Good day -

I engage the LOC on autopilot to first intercept the localiser and then APP after that. Strangely the last couple of days, the aircraft (autopilot) will then make a sharp left or right 'away' from the localiser.

Example: I fly a heading of 030° to intercept the LOC on 090° the aircraft then start to turn LEFT in sharp bank angle and you have to disconnect the autopilot and fly manually resulting in a very unstable approach.

As far as I can see everything is normal and there are no settings that could cause this. The only plugin is Pro/ATC but it is not set to handle the autopilot. It is now becoming annoying seeing that it pops up randomly.

Hope there is an explanation or something I can do to prevent this.

Regards

Terblanche

[± 2800 hours in PMDG 738NGX]

 

Do you have the correct course selected for the LOC? I.e. 090 dialed in?

 

 

The only plugin is Pro/ATC but it is not set to handle the autopilot.

 

It might not handle the autopilot but it could interfere with it working correctly on your system. If this issue began after ProATC was installed I would uninstall it and see it the issue continues.

Do you have the correct course selected for the LOC? I.e. 090 dialed in?

 

 

Hello Matt, does it matter ?

 

1) The localizer signal is unique regardless of what is set in the MCP, but you would know better.

 

2) I have mine configured so that it is automatically set in the MCP when the signal is attained with the correct frequency.

 

However some ILS´s have the same frequency for both opposite runways, maybe there is confusion there.

 

Also, the OP´s problem has happenned to me when I am coming in to intercept the localizer in LNAV mode instead of HDG SEL.

Hello Matt, does it matter ?

 

1) The localizer signal is unique regardless of what is set in the MCP, but you would know better.

 

2) I have mine configured so that it is automatically set in the MCP when the signal is attained with the correct frequency.

 

However some ILS´s have the same frequency for both opposite runways, maybe there is confusion there.

 

Also, the OP´s problem has happenned to me when I am coming in to intercept the localizer in LNAV mode instead of HDG SEL.

 

 

Even though in a lot of planes, it wouldn't matter, the autopilot on the 737 does look at the MCP course to judge correction. I've never flown a plane that does the auto-dialing of the course, so I don't know how that would figure in.

 

No matter how you join (HDG SEL, LNAV, CWS R, or none) it shouldn't change how it reacts once you've got LOC capture.

 

Does the LOC identify correctly?

Thank you all for your input ...

Let me explain the last example:

• Flight from Kastela (LDSP) to Friedrichschafen (EDNY) heading 300°
• At FHO225/11 starts turning right for ARGEV intersection
• LOC comes alive on 111.90 [Rwy 06 (059°)] and it is set in 'course'
• Altitude 4000" and one tick underneath GS
• Next moment the plane makes a sharp turn left as if it wants to make a 180° away from the airport

Let me try and duplicate it without ProATC and see if that is the problem although I've been using ProATC for almost 6 months and never had this problem. The last week however it keeps happening ad randomly.

Thanks Matt, the autodial is an option in the sim only, cant remember if it is FSX or the NGX.

 

OP, I know exactly what you mean.....has happenned to me too.

 

Hopefully we will get more replies with answers.

There is a setting in the PMDG CDU  MENU, for LOC capture. Check that to see if it makes any difference?

Please have a look at

 

http://www.avsim.com/topic/123617-reciprocal-runways-same-ils-freq-help/

 

It appears that this is at the heart of the puzzle. The ILS frequency of both runways 6 and 24 at EDNY is the same, which is not uncommon for reciprocal runways. In the real world, this is no problem as only one ILS course is active at any given time. What the OP appears to be experiencing is that the sim suddenly picks up the ILS of the reciprocal runway (which would be 24) and the aircraft responds "correctly" to that input, but not to yield the desired result.

 

I have no idea exactly how FSX or its offspring decide which of the two ILS courses to make active. Maybe it's decided on the basis of the prevailing winds, but maybe not. There might be some interaction with the ATC add-on that decides which of the ILS courses to activate, hence it might be a good idea to turn that off and see how the base simulation works. This may all be set-up somehow in the various scenery files, but that's a black hole for yours truly.

 

John

 

EDIT

 

Just did a simple experiment. Lined up on runway 24 with 15 knot headwind. With the receiver tuned to 111.9, the shared ILS frequency, PFD showed the correct IFHW identifier for the westbound localizer. I then taxiied down the runway and about halfway, the PFD switched to IFHE, which is the identifier for the eastbound localizer. In addition the localizer display began to "reverse sense" as is characteristic of a back course track. This is in P3D v2.5. So it's not the wind that activates one localizer rather than the other, but rather just the position of the aircraft. Why the OP would have observed that sudden reversal is not clear unless it was the add-on ATC.

 

This also suggests that it would be a bad idea to use the ILS localizer as a departure aid for runway alignment in cases where the reciprocal runway shares a localizer frequency.

My feeling is that there is an element of truth in all of above although I've never seen that the FMC will change the course if you select an APP and the CDU display it as Runway06/59°

I do however think I discovered the CULPRIT -

For some strange reason, after all these years, the AIRAC for some ILS frequencies is incorrect. I revisited some of the airports that has this problem and discovered the following:

• EDDL Düsseldorf Rwy 23L - the frequency should be 109.90
• EDDK Köln Rwy 32R should be 109.70
• EDDP Leipzig Rwy 08R should be 111.90
• EDLP Paderborn Rwy 05 should be 111.70
• LOWS Salzburg Rwy 15 should be 109.90
• LIBD Bari Rwy 07 should be 111.35

It seems the ADDON scenery's frequencies are different and therefore the CDU display a freq that is set in the NAV RADIO but in fact the freq is different. Even when you put in the correct (above mentioned) freq, the ProATC will change it automatically to the one it has in its database therefore you see the LOC

and GS come alive and when ProATC (using the same AIRAC) clear you for the approach it then sets the radio to the 'wrong' frequency resulting in a very confused autopilot  :smile:

 

I suspect that there must be a couple of more such discrepancies between AIRAC and the ADDON scenery's ILS frequencies. Maybe PMDG, if they follow this, could ask Navigraph to update their database - or will it interfere with the frequencies for default airports because not all simmers have the payware airports that most of us do?

 

At least now I am aware of this and could set the 'correct' freq in the standby NAV RADIO as well and then quickly switch to it and still maintain the approach.

 

Regards

Terblanche

Have do the following steps inside ProATC:

 

1) Imported AIRAC data

 

2) Executed makerwy in the sim's root folder (can be commanded inside ProATC if ProATC and the sim are on the same machine)

 

3) Executed "Align scenery with AIRAC"

 

By doing these steps, the co-pilot should set the frequency found in the scenery.

Great! Thank you Jarkko

... I'll try that.

:smile: