Juergen

Changing ILS Frequency in FMC

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Hi,

I was on a flight from OPKC (Karachi) to OMDB (Dubai) and at flying the STAR (BUBI1B) to runway 30R, I checked the NAV/RAD ILS frequency. I found that the wrong frequency was entered and tried to change it manually.

Th MCDU would not allow me to change the frequency and I had to fly the approach manually. I can't remember the exact wording of the message, but manual entry was NOT possible. BTW I was NOT on final yet and the approach was NOT armed. Also runway 30R was selected in the Arrival?approach page.

How can I change the ILS frequency manually once it is shown in the FMC/NAV RAD page.

Thanks for help

 

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Hi,

I believe? I can answer my own post:

I flew an ILS approach with FSiPanel to Rwy 30R in OMDB and the correct ILS frequency was selected in the NAV/Rad page.

That said, it must have been that I selected the wrong runway by mistake when entering the Arrival into OMDB on my flight from Karachi to Dubai. If that was the case and me NOT changing the runway in the Arrival page, I am pretty sure the FMC does NOT allow an ILS frequency change on the NAV/RAD page!

Any comments would be appreciated

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The format is xxx.xx/yyy (i.e. you must enter the frequency AND the correct front course - e.g. 110.90/271). Anything you enter manually will override the automatic entry.

I am reasonably sure you should be able to tune any frequency and/or course you want regardless of the selected runway/approach. However, you may get an message alerting you to the mismatch (IIRC).

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I am absolute positive I entered the ILS frequency and front course in the format you posted and still it would NOT let me change. The message was not "ILS MISMAtch", but something ......NOT ALLOWED. I don't think I can recreate the situation, but I certainly will keep an eye out for it

Thanks for your reply

 

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You must insert an "M" at the end of the ILS frequency and Runway QDM.

Example:

110.10/335M

 

 

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1 hour ago, Copper. said:

You must insert an "M" at the end of the ILS frequency and Runway QDM.

Example:

110.10/335M

 

 

Not true, the FMS will automatically enter a M if manually entered, A if automatic. (FCOM 11.50.8)

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So what could be the reason I couldn't enter the ILS/Course into the FMC?

Thanks

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Hi,

FCOM gives the following:

All three ILS receivers can be manually tuned from the NAV RADIO page unless
ILS approach tuning inhibit is active.
ILS approach tuning inhibit is active when:
• the autopilot is engaged and either the localizer or glideslope is captured
• the flight director is engaged, and either the localizer or the glideslope is
captured, and the airplane is below 500 feet radio altitude, or
• on the ground, the localizer is alive, airplane heading is within 45 degrees
of the localizer front course, and ground speed is greater than 40 knots
ILS tuning is enabled by disengaging the autopilot and turning OFF both flight
director switches.

Are you sure you were not in one of these conditions?

Another possibility would be that the frequency you try to enter is not valid (VOR frequency instead of ILS frequency). Though this would return an "Invalid entry".

It worked on the FSX version so I don't see why it wouldn't work on the P3D version. But I will try during my next flight to confirm that. I confirm, it works also on my side on P3D v4.

Edited by Budbud

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It works. I have done it a few times. Eg. 110.10/335

If it does not work open FSX planner and check what freq it says for that runway.

I have also done that, checked FSX flightplanner and used that freq.

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5 hours ago, PerWel said:

It works. I have done it a few times. Eg. 110.10/335

If it does not work open FSX planner and check what freq it says for that runway.

I have also done that, checked FSX flightplanner and used that freq.

I don't follow you.  Do you have a problem?

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Hi Dan, 

Per is just answering to Juergen who is the OP asking.

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Hi All,

I can not say with complete certainty whether I was or was not in one of the conditions described by "Budbud".

I will try again on a later flight.

Anyway, thanks for all the Info and Help

 

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I use to fly to Dubai OMDB for my VA and I have often experienced this problem. The referenced STAR BUBI1B runs parallel to both runways 12L and 12R as a left downwind, and after passing the airport, you should turn a base LEFT to join the 12R localizer. BUT, when turning this base, you pass in front of the 12L localizer and, at this very moment, the FMC changes automatically the 12R "IDBE" ILS letters for the 12L"IDBR" ILS letters, and the FMC sends the message of ILS mismatch. 

Attention to this: it changes the letters but doesn't change the frequency, thus emitting the message. 

This also happened to me arriving in Miami KMIA. The FMC was programmed to one of the parallel runways, but when passing in front of the other, it captured it's ILS frequency. 

How to avoid this? Normally, this is a situation in which you're preoccupied with other procedures for safe landing and then, at that point, you have to quickly peel a pineapple!

Just to clarify one detail : the BUBI1B STAR attends to both runways 12L and 12R. 

Best,

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9 hours ago, Heronjr said:

How to avoid this?

Keep your sim scenery and your nav data up to date. Nav data being up to date is all well and good, but keep in mind that it updates to match the real world. If you're not keeping your sim scenery up to date for the real world...well...it's gonna cause issues.

