Yugoslavia - Heroj Class (P 821) mid-life refit (Thomson Sintra Eledone Sonar)

DB Selector

DB3K

Baseline

260 P 821 Heroj

Hypothetical

Name

P-821 Heroj [Heroj Class] (P-821, P-822, P-823) -- Yugoslavia [-1992] (Navy), 1986-1992, Mid-life refit

Class

Heroj Class

Country

Yugoslavia, Serbia, Montenegro

Service

Navy

In Commission

1986-1992 [Yugoslavia], 1992-2004 [Serbia], 1992-2004 [Montenegro]

Length (m)

50.4

Beam (m)

4.7

Draft (m)

4.3

Standard Displacement (t)

614.5

Submerged Displacement (t)

705

Empty Displacement (t)

No response

Max Depth (m)

-210

Complement

Primary Propulsion Type

Diesel/Electric

Propulsion

2x MTU 12V 493 Diesels 1x Rade Končar ICVU 2-994-8 Electric Motor

Flank Speed at Surface (kt)

Flank Speed Submerged (kt)

Range (nm) at Speed (kt)

2300nm @ 10kts (surface) 1800nm @ 10kts (snorkel, periscope depth) 170nm @ 16kts (submerged)

Range (nm) on AIP

No response

Fuel Capacity (kg)

30500

Sensors

1x Decca RM 1290A 1x Generic Submarine Periscope 1970s 1x Iskra RDL-13 [ESM] 1x TSM 2275 Eledone [DSUV 2H + DUUA 2D] (DSUV 22 System, Yugoslav Heroj & Sava) 1x DUUG 5 1x DUUG 6 [M5]

Mounts

3x 533mm TT (53-56VA (loaded), SET-53ME, 2x Mine AIM-M.70, 2x Mine AIM-M.82) 1x 533mm TT (53-56VA, SET-53ME (loaded), 2x Mine AIM-M.70, 2x Mine AIM-M.82) 2x Signal Ejector (2x Generic Acoustic Decoy -- 1980s (4 loaded))

Magazines

1x 53-56VA (loaded) 1x SET-53ME (loaded) (2 torpedos) or (2 mines and 1 torpedo) 2x Mine AIM-M.70 (magazine option) 2x Mine AIM-M.82 (magazine option)

20x Generic Acoustic Decoy -- 1980s

Comms/Datalinks

9CSI 600 STINA HF Radio [Secure] VHF Radio [Secure] UHF Radio [Secure]

sub Codes

Snorkel

Comments

The only Torpedos which Yugoslavia had were 53-56VA, SET-53ME and 53-65KE (which couldn't be used by Heroj because of the Torpedo length). The loadout is usually 6 torpedos (4 in tubes 2 in magazines), one SET-53ME torpedo is loaded for self defense against subs and one is in the magazine.

All Heroj Class Submarines P 821, P822 and P823 had a mayor overhaul and modernisation phase between 1985 and 1987. A new Decca 1290A radar was installed along with a Thomson Sintra Eledone active/passive sonar which is quoted by a submariner as "being able to track 4 targets simultaneously and provide torpedo targeting data for two targets simultaneously." The sonar is designated as Eledon TSM 2275, the source is, Ratni Brodovi Jugoslavenske Ratne Mornarice 1945-1991, from 2021. Information is very scarce on the new sonar but it is allways described as highly advanced. It is likely an Eledone subtype for the Heroj and Sava Class submarines like the other Eledone variants for other subs. The Heroj had no flank array sonar. Also an unnamed Thomson acoustic intercept sensor was installed (also likely a part of the Eledone sonar suite, take a look at the Walrus and Agosta class as an example). Also both Heroj and Sava Class were equiped with the RDL-13/T radar locator esm/elint/rwr system. I guess it was also installed during the upgrade. I can't find any information regarding this one except that it was able to monitor 42 radar sources. Because of the new automated systems the crew could be reduced to 26.

The Heroj had acoustic decoys before the upgrade and a newer version after the upgrade.

The Heroj Class is generally described as a very quiet sub, the noise levels were on par with western subs in the 70s. Originally it had a 2 knot "sneaking engine" which was removed as it was unnecessary. The propulsor is made from the sound damping alloy Sonoston.

Sources

New collection of information on Yugoslav Navy ships and submarines from a plethora of sources (some never cited before): Ratni Brodovi Jugoslavenske Ratne Mornarice 1945-1991, Zvonimir Freivogel, Zagreb 2021, ISBN: 9789533660042

https://imgur.com/wKCGkA2 https://imgur.com/HklYLtr

Program of prototype testing on submarine B-71, HA testing of sonar Eledon, Milošić, Zvonimir, Brodarski institut Zagreb, 1986: https://www.bib.irb.hr/374779 Results of final HA testing of sonar Eledon on reconstructed submarine B-71, Milošić, Zvonimir, Brodarski institut Zagreb, 1986: https://www.bib.irb.hr/374777

Photos from Paluba, Museum Submarine P 821 Heroj: Decca RM 1290A: https://imgur.com/wU7Fg98 Thomson Sintra Eledone: https://imgur.com/3gavPd3 Atlas Krupp Echo Sounder: https://imgur.com/lOsjhTR https://imgur.com/6cKK2U0 https://imgur.com/uDk86LK https://imgur.com/Pqm0HNK

Torpedo and Mine inventory in 1991 (from the Monograph "Podmornicarstvo Jugoslavije", 2012): https://imgur.com/g6dkflO

Yugoslav Navy Submariners, Paluba Forum (ctrl+F Eledon): http://www.paluba.info/smf/index.php?action=printpage;topic=3870.0

"My former job. Sonar "Eledon" is a wonderful digital device, the ability to track 4 targets and directly transmit data to a torpedo computer for 2 targets. The lower round screen is a panoramic indicator and the upper, square one is a directional time indicator."

"The P-823 was under modernization in early 1985 in Šibenik, when the Thomson-sintra Eledone sonar was installed. Then the entire stern section was separated. I visited that submarine when they had already put the stern section back in place. Just then, they showed me a motor for driving at low speed, allegedly up to 2 knots."

The Heroj and Sava Class Submarines were very quiet:

"Obviously the sneaking engine proved to be unnecessary. The Brodarski Institute from Zagreb had an extremely strong and high-quality team that dealt with hydroacoustics and did a lot of research on the hydrodynamic noise of submarines. Noise data was kept secret and remained so. As far as I know, the last large-scale research of hydrodynamic noise and many others was conducted by BI at the end of 1987 in the area of Rogoznica. At that time, all submarines passed through the test site in various modes of driving under the sea and on the surface. VPBr and PČ participated in the research. As I myself participated in the research, I know that the results for P were very favorable, ie it was concluded that they have very little noise and that up to a speed of 4 knots they are noiseless. We were convinced of the noiselessness personally in the way that one P was lying on the bottom and the other was passing at different distances and driving modes. At a distance of 2 cables we did not hear P driving with 4 knots. The submarines at the time had a very high quality Thompson Eledon sonar."

cable: 100 fathoms, 1/10 nm

Museum Submarine P 821, post by Oricareb: http://www.paluba.info/smf/index.php?topic=3870.1050

"The burden of the unexplained past: He recalls that the submarine was not restored to its original condition in 1967, "because they were not the same devices then" and over time, more modern ones were installed. In particular, PEG-PEL is more recent and has replaced the Russian-made instrument. The torpedo computer was also Russian, "very complicated to operate, and did not give adequate results." Bulatović adds that they planned to install a more modern device, but then the former state collapsed ..."

"He also shows the radar detector indicator, on which 42 targets could be monitored at the same time, but he also notes that it was rarely used because it served only during the surface driving."

Post by Plavnik: http://www.paluba.info/smf/index.php?topic=3870.msg275952;topicseen#msg275952

"During the reconstruction of 821 submarines, a new type of False Echo Thrower was installed on the P-822 sometime in 1986."

AIM-M.70 and AIM-M.82 mines: https://imgur.com/J1qklPO

PygmalionOfCyprus / cmo-db-requests