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ahinterl

MD-11 (FS9): Some questions on descend/approach

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I've made some screenshots for things that are unclear to me.Picture 1:When descend is automatically initiated, I get different results at times though I always prepare the situation in the same way. The only difference is the route flown.Situation 1: Descend starts "silently", but VNAV (in magenta) with a fixed descend rate becomes the active mode.Situation 2: Descend is somehow visually indicated by alternate blinking "VERT ALERT" and "PROF TO xxx".What's the reason I get these different descend scenarios? Altitude is dialled down way before the T/D is reached.Picture 2:Speed target for LAFFO is 189, but the FMS chooses and holds 180. Why that? I guess because flaps 15 is set. Since I miss the appropriate tables, I can only guess that the plane flies the optimum (maneuver?) speed for flaps 15.Picture 3:When line/triangle is selected in the PMDG options menu, I saw that the symbol on the altitude tape (red arrow) appears and blinks at the markers (I, O). In the situation depicted on the screenshot, the symbol appears in amber, and I have no explanation why it appears.Picture 4:Though the manual says the radar altitude box moves upwards, it doesn't for me, the only thing moving upwards is the rising runway symbol. On the rising runway symbol, I somehow miss the "E" symbol of which the manual says it depicts localizer deviation.And what does the indication "100 FT" (right lower portion of the PFD) mean?Another one: You can see the indication of the ILS at the left lower portion of the PFD (IYJ). Sometimes I get a distance shown there as well, sometimes not like on the screenshot, why this? Doesn't the ILS include distance data?Final question: Is it normal that the MD-11 has such a high nose up attitude during descend and approach? At times, I have the impression that pitch reaches 7,5 degrees nose up especially when the G/S is chased.Edit: I read somewhere some planes have high pitch angles during approach due to their wing design, EMB-170/190 and MD-11 being one of them...Andreas

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Let's have a go... :DNow, I only have around 100 hours on the PMDG MD-11 (just so as not to confuse anyone into thinking I had real world time on the aircraft...), and I have only really scratched the surface of the systems depth here...1: The MD-11 does not have the mode VNAV, it is PROF for Profile...When you reach the calculated top of descent, T/D, the aircraft only begins descent if you have reset the altitude in the flight control panel, FCP. If you have done so, then the aircraft begins to descend to the set altitude or the next profile constraint. If you set the altitude of any profile constraint in the FCP, then you will see PROF TO XXXXX and PROF XXXX both in magenta. If the altitude you set is not an altitude constraint or final PROF altitude in the FMS, then the altitude corresponding to PROF TO will be white, as in your example in 2.Now, when you are descending to an intermediate constraint and you reach it, the aircraft might level out and hold that altitude. Once you have passed the waypoint at which the constraint applied, and the FCP alt window is set accordingly, the aircraft will then contimue with the descent... VERT ALERT will flash, warning you of the next descent phase, the alt in the PROF annunciation below will be the next programmed constraint, and the VERT ALERT will at some point change back to PROF TO XXXXX as previously described.2: I need to ask a question here: Is the constraint speed AT, AT or above, or AT or below? The magenta dot implies FMS managed speed, and by setting flaps 15, the speed will reset to the FMS managed speed for the flaps regime I believe, though I could be talking oput of my rear here :DTo be honest, I tend to switch over to manual speed control on approach, and hold 220 a lot longer unless otherwise informed by ATC... she slows down really quickly when you throw the gear out and drop more flaps...3: The altitude window in 3 blinks when you cross 1000ft above your set PROF altitude, BB also comes in with "Altitude" just to let you know... You may notice that it starts blinking at 3200ft when you have a PROF of 2200ft set...4: No idea on the E symbol, not got that far yet...The indication "100FT" in your screenshot is the QNH altitude of the aircraft. Your radar alt is 20ft, your aircraft alt at the set QNH of 29.92 is 100ft, so your field alt is 80ft... In pic 3, you are at 3120ft QNH 29.92... It is just a slightly more accurate reading than the tape...Not all ILS have DME associated... All basic ILS is is a pair of beacons, one depicting the glideslope, the other is the extended runway centreline (in most cases, I am aware of the offset LOCs...) You only get distance if there is a DME associated with the ILS...Furthermore, you are right about the MD-11, it has quite a pitch angle on approach, just check out the landing shots on airliners.net and so on...Hope this helps a little with understanding (and that I haven't complicated issues or even told a load of nonsense... If so, I gladly stand aside to be corrected by someone who knows a lot better than me)... it certainly does for me, going through your questions one by one helps me to understand the systems more as well...Andrew

