Mi-24 NAV & Targeting system capabilities

[randomTOTEN]

1 hour ago, SnuggleFairy said:

So far in my tests, I can't figure out what KM-2 actually affects. No matter what the values I set, nothing is affected.

Same. Nothing changes, even when I set a value of -30.0°

I've also discovered that the DISS-15 in the Mi-24P has an error of 1.3° East. I.E. when you calculate the desired magnetic course, subtract 1.3 from the answer for this correction.

1 hour ago, SnuggleFairy said:

Also Mi-8 has a similar system - KM-8.

I don't see that. There is no reference to this equipment in the flight manual.

1 hour ago, SnuggleFairy said:

You should be able to set magvar there and it should do the same - make the aircraft systems work in true headings.

You can do that with the ZK switch on the bottom right of the SU-26 control panel. Just adjust the DG (in GPK mode) until it indicates current True Heading.

1 hour ago, SnuggleFairy said:

But i cannot find where this KM-8 is mounted.

I don't think we have it. I know that control is in the L-39 Cockpit. But as I understand it, it's basically broken.

Edited October 21, 2021 by randomTOTEN

[SnuggleFairy]

11 minutes ago, randomTOTEN said:

You can do that with the ZK switch on the bottom right of the SU-26 control panel. Just adjust the DG (in GPK mode) until it indicates current True Heading.

 

Yes, you're right, we can do that.

11 minutes ago, randomTOTEN said:

I don't see that. There is no reference to this equipment in the flight manual.

There's no reference indeed. I found it here and here:
https://infopedia.su/17x103f.html

https://studfile.net/preview/9728285/page:8/

Unfortunately it's in Russian

[Tarres]

52 minutes ago, randomTOTEN said:

Same. Nothing changes, even when I set a value of -30.0°

I've also discovered that the DISS-15 in the Mi-24P has an error of 1.3° East. I.E. when you calculate the desired magnetic course, subtract 1.3 from the answer for this correction.

 

 

I´ve had the same problems.

It seems that the Gerben-1/KM-2 systens are WiP.

[randomTOTEN]

2 hours ago, SnuggleFairy said:

I found it here and here:

Good references, thank you!

I have a suspicion that KM-2 and KM-8 are different versions of the same device.

From the next page: https://infopedia.su/17x1043.html

Quote

Коррекционный механизм КМ-8 предназначен для:
- связи индукционного датчика ИД-3 с гироагрегатом ГА-6;
- устранения четвертной и инструментальной погрешностей с помощью лекального устройства;
- ввода магнитного склонения;
- приведения в полете магнитного курса к ортодромическому.

В коррекционном механизме установлены два сельсина: один служит для согласования ротора этого сельсина с положением чувствительного элемента датчика ИД-3 относительно направления горизонтальной составляющей магнитного поля Земли, второй - для передачи на гироагрегат ГА-6 сигналов курса, принятых с датчика ИД-3 и откорректированных в коррекционном механизме с помощью лекала и кремальеры.

Which google translates:

Quote

Correction mechanism KM-8 is intended for:
- communication of the induction sensor ID-3 with the GA-6 gyro unit;
- elimination of quarter and instrumental errors using a curvature device;
- input of magnetic declination;
- bringing the magnetic course to orthodromic in flight.

Two selsyns are installed in the correction mechanism: one is used to match the rotor of this selsyn with the position of the sensor ID-3 sensor relative to the direction of the horizontal component of the Earth's magnetic field, the second is used to transmit the course signals received from the ID-3 sensor and corrected to the GA-6 gyro unit. in the correction mechanism with the help of a template and a ratchet.

So seems it is a device foreign to western aircraft. About the nearest approximation we have are the correcting magnets within a mechanical compass. It seems with this any heading reference can be set. You can simply correct for deviation, or enter the local variation and use it to indicate true. Or anything else really...

But it doesn't slew our gyros in the simulation. Outside the KM-2, I see no way to slew our gyros in the Mi-24P. In the Mi-8MTV2 we have the ZK switch on the SU-26.

Clearly the map display is WIP so I assume the gyros just aren't talking to it yet.

The next question is are the gyros talking to the DISS-15?

Edited October 21, 2021 by randomTOTEN

[randomTOTEN]

I also don't know the term "quarter deviation" ("четверть отклонения")? In this context.

[SnuggleFairy]

35 minutes ago, randomTOTEN said:

The next question is are the gyros talking to the DISS-15?

