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Assistance with RSBN


Weegie
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I have no idea if its because of changes or if the manual is a bit out of date but I was tying myself in knots trying to understand the KPP director, the NPP needles, Directional beacons and the associated radials.

 

From what I understood from the manual and posts told me

 

Radials were always from the beacon

 

The "Leatherneck" implementation of the director providing solutions to guide you to a radial, could not be used if the radial was behind the beacon

 

Based on the above to fly to a given beacon, you selected the radial 180 degrees from your desired heading, to use the radial on your side of the beacon.

 

After a bit of experimentation my experience so far is

 

You select the course pointer to point to your beacon at a desired heading, in the case of a runway that would just be the published heading for it (example Batumi 126 degrees, Kobuleti 70 degrees etc)

 

If flying to the beacon you fly the "heads", or arrows of the pointers

 

If flying from the beacon you fly the "tails" of the pointers

 

The director does not seem to care if you are flying to or from the beacon and will issue directions to place you onto the desired radial.

 

While I normally do fly a manual interception, I could not help but notice that the director seems to be issuing similar instructions

 

If I'm correct its very simple but there seems to be so much conflicting and wrong information on how to use the system

 

If I'm wrong, I'd love to be placed on the path of spiritual enlightenment

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looks like yuo are doing it right... all you are doing with radial nav is flying angles between intercept points (beacons) you can use them to find new waypoints in the wild. Did you read Chuck's guide on them?

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Thanks for the confirmation doom

 

Yeah I read Chuck's guide, but in that he has the course heading arrow around the other way, so he is including the 180 degree offset. Of course what added more confusion was when the needles were then swapped around in an update, some time ago.

 

The conflicting info was getting me very confused (which is easy to do).

 

So I just started to experiment using different headings for the course arrow and BINGO setting it the way I started to behave like it should.

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That's also how I see it, if you intercept a radial alpha FROM a station (I suppose that's what you call "the radial on your side of the beacon"), the 3K course needle points to alpha-180°, so that it actually points to the station and not from it. Otherwise it seems to confuse the director, though you could still intercept it manually on the NPP.

 

If you intercept a radial alpha TO a station, the course needle must be set to alpha.

 

It's what the manual describes pp. 114-116, or at least how I understand it. :)

 

I noticed that if your current bearing is too far off from the radial, the director may point the wrong way, "thinking" you want to intercept to the station and not from it, which makes sense. Once your bearing gets in the general angle of the desired to/from radial, it'll adapt.

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Ok that seems to clear it up, Redglyph, I re-read the manual pages and yes I agree now what it states makes sense.

 

Initially on the first read that's not what I took from it all ...............guess that's just me though :doh: clown_2.gif

 

Thanks guys for the confirmation


Edited by Weegie
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It's not just you ;) This is easily confusing, doing some "live" tests really help understand how it works, which you did.

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There is a very good reason why the bank director behavior makes no sense. It's not supposed to function with RSBN. It is a complete work of fiction. Ignore it.

 

The only time the bank needle should be energized is when the SAU command or automatic PRMG landing mode is running. At all other times it should be sitting limply in the middle of the instrument just like when the battery is disconnected.

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It's not just you ;) This is easily confusing, doing some "live" tests really help understand how it works, which you did.

 

Nice to know I was not the only one.

 

I think I might try to make a video to explain how to set it up and do a simple interception. That might clear it up a little for others.

 

The manual, Chuck's Guide, JohnXXX's videos and above all you good people here, especially have helped me.

 

Thank You for that


Edited by Weegie
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There is a very good reason why the bank director behavior makes no sense. It's not supposed to function with RSBN. It is a complete work of fiction. Ignore it.

 

The only time the bank needle should be energized is when the SAU command or automatic PRMG landing mode is running. At all other times it should be sitting limply in the middle of the instrument just like when the battery is disconnected.

 

You answered another question for me on a related topic in another thread Frederf.

 

The explanation was clear, and in great detail, helping me to understand the director. It was that explanation that led me down the road of learning how to manually intercept a given radial using the NPP.

 

As a work of fiction which I rarely use though, the director was still bothering me. It should work (of sorts) therefore I was probably doing something wrong.

