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herman747

B747-400 FMC: ILS will not autotune

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I've read carefully several topics concerning ILS autotune but still have the following problem/question:After selecting the ILS RWY on the DEP/ARR page and activate etc... the ILS-freq is SOMETIMES not tuned automatically. ILS-MLS shows PARK on the NAV/RAD page.If I select other RWYs, change the route, even another airport, it won't help: ILS-MLS remains on PARK! Tune the ILS manually is no problem but I like to know whats causing the FMC to refuse SOMETIMES autotuning the frequency.I've the FEELING that autotune works ok if I program the approach in a early stage of the flight. Once the ILS is correctly autotuned, it continues to work correct during the flight.Herman

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Guest Buck Bolduc

>I've read carefully several topics concerning ILS autotune>but still have the following problem/question:>>After selecting the ILS RWY on the DEP/ARR page and activate>etc... the ILS-freq is SOMETIMES not tuned automatically.>ILS-MLS shows PARK on the NAV/RAD page.>>If I select other RWYs, change the route, even another>airport, it won't help: ILS-MLS remains on PARK! >>Tune the ILS manually is no problem but I like to know whats>causing the FMC to refuse SOMETIMES autotuning the frequency.>>I've the FEELING that autotune works ok if I program the>approach in a early stage of the flight. >>Once the ILS is correctly autotuned, it continues to work>correct during the flight.>>Herman >>>>>>Press the key in the upper left corner of your FMC keypad.The press the LSK--> Index.then the bottom left LSK will---> Approach.Press the LSK next to it and you will see two speed and flap settings.It may say 158@25 degrees.-----------149@30 " "Using the right side LSK next to whatever speed/flap setting you want will put it in the scratch pad.Then up load it to ____/_____ bottom Right LSK.Next go to the Legs key and go to the page with the runway listing.You will see the speed and airport elevation. NOTICE the speed got addjusted to what you did WRT the approach setting.At this point your ILS is autotuned!Now... if you do this too early in the flight the FMC will show the approach for the airport you just left, so dont be in a hurry to set up your speed/flaps setting until your about halfway thru the flight.

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Hi Guys,I will add my two cents worth and hope it helps, Herman the fmc page that you refer too only auto tunes to the ILS of your destinationAirport when you get about halfway through your flight. And yes youhave to set your approach page flaps speed as well try 30/145 I nevergo wrong with that setting. I hope this is of some help to you. Cheers Greg Bisset YSSY


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Thks so far,I've tried ILS autotune this evening twice and it worked correct if I select the ILS departure rwy after passing halfway through my flight.(flight: EBBR DCT HELEN DCT RIVER EHAM, ILS-18R select just before RIVER, NAV/RAD shows 110.10/186 PARK, just before RIVER HDG016-SELECT, after a few miles the NAV/RAD shows 110.10/186A) It was not necessary to set the approach speed/flaps, the ILS freq/crs showed up before setting the approach speed/flaps.I'm not sure if selecting the RWY before halfway is the problem, I will continue testing and keep you informed of the progress.Maybe PMDG support can give the conditions which must be true to autotune the ILS. I did not found it in the manual.Herman

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You have to do the following things in order for the FMC to autotune.1. Select an ILS approach on the ARR page.2. Close up the discontinuety on the LEGS page with the ILS runway you're landing on (up-select the ILS runway). This only applies if you're not using a STAR, and are following FS-ATC vectors.3. Make sure (this is probably the reason that your FMC will not autotune) that the ILS runway you're going to land on, is on top in the LEGS page.Best regards,Jon


Jon Kinket

Take it, or leave it.

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Guest nicam

just check to see if your AIRAC No. is the same as your sids/starsif they are not you can encounter this problem also.Michael

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John and Michael:John: I'll will check your points if autotune fails, but so far it didn't. What do you mean with pt3: I doubt if the runway must be on top of the legs page because at that point you are already approaching the runway. I think most of the ILS legs will start at a fix where you can capture the ILS. Did you mean that the first ILS fix must be on top?Michael: I upgraded yesterday the AIRAC and SID/STARS to the latest versions, after that I had 2 flights without any problem BUT still NOT SURE if the problem is solved because I have the problem irregularly.Thks,Herman

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I studied the manuals (again) and I found in the little FMC manual (which is in the DVD box) 3 constraints for autotune ILS:- within 200 miles of top of descent- approach procedure is selected - approach procedure entered in the RTE LEGS flight planQuestion: Is ILS autotune disabled when you are not flying on VNAV and there is NO top of descent calculated and/or displayed in the ND ?Herman

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>John and Michael:>>John: I'll will check your points if autotune fails, but so>far it didn't. What do you mean with pt3: I doubt if the>runway must be on top of the legs page because at that point>you are already approaching the runway. I think most of the>ILS legs will start at a fix where you can capture the ILS.>Did you mean that the first ILS fix must be on top?>>Michael: I upgraded yesterday the AIRAC and SID/STARS to the>latest versions, after that I had 2 flights without any>problem BUT still NOT SURE if the problem is solved because I>have the problem irregularly.>>Thks,>Herman It's not about that you're already approaching the runway. It's about that your next active leg is on top in the LEGS page. In this case that's the ILS runway. And yes I meant the ILS runway not the first ILS fix. But I must say that I use this procedure without any problems when using FS ATC vectors. If you're using a STAR, then eventually the ILS runway will come up on top of the LEGS page also, so it's basically the same procedure.The problem with FS ATC is that you have to deviate from your flight plan when you start receiving vectors to final. At that point it's best to up-select the ILS runway on top of the LEGS page. It has always worked for me this way.You don't have to have VNAV enabled for autotune to work. I fly without VNAV all the time.You mentioned "within 200 miles of top of descent". This has to do with the ILS frequency and approach course being displayed on the NAV RAD page (e.g. if you're within 250 miles of top of descent, the NAV RAD page will show PARK instead of the frequency and course).Jon


Jon Kinket

Take it, or leave it.

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