Not according to my tests. No matter what you put there, in Gyro mode the Diss-15 holds 0 deviation when flying indicated(desired) magnetic heading, until after about 60kms the HSI deviates about 10 degrees to the right resulting in about 5-7km "left" deviation on Diss-15 nav panel upon arrival at your destination after 100km flight. I've done the tests on Caucasus, i don't think it's the same on all maps.

 

59 minutes ago, randomTOTEN said:

I also don't know the term "quarter deviation" ("четверть отклонения")? In this context.

didn't know what that was either, but here i found:

https://www.msun.ru/upload/folders/edu_lit/kaf/tss/hyrodev.pdf

"Было замечено, что при кач-
ке установленный на судне ГК имеет значительные погрешности, носящие
четвертной характер, то есть достигающие максимальных значений на рум-
бах NE, NW, SE, SW и обращающиеся в нуль на румбах N,S,E,W."

This stuff is boat related, but I think the gyro compasses are similar. I'm not an engineer and i don't fully understand how everything works, but from my limited understanding "quarter deviation" is deviation in gyro compasses during rocking of the vessel/aircraft that reaches it's peaks when facing NE NW SE SW, and it goes to 0 when facing N S E W. So "in quarters" kind of thing. It's something to do with fluid level in or around the gyros, not sure.

 

I also found that KM-8 is supposed to be installed behind the left pilot seat. You can kinda see it here behind pilot's left shoulder:

https://www.360cities.net/image/helicopter-mi-17v5-the-world

And you can also check this one out:

https://www.360cities.net/image/cockpit-mi-8-helicopter-radom-airshow-2011

You can see what looks like the ГА-6 and АС-1, but the KM-8 is blocked by the seat

 

[randomTOTEN]

So....I have a hypothesis....

Placing the Gerben-1 mode knob in ZK doesn't actually put the system into any operating mode. The GMK-1 only has 2 operating modes. "GYRO/MAG aka GPK/MK"

The far left position HDG aka ZK enables the "latitude" knob to become a heading adjustment knob. Not how it currently works.. but just an idea.

 

Also looking at images of the panel on the internet. The three round black objects on the left are lights. Top to bottom: Automatic, "TB," Off or Fail....?

The part number for the Gerben-1 is PU-38B or perhaps just PU-38

Edited October 22, 2021 by randomTOTEN

[SnuggleFairy]

24 minutes ago, randomTOTEN said:

So....I have a theory....

Placing the Gerben-1 mode knob in ZK doesn't actually put the system into any operating mode. The GMK-1 only has 2 operating modes. "GYRO/MAG aka GPK/MK"

The far left position HDG aka ZK enables the "latitude" knob to become a heading adjustment knob. Not how it currently works.. but just an idea.

Possibly. Yeah i couldn't figure out any way to move the HSI in the ZK mode.. maybe only adjustable by ground crew? Need an expert who can tell us how things actually work

59 minutes ago, randomTOTEN said:

Also looking at images of the panel on the internet. The three round black objects on the left are lights. Top to bottom: Automatic, "TB," Off or Fail....?

The part number for the Gerben-1 is PU-38B or perhaps just PU-38

I found this:

https://rykovodstvo.ru/exspl/20494/index.html?page=5

It says Auto light comes on when the latitude is determined and fed from a GPS i guess. "Fail" light comes on with gyro failure. They didn't explain what TV light is.

Also the previous page on that document explains how to operate the deviation compensator and it sounds like you just put it into ZK and set the mag var and it should align the HSI... then it can me switched into its main operating mode GPK

[randomTOTEN]

SnuggleFairy,

this is great stuff, nice job finding it!

[randomTOTEN]

Quote

В случае необходимости выставки курсовой системы по заданному курсу тумблером В4 "ЗК-ОТКЛ" на пульте управления ПУ-39Б включается режим "ЗК". (ВЗ находится в положении «ГПК»). С целью миниатюризации курсовой системы в ней в качестве задатчика курса используется не отдельный прибор, а дополнительно синусно-косинусный трансформатор коррекционного механизма КМ-2Б.

Ввод заданного курса _З осуществляется расположением на лицевой панели КМ-2Б, вручную - кремальерой, полуавтоматически - двухполюсным переключателем. Отсчет заданного курса производится по счетчику "СКЛОНЕНИЕ". Включение режима "ЗК" сигнализируется загоранием лампочки на КМ-2Б.