 

Hence the further testing and ultimately this thread.

 

As mentioned in the previous post if I do get around to a video on it, then its nice to show all the features that are implemented, fictional or not.

 

Total pain that the Track Replay function isn't working either, although its far from the only module that suffers from this problem.

 

I'm grateful for all (and any) help, I get.


Edited by Weegie
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I never ever learnt the NAV system even when i did ground school but no flight training became expensive . But the 1st time I tried these navs in my years of simming is in the Mig21. Though I don't understand it too well but i just follow the CDI that i have set and usually intercept it. I may get offset though.

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There is a very good reason why the bank director behavior makes no sense. It's not supposed to function with RSBN. It is a complete work of fiction. Ignore it.

 

The only time the bank needle should be energized is when the SAU command or automatic PRMG landing mode is running. At all other times it should be sitting limply in the middle of the instrument just like when the battery is disconnected.

 

Are you saying the directional needles are a fiction and only used in PRMG mode? If there's a thread discussing it, I'd be interested to know, just out of curiosity for the real aircraft itself. I've seen this discussion but no source for this piece of information, and from the "official" manual translated to English for some non-Russian-speaking countries (*), I understand the vertical localizer pointer works in both modes. Was it false advertising? ;)

 

 

(*) If that's what it is... Mig 21Bis Pilot`s Flight Operating Instructions, available for instance on Avialogs

RSBN2.png.cdb65af7f27053f85c3d886ff4f2a1f1.png

RSBN1.png.2c6afea72c1f1aa5ee8fa1a5a9218af0.png

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Nothing in the manuals of either the MiG-21 or L-39 suggests that the NPP localizer needle (item 5, left diagram, vertical needle) is involved in RSBN navigation i.e. functioning as a CDI as in a Western HSI. However someone said that in the L-39 it does. No evidence was provided to support this and I don't care to argue either way.

 

What the MiG-21 and L-39 manuals do make very clear is that the KPP course position indicator (item 8, right diagram) does function in RSBN navigation in much the same was the CDI of an HSI would and is the primary indication of on course position. This is the item which is referred to in paragraph (b) of your publication. It is not false advertising just not reading the manual carefully.

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This just gets more and more interesting.

 

Last night I completed a short hop from Kobuletti to Batumi in the evening over the water using the RSBN & PRMG nav and recorded it on video.

 

So I get the NPP and all the needles doing what I'd expect, the director vertical needle also provides me course indications as well.

 

I go back and check the KPP course indicator on the video and its moving around too. At first I thought it was mimicking the director but its not, it's mimicking the vertical localiser bar on the NPP.

 

The manual states its course deviation and should be used to fine tune the course heading. I understand course deviation, so should I just ignore these indications until on my desired radial and then use them to fine tune my heading as required, or can it be used in some other way?

 

One more question is what is the scale? On the NPP there are 4 dots again mimicked on the KPP course indicator. Anybody any ideas what these dots represent?

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So looking at the video and rotating the course heading pointer, when on the runway at Kobuletti it would appear that the gaps between the dots represent 1 degree deviation between the beacon pointer and the course heading pointer.

 

Moving the course setting pointer to the left relative to the beacon pointer throws the localiser bar to the right and vice versa.

 

I can see how it would inform me if I was flying with course pointer and beacon pointer aligned or slightly off, but I'm still a bit unsure of exactly what is trying to tell me and how to interpret these instructions

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Nothing in the manuals of either the MiG-21 or L-39 suggests that the NPP localizer needle (item 5, left diagram, vertical needle) is involved in RSBN navigation i.e. functioning as a CDI as in a Western HSI. However someone said that in the L-39 it does. No evidence was provided to support this and I don't care to argue either way.

 

What the MiG-21 and L-39 manuals do make very clear is that the KPP course position indicator (item 8, right diagram) does function in RSBN navigation in much the same was the CDI of an HSI would and is the primary indication of on course position. This is the item which is referred to in paragraph (b) of your publication. It is not false advertising just not reading the manual carefully.

I was talking about the KPP, not the NPP needle. The latter does move in navigation mode in the DCS module, indeed, not sure what to make of that.

