat H8K could have had nothing to do with the KMX.

 

[Shinpachi]

Japanese side understanding is that it was sea marker(dye).
As exact color is unknown, no way but to obey modern common knowledge for green IMO.

Source: 国際化工/海面着色剤（DYE MARKER）国交省承認/第3799号