Эти же органы управления на КМ-2Б используются в режиме магнитной коррекции (МК) для введения магнитного склонения . Ввод магнитного склонения позволяет перейти от магнитного курса к ортодромическому:

Functionally translated by Google;

Quote

If it is necessary to exhibit the course system at a given course, switch B4 "ЗК-OFF" on the control panel PU-39B turns on the "ЗК" mode. (OT is in the position of "GPK"). In order to miniaturize the course system, it uses not a separate device as a course generator, but additionally a sine-cosine transformer of the KM-2B correction mechanism.

The set course  _З is entered by positioning it on the front panel of the KM-2B, manually - with a rack, semi-automatically - with a two-pole switch. The set course is counted according to the "DECLINE" counter. The inclusion of the "ZK" mode is signaled by the light coming on on the KM-2B.

The same controls on the KM-2B are used in the magnetic correction (MK) mode to introduce magnetic declination . Input the magnetic declination allows you to go from a magnetic course to the great circle:

I think that about completely answers my questions of how the system operates. KM-2 panel really is central to the operation of the gyro system. Despite claims in the latest update, it's still not done yet, but the progress is encouraging. I'm excited to use the system as it matures.

 

2 hours ago, SnuggleFairy said:

It says Auto light comes on when the latitude is determined and fed from a GPS i guess.

Just to clarify my understanding, it uses the phrase NV computer. I understand that to be also an INS. It's probably fair just to say the source is any sort of Area Navigation system which can continuously track the latitude. As they probably call GPS an NVU of some sort as well...

The real meat and potatoes is 2 pages prior to your link!

[SnuggleFairy]

11 hours ago, randomTOTEN said:

Just to clarify my understanding, it uses the phrase NV computer. I understand that to be also an INS. It's probably fair just to say the source is any sort of Area Navigation system which can continuously track the latitude. As they probably call GPS an NVU of some sort as well...

yeah, anything that can calculate the latitude. I bet different countries use different systems. That light basically means "don't touch the latitude adjustment knob" lol

[VitMax]

On 10/22/2021 at 1:45 AM, randomTOTEN said:

I also don't know the term "quarter deviation" ("четверть отклонения")? In this context.

On 10/22/2021 at 2:55 AM, SnuggleFairy said:

didn't know what that was either, but here i found:

"Четвертная погрешность" means "quadrantal deviation". It is type of error in magnetic compasses that changes it's sign (and also fully disappears) four times during a full 360 degrees turn. It is caused by soft magnetic materials in an aircraft near the compass location.

In case of KM-8 this error is removed before magnetic heading data is fed from induction compass to gyrocompass.

It is basically the same as permanent magnets in regular magnetic compasses that are used to remove deviation.

And about KM-8 itself: basically, KM-8 is an intermediate device that turns magnetic course received from induction sensors into orthodromic course that is shown on gyrocompass indicator (UGR-4UK in case of Mi-8). And Mi-8 does have KM-8 as a part of GMK-1A gyromagnetic course system.

As for KM-2, the idea behind it is the same. The main difference is that it has separate control panel. In case of Mi-8, orthodromic course can be set up on PU-26 (main course system panel on the overhead) with ЗК switch. How it's supposed to be done in Mi-24, I'm not sure. I've read description of Greben, but it's still not very clear to me, to be honest.

Edited October 24, 2021 by VitMax
added part about KM-8 and KM-2

[SnuggleFairy]

2 hours ago, VitMax said:

And about KM-8 itself: basically, KM-8 is an intermediate device that turns magnetic course received from induction sensors into orthodromic course that is shown on gyrocompass indicator (UGR-4UK in case of Mi-8). And Mi-8 does have KM-8 as a part of GMK-1A gyromagnetic course system.

As for KM-2, the idea behind it is the same. The main difference is that it has separate control panel. In case of Mi-8, orthodromic course can be set up on PU-26 (main course system panel on the overhead) with ЗУ switch. How it's supposed to be done in Mi-24, I'm not sure. I've read description of Greben, but it's still not very clear to me, to be honest.

For the Mi-24, there's a panel in the operator's seat, by his left shoulder

[VitMax]

22 minutes ago, SnuggleFairy said:

For the Mi-24, there's a panel in the operator's seat, by his left shoulder

Yeah, I know, that's correction mechanism panel. But there's also ЗК (задатчик курса, course selector) mode on main Greben panel, and I'm not sure, what it's for. In other gyromagnetic course systems, like GMK-1A from Mi-8, course selector is used in ГПК (gyrocompass) mode. And in Greben ГПК and ЗК are two different modes. Not sure, what's the difference.