 

I see what you mean, in the DCS manual, the command pointer is called director too. They also mention that the item 8 discussed earlier is "an auxiliary PRMG needle", which sounds like it's only used in landing mode, whereas it actually works in landing/letdown mode OR in navigation mode, just differently. It seems fine in the DCS module though. As for the command pointer, perhaps they misread the manual, perhaps it's just a bug, who knows.

 

This just gets more and more interesting.

 

Last night I completed a short hop from Kobuletti to Batumi in the evening over the water using the RSBN & PRMG nav and recorded it on video.

 

So I get the NPP and all the needles doing what I'd expect, the director vertical needle also provides me course indications as well.

 

I go back and check the KPP course indicator on the video and its moving around too. At first I thought it was mimicking the director but its not, it's mimicking the vertical localiser bar on the NPP.

 

The manual states its course deviation and should be used to fine tune the course heading. I understand course deviation, so should I just ignore these indications until on my desired radial and then use them to fine tune my heading as required, or can it be used in some other way?

 

One more question is what is the scale? On the NPP there are 4 dots again mimicked on the KPP course indicator. Anybody any ideas what these dots represent?

 

The KPP course director - the top indicator of the KPP, item 8 in the right figure above, has two different behaviour, the one in navigation, and another one in landing/letdown mode, where it ignores the course set on the NPP and uses the runway alignment like a localizer needle would for an ILS - provided the localizer features horizontal guidance, of course, I've just tested one that doesn't and the needle is pretty useless in that mode. That's actually set in the MIG-21bis\Cockpit\Systems\R_NAV_data_Caucasus.lua and R_NAV_data_Nevada.lua files for the Mig-21bis, when the runway heading is provided, which seems to be the case for all airfields in the Caucasus file.

 

The dots usually mark an approximate 2° deviation (hence about +/- 8° max), but I haven't verified whether it was the case here. Different times, different country, could be different.


Edited by Redglyph

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Our terminology is all over the place. The yellow needle on the FDI is a bank director needle. The white bar on the top of the FDI is the course position indicator. The difference between a director and an indicator is that a director is directive in nature. It says "bank more" or "bank less" which are immediate attitude adjustments by the pilot. An indicator indicates a position. There is no immediate change of aircraft attitude which will satisfy being off course. Indicators tell you where you are while directors tell you what to do.

 

Yellow needle = bank director

White bar = position indicator

 

Yes I know in the DCS module the bank director isn't working so much like a bank director. When it wants a large heading change it should indicate more bank up to a limit of about 35° (assuming it should work for RSBN navigation which it shouldn't). Right now the commanded bank is unlimited until you get to the desired heading. In SAU command landing mode it is entirely possible to be left of localizer but have so much right bank the director tells you to bank more less (or less right), which is how it should be.

 

In the DCS module the NPP localizer needle and KPP position bar are exact mirrors of each other. I don't know if the NPP LLZ needle is supposed to work in RSBN but if it does I'm sure they would be mirrored info on the exact same scale. They are correctly both providing the same information on the same scale when in LANDING mode (showing PRMG LLZ position).

 

I do know that the localizer needle's extreme dot corresponds to the limit of the PRMG "exchange rate zone" localizer beams' mixing zone. The exact angular width depends on how that particular PRMG installation is set up (3-6° total width by memory). There is a spec for how wide the middle section of the scale is at the threshold (less than runway width). Long runways would have narrower LOC patterns than short runways. It's pretty much how ILSs are set up.

 

What we're missing in the DCS module is that the LLZ signal zone is no less than 30° wide by spec. There is a left zone, right zone, and a mixing zone in the middle. When in the left zone the "K" KPP flag will be black and the localizer needle will be all the way to the right side. The airplane doesn't know where exactly it is in the left signal zone (8°, 10°, 12°, whatever) just that is in the left zone somewhere.

 

What the RSBN navigation scale is I don't know. It would probably be similar to the scales used in Western VOR or TACAN HSIs.

