reported Type G7a (TI) torpedo problems

[Northstar98]

Hi everyone,

 

Found a small bug with the G7a T1 torpedo, fired from the S-130 Schnellboot; when fired past a certain distance, the G7a T1 enters a snake search pattern, where the torpedo turns left and right - this is inaccurate as the G7a T1 is the most basic G7 torpedo, with only gyroscopic guidance.

 

What happens when these torpedoes are fired, is that they initially run straight for a few metres and then will turn to a predetermined course (called a gyroangle, which can be +/- 90° from the launch bearing) and will climb/dive as necessary to reach and maintain a pre-selected depth (1-12m); after that the torpedo runs straight, until it either explodes (with fairly unreliable impact and/or magnetic proximity fusing) or runs out of steam.

 

In the track below, the torpedoes start the snake pattern at around ~6m20s into the track - corresponding to a distance of a little over 7.3km from launch.

 

 

The only WW2 torpedoes that should perform a snake search pattern (EDIT: nope) are the G7es T4 Falke and G7es T5/T11 / Zaunkönig I / Zaunkönig II; these are electrically powered, passive acoustic homing torpedoes. The behaviour of these at launch is similar to the G7a T1, in that after a short distance they will climb/descend and turn to a predetermined course, then after 400m of travel, the torpedoes will activate, performing a snake search pattern until they hear something - they then essentially use 'bang bang' guidance to home in on the loudest thing they hear, using 2 hydrophones (one on each side). EDIT: they don't actually perform a snake search pattern - it's an effect of the 'bang bang' guidance, which causes the torpedo to oscillate left and right as it is guiding.

 

There are a few other issues with the torpedo, which are detailed below but they are not the focus of this thread.

 

 

Latest OB, specs down below, clean DCS build (only changes are default payloads, templates and countermeasure programs).

 

Spoiler

Other Issues:

 

• The bubble effect of the torpedo leaves something to be desired; at the moment it appears as a thin, puffy grey cloud, that only seems to be visible from directly above and behind the torpedo; it's almost invisible from the perspective of the target. A better representation would be a longer and thinner version of our current wake, forming a distance behind the torpedo (depending on the torpedo's depth - the deeper the torpedo, the further back the trail). Obviously a dedicated effect (such as what's seen in SH4) would be ideal.

 

 

• The torpedo has 3 speed settings which also affects the maximum range:
  • 30 knots - 12km
  • 40 knots - 7.5km
  • 44 knots - 5km

At the moment the torpedo does 37 knots, but it does get the approximate range at that speed accurate; ~7.5km from testing.

 

• The torpedo has its control surfaces and propellers animated; however the propellers IRL are contra-rotating, and in the modelviewer you can see that the blades are pitched opposite directions, but the whole assembly rotates in the same direction, which would not only cause the torpedo to roll (which is why they're counter-rotating in the first place) the thrust from the propeller would cancel out.

 

• The torpedo has a small 2-bladed turbine on the front of it, in front of the impact fuze; unfortunately in DCS, it isn't animated. IRL this is used to arm the torpedo after a set range (150 - 300m depending on the type of turbine used).

 

• The impact fuse also doesn't seem to be modelled correctly, the nose cap is present, but the fuse has 4 small fins that project from openings in the nose, they can also be seen here in this blueprint.

 

G7a_T1_Torpedo_Snake.trk

Edited June 21, 2021 by Northstar98

[NineLine]

Nice post, I myself am not up on Torpedoes, so this is interesting, for interest sake what is your source of the info incase the team wants reference. Thanks!

[Northstar98]

Hi Nineline; all the above information is just what I dug up and was able to corroborate on the internet, though even torpedoes entry on wiki has a good breakdown on the specs (though the reference material for said specs seems hard to come by, however a fair amount of specs are corroborated on other sites). It also describes what the small, 2 bladed turbine does on the front - it's a safety device that arms the torpedo after a certain distance.

 

http://www.tvre.org/en is my main source of information; it has details on the after launch behaviour - torpedo should travel 9.5m before starting its turn; turning radius of the torpedo is 95m, it's also a pretty good dive into fire control calculations, as well as the FCS of Kriegsmarine submarines. It also has items like this handbook which on page 62 describes the gyroangle limitations: "The torpedo fire control system allows for launching torpedoes with the gyro angle in range from 0 to 90" (presumably on either side).

