ILS Vertical Bar Error

[bbrz]

1. The in game info is correct for flying in DCS

2. You can't fly real world charts in DCS or vice versa without modification.

1. No, it isn't. If this would be the case the rwy numbers would read 12/30.

2. I don't expect that. It would be already nice if the in game data would match (see point 1) and the instruments would work correctly (HSI course selector).

Edited July 3, 2018 by bbrz

[Frederf]

Batumi is RWY 31 because that's the name of the runway in real life. It is positioned on a ~305.6° grid heading in DCS. In reality it is a 310.7°TH, 306°MH. Its magnetic heading in DCS is 299.4°.

 

The line of longitude closest to Batumi is a 354° grid heading which is obviously 360°TH by definition. So there's your ~6° difference between real world and DCS runway magnetic heading.

 

You just have to accept that DCS is portrayed as a flat Mercator projection of a round Earth where lines of longitude don't run vertically on the paper. In any case you must not assume that the runway numbers have anything to do with the runway magnetic courses. Yes in real life most times the runway is named for the closest round number but not always. Look at your approach procedure to get the ILS inbound course value. Do not assume it based on the runway's name.

 

HSI works perfectly fine. It's only the bank steering bars for ILS guidance which are wrong. Stow the bars and fly the approach like you were trained.

Edited July 7, 2018 by Frederf

[bbrz]

1.In any case you must not assume that the runway numbers have anything to do with the runway magnetic course.

2.Yes in real life most times the runway is not named for the closest round number but not always.

3.HSI works perfectly fine[/quote

1.?

2.?? The rwy designator is always for the closest named MH. The only exception are parallel runways…but I don't see one at Batumi.

3. Since I don't have the A-10C I can't check for myself, but from what I've read you have to set the exact inbound track on the HSI for correct guidance?

[Frederf]

No one flies an ILS approach without reading the procedure first. "Cleared for the 09 left ILS approach." OK, look at the approach plate, localizer course is 087 and set. It is never done that you read the runway name and just set that value on any instrument without further thought. That's the point where you'd look at the approach plate and think "Huh, weird 300 for 31, oh well." But life would go on. Yes real runways round as expected so often as to be a rule and Batumi in the flesh is no exception.

 

The mapping of real spherical terrain on a rectilinear grid that tries to look real, be named real, and follow real conventions... something has to give. If they named it runway 30 then someone else would complain that Batumi's runway is named 31. Or they could model the terrain itself distorted by map projection which would look weird. Or they could make traveling in straight lines change heading and vice versa. Short of actually modeling it as a spherical planet surface there has to be something wrong and this is probably the most minor error to suffer. I guess the slightly better fix is to have the ATC and the painted textures on the runway ends be programmatically dependent on their magnetic headings for that particular date and place. Like if you ran the sim in 1950 and 2050 the runways might be called different names. You wouldn't be able to display real charts in modules or GUI though without running the risk of a discrepancy.

 

The A-10C system that suffers is the bank guidance pointer. The CDI works fine to show localizer alignment. It shows left when you're left and right when you're right. As per reality you can mis-set the CRS knob by any value you like and the CDI works; it's just the "picture" will be crooked.

 

And provided you know the magic setting for the CRS knob the bank pointers can provide the information correctly as they are supposed to. I would have to recheck if that setting and the actual magnetic localizer course are the same or different. If the former, hooray, if the latter boo.

 

As long as the command pointers are stowed and you've set the DCS-appropriate inbound course (not worrying about the runway's name), it's indistinguishable from perfection. And I know the command pointers are nice but I've done plenty of CDI/GS only approaches in FSX, etc. so I view the command guidance as a luxury.

[LeCuvier]

Well, thanks for all this detail and thanks for the work-around.

Fact is, the vertical bar points to the wrong direction and that's a bug. That's why I started the thread. and I hope ED will do something about it (I'm an optimist).

[bbrz]

And I know the command pointers are nice but I've done plenty of CDI/GS only approaches in FSX, etc. so I view the command guidance as a luxury.

Don't know what a 'CDI/GS only' approach is, but apparently you aren't a RL pilot, otherwise you would know that e.g. even a raw data ILS approach is a lot more work than an ILS approach flown with an FD.

FSX is a very bad example because due to the micro steps of the ILS/FD needles you can't fly an ILS/LOC/VOR approach, with or without FD like you would IRL.

