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Guest Totalbeginner

MD11 HDG/TRK confusion with APPR rose showing???

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Guest Totalbeginner

Ok, here goes...Yesterday I decided to practice some hand flown circuits in the MD11. I had the ILS tuned and the correct RNWY QDM entered in the NAV/RAD page and decided to select the APPR rose on the NAV display. Now, it just so happens that at 2000ft I had a steaming 40kt crosswind. As my mental arithmetic is so bad, I thought it would make life easier if I changed the heading mode to TRK. Sure enough, my current track was displayed in the window and the compass rose swung round too. Great I though, all I need to do now, is line up the TRK bug with the tail of the CDI pointer and that should make the aircraft track downwind, exactly parallel to the runway QDM. Wrong!! Instead I drifted straight through the back course of the ILS. I noticed that when selecting TRK, the CDI did not move with the compass rose, is that normal?I'm so confused, I can't get my head around it! When selecting TRK in map mode, the magenta route moves, so shouldn't the CDI move witht the compass rose?Really interested to see if someone can get their head around it!Regards,Martin Neep

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Martin,My head is spinning too trying to understand what you are attempting to accomplish. The track information is only available in the MAP mode, it doesn't exist in the APPR mode so I am not sure what you are lining up with what. There is no CDI on the map mode, in other words you either have CDI or TRK but no both, they belong to separate displays. It seems to me you are mixing up two different displays. Perhaps if you attached a picture it would be clearer. Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg

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I think what he is trying to say is that he is flying in HDG select mode, and he switched it from HDG to TRK mode, and hes wondering why the aircraft is drifting laterally across the ground and not maintaining the track. So in other words, flying in TRK mode should correct the drift caused by the crosswind

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Guest Totalbeginner

>I think what he is trying to say is that he is flying in HDG>select mode, and he switched it from HDG to TRK mode, and hes>wondering why the aircraft is drifting laterally across the>ground and not maintaining the track. So in other words,>flying in TRK mode should correct the drift caused by the>crosswindKind of...Oh god, this is going to be hard to explain!!!Here is the first image. You can see I have a strong crosswind. I have aligned the green diamon (trk) with the CDI and it's 100% clear in this picture that the aircraft is tracking correctly. I also confirmed this in map mode.http://martinneep.zenfolio.com/img/v4/p58462757-5.jpgNow in the next image, I have pressed the TRK/HDG switch above the HDG window. The compass rose is now displaying TRK instead of heading. The little aircraft symbol is now pointing to the heading, which is correct. Bear in mind, that the aircraft HAS NOT changed heading... what is the CDI now pointing at? Surely the white bug (which is now referenced to TRK) should be in line with the tail of the CDI. It makes sense, as we can see from the previous picture that the A/C's track is parallel to the CDI QDM.http://martinneep.zenfolio.com/img/v5/p428756975-5.jpgI really hope that makes sense!Martin Neep

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Martin,Now I understand what you mean ...You had asked: > the CDI did not move with the compass rose, is that normal?It very well may be normal although someone with better knowledge of the aircraft should chime in.Perhaps this case is a perfect illustration why mixing track and CDI on the same display is a folly ...Please notice that having TRK at the top of the display is in itself an abnormality - the physical display (the LCD plate) itself is mounted to the aircraft so the display should point where the aircraft is pointing. All of a sudden the whole display is skewed and twisted in relation to the body of the aircraft.It is entirely possible that when you select TRK at the top the ILS (course) information is "riveted" to the body of the aircraft so it does not get rotated, so your magenta pointer does not move.I would never use HSI with the TRK mode, precisely because of confusion like this one. TRK is really meant to be used in the MAP alone. If I recall Boeing would simply not allow you to combine both (TRK and CDI) in the same display.Perhaps someone from PMDG should confirm this is not a bug.Also a practical advice regarding such a crosswind --What are the surface winds? If they are similar to those at 2000 ft safe landing may not be possible.And then ... if you really want to fly a race track pattern with such winds - you do NOT want to fly a parallel (downwind leg) track to the runway, in fact you want to fly a double or triple the normal wind correcting angle. If you kept a perfect parallel track you would quickly run out of room when making 180 deg turn to base/final. You may read about it in a typical IFR textbook when they talk about holding patterns.Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg

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The APPR screen compass rose is set by the CRS, not desired track. Ideally, the course and track should be the same when on the localizer and the compass rose will be rotated by an angle equal to the wind correction angle. However, finding the correct wind correction angle becomes twice as difficult as the time proven method of flying a cross wind approach.Keep everything in MAG mode, set up the APPR screen and use the HSI presentation (Horiz Situation Indicator). Add wind correction until the needle stops drifting then use minor corrections to keep it near center. This skill takes time to acquire, and you have discovered one of the great challenges of instrument flight. Not only are you looking for the correct angle to freeze the localizer needle but you are also setting up a descent to nail the glideslope. Meanwhile, the winds are changing as you descend (they always do) and everything gets progressively sensitive as you get closer to the runway. You better have everything set up before the last 500 feet because from that point inward everything becomes so sensitive that if you are still looking for the right corrections you might as well go around.

