ADF/NDB Confusion

[Frederf]

Just recently I've been trying out the NDB function. I started a training mission which placed my on KRY'MSK airbase which happens to be where some NDBs are.

 

According to ABRIS the 4 NDBs at that airfield are (from N to S):

 

KD 833 -.- / -..

D 232 -..

F 232 ..-.

KF 833 -.- / ..-.

 

According to the placard inside the right cockpit wall channel 3 (Krymsk) is

Outer: KW, yuO

Inner: K, O

 

So I decide to try listening to the morse code identifiers that I hear on channel 3 in both the inner and outer sources.

 

Outer: ..-. / .- (FA)

Inner: ..- (U)

 

--------------------------------

 

I look up the ARK.lua and it defines channel 3 as "Krymsk" but now I see how to change the channel frequencies I think.

 

[3] =

{

[ADF_HOMER_FAR] = 833000.0,

[ADF_HOMER_NEAR] = 232000.0

}

This seems to work except that when there are two stations on the same frequency (say the 2 inner NDBs at Krymsk) the RMI needle will not switch from one station to the other despite flying closer to one or the other. I haven't tried destroying one station via weaponry however. Edited February 1, 2009 by Frederf

[bengo]

Bumpety bump

 

I too would like to know how to switch from 'one inner-NDB to the other-NDB'

[Frederf]

Oh, that's easy. There's a switch at the bottom of the center stack that has INNER-AUTO-OUTER or something like that.

[bengo]

Dang, a typo. It should have been:

....from 'one inner-NDB to the other inner-NDB' :doh:

[Frederf]

I suppose in real life two broadcasting NDBs on the same frequency would "compete" for the RMI needle based on their respective broadcasting tower and ranges. I would assume that the needle would switch from pointing to one to the other when that one was the more powerful signal due to range.

 

In US civil aviation (my experience) NDBs of the same frequency are never placed anywhere near each other. I do not know if the ADF radio would tend to pick the loudest one or perhaps take on a hybrid RMI indication receiving signals from both stations.

[EvilBivol-1]

I believe NDBs transmit from only one end of the runway, depending on wind direction.

[Frederf]

Ah so in real life the "A" set of IM/OM and the "B" set of IM/OM would never be on at the same time? The "A" set if the landing direction is one way and the "B" set if the landing direction is the other?

 

This might be simulated properly then because I was unable to get the needle to point toward one of the stations on either inner/outer setting. Perhaps those stations were simply off.

[EvilBivol-1]

I believe that is the design in the simulation, yes. I'm not sure if that's also how they operate in reality.

[Frederf]

Fantastic! It's a perfectly sensible method of NDB use which if not used so in reality, might as well be for how blithely elegant it is.

 

Now all that remains is the morse code confusions.

[bengo]

Thank you

[EinsteinEP]

I believe NDBs transmit from only one end of the runway, depending on wind direction.

I may be misreading your post, EvilBivol-1. If so, please accept my humble apologies in advance.

 

NDBs transmit in all directions, hence the nomenclature "non-directional beacons", and are used in radio navigation. NDBs are very different beings than the inner, middle, and outer markers that are placed along runway approaches for use in making landing approaches using instruments instead of visual cues. Markers are radio beacons, to be sure, but they transmit directly up (a cone of only about 45deg from straight up, I think) and are very low powered (3 W). The lowest power NDBs are around 50W but can get up to 2,000+ W. I don't have statistics, but I'd assume 1,000W is pretty standard power for an NDB.

 

An ILS system (including the OMI markers) may be brought down, due to maintenance or faults, but the marker beacons are not switched off and on depending on which way the wind is going. Every marker transmits at the same carrier freq (75 MHz), with the outer, middle, and inner markers modulated with a specific tone for their position (e.g., there's a characteristic tone for outer markers that's distinguishable from the inner and middle marker tones),but they can't conflict with each other since they only transmit straight up!

 

Some confusion may arise from the fact that NDBs are SOMETIMES co-located with a marker, but they are still two separate transmitters with two separate purposes. The just happen to be roommates.

 

Every marker beacons transmit on a carrier frequency of 75 MHz while each NDB has a unique frequency between 190 kHz to 535 kHz. NDBs are placed and freqs are assigned so that there are no conflicts between them - although mistakes CAN happen, this would be a big mistake, and I sincerely doubt that the FAA would tolerate overlapping NDBs for long.

 

I've assumed NDBs and markers are modeled as separate thingies in Black Shark (haven't experimented with radio nav yet - still working on hovering without crashing!) but this post makes me wonder if there hasn't been some confusion between markers and NDBs... will have to check now.

Edited July 7, 2009 by EinsteinEP

[Frederf]

NDBs transmit in all directions

 

He means if there are 4 NDBs at an airport, only 2 NDBs will be running at one time, the downwind IM and OM NDBs (those that you would fly over just before landing). The NDBs upwind of the runway would be off (those you fly over just after taking off).

 

Yes I know that I shouldn't confuse NDBs with markers. They are two separate things that only happen to be co-located sometimes. It's perfectly normal for there to be NDBs without a marker and markers without NDBs. I don't think the Ka-50 understands markers (OM, MM, IM) at all, only NDBs. We should call them "outer NDB" and "inner NDB" or even less confusing "NDB that is generally next to the outer marker if it exists" and "NDB that is generally next to the inner marker if it exists."

 

I assume that ED made 3 types of radio markers in the realm of NDBs and markers. Markers alone, NDBs alone, and combined NDB/Markers which if implemented correctly is functionally the same as having them strictly separate. The only difference being that the combined NDB/marker is just a programmer's shortcut to having two colocated independent stations. However it would be cool for one or the other component of the NDB/marker system to be destroyed by a stray artillery shell which is something you'd only get if they were strictly separate programming entities.

 

Of course the Ka-50's 10 ADF channels can store 20 ADF frequencies that have absolutely nothing to do with each other geographically. You can program channel 6-inner's frequency to be one NDB frequency and channel 6-outer's frequency to be another NDB 1,000 km away.

Edited February 10, 2009 by Frederf

[EinsteinEP]

He means if there are 4 NDBs at an airport, only 2 NDBs will be running at one time, the downwind IM and OM NDBs (those that you would fly over just before landing).

I'm really not trying to argue about sematics, but while there are IMs, OMs, and NDBs there's no such thing as IM NDBs and OM NDBs: you use an ADF to navigate via NDBs while in flight and your plane (if equipped) sounds an alert when you fly over an IM, MM, or OM on final approach. You do not get bearings to markers and there are no alarms when you fly over NDBs. They are two separate things. In fact, there's a dead zone over the top of an NDB and markers only transmit straight up, NDBs each have unique frequencies and markers all transmit on the same freq, and NDBs are high powered while markers are very low powered, you use NDBs while navigating between airfields and only use markers when on final approach, so one could say they're exact opposites.

 

We should call them "outer NDB" and "inner NDB" or even less confusing "NDB that is generally next to the outer marker if it exists" and "NDB that is generally next to the inner marker if it exists."

Calling NDBs by marker terminology makes it more confusing! NDBs are identified by their frequency, not what marker they happen to be close to (e.g., "I'm headed towards the 373 NDB and 225 is 20 deg to my right."). NDBs can be associated with geographical features (e.g., "I'm picking up the Tuapse NDB, but the Kiorsky field NDB is still too far away...").

 

This thread really has my curiousity peaked - I'll have to check it out tonight.