Edited July 4, 2018 by bbrz

[LeCuvier]

@Frederf: you are apparently an expert and you don't mind flying with a defective localizer bar. And I'm sure RL pilots are trained to work around such a problem when it's caused by battle damage. But neither an air force nor a commercial airline would accept delivery of an aircraft where that localizer bar is systematically wrong.

The purpose of this post is to identify a bug, and I suggest we leave it there.

[nessuno0505]

Interesting discussion. I'm not a RL pilot but I go sailing, so I'm aware of problems related to true / magnetic / instrumental courses / headings / bearings. But here would Be interesting also to know if the issue addressed by LeCuvier is considered a bug by ED or not, and if not why. Can we have an answer from an ED tester about this topic?

[Frederf]

It is desirable that the bank steering bar behavior when in the ILS mode be corrected. It has been reported before in detail. The term "ILS vertical bar" is going to cause confusion. There is no item in the airplane with this name.

 

While the steering bars are nice to have it's not that much more workload to fly off the CDI. For example a back course ILS approach would require stowing the steering bars and an A-10 pilot would do so as normal procedure.

 

After testing I'm happy to report that a full 5 degree CRS error causes a consistent 1/3rd dot CDI misalignment when the command steering is followed. At DH of 200' this is a lateral displacement of about 60' in the direction of the misalignment (125 set and steering brought me in right of localizer center), about half way from the runway centerline to the edge at Batumi. So even with a moderate CRS input error steering is:

1. Normal in direction

2. Converging

3. Limited in magnitude

 

When CRS is set as one would normally do for an ILS approach (equal to the MH of the runway) the steering is exactly correct. There's no misalignment between normal CRS input and steering display. That's good news. We shouldn't have to set CRS to any specific value for command steering but since we do it's fortunate that it doesn't demand a different value than we'd normally set. If you set CRS knob to within +-1° of runway MH bar steering is close enough to be no factor.

[LeCuvier]

When CRS is set as one would normally do for an ILS approach (equal to the MH of the runway) the steering is exactly correct. ...

The flight manual only desribes the use of the ADI's Localizer and Glide Slope Bars. Can you describe the process you use in slightly more detail so a non-pilot can understand it?

 

You mention the use of MH (magnetic heading I guess).

What's the source for this info? Example Kobuleti: The F10 map only provides Runway numbers 07 and 25 which would suggest 70°/250°. The document "DCS_VAD_Charts_FC3.pdf" indicates runway heading as 250°/70°.

The document "DCS_VAD_Charts_A10C.pdf" says its 244°/64°. The divert page on the CDU doesn't give any info on heading.

[bbrz]

comprehensive explanation deleted due to LeCuviers s....d complaint.

Edited July 5, 2018 by bbrz

[LeCuvier]

The important point is that the ADI bars are not Localizer and Glideslope bars. The manual correctly calls them bank and pitch steering bars.

Rather than commenting on the usefulness of this statement, I quote the DCS A-10C manual, page 475, in the chapter "Navigate ILS Glide Slope and Localizer":

"Localizer and Glide Slope Bars. When this horizontal bar is centered on the ADI, you are flying down the glide slope projected by the ILS vertical steering component. If the bar is above the center of the ADI, it indicates that you are below glide slope and you need to increase altitude. The vertical localizer bar indicates if you are left or right of runway alignment. If the bar is right of ADI center, fly to the right to center it. For a proper glide slope approach, you want the two bars centered and forming a perfect cross on the ADI (aka “center the bars”)."

End quote.

Edited July 5, 2018 by LeCuvier

[bbrz]

Rather than commenting on the usefulness of this statement

That's one of the reason why I prefer to be INACTIVE and I deeply regret that I tried to help you understand how these things actually work. Btw, it's not my fault that the A-10C manual is incorrect.

[LeCuvier]

That's one of the reason why I prefer to be INACTIVE and I deeply regret that I tried to help you understand how these things actually work. Btw, it's not my fault that the A-10C manual is incorrect.

The DCS A-10C manual is all I've got for reference. Therefore, your saying "The manual correctly calls them bank and pitch steering bars" seemed to infer that I cannot read, or don't understand what I read. That unfortunately upset me a bit. I'm sorry about that.

[bbrz]

The DCS A-10C manual is all I've got for reference. Therefore, your saying "The manual correctly calls them bank and pitch steering bars" seemed to infer that I cannot read, or don't understand what I read.

Most likely. Suggest to read page 112-113

[eaglecash867]

The magnetic heading of Batumi's runway is 299/119, so, according to the FAA (and the rules may not be the same elsewhere in the world), and assuming the average 0.1 degree of annual change, it should have been re-marked about 60 years ago.

