Sonar -Desperate War of Japan in the Pacific

IJN sonar

Type 93 sonars on surface vessel
Method	Accuracy	Range
Passive	10deg at 12kt 3deg at 12kt	1,000m 6,000m
Passive	- at 8kt - at 6kt	500m 1,000m
Active	2deg at 12kt +/-200m at 12kt	Max 2,000m Min 300m

Type 93 model 3
Method	Active
Frequency	17.5kHz
Aperture	12deg
Max range	1,300m at 12kt 1,000m at 14kt
Min range	500m
Accuracy	3deg 100m

Type 93 passive sonar in 1937
Target speed	Range
3kt	1,700m at 1.5kt 1,000m at 4kt
4kt	2,800m at 1.5kt 2,300m at 4kt
5kt	3,000m at 1.5kt 2,300m at 4kt

Type 3 sonar specifications
Frequency	13, 16kHz(alternate)
Aperture	30deg
Max range	2,000m at 12kt 1,200m at 14kt
Min range	150m
Accuracy	100m 2deg
Display	CRT

Type S active sonar
on U-boat
Frequency	15 kHz
Power	5 kW
Pulse	20 ms
Accuracy	±2° at 4,000 m

Sonars were equipped with destroyer escorts in fall 1942, though IJN had developed passive and acitve sonar in 1933. Its detector was dynamic microphone. There was an argument that IJN should adopt crystal type detector or not in the beginning of the Pacific War.^[3] The table shows both specifications. Passive type was called type 93 passive sonar ( 93 shiki choonki). Active type was called type 93 active sonar ( 93 shiki tanshingi ). The active sonar could hardly detect a target inner range 300 m. Detectors of type 93 passive were 16 dynamic microphones on the pherial of diameter 3 m.

I suppose that it was impossible to measure distance of a target in case of type 93 passive sonar. Another data of type 93 might be in fact. It shows that dead distance was 500 m. I find how allied hunter killer tactics was effective considering the dead distance.

Destroyer Kagero got a range 3,200 m at 8 kt, 1,000 m at 14 kt applying for type 93 passive sonar. Destroyer Hatsuzuki got a range 5,000 m at 6 kt, 2,600 m at 12 kt and 2,000 m at 14 kt.^[4] There is another data of passive sonar tested in submarine school in 1933.^[7]

IJN dispatched military delegation to Germany in 1941. IJN was trying to copy French SCAM then. IJN found active sonar important. IJN Laboratory began to develop the new active type sonar with NEC in 1941. NEC made 30 to 50 sonars at month in 1943.^[1] This type was called type 3 ( 3 shiki tanshingi ). Transducer of the original German type was crystal. So 2 German sound engineers came to japan on a German cruiser in 1943. One was an expert of production of the crystal. Toshiba was to product the crystal, but the factory was destroyed before production by B-29 air raid in 1945.^[2]

According to Hirota, U-boats adopted Type S active sonar. But German submariners hardly used active sonar.^[5] An IJN engineer proposed a new way how to detect a surface ship. It was to equip detectors at bow and stern of a submarine. IJN did not approve it at first. Its method looked like German GHG which had 24 detectors, I suppose. In the end of the Pacific War, there were a lot of stock of the new type sonars, though IJN had not have enough submarines suitable for them any more.^[3]

Sonars of RN destroyer escorts had range of 1,100m to 1,400m in the Atlantic Battle.^[6]

It was necessary like hedgehog or squid to attack forward for IJN. Or a pair of a hunter detecting a submarine and a killer attacking it was the best way like DE-635 England. But it was to too late to shipbuild a lot of kaibou kan. Kaibou kan was smaller than corvette. After all Japan lost a lot of merchant ships and crews' and soldiers' lives aboard.

Kansen, No217
[1] Nakagawa, p188-189
[2] Toshiba
[3] Nakagawa, p193-194
[4] Chouon-ki
[5] Hirota, p442
[6] Peillard, ge, p333
[7] Gunzo, type 13 submarine chaser p13, No51