 

The site also has a pretty good in-depth look at torpedo fire control: http://tvre.org/en/gyro-angled-torpedoes (however, this mostly goes over WWI torpedoes, though it does corroborate the torpedoes running straight for a short distance before turning, as well as the torpedoes behaviour (which is common for G7a/G7e T2-T3, only difference is speed and range):

 

Quote

A torpedo after leaving the tube and before starting its turn, covered a distance called reach (Germ. gerade Vorlauf), which depended on the torpedo type (types C/06 and G/6 - 10 m, type G/7 - 15 m, type G7a and G7e – 9.5 m). Then it started its turn with a radius that also depended on the torpedo type (type C/06 - 145 m, type G/6 - 100 m, type G/7 - 105 m, type G7a and G7e - 95 m). After finishing its turn the torpedo ran straight toward the target

 

Here's an entry corroborating the speed of the torpedo (though only says that the torpedo had impact fusing).

 

Here's a diagram of the gyroscope system (here on a flat-nosed variant of the G7es T5 Zaunkönig I passive, acoustic homing torpedo) - AFAIK this seems to be a common gyroscope to all G7x torpedoes, which would also imply that the acoustic torpedoes have a similar initial guidance scheme of the pure gyro-angle torpedoes). You can also find a manual for the Type VIIC u-boat on the same site.

 

And here is a comprehensive set of plans for the G7a T1 (including war-shot and exercise warheads, you can see the fins on the nose of the torpedo - which aren't present in the DCS version).

 

 

One thing is for certain is that the G7a T1 definitely does not enter a snake search pattern - it is a straight running torpedo only - it should travel 9.5m then turn (with a radius of 95m) and climb/descend to a predetermined depth and course (1-12 to 1-15m, depending on sub-variant).

 

The snake-pattern the torpedo currently does currently is more reminiscent of what a modern active/passive acoustic homing torpedo would do (such as a Mk48 torpedo) - the only WW2 torpedoes I know of that have any homing capability at all are the G7e T4 and G7es T5/T11 which are basic, passive acoustic homing. The other one is the Mark 24 torpedo, which an air-dropped ASW torpedo using passive homing (it has hydrophones not just for left/right but also up/down, allowing for 2-axis guidance, which is necessary for engaging something that can change its depth).

 

There are variants that have programmable search pattern (the Fat and Lut, the former doing a loop (straight legs, with 180° turns), the latter being more advanced and programmable. AFAIK these will also be set-up like the gyroangle torpedoes (i.e will have the same launch profile - 9.5m straight, turn to bearing with a radius of 95m)

Edited February 23, 2021 by Northstar98

[WinterH]

18 hours ago, Northstar98 said:

The only WW2 torpedoes that should perform a snake search pattern are the G7e T4 Falke and G7es T5/T11 / Zaunkönig I / Zaunkönig II

As far as I know, these shouldn't perform a search pattern either, but only directly home in on a sound source if they find one, and just run straight if they can't.

However, both G7a and G7e torpedoes could be fitted with a Fat or Lut pattern running kits as you mention in your last post. I don't know if pattern running torpedoes were used on Schnellboot, or just uboats.

[Northstar98]

7 hours ago, WinterH said:

As far as I know, these shouldn't perform a search pattern either, but only directly home in on a sound source if they find one, and just run straight if they can't.

 

I think you're correct, I might be confusing the snake search for the bang-bang guidance (which kinda looks like a snake pattern). How it works is if the left hydrophone gets a stronger signal than the right, the torpedo goes full left rudder until the right side becomes more dominant, whereby it goes full right rudder until the left side is more dominant and so on until it hits the target.

 

Quote

However, both G7a and G7e torpedoes could be fitted with a Fat or Lut pattern running kits as you mention in your last post. I don't know if pattern running torpedoes were used on Schnellboot, or just uboats.

 

Yes, and as far as I can dig up, the Fat pattern for the G7a is essentially straight legs of ~1.2km - 1.8km (pre set) then followed by alternating right/left 180° turns of radius 175-185m (again pre set), drawing a pattern that looks like this (for G7e torpedo). It keeps doing the pattern until it hits something or runs out of fuel.

Edited January 30, 2021 by Northstar98

[Silver_Dragon]

Version 2.7 I see some problems on the G7a(TI) torpedoe.

 

- Only have a speed setting: 37 knts on 2.7. Real TI torpedo has 2 setting for submarine (30kn & 40kn) and on E-boat & Torpedo boats with a Third setting (44kn)

- Torpedo Depth has the same of the laucher submarine on 2.7, but the TI has 1 to 12 meter Depth setting before launch. After launch, the torpedo maintain the same seting depth by a hidrostatic sensor and a pendulum.

- Torpedo range has 5.3 NM only on 2.7, (9815,6 metters). but the TI has 2 setting for submarines (12000m / 6.47NM (30kns), 7500m / 4.04NM (40kns)) and on E-boat & Torpedo boats (5000m / 2.69 NM (45kns)).

- "bubble effect" I suppouse has some smoke, apears upper surface and no deploy a torpedo trail.