 

When we install a new EFIS system and we're doing in-flight AHRS magnetometer drift checks and that sort of thing by making various 90 degree turns and flying approaches, we're not taking true heading from a chart and applying magnetic variation before we set our course needle. We are taking the runway number from our clearance (in this case "Clear to land 35 right", dialing our course needle to 350, and seeing how the needles look compared to the visual picture. If our clearance said "Clear to land 35 right" and we had to deviate our course needle by 11 degrees to center the needle, and we went ahead and released that aircraft? Someone is going to have an accident, and I am probably going to go to jail since my signature is on the 337.

 

Also, if a customer with an FD-109 (similar FD system to the A-10C) tells me his lateral dev bar on his FD is pointing 11 degrees to the left of magnetic, I'm not going to tell him to just turn it off and fly his HSI. In fact, in that situation, the aircraft can't fly again until that equipment is fixed if it can't be MEL'd.

 

I think we just need to admit that the friggin thing is broken and ask that, whatever the problem is, gets fixed. :D

Edited July 5, 2018 by eaglecash867

[Yurgon]

The magnetic heading of Batumi's runway is 299/119, so, according to the FAA (and the rules may not be the same elsewhere in the world), and assuming the average 0.1 degree of annual change, it should have been re-marked about 60 years ago.

[...]

 

For crying out loud, yes, we know this is wrong in DCS. I don't remember how often you made that point, but everyone knows it by now.

 

According to SkyVector, the actual and current runway heading for Batumi Runway 13 is 126°, which should be well within FAA rules.

 

Frederf made several attempts to explain why that's not the case in DCS, and we probably would be arguing why DCS calls it Runway 12 when, cleary, in the real world it's Runway 13, that's there on Google Maps for everyone to see.

 

So for the love of whatever you believe in, it's wrong in DCS, for reasons outlined several times, it's probably not going to get fixed anytime soon, and until then live with it or don't.

 

I guess anyone who's read this thread this far will remember the actual DCS Batumi Runway 13 heading for the rest of their lives, so at least no one will crash land there just because the runway has the wrong designation. :D

[Frederf]

Rather than commenting on the usefulness of this statement, I quote the DCS A-10C manual

Sloppy wording on the part of the manual.

 

The flight manual only describes the use of the ADI's Localizer and Glide Slope Bars. Can you describe the process you use in slightly more detail so a non-pilot can understand it?

 

The steering bars are directive for attitude. If the bank steering bar is right, bank more right. If the pitch steering bar is up, pitch up. Compliance with the steering directions doesn't correspond directly to any position in space, only that your attitude is equal to the desired one as calculated by the airplane's computer to fly from your present position to the centered position. Following the director should converge your position to the correct one over time.

 

Command steering is directive to adopt a certain calculated attitude. Take a certain situation, left of center, computer commands 22 degrees of right bank. If your current bank is 10 degrees right then the steering is going to command you to roll 12 degrees more to the right. Given the exact same situation if your bank is 40 right the steering is going to command you to roll 18 degrees to the left (relative to current). From this we can say that you cannot determine your position by the bank command pointer display.

 

The primary position indicators are the CDI and GS which are descriptive of position. Notice the difference in language "director, directive, command" compared to "indicator, descriptive". One tells you what to do and the other tells you what is happening. If you are left of center CDI will show that regardless of your attitude (within reason, don't ask me what it shows if you're inverted).

 

The procedure for reading, interpreting, and maneuvering based on position information for an ILS approach is a deep topic. There are lots of civil procedure instructional videos around. The most efficient summary I can give is:

 

1. There is some procedure that takes you from the en route structure and dumps you at an intercept to the localizer crossing at about a 30 degree angle or less at an altitude where you'll establish localizer first before the vertical guidance becomes a factor.

 

2. As the CDI starts to align you turn toward the runway heading such that alignment occurs by the end of the turn.

 

3. You monitor the CDI for drift picking headings intelligently to drift toward alignment or to maintain it. "I'm drifting left, better try +10 degrees heading. Too much? Take away 5." That sort of thing. It's the same thing as TACAN area navigation but just more sensitive.

 

4. Vertical is the same as lateral except you reference vertical speed instead.

 

You mention the use of MH (magnetic heading I guess).

What's the source for this info? Example Kobuleti: The F10 map only provides Runway numbers 07 and 25 which would suggest 70°/250°. The document "DCS_VAD_Charts_FC3.pdf" indicates runway heading as 250°/70°.

