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Guest FrancoisH

[MD-11X] Overfly waypoints in STAR and afterwards turns...

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Guest FrancoisH

Hello,I'll explain here what I want to know. I made a flight from CYWG to EBBR today and on final, I got this procedure, I know the chart is for 25R and I selected 25L but it's the same for both approach (I took the wrong chart when making the screen) : http://img186.imageshack.us/img186/6057/ebbr01cb0.jpgBut when I look at the FMC, I see this trajectory :http://img183.imageshack.us/img183/8039/ebbr02xl7.jpghttp://img412.imageshack.us/img412/6015/ebbr03mf5.jpgThen BRUNO VOR is fly-over waypoint... then the plane will go over then turn right and try to intercept back the trajectory... this is not possible then to get what is necessary here : go trough then proceed direct to the point ?The solution is to add an intermediate waypoint after BUN maybe to force the turn on the right without going back to the trajectory.Regards.

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Francois,This behaviour has been noted and reported as a wanted feature by one of our most "active" beta testers. The idea was that after each flyover waypoint the next is a direct to waypoint. Well, PMDG SID/STARs scripts allow for this by adding FIX xxx OVERFLY DIRECT TO yyy. The latter bit is missing though from all related procedures from the Navigraph data.My reply at the time was that it is not for the FMS to decide what is a direct to waypoint and what is not. In other words this should be added specifically and **deliberately** by the procedure author, otherwise you open a can of worms.Best,VangelisPS. For the record I agree with you.===================================== E M V Precision Manuals Development Group www.precisionmanuals.com=====================================


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E M V

Precision Manuals Development Group

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These problems will be solved when we move on the ARINC424 formatted procedures instead of text files. One workaround is to DIR TO the next fix after BUN while in the turn, which will straigten out the path to the fix instead of the backtracking. You can try adding a TURN RIGHT DIRECT after the OVERFLY BUN command in the procedure to see if that works too.The Navigraph procedures are automated translations.... believe me, that is the only way one can create so many files in so many variations each month. I work real hard keeping 68 up to date, and I'm still catching up with the computer failure I had a month ago..trying to make 0811 on time. The ARINC424 format will make the automation process more effective at giving the pilot what is intended on the chart.Just an afterthought, if there is a narrative for this procedure does it specify that BUN is a flyover or that you should fly past the VOR or does it allow a flyby? It could be the latter and the drawing is a simplified path for both the holding case and the without holding case. Worth checking.


Dan Downs KCRP

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Guest FrancoisH

Hello there,Sadly the procedure as no narrative description appart for the missed approach part, as always. Anyway I should say that I understand your point. In the past I MADE procedure for some airports and I know how this things had to be finely tuned to be correct or close of the charts...I often had to add some intermediate waypoint to force turn on the right side or to force the plane to follow trajetory it should follow.I think the overfly then turn to get back the track is a good thing, especially to keep plane into procedures protections even I do not know how real FMS act in this case.Anyway it's complex things and I hope you'll find a way around it soon. In the meantime, I'll continue to use my little tricks to go around these problems ;)Regards.P.S. I'm sorry to post so much about things I find sometime odd. I'm not (yet) a real pilot, even at least PPL, but I do try to improve my knowledge as a hobby, as many around here. So I prefer to ask for everything I don't understand, especially when it come to fly on such great (virtual) bird.

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>P.S. I'm sorry to post so much about things I find sometime>odd. I'm not (yet) a real pilot, even at least PPL, but I do>try to improve my knowledge as a hobby, as many around here.>So I prefer to ask for everything I don't understand,>especially when it come to fly on such great (virtual) bird.You keep at it Francois - as a result my knowledge is increasing by leaps and bounds as I had not even thought about the question let alone the answer.


William Hall

 

 

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Hello all,I would like to ask you if this is the procedure in real world FMC's, if so then I will do with it. I have thought of modifing the .txt files but it would take a huge amount of time (Dan, I have enormous respect for your work because of this).However, this issue can be a problem on approaches, especially on base turns, the glideslope will come alive way before you complete the turn. I overcome this by going to HDG mode or by a direct-to as it was described earlier in the thread. Hopefully the new ARINC424 format will solve this.Happy landingsEDIT: Spelling

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The ARINC424 format is planned (last I heard) for the NGX, but it will not be compatible with the script-based FMC data.In this specific case, flying the above approach in real world, I would pass over the station then turn right to the a heading of 216 to intercept the localizer... there would be no way to intercept right at the fix indicated on the localizer at 10.9 DME, might be a little before or a little after depending on wind, how standard my rate of turn actually was, and how close to a heading of 216 I held (that alone incurrs an error of at least +/- 5 deg). There is a misconception among non-instrumented rated that we are always on the same track as indicated on a chart. Watching a radar screen will confirm this happens rarely in real world.. RNAV procedures help but every flight still has it's own track over the ground.Note that the approach designer allowed over 5 nm from the IF to the FAF, based on my knowledge of TERPS this is to allow for the variances I mention.The ARINC424 procedures work best with RNAV procedures where you have a distinct fix-leg fix-leg structure. Many pre-RNAV proceduresare difficult to encode because they have floating fixes such as this example above. Unless the arc past the VOR is defined in the procedure such the aircraft tracks it (ARINC has a FIX-ARC to FIX leg definition) then the windage will create different tracks across the ground assuming you are doing a standard rate turn through the air (which you should). Lots of devil in the details. So, ARINC424 will be an improvement but there will still be some variance in how a non-RNAV approach might be encoded.


Dan Downs KCRP

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Guest FrancoisH

That's why even when it show correctly on the ND, I prefer to follow the procedure using my VOR and ADF receiver ;)

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