 

The KPP course director - the top indicator of the KPP, item 8 in the right figure above, has two different behaviour, the one in navigation, and another one in landing/letdown mode
Close but not quite. The KPP course position bar has two functions as you say but the NAVIG. and LETDOWN function are the same. In NAVIG. and LETDOWN the KPP course position bar reflects the alignment of the course and bearing needles. LETDOWN and NAVIG. are both RSBN functions and almost identical except LETDOWN adds the vertical component. They are both RSBN navigation.

 

In LANDING mode the KPP position bar reflects PRMG LLZ signal (position) which is different from the other two modes.

 

The manual states its course deviation and should be used to fine tune the course heading. I understand course deviation, so should I just ignore these indications until on my desired radial and then use them to fine tune my heading as required, or can it be used in some other way?
The KPP course position bar provides position information but no directive information. When you roughly intercept the radial turn to face the station and observe the bar on the scale. If you are not on the center of the scale make a heading change to drift the bar toward the center. When the bar is centered in the scale change heading to face the station. If there is a wind to the side and you drift off course despite pointing at the station you have to re-intercept and try a different heading to counteract the drift.
Edited by Frederf
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Thanks AGAIN!! Frederf & also Redglyph

 

As usual I'm guilty of NOT being specific, all my inquiries, relate to RSBN mode and the Horizontal Position Indicator, the top horizontal bar on the KPP, for last couple of posts.

 

Ferderf your explanation is going to take a few more reads in order that I can fully absorb what you are trying so patiently to impart.

 

That said I think I understand now what to use the Horizontal Position Indicator for.

 

Apologies for my sloppy terminology, I'll try to improve and in future, include a description of where the relevant needle is located to make it clearer. In case I botch it again, which is highly probable. :poster_oops:

 

It's great when somebody who has went through the pain of acquiring this knowledge imparts it freely to the rest of us without having to first decode what the hell the question is clap_2.gif

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Thanks AGAIN!! Frederf & also Redglyph

 

As usual I'm guilty of NOT being specific, all my inquiries, relate to RSBN mode and the Horizontal Position Indicator, the top horizontal bar on the KPP, for last couple of posts.

Thanks for starting the discussion, it was an interesting topic! :)

 

The terminology differs from one source to the next in this case, it seems, and there are some exotic elements as well, "directional needles", "command control pointer" or "bank/pitch director" are not standardized terminology.

 

I think we're all just trying to find common ground here ;)

 

Close but not quite. The KPP course position bar has two functions as you say but the NAVIG. and LETDOWN function are the same. In NAVIG. and LETDOWN the KPP course position bar reflects the alignment of the course and bearing needles. LETDOWN and NAVIG. are both RSBN functions and almost identical except LETDOWN adds the vertical component. They are both RSBN navigation.

 

In LANDING mode the KPP position bar reflects PRMG LLZ signal (position) which is different from the other two modes.

That is from the previously mentioned document. If there is something "not quite", as you say, that's another difference in the DCS module. I haven't checked the letdown mode recently (shown as "proceed" in the English cockpit, for some obscure reason), so I just did and that's not entirely what I expected.

 

Normally - meaning from this original manual - the KPP top needle (8 on the FDI figure) indicates the course deviation in navigation mode, and the relative position of the localizer in landing and letdown modes. The left needle (4 on the FDI figure) indicates the relative position of the glide path in landing and letdown modes, and is not specified in the navigation mode.

 

What I observe in DCS is that the top needle shows the relative position of the localizer in letdown mode, and the left needle shows ... something else ... in letdown mode.

 

The "K" course fault flag is set in both navigation and letdown, and the "G" glide path fault flag is set in letdown mode.

 

But before saying it's wrong in DCS, I should probably admit it's quite possible that the functionality of those devices has varied during the model's lifetime, or depending on the "customer", although we'd expect the indicator's aspect to change too. It's also probable the translator made mistakes, the manual in question relates to the Mig-21bis, is in English (with Russian labels) and has some Arabic annotations and seals, it seems legit enough. The references to the radio navigation and landing systems are the same as the DCS manual, the same goes for the automatic flight control system. Yet the cockpit also shows some differences from the DCS cockpit, for example the battery gauges, or the magnetic declination indicator: that could not have been lost in translation.