Edited February 11, 2009 by EinsteinEP

[EvilBivol-1]

Einstein (humble, huh? :)), I think there is indeed some misunderstanding. This may be due to western/eastern difference in practice or it could be a terminology translation issue. In Russia, there are three NDB types - Separate NDB (navigation), Outer NDB and Inner NDB (approach). Marker Beacons are co-located with NDBs to indicate flyover and as you point out, operate at the 75MHz frequency and point straight up, while the NDBs operate separately on their own frequency to 360 deg. All of this is modeled and usable in Black Shark. I believe every station, whether NDB or marker is modeled individually.

 

More info here:

http://forums.eagle.ru/showthread.php?p=419038#post419038

Edited February 11, 2009 by EvilBivol-1

[EinsteinEP]

I totally see where the confusion is coming from: there's a switch at the front of the cockpit that says "Inner", "Auto", and "Outer" and is labeled "NDB". When you flip these switches the ADF needle points to the different MARKERS.

 

[edit: thanks for the PM, EvilBivol! Saved me from making even MORE of an a$$ of myself. Granted, I'm no commerical flyer, but as a private pilot in the US, I've never run into the practice of placing NDBs with both the Inner and Outer markers. They're rather sparse on the west coast of the West, at least. I humbly concede and owe Frederf an apology - apparently the correct terminology IS Inner NDB and Outer NDB when flying in Russia! Guess I better go relearn my radio navigation! Spasibo!]

Edited February 11, 2009 by EinsteinEP

[Frederf]

I'm really not trying to argue about sematics, but while there are IMs, OMs, and NDBs there's no such thing as IM NDBs and OM NDBs

 

While there certainly aren't such things in real life, I don't know if in the sim if there aren't "hybrid" marker-NDBs as a method of placing them close together.

 

Thing is, we're kind of stuck with the terminology plastered all over the manual and cockpit. The switch for the two frequencies on a given ADF channel is clearly labeled as 'outer' and 'inner.' I guess we could refer to the NDBs when they are two-per-runway-end as "near" and "far."

[EvilBivol-1]

When you flip these switches the ADF needle points to the different MARKERS.

No, it's pointing to different NDBs, which function as locator/homer/approach stations for the airport and have marker beacons attached.

[bengo]

Hi,

sorry to recycle such an old thread, but I think we should try to recycle as much as possible to save the environment. Even internet forum-threads.:D

I've got two new questions on this subject. Forgive me if these seem noob-questions, I'm just trying to understand the concept.

I'm flying the "Convoy Hunt" mission out of Kobuleti. Is there any way to get the RMI on the HSI to point towards the airfield-NDB other than changing the ark.lua-file ?

 

I've tried to use the R-800 radio to pick up on the Kobuleti-NDB, but it seems these NDB's are on a higher frequency then what I can select on the radio. Is that correct ?

I've still got to try the RMI on HSI in ABRIS though, so that might be the solution to my problem.

Thank you.

[Bee_Sting]

that's why instruction VIDS are so important!

[Mugatu]

Speaking of 2 NDB approaches (never seen one or flown one)

 

http://www.rvs.uni-bielefeld.de/publications/Incidents/DOCS/ComAndRep/Dubrovnik/summary-T43.html

[bengo]

that's why instruction VIDS are so important!

Ah cool : a picture (or vid) says more then a thousand words. Is it in one of the producer's note's ?

[Frederf]

Is there any way to get the RMI on the HSI to point towards the airfield-NDB other than changing the ark.lua-file ?[/Quote]

 

There are 8 ADF channels (16 frequencies) available to the pilot while flying. These are set by the mission/LUA before flying. If none of these channels match the frequency of the NDB you want to use then you cannot use it.

 

it seems these NDB's are on a higher frequency then what I can select on the radio. Is that correct?

 

The radio at the front left side of the cockpit is VHF2, the ADF channel selector knob is on the right rear of the 4 blue AP buttons about 15cm.

 

got to try the RMI on HSI in ABRIS

 

The ABRIS RMI gets its info from the same place as the dash panel HSI. There is only one ADF radio in the Ka-50. You cannot tune the ADF through the ABRIS.