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Ok i'll try to answer to what I know :( Picture 1:Situation1: This is the normal behaviuor.Situation2. In this specific case you have an altitude constraint of 11000ft that will be cancelled once you pass the waypoint with that constraint. Vert Alert is advising the crew of an altitude change in profile mode, so that if the crew wants, can override this ( Perhaps you selected a lower altitude and the you put the knob back to 11000ft, or did you just reach 11000ft at the moment you took the shot?)Picture 2:Yes that is correct, if the aircraft has speed control (three dashes in the speed readout), it will select the best speed for the given flap setting.Picture 3:Same as picture 1 : there you have in the FMS an altitude constraint of 2200 feet, and you just passed 3200 feet. Even though you selected 1500ft in the altitude selector, the plane will go for 2200ft to meet the constraint, unless you clear it via the FMS or you fly over the waypoint for which the altitude constraint is set. 1000ft before reaching the altitude there is an aural warning in the MD11 saying "Altitude" and the triangle will briefly flash in amber.Picture 4:If you compare the picture with picture number 3 you can see that in pc 4 you have the radar altitude box showing 20ft, in picture 3 there is not.100FT should be the QNH altitude... as you can see you are about at 20FT RA and the altimeter is showing about 100ft.For the ILS: ILS is composed at leat of a LOC+GS. To have DME you have to tune a VOR on NAV2, you can check that on the approach plate, usually you find XXX DME required. There is also the ILS/DME that provides also distance measurement.RegardsStefano

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1: The MD-11 does not have the mode VNAV, it is PROF for Profile...
That was a typo on my side, should read "V/S".Andreas

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Thank you all for the clarifications.

Now, when you are descending to an intermediate constraint and you reach it, the aircraft might level out and hold that altitude. Once you have passed the waypoint at which the constraint applied, and the FCP alt window is set accordingly, the aircraft will then contimue with the descent... VERT ALERT will flash, warning you of the next descent phase, the alt in the PROF annunciation below will be the next programmed constraint, and the VERT ALERT will at some point change back to PROF TO XXXXX as previously described.
As said, I had the blinking "VERT ALERT" when I did nothing else but cruising without any playing on the altitude knob (just discovered I can set a new crz alt and initiate an immediate climb by dialling a higher altitude during cruise). So, there were no intermediate level offs, the altitude dialed in before T/D was always lower or at the altitude of the next constraint.Having seen "normal" transitions to descend (the "silent" ones), I just cannot explain why I sometimes get nothing and sometimes a flashing "VERT ALERT"...Leaves the question why the plane sometimes descends with a fixed V/S instead of PROF (and tends to severely undershoot the vertical path) and I cannot change that mode (hitting PROF does nothing, everything is magenta already)...For the ILS, I guess I have to watch if I can get any DME information on VOR2 for instance.Andreas

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Just a point to make:Sometimes the DME transmitter uses the same frequency as the ILS, so you will get DME information associated with the ILS...See http://www.airnav.com/airport/OKC/ils/17L for an example... you can see the DME frequency is the same as the ILS...Where this is not the case, you will need the DME frequency on NAV2 set to display the data for the approach...An example, I believe, is the ILS CATII & III or LOC 27R EDDV... DME is HAD on 113.95, the ILS is 108.90...Andrew

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2. Is 189 a constraint or a prediction? It seems to be in small font, and so my guess is that it's a prediction, and so the FMS is only showing that for your planning purposes. When in FMS SPEED mode, the FMS will slow according to the internal logic (posted on the PMDG wiki page I think).4. The RA readout doesn't move, just the rising runway. Probably just a typo in the manual. The LOC deviation scale is displayed just fine. Not sure what "E" you're talking about.There's a bit of confusion about DME and ILS. Some ILS installations have DME associated. In that case, the chart will show ILSDME RWxx. The DME will appear at the lower left of the PFD. Be advised that the DME may not show the distance to the touchdown spot, so check the chart to make sure.What somebody described earlier about tuning a VORDME to get distance information is NOT a valid substitute for ILS DME unless depicted on the chart. I advise against doing this. The VOR may be located some distance away, and thus you'd misinterpret the information. You'd have to rely on marker beacons and/or intersections to determine your progress on the ILS.Paul

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Thank you all for the replies.I checked the ILS thing again, and even in the FS map view, one can clearly see whether an ILS is associated with a DME transmitter by simply clicking on the green wedge, the information popup window identifies ILS as "ILS/DME" if a DME is present, which is not for the airport I've chosen.Andreas

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