 

So LN's sources were obviously different, it could be interesting to ask them whether the specs of those indicators were also slightly different, or simply misinterpreted in either version. If the navigation system is not entirely correct, that doesn't really annoy me because they are not significant differences, but I know many people in the DCS community are keen to get any module as genuine as possible, which I perfectly understand, it adds to the perceived realism.

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The manual you reference (MiG-21bis Pilot's Flight Instruction, 228 pages) and the DCS module are in agreement about the FDI lateral indicator. In the FDI section, p. 47 paragraphs (b) and ©.

The FDI can indicate the following (Fig. 18):

(b) assigned track position with respect to the aircraft (when the RSBN equipment is used in the NAVIGATION mode in order to maintain a constant azimuth in flying TO or FROM the beacon); this is indicated by the vertically-disposed, localizer course/assigned track position pointer (bar);

 

© position of the assigned flight path with respect to the aircraft (when the RSBN equipment is operating in the LETDOWN mode, or when it is used in the LANDING mode, the CCI failure warning flags closing their windows); this is indicated by the horizontally-disposed, glide path/assigned altitude position pointer (bar) as well as by the vertically-disposed, localizer course/assigned track position pointer (bar);

 

This track position pointer is functioning the same role in the same way in both nav and descent modes both in the documentation and in DCS. What is confusing is the way this document organizes the three modes into two paragraphs. It chooses to bundle the regime without vertical indication in one paragraph and the regime with vertical indication in another. This uses less words total but doesn't reflect the fact that it is the nav and descent modes which have the most in common and not the descent and approach modes.

 

If you were 2-dots off track and rapidly flipped between NAVIG. and LETDOWN switch positions the FDI pointer wouldn't change since your track position was the same in both cases. However if you were also inside the localizer signal area and rapidly switched between NAVIG and LANDING (or LETDOWN and LANDING) modes you probably would see the pointer change because your track position and your localizer position probably aren't the same.

 

If someone exploded the RSBN station with dynamite the Navig. and Letdown modes would cease to function but the Landing mode would work just fine (except for the bearing pointer). Letdown mode is simply Navig. with vertical guidance added. If someone exploded the PRMG station then Navig. and Letdown would work but Landing wouldn't. There is no localizer in letdown mode as there is no localizer in RSBN. The only localizer is placed ~1000m beyond the end of the runway aimed at the approach end and is part of the PRMG equipment.

 

===

 

The "K" and "G" flags on the CCI (NPP) represent the validity of the localizer and glide slope needle information. They only show black (valid) when in LANDING mode and receiving the localizer or GS signal respectively. Use of the LETDOWN mode should not close the "G" flag or alter the CCI GS needle. The letdown path is not a glideslope. Essentially the only parts of the CCI which should function in the RSBN modes (NAVIG/LETDOWN) is the bearing needle. On the FDI the lateral pointer shows track position in both modes and in LETDOWN the other pointer shows vertical position.

 

I strongly discount the idea of major functionality deviations regarding the POLYOT function for no given reason or translation errors which would have to be widespread and systematic to selectively deceive in several coordinated places in the manuals. Combined with comparatively blatant errors in modeling other systems I apply Occam's Razor.

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They're not in agreement. As you quoted, but you let the LANDING word in grey, the manual shows "relative position" (let's call it A) in navigation, and "flight path" (B) in letdown/landing, it's not confusing at all.

 

Pilot's Flight Operating Instruction manual: (A) navigation, (B) letdown / landing.

DCS behaviour: (A) navigation / letdown, (B) landing.

 

So for example in DCS, if you change the course on the CCI/NPP, it will move the top needle on the FDI/KPP in navigation mode and in letdown mode, but not in landing.

 

I can try and put this in a table.

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The reason why the words are "assigned track position" for NAV is that this is a showing only horizontal. The words are "flight path" for LETDOWN and LNDG because it is showing a three-dimensional path of horizontal and vertical. What defines the path (horizontal + vertical) is different in LETDOWN vs. LANDING mode though.

 

[TABLE=head]MODE|Horizontal|Vertical|Term

NAV|RSBN Course Position| None | Track

LETDOWN|RSBN Course Position| Distance-based Altitude| Path

LANDING | PRMG Localizer Position| PRMG Glide Slope Position| Path[/TABLE]

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