- on 2.7, when the torpedo has near to reach max range, start to make S turns. That is not realistic and detonate. The real TI continue running with the same bearing, at max speed. When reach max distance, stop your engine and sinking without detonate.

- on 2.7, the torpedo has only detonate by contact (Pi1 pistol, mechanical), but the limitations has not implemented (min 16 degress impact). No magnetic pistol implemented. (some old LOMAC DCS ships has none under water hull and has traspased without detonate).

- On 2.7 Type VII Uboat turn heading to torpedo bearing before launch torpedoe, that has not realisitc. The TI has mechanical gyroscope powered by pressurised air (GA VIII) with anglesetting mechanism (+/- 90 degrees from initial course after launch) to all G7a torpedoes.

 

http://www.tvre.org/en/gyro-angled-torpedoes

 

- Type VII can launch single torpedoes one to one from TT (fore/aft) with the same giro angle setting and salvo mode on forward torpedo tubes with:

- 2 torpedoes (Tube 1-3/1-4/2-3/2-4)
- 3 torpedoes (Tube 1,2,4/1,3,4)

- 4 torpedoes

Torpedo spread can be adjusted from 0 to 20º.

 

More info:

http://www.tvre.org/en/torpedo-fire-control-system-on-german-u-boats

 

 

Edited May 5, 2021 by Silver_Dragon

[xvii-Dietrich]

3 hours ago, Silver_Dragon said:

- on 2.7, when the torpedo has near to reach max range, start to make S turns. That is not realistic

 

The G7a making "S-turns" would be either the FAT ( Federapparattorpedo) or LuT (Lagenunabhängiger Torpedo) versions. The G7a T1 had several of these variants. They were specifically designed to go into the said S pattern into order to criss-cross the path of a target (esp. effective when multiple ships were involved, such as a convoy). The FAT were introduced in 1942 and the LuT in 1944.

 

http://navweaps.com/Weapons/WTGER_WWII.php
https://www.uboat.net/technical/torpedoes.htm

[Silver_Dragon]

21 hours ago, xvii-Dietrich said:

 
The G7a making "S-turns" would be either the FAT ( Federapparattorpedo) or LuT (Lagenunabhängiger Torpedo) versions. The G7a T1 had several of these variants. They were specifically designed to go into the said S pattern into order to criss-cross the path of a target (esp. effective when multiple ships were involved, such as a convoy). The FAT were introduced in 1942 and the LuT in 1944.
 
http://navweaps.com/Weapons/WTGER_WWII.php
https://www.uboat.net/technical/torpedoes.htm

ED has making a G7a TI, not a G7a Lut or Fat. I know that versions by previous sub simulation games. and available info:

 

Lut has a pattern gear selectable to make turns to left or right, to make perperdicular turns to a bering and not make S-Turns. The torpedo has diferent to the G7a T1 and only travel to 30 knots at 12500 meters range.

http://www.tvre.org/en/torpedo-fire-control-system-and-fat-torpedoes

 

The FAT meanwhile can make a particular "S-Turn", has a evolution of Lut Torpedoes with a mechanist integrate on giroscope with make a very range of patterns, configurable previously launch.
https://translate.google.pl/translate?sl=pl&tl=en&js=y&prev=_t&hl=pl&ie=UTF-8&u=http%3A%2F%2Ftvre.org%2Fpl%2Fsystem-kierowania-ogniem-torpedowym-a-torpedy-lut&edit-text=

 

ED need build realistic torpedoes, no "grafting" weapons.

Enviado desde mi RNE-L21 mediante Tapatalk

Edited May 6, 2021 by Silver_Dragon

[xvii-Dietrich]

12 hours ago, Silver_Dragon said:

ED has making a G7a TI, not a G7a Lut or Fat.

 

The LuT and FAT are still G7a TI torpedoes, just sub-variants (no pun intended).

 

Otherwise, it would be like saying that they are making an FW190, not an A8.

Or, as a more pertinent example, the Type-VIIC U-boat.

 

ED are not partcularly precise on nomenclature or spelling. The current Mission Editor namespace has a lot of such imprecision. In any case, even though the torpedo is labelled as a general G7a TI, it is modelled as a G7a TI FAT. So the S-turn pattern could be expected... especially for 1944+, which is the time period of the two WW2 maps.

[Silver_Dragon]

1 hour ago, xvii-Dietrich said:

 

The LuT and FAT are still G7a TI torpedoes, just sub-variants (no pun intended).

 

ED are not partcularly precise on nomenclature or spelling. The current Mission Editor namespace has a lot of such imprecision. In any case, even though the torpedo is labelled as a general G7a TI, it is modelled as a G7a TI FAT. So the S-turn pattern could be expected... especially for 1944+, which is the time period of the two WW2 maps.

 

Has only a "Frankentorpedo", no a acurated weapon and ED make all available weapons, but ok, I not going to open a discusion about them.

Edited May 6, 2021 by Silver_Dragon

[Northstar98]

Just as an update, as of DCS 2.7.2 this is still happening.

 

After travelling a fair way, the G7a T1 starts doing a snake search pattern - something more appropriate for an active/passive acoustic homing torpedo, when fired at range it can cause the torpedo to miss the intended target (in the track it hit the stern of the target, but only just). Details are above.

 

The G7a T1 is just a straight runner, once it's at it's pre-set depth and course, it just runs straight until it fuses or runs out of fuel.

G7a_T1_snake_272.trk

[QuiGon]

I have nothing useful to add to this, but I just want to say, that it amazes me how far this flight sim has come, that we're now at a point where we're "complaining" about Torpedo search patterns! I love it!

[Northstar98]

46 minutes ago, QuiGon said:

I have nothing useful to add to this, but I just want to say, that it amazes me how far this flight sim has come, that we're now at a point where we're "complaining" about Torpedo search patterns! I love it!

 

Well, it's still very much early days for them yet - there's still some behaviour still missing and the wake is just a regular smoke trail (which looks pretty bad IMO), but yes, it's great that DCS is expanding its environment.

[Silver_Dragon]

When I put the same post some months ago, I only recevie "attacks" and hide my post by thinking, "that a waste of time", now has perfect.... 

Edited June 20, 2021 by Silver_Dragon

[Northstar98]

1 hour ago, Silver_Dragon said:

When I put the same post some months ago, I only recevie "attacks" and hide my post by thinking, "that a waste of time", now has perfect.... 

 

 

You were attacked for reporting what is clearly a bug?

 

I wouldn't put it at the top of the list of priorities, nowhere near it, but that doesn't mean it shouldn't be reported.

Edited June 20, 2021 by Northstar98

[BIGNEWY]

threads merged

[Silver_Dragon]

My research about german torpedoes on 2019, when Wags talk about them.

 

 

[Silver_Dragon]

Theory of underwater explosions
https://www.researchgate.net/publication/251393757_Underwater_Explosion_Phenomena_and_Shock_Physics

Long-Range Detection and Location of Shallow Underwater Explosions Using Deep-Sound-Channel Hydrophones
https://www.researchgate.net/publication/241194376_Long-Range_Detection_and_Location_of_Shallow_Underwater_Explosions_Using_Deep-Sound-Channel_Hydrophones
 

[Silver_Dragon]

Meanwhile has a G7e electric torpedoe, that show interesting mechanism, giro angle, depth keping, detonator and other funtionality on G7 torpedoes and Uboat Type VII torpedo launch system. The video has WIP and missing something.

 

G7 Torpedoe has diferente tails, propellers and detonators.

Edited July 3, 2021 by Silver_Dragon

[Northstar98]

4 hours ago, Silver_Dragon said:

Meanwhile has a G7e electric torpedoe, that show interesting mechanism, giro angle, depth keping, detonator and other funtionality on G7 torpedoes and Uboat Type VII torpedo launch system. The video has WIP and missing something.

 

G7 Torpedoe has diferente tails, propellers and detonators.

 

 

While not related to my thread, I should mention that the propeller for the current G7a TI torpedo is incorrect, the real propellers counter-rotate, but in the modelviewer, they rotate in the same direction, which would cause the thrust to cancel out, and the torpedo to roll.

 

The nose of the torpedo are missing the 4 'prongs' of the impact detonator, and the arming turbine on the front isn't implemented.

 

The bubble wake the torpedo leaves is currently a regular smoke trail - and doesn't bare much resemblance to a real wake (see SH4 for a bubble wake done right).

 

Though the guidance issues are more of a pressing issue for me.

[Northstar98]

Hi, just wanted to mention that this is still an issue.

 

After about 6-7km the G7a TI torpedoes begin a snake-like search pattern, that's more reminiscent of a post WWII guided torpedo. The G7a TI, once established on it's course should run straight, at a preselected depth until it either hits something or runs out of steam.

 

The real life torpedo when launched, should initially run straight, then after 9.5m it should turn to a preselected course (known as a gyroangle, and turns with a radius of 95m (obviously if it's aimed down the same course as the launching vessel, it won't turn), and ascend/descend to a preselected depth (1-12m). The gyroangle can be as much as ±90° off of the launching vessel's boresight.

 

Also, the real torpedo has 3 speed settings, which also determines the maximum range of the torpedo, these speed settings are as follows:

• 30 kts and 12km
• 40 kts and 7.5km
• 44 kts and 5km

Right now the torpedo does 37 kts and has a maximum range of ~8.2km

 

There are also other, more minor issues, which are described in my OP.

G7a_T1_snake.trk

[NineLine]

Reported, thanks.