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IAN Approach

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Hi everybody, I have a very silly question. What is a IAN Approach and how does it work with the NGX. I only know that it is something special from Boeing and I also remember, that NAV 1 and NAV 2 have to be switched for example to the VOR frequence (I do not know wether this is correct). In the FMC of the NGX there are no IAN Approaches stored. Is the use of a VOR Approach recommended. And how does it work. What is the correct procedure?. HDG mode to the IF point and then swich to APP ? I am not a profi, so be patient with me Thank you

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Integrated Approach Navigation (IAN) As far as i am aware, this is company specific.Unfortunaly i cant say more than that. ( Because i dont know!)


Regards

Luke M

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NAV1 and 2 have nothing to do with it actually - IAN works completely off the FMC. If you have an approach loaded and are not receiving a valid radio navaid signal, it will default to using IAN. FAC (final approach course) is the roll mode and G/P (glidepath) is the pitch mode. It's like an ILS but created "virtually" by the FMC. You can fly hybrid approaches too (try the LLZ 27 at KSAN for instance) where the lateral mode is VOR/LOC but the vertical mode is G/P because there is no glideslope on that approach, it's localizer only. You can fly ILS backcourses with IAN as well, something the NG can't normally do without it.


Ryan Maziarz
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"Airplanes with IAN are capable of using the MCP APP switch to execute instrument approaches based on flight path guidance from the FMC. Approaches using IAN provide the functions, indications and alerting features similar to an ILS approach. Although non-ILS approaches using LNAV and VNAV can still be performed, IAN is normally used in place of LNA V and VNA V because of standardized procedures.Approach types that can use IAN: • RNA V • GPS • VOR approach • NDB approach • LOC, LOC-BC, LDA, SDF, TACAN, or similar approaches."Basically you get to use ILS techniques for other approaches. Instead of being in LNAV/VNAV, you use APP. It sounds nice, but a lot of airlines won't pay for it to be installed, I imagine.


Matt Cee

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I have read what little is written in the FCOM/FCTM about this ( complete discussion on how to fly the approaches but little or nothing on how it needs to be setup in the FMC to make it IAN instead of RNP). As far as I remember, Ryan, at least one radio has to be tuned to a navaid. It says radios with an "s" but specifies that only ONE CMD can be used. If neither radio has a valid frequency (and correct course setting(?) ) then it only allows an Lnav/Vnav, I think. Please correct me if I am wrong and if you have experience flying these approaches please provide a more thorough and complete explanation of what is required in the FMC. For example, if flying a nonprecision approach using IAN, should we select GS = ON in order to get GP to display or do we leave it off? On most of my attempts no matter how I set them up usually I end of just getting a Vnav Path displaying as pitch mode. The exception was flying a VOR/DME approach to MMMY. That time I was able to get FAC and GP displayed on the annunciator once I selected APP. I also just completed what I thought was going to be an IAN approach to BC 29R at Tuscon. It armed Loc-BC and GP when I selected APP and activated Loc-BC roll mode when captured but never activated GP portion until after last step down fix but instead continued to display Vnav Path as active pitch mode. I attribute this to the fact that FMC leg page only was displaying GP info for that last leg of approach. Just guessing but it did a perfect job, anyway! BTW I DID have GS=ON selected this time. (I am having problems reloading "saved" situations so in order to run each test I have to start a new flight on the ground which is making it quite time consuming and as I mentioned I am just using trial and error until I can get some definite guidance.)


Craig Williams

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You can fly ILS backcourses with IAN as well, something the NG can't normally do without it.
I believe the NG can fly LOC/BC, you just have to do it in LNAV and not VOR/LOC.

Matt Cee

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Hi to everybody, thank you for your very quick and informative response. Ryan, I would be very happy, if you could provide us with a very short IAN-Tutorial here in the forum like Craig suggested. Shoudl we select GS = On to get GP etc. That would be great.Its realy nice to see, that the NGX could do things, I have never seen and heard before. Markus

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Hi everybody, I have a very silly question. What is a IAN Approach and how does it work with the NGX. I only know that it is something special from Boeing and I also remember, that NAV 1 and NAV 2 have to be switched for example to the VOR frequence (I do not know wether this is correct). In the FMC of the NGX there are no IAN Approaches stored. Is the use of a VOR Approach recommended. And how does it work. What is the correct procedure?. HDG mode to the IF point and then swich to APP ? I am not a profi, so be patient with me Thank you
Look on page 5.60 of the FCTM. It will give you more information. Also do "advanced search" in Acrobat reader using word only and case sensitive. It will give you a lot of data on RNP, FAC, and IAN.Don

Don Lillard

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I just experienced something unexpected, related to IAN, that may well be an FSX issue but curious to understand or fix if possible. Coming into LFMN (Nice, France) 04L, correctly tuned to ILS, single channel approach under CMD A - though both ILS frequencies correctly tuned. Hadn't yet studied IAN, but noticed FAC and G/P annunciations and apparently approach was going just fine as if ILS. HOWEVER, both visually and on VSD, I could soon see that the flight vector was trending to land short of the runway, into the sea - and it did! - Is this an FSX problem with LFMN 04L ILS 109.95? Curiously I didn't find any other posts on LFMN glideslope being incorrect as to glide (just azimuth, which is simply faithful to RW)- What sort of issue might NGX FMC have detected to cause it to flip automatically to IAN approach, when both ILS frequencies were correctly tuned and course correct?- Is it reasonable to expect NGX FMC to correct for the glideslope error I describe [landing short]? Presumably the NGX FMC can't correct for inaccurate ILS data in FSX regarding runway threshold, if that is where the problem lies?? Or should NGX FMC have used different data to compute its own threshold for 04L and therefore produced an accurate glidepath? Any insight and advice would be much appreciated. LFMN is a favourite airport. I will be landing using LOC and V/S next time, with VMC HGS - which should cure the problem in practice. But that won't be much good in French fog! Thanks as always, David