The document "DCS_VAD_Charts_A10C.pdf" says its 244°/64°. The divert page on the CDU doesn't give any info on heading.

 

I found MH by putting an A-10 on the runway in the mission editor and looking through the CDU pages to find my current magnetic heading XXX.X°. Your process of assuming MH from the runway's name is inexact at best. It's a bad habit I see a lot in flight simming. The real source for localizer heading is the FLIP chart in the cockpit which would be a military publication of approach procedures relevant to your mission. The CDU info is a good start but not enough info to fly a full blown procedure from.

 

The MH on the visual or ground charts are sufficient for DCS within a decade of the published date. If you set a CRS of 244 for runway 25 your ILS equipment will provide correct guidance, command steering and all.

[Ramsay]

For info:

Example Kobuleti: The F10 map only provides Runway numbers 07 and 25 which would suggest 70°/250°.

Kobuleti measures as 70°/250° True using the F10 ruler.

 

TL;DR: The two DCS_VAD_Charts were written for different aircraft, FC3 and A-10C, one uses True bearings and the other Magnetic.

 

Detail:

 

1.

The document "DCS_VAD_Charts_FC3.pdf" indicates runway heading as 250°/70°.

 

FC3 Aircraft have simplified navigation systems, so use True North (Grid North) as defined by the F10 map ruler (even for their magnetic compasses).

 

- All tracks are given to true north with a tolerance of ± 1°.

- All runway designations were taken from the DCS map (true north).

- The taxiway names have been revised and do not match the in game TWY designations. This was done to achieve a greater realism and to enable the support for human controlled ATC procedures.

 

 

2.

The document "DCS_VAD_Charts_A10C.pdf" says its 244°/64°.

 

The A-10C has a 'full fidelity' system model, so subtracts the local magnetic declination (+6°) for appropriate instruments.

 

So the A-10C can fly the approaches with it's compass, HSI, etc. the charts use Magnetic bearings

 

 

- The magnetic variation contained in the DCS A-10C module was taken on the maps with a tolerance of ± 1°.

- All tracks are given to magnetic north.

- All directions and positions correspond to the CDU of the A-10C.

- All runway designations were taken from the DCS map (true north).

- The taxiway names have been revised and do not match the in game TWY designations. This was done to achieve a greater realism and to enable the support for human controlled ATC procedures.

[nessuno0505]

I'm sorry, I'm not native english nor RL pilot and all this thread is becoming a little bit difficult for me to follow... can someone give a clear answer to the following question?

 

Are a-10c vertical bars bugged? Y o N

[LeCuvier]

@Frederf: Thanks for the complete and concise answer! I will have to read this several times and practice.

And special thanks for taking the time to write this! Very much appreciated!

[LeCuvier]

I'm sorry, I'm not native english nor RL pilot and all this thread is becoming a little bit difficult for me to follow... can someone give a clear answer to the following question?

 

Are a-10c vertical bars bugged? Y o N

I'm like you, but you should really take the time to read what Frederf wrote!

Yes. What you refer to as the "vertical bar" is the banking bar, and it's bugged. But if you set the course to the magnetic heading of the runway it will work ok. You can find the magnetic heading of the runway in the document "DCS_VAD_Charts_A10C.pdf" in the folder "...\Eagle Dynamics\DCS World\Doc\Charts".

[nessuno0505]

Why do you say it's bugged if it works ok by setting the correct magnetic heading?

So maybe what is "bugged" is not the instrument itself, but the runway name / ID that does not match with its magnetic heading as it is in the game and the information provided in the manual.

If this is the problem, a chart with the correct magnetic headings is available in this topic, can be converted in ipg and put in the kneeboard, thus providing the correct info to use ILS.

Is my understanding correct? If yes, I'm fine. If no, then what is the instrument-itself related bug?

[bbrz]

Why do you say it's bugged if it works ok by setting the correct magnetic heading?

I assume you mean the set course, not the set heading. The problem is that IRL the set course doesn't matter.

You can set any course you like on the HSI and the CDI/FD bank steering bar will bring you exactly to the runway centerline...only if the needles are centered of course.

[nessuno0505]

Yes, you are correct I meant course not just heading.

So IRL course SET on HSI is independent by FD steerng bar, the latter instead depending on ILS. So if you catch ILS system you have just to follow the flight director regardless your HSI situation. Is this correct? While in DCS you have to correctly set your course on HSI to have the steering bar properly placed.

Edited July 6, 2018 by nessuno0505