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Hmmm, I'm an airline pilot and although I fly conventional gauges, logic tells me that even though Douglas "wants" you to fly the track mode only in MAP mode, it should not allow conflicting information to be displayed. 1. Gathering from the degree of automation in the MD-11, if indeed this was not possible they should at least put a red X where the CDI was or something.2. The TRK / FPA were implemented especially for non-precision approaches. I can't imagine that a non-precision approach has to be flown in MAP mode. It does not make sense. The CDI information takes information from the course you enter. In the first picture it seems the user entered 047

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Guest Totalbeginner

I agree, I think it's a bug.I have a friend who is an Airbus driver and we were discussing it. Apparently the Display in the Airbus is very similar, and can also be set to display TRK in the APPR rose.He said that 100% for sure the CDI should move, otherwise it would be just pointless to have it there.Regards,Martin

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Guest Kasper Hanselman

I disagree, I don't think it is a bug.Pushing the HDG TRK button only changes what the bug is tracking.So in the first picture HDG is 241 which leads to a track of 227.After pushing the bug shows track 227 and the plane is pointing to 241. So nothing has indeed changed, which is as expected. The CDI still points to the ILS.I am not sure why this is confusing?

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Guest Zenra

The CDI should point to the CRS set along with the ILS station on the MCDU, and should remain independent of TRK/HDG. I guess the OP is saying that the ONLY change made between the first and second screen shots was a press of the HDG/TRK button? If so, the way I understand things, the CDI needle should remain pointed at the same compass rose position (~47

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Guest Kasper Hanselman

If you look closely you will see that the distance to the ILS is 0.8 nm (about 15%) closer in the second picture. With a 40 miles cross wind I don't think the drift is excessive. Furthermore, in the operations manual the workings of the HDG TRK function is explained. It does not has any influence on the CDI.

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Guest Totalbeginner

>The CDI should point to the CRS set along with the ILS>station on the MCDU, and should remain independent of TRK/HDG.> I guess the OP is saying that the ONLY change made between>the first and second screen shots was a press of the HDG/TRK>button? If so, the way I understand things, the CDI needle>should remain pointed at the same compass rose position (~47

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Guest Totalbeginner

>I disagree, I don't think it is a bug.>>Pushing the HDG TRK button only changes what the bug is>tracking.>So in the first picture HDG is 241 which leads to a track of>227.>After pushing the bug shows track 227 and the plane is>pointing to 241. So nothing has indeed changed, which is as>expected. >>The CDI still points to the ILS.>I am not sure why this is confusing?Let me put it another way...The aircraft heading and track are displayed correctly in both images. The ILS course is set to 045 deg, so what is the CDI pointing or referenced to in the second image? It's pointing at 030 deg which means absolutely nothing.This means one of two things. Either, it's a bug and the CDI should still be pointing towards 045. Or, the CDI should be crossed out / disappear to prevent confusion.Martin

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>If you look closely you will see that the distance to the ILS>is 0.8 nm (about 15%) closer in the second picture. :-zhelpSorry, but you seem to have some serious gaps in your knowledge how HSI/CDI works. The distance to station has/should have no influence how CDI points. Please consult some textbook on HSI. This is not a NDB needle which always points to the station.>It does not has any influence on>the CDI.Correct, it should have none, contrary to the situation shown above.Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg

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Guest Kasper Hanselman

>Let me put it another way...>>The aircraft heading and track are displayed correctly in both>images. The ILS course is set to 045 deg, so what is the CDI>pointing or referenced to in the second image? It's pointing>at 030 deg which means absolutely nothing.>>MartinHm, maybe it points to the TRK in stead of HDG? 241-227 = 1445 -31 = 14?

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Martin,Based on the scenario you discribed, did some flights observing the APPR Mode.Observed that the CDI pointer, in TRK mode, is not drawn correctly when there is a X-wind. Or to say it otherwise, the CDI is miss aligned by the amount of crosswind component.This can even better be observed when flying a VOR radial, set via the NAVRAD FMS Page, then select the VOR Mode and TRK on the ND.The CDI and RMI for the station have a difference proportional to the crosswind component.Hope this will be corrected in the FS9 version and the FSX Update.Regards,Harry

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Xander,Thanks for your very matter of fact contribution.>Hmmm, I'm an airline pilot and although I fly conventional>gauges, logic tells me that even though Douglas "wants" you to>fly the track mode only in MAP mode, it should not allow>conflicting information to be displayed.Have been an airline pilot too, of which I flew MD11's for 11 years. So I can confirm Douglas does NOT "want" you to fly track mode in MAP mode only. >1. Gathering from the degree of automation in the MD-11, if>indeed this was not possible they should at least put a red X>where the CDI was or something.No red X is needed because flying TRK on VOR and APPR modes is valid as well.>2. The TRK / FPA were implemented especially for non-precision>approaches. I can't imagine that a non-precision approach has>to be flown in MAP mode. It does not make sense.Indeed, the primary navigation modes in this case (non-precisionapproaches) are VOR or APPR mode. >The CDI information takes information from the course you>enter. In the first picture it seems the user entered 047

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Guys, thanks for your feedback. We will look at this issue for the next update.

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Guest Kasper Hanselman

You are correct, I had some wrong assumptions.

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