David Abrahams

 

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I just experienced something unexpected, related to IAN, that may well be an FSX issue but curious to understand or fix if possible. - What sort of issue might NGX FMC have detected to cause it to flip automatically to IAN approach, when both ILS frequencies were correctly tuned and course correct?
The RW NG pilots who monitor these threads, unfortunately, have been notably silent concerning IAN procedures and the topic has been brought up in several threads. As to what you experienced, David, I have noticed that normally when I have selected an ILS procedure in the APP/DEP menu in FMC it automatically sets the G/S to ON. If, however, for some inadvertent reason you had accidentally changed it to OFF ( It appears in 2 places in the FMC ) then the FMS would treat it as a localizer only approach and create its own GP based on NGX database for that runway. Are you using 3rd party scenery or stock FSX scenery for LFMN? The reason I ask is that the info in the NGX database concerning runway 4L may be different than your scenery -- hence the wrong glide path being created by FMS. Sorry I couldn't be of more help.

Craig Williams

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Thanks, Craig. Much appreciated. I don't hold anything against our RW colleagues: they (including, I guess, you) must feel themselves inundated with requests for RW experience and advice. As we all know, this is only a mark of the excellence of the product. It stuns me every time I refer to the FCOM, how much the NGX actually has. That aside, I'll watch for your GP on/off pointer. Using stock LFMN scenery, so it can't be that ... Would you happen to know what files to inspect in order to see whether there is a disparity between FSX and NGX databases for LFMN? Or is it all locked up and invisible? I am not a hi-techie, and get very, very nervous about changing files, frankly, but it would be good to understand the issue. Again thanks. Best wishes, David


David Abrahams

 

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Sorry I didn't get back with you sooner, David. The NGX database is current if you updated it or if you did not then it would be the most recent prior to current. The info should be available on Airnav.com. I think they stay current. As for what is in stock FSX, I recommend an AFCAD disassembler. I find Airport Design Editor (ADE) very user friendly and I, like you, am not a techie!. What would stand out is if runway lengths have changed. Also note the ending and beginning coordinates in Airnav and compare them to what is in the AFCAD file. I have tried a simulator flight into Nice but with another commercial product which was not as sophisticated and only used the info encoded within FSX so I had no issues. I will try a flight with the NGX to runway 4L ( I also have stock scenery) to see if I can duplicate your problem.


Craig Williams

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Many thanks, Craig. Much appreciate your insights and interest. Please: no need to apologise! Will certainly take a look at ADE and look fwd to news of your own experience of LFMN 4L x NGX in due course. Best wishes, David


David Abrahams

 

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I have not forgotten you, Dave. Just not had the time to fly until this morning. Completed a flight from Manchester to Nice and made sure my ASE WX favored landing East so I could request ILS 4L. I used the MUS NDB transition (even tho FSX does not have MUS NDB it still can be used as a waypoint by FMC). I noticed that when I was on Loc inbound and descending to 4000 msl, I too had Localizer with "GP" instead of "GS" on the annunciator. But when I leveled at 4000 and proceded further along the inbound it changed to "GS" and the GS indicator appeared on my ND. After interception I was able to fly the standard ILS procedure to DH=200 (since my Vref was 135) as a category C Cat I approach. I disconnected at DH and landed normally within the TDZ without having to perform any unnatural maneuvers. I was curious, however, since you said that FMC had given you a GP that brought you short of the threshold. Did you attempt an autoland? The charts I have show 4L as Cat I only which means you fly and land manually after the DH (200 agl if category C, 220 if category D). Of course in our world of simulation, your license probably won't be in jeopardy, lol. But if not autoland then how did you determine that the GP was too low? Was it because the PAPI on the right are in the "red"? If so, then I can explain. The PAPI for this runway are set at 3.5 degrees in FSX and NOT COINCIDENTAL with the normal 3 degree GS so you will come in UNDER the papi at the DH on 4L. Reason for this seems to be that the approach plates indicate a much higher glide path for a localizer-only or visual approach. Hope this info is helpful. I did not attempt a partial IAN by flying the localizer-only with G/S=OFF. I can't find any info that the runway length or runway position at NCE has changed since FSX database was installed so I would imagine, unless NGX has corrupted data, that FMC would create a glide path that would end 50 ft above the threshold which would be identical to 4L ILS.


Craig Williams

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UPDATE: I had saved an enroute situation so I returned to it and this time requested LLZ (localizer only) for 4L but did not put in localizer freq. FMC generated a flight path and glide path. When I was on vector for final approach my annunciator showed "FAC" and "GP" as expected. I armed "APP" and AP intercepted "FAC" azimuth and I was able to use PFD with GP down to 390 msl ( my MDA). This time the papi showed that I was actually above ( don't understand why ) but I was in position to make a normal landing without any abnormal adjustments to pitch. I was, however, off runway heading to the left by about 1 degree (difference FSX to NGX database, I assume). I flew FMC missed approach and re-entered requesting vectors to ILS 4L. This time papi showed "on pitch" when I reached DH! Now I have not the slightest idea why these were so different. One thing to note, however, is that on this last approach, I DID NOT ever get a GS on the annunciator. I flew entirely using the FMC generated GP but used ND as though it was full ILS (which FMC data showed that it was). Again, I haven't a clue why I did not get GS this time.


Craig Williams

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