[SnuggleFairy]

5 minutes ago, VitMax said:

Yeah, I know, that's correction mechanism panel. But there's also ЗК (задатчик курса, course selector) mode on main Greben panel, and I'm not sure, what it's for. In other gyromagnetic course systems, like GMK-1A from Mi-8, course selector is used in ГПК (gyrocompass) mode. And in Greben ГПК and ЗК are two different modes. Not sure, what's the difference.

Oh yes, you're right, I'm not sure myself. Maybe ground crew does it?

[Tarres]

Some ideas, unfortunately not being able to confirm this.

It seems that the Greben (or similar) is/was fitted in helos/airframes that have some kind of "autopilots" (course selectors/ route mode) like the KA-32 civilian models, Mi-26, Mi-17 (before they got western avionics).

Helos and airplanes without "autopilots route mode/course selectors" were fitted with GMK-1 or similar. 

Maybe with "Autopilot", or "course selectors in the former USSR", the Gerben or similar is compulsory?

Something like:

Set MagVar in the KM-2 (or similar), set the Greben in "tune" mode, set the latitude in the Greben, push the synch button to synch the KM-2 value, set the Greben in oper. mode.

Select the operating mode.

And we´ve got 3 operating modes, two of them like in the Mi-8, gyro, and mag, and a third one, the HDG (ZK) mode.

But with the system WiP it´s a bit difficult to say something,

 

[VitMax]

On 10/22/2021 at 8:13 AM, randomTOTEN said:

Just to clarify my understanding, it uses the phrase NV computer. I understand that to be also an INS. It's probably fair just to say the source is any sort of Area Navigation system which can continuously track the latitude. As they probably call GPS an NVU of some sort as well...

On 10/22/2021 at 7:22 PM, SnuggleFairy said:

yeah, anything that can calculate the latitude. I bet different countries use different systems. That light basically means "don't touch the latitude adjustment knob" lol

I have a feeling that the ability to to use automatically calculated latitude was included for non-existent equipment that could theoretically be created in the future. At least, that was the case with TKS-P2 (used in Tu-154). This system also had input for latitude information, but it was never used, since device that could provide latitude information didn't exist at the time.

On 10/22/2021 at 5:32 AM, SnuggleFairy said:

It says Auto light comes on when the latitude is determined and fed from a GPS i guess. "Fail" light comes on with gyro failure. They didn't explain what TV light is.

According to this article, TV light is just not used at all. Though, it doesn't explain, why this light exist in the first place.

8 minutes ago, Tarres said:

Some ideas, unfortunately not being able to confirm this.

It seems that the Greben (or similar) is/was fitted in helos/airframes that have some kind of "autopilots" (course selectors/ route mode) like the KA-32 civilian models, Mi-26, Mi-17 (before they got western avionics).

Helos and airplanes without "autopilots route mode/course selectors" were fitted with GMK-1 or similar. 

Maybe with "Autopilot", or "course selectors in the former USSR", the Gerben or similar is compulsory?

Something like:

Set MagVar in the KM-2 (or similar), set the Greben in "tune" mode, set the latitude in the Greben, push the synch button to synch the KM-2 value, set the Greben in oper. mode.

Select the operating mode.

And we´ve got 3 operating modes, two of them like in the Mi-8, gyro, and mag, and a third one, the HDG (ZK) mode.

But with the system WiP it´s a bit difficult to say something,

I'm not sure about that. I feel that having a separate mode for selecting course is just a weird design quirk. TKS-P2 (from Tu-154) -- basically, the best soviet course system of the time -- has the same operation logic as GMK-1A from Mi-8. You change the mode into GPK, and then set your current true heading (or any other heading, if you want). GPK-1A works the same way. And both of these systems don't have tune/work switch either.

[randomTOTEN]

On 10/24/2021 at 11:17 AM, VitMax said:

It is caused by soft magnetic materials in an aircraft near the compass location.
...It is basically the same as permanent magnets in regular magnetic compasses that are used to remove deviation.

Thank you for the confirmation.

On 10/24/2021 at 11:17 AM, VitMax said:

And Mi-8 does have KM-8 as a part of GMK-1A gyromagnetic course system... In case of Mi-8, orthodromic course can be set up on PU-26 (main course system panel on the overhead) with ЗК switch.

Yes, agree.

On 10/24/2021 at 1:29 PM, SnuggleFairy said:

How it's supposed to be done in Mi-24, I'm not sure.

I feel my understanding is getting better. They share a lot of similarities, but some important differences.

Quote

But there's also ЗК (задатчик курса, course selector) mode on main Greben panel, and I'm not sure, what it's for.

My understanding is it cuts out signal from Induction (Flux Gate) sensor. KM-2 correction value remains as the only signal.

On 10/24/2021 at 2:12 PM, SnuggleFairy said:

Maybe ground crew does it?

No, I think it is as duty of the Pilot Gunner.

On 10/24/2021 at 3:07 PM, Tarres said:

t seems that the Greben (or similar) is/was fitted in helos/airframes that have some kind of "autopilots"

I would describe it as a directional indication system. An autopilot's operation would be dependent on it, but Greben/GMK-1A would be independent from any autopilot.

On 10/24/2021 at 3:07 PM, Tarres said:

Set MagVar in the KM-2 (or similar), set the Greben in "tune" mode, set the latitude in the Greben, push the synch button to synch the KM-2 value, set the Greben in oper. mode.

Select the operating mode.

I think this is a correct use of the system. Have no idea what the "tune" mode (bottom switch) is supposed to do. Seems everything can be done in the OPERATE mode. In the Tu-154 that's a selector for independent gyros a.k.a. a 2 gyro system "GMK-2."

According to the maintenance tests, if I understand them correctly.. mode ZK directly controls the HSI. I.e. if I set a declination value of +30°, set ZK, and press the Synchronize button, the Heading Indicator is supposed to slew to 030° +/-1° at a rate of minimum 10°/sec.

[SnuggleFairy]

19 minutes ago, randomTOTEN said:

According to the maintenance tests, if I understand them correctly.. mode ZK directly controls the HSI. I.e. if I set a declination value of +30°, set ZK, and press the Synchronize button, the Heading Indicator is supposed to slew to 030° +/-1° at a rate of minimum 10°/sec.

From what I understood, the synch button is "fast align" button. When in MAG mode the HSI is automatically aligning with the compass, but slowly and synch button just makes the process faster. There could be some other functions for this button, but I couldn't find anything except what I described above

[randomTOTEN]

17 minutes ago, SnuggleFairy said:

From what I understood, the synch button is "fast align" button.

Correct.

17 minutes ago, SnuggleFairy said:

When in MAG mode the HSI is automatically aligning with the compass, but slowly

2-4 degrees per minute. And only when the attitude is within limits to prevent signal removal by (I think) VU-12.

17 minutes ago, SnuggleFairy said:

synch button just makes the process faster.

10+ degrees per second.

27 minutes ago, SnuggleFairy said:

There could be some other functions for this button, but I couldn't find anything except what I described above

I agree with you, I don't think there are.

[randomTOTEN]

So per the latest newsletter,

Quote

With it [the KM-2], the Co-Pilot Gunner (CP/G) will have to dial magnetic variation into the KM-2 to get the true heading on the RMI.

This made me question the significance of True Headings for the Greben. I had noticed in testing that the map display had a drift of 7° Left when flying True North on my test mission. I decided to test if there would be any drift flying Gyro North (currently can only be set to Magnetic North in mode MK).

My test was successful, so the map display appears to referencing the Gyro for direction information. If you fly an indicated heading of 000°, the crosshair moves directly up on the map display (currently oriented to True North)! So that part is correctly modeled!

[AeriaGloria]

6 hours ago, randomTOTEN said:

So per the latest newsletter,

This made me question the significance of True Headings for the Greben. I had noticed in testing that the map display had a drift of 7° Left when flying True North on my test mission. I decided to test if there would be any drift flying Gyro North (currently can only be set to Magnetic North in mode MK).

My test was successful, so the map display appears to referencing the Gyro for direction information. If you fly an indicated heading of 000°, the crosshair moves directly up on the map display (currently oriented to True North)! So that part is correctly modeled!

Which map? They all have different magnetic variation, I always thought it was evenly applied to all headings. For example I think Caucuses is -2. Syria +5

[randomTOTEN]

3 hours ago, AeriaGloria said:

Which map?

Caucasus. Yeah it will apply to all headings since it's a rotation of the entire compass rose.

[randomTOTEN]

Looks like a demonstration of the KM-2 with the Greben in mode "MK." But the presenter doesn't show us the gyro mode. This is probably sufficient for the majority of users.

What's interesting is that the translated documentation makes no mention of the gyros slewing during use of the TEST button on KM-2, but considering how the system works in MK, this would make sense. It wouldn't make sense in any other mode.

It will be interesting to see if this is the limit of the simulation, or just scratching the surface.