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Hi Kyle,

My scenery and aircraft are updated monthly to the last Navigraph AIRAC (1706) and all the OMDB scenery frequencies are the same of the real world published charts, as it is a high quality commercial add on (Fly Tampa  Dubai Rebooted). 

I repeat, the problem is,  when coming left downwind, as the aircraft turns base to 12R , it captures the letters of runway 12L (IDBR) but maintains the frequency 109.50, which is the correct 12R frequency, thus provoking a mismatch and spoiling the approach. You can clearly see the wrong letters on PFD/MFD

Otherwise, if I come from the right downwind, i.e. using other STAR, the aircraft correctly captures the ILS 12R and does the approach as programmed. 

I'll rephrase the question: Why the aircraft picks another runway data if the FMC is already programmed to the original one? 

Does this happens in real world? If so, how to avoid?

Please see the BUBI1B STAR (page 10-2) and the ILS approaches ((pages 11-1 to 11-2) at:

http://vau.aero/navdb/chart/OMDB.pdf

Try this approach with a QOTS programing it to land on 12R using this star. 

Best

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10 minutes ago, Heronjr said:

My scenery and aircraft are updated monthly

Your scenery is not updated monthly. This is false.

10 minutes ago, Heronjr said:

You can clearly see the wrong letters on PFD/MFD

This is data reported by the sim, itself, not the aircraft or the aircraft's database. In other words, our code is reading what your sim is providing to it.

11 minutes ago, Heronjr said:

Why the aircraft picks another runway data if the FMC is already programmed to the original one? 

I answered this in my earlier post: your aircraft data (real world), does not match up with the sim (not real world). Update the sim.

12 minutes ago, Heronjr said:

Does this happens in real world? If so, how to avoid?

It does not. They ensure their data matches. You, on the other hand, have not.

Check by doing the following:

Load the sim, and go to an airport where you are seeing this issue. Open the simulator's map. Click on one of the runways where you are seeing the issue and observe the data. I'm willing to bet it's the wrong data.

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11 hours ago, Heronjr said:

Normally, this is a situation in which you're preoccupied with other procedures for safe landing and then, at that point, you have to quickly peel a pineapple!

This is why the crew does a pre-arrival briefing.  The approach is studied, and in the sim you can verify frequencies on the platform map, missed approach planned, alternates, expected arrival, and anything unusual.  Good time to start this is before TOD before it gets busy.

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Sorry, you're correct Kyle, my scenery is not monthly updated. Only the aircraft and tools which have Navdata contracted.

My FSX Map of FlyTampa OMDB says for ILS data:

12L - IDBL - 110.10

12R - IDBE - 109.50

30L - IDBW - 111.30

30R - IDBR - 110.90

Which are exactly the numbers/letters shown in the 2017 published approach plates on the link I gave you.

The change I saw while turning base was on the identifiers (IDBE to IDBR) but the frequency on NAV/RAD was still 109.50, however, the approach failed.

In order to organize our discussion, at that time, I put the navigation on HDG, made a turn, rebuilt the approach on DEP/ARR page, and intercepted the localizer 30R from the right and it did work, proving that the scenery frequencies were the same as the aircraft frequencies.

Best

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12 minutes ago, Heronjr said:

The change I saw while turning base was on the identifiers (IDBE to IDBR) but the frequency on NAV/RAD was still 109.50, however, the approach failed.

You had IDBR on the PFD when the frequency was set to IDBE 109.5?? That is unexpected.  The FlyTampa scenery still has the correct frequencies for the ILS. I cannot think of any way for IDBR to appear on your PFD.

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Dan,

Yes, IDBR was set to IDBE and I lost data for approach. Before turning base, I could see the IDBE, the LOC and the GS for the assigned runway 12R. This has happened to me twice on OMDB and once at LatinVFR KMIA.

My guess is I was intercepting the localizer on LNAV, and there is a warning on FCOM about this. (NP.21.47), but I'm not sure if this is exactly the case.

I will make some tests on this circuits and see if using HDG to join works.

Best,

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Suggestion: fly the approach with some other airplane, and see what happens. That should tell you for sure whether it's your simulator, or a bug in PMDG aircraft.

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13 minutes ago, Heronjr said:

Yes, IDBR was set to IDBE

You lost me here.  Two different ILS frequencies, you cannot set one to the other.

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I have just flew the approach 12R to OMDB using BUBI1B star.During the downwind leg, it correctly tuned the ILS 12R on 109.50 IBDE (as always).

Then, before the base left turn, I deactivated LNAV and did the turn using HDG. It captured the LOC and G/S like a charm. You can leave VNAV as you wish, or FLCG.

Juergen, try your fly to OMDB turning to final using HDG instead of LNAV.

Please, read the warning in FCOM (NP 21.47). I don't know if that's the answer. Don't think it's a bug.

Best,

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Hi,

The ILS autotune has nothing to do with the roll mode used. It just look up in the nav database the frequency and course corresponding to the ILS selected in the DEP ARR page of the CDU.

The warning in the FCOM just refers to the fact that the interception of the localizer may not be achieved when using LNAV. But in now case it refers to a loss of the ILS data.

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