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martinlest2

AFCAD & Navaid question

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Hi.I have a gut feeling that this is a stupid question, but can't work out why, so here goes: can anyone tell me why all the AFCADs for Innsbruck LOWI I have seen (inc. that for innsbruck-lowi_v2.zip), have the localiser offset to the runway heading (rwy 26) by several degrees? That means that when the a/c intercepts the localiser, it arrives at the threshhold at an angle. I can't see any advantage to this, as the terrain would seem to allow a normal approach, correctly lined up with runway 26 at 260 degs. The disadvantage when you land several degrees at an angle is trying to keep on the runway centre line at touchdown (crosswinds notwithstanding!). I usually cut off the AP a bit earlier and hurry to line up manually at the last moment (a bit hairy sometimes), but I'd far rather approach square on to the runway, as is usual. The documentation I've read states that real-world approaches to LOWI are supposed to use the AutoPilot as far as possinle, so a VFR landing is not really very true to life.I could just rotate the navaid in AFCAD2, but I suppose the offset was put there for a reason, especially as more than one AFCAD has the same thing, even if I can't see what it is! Anyone able to enlighten me? Thanks!Martin

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ILS is both lateral and vertical navigation. I believe in case of LOWI the offset is necessary for ILS (or rather LOC-DME in this case) to avoid very steep angle of descent (which would be necessary if it was a classic ILS path), due to the necessary cleared space between the surrounding mountains.This is what comes to my mind.

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Approach charts are here:http://www.vacc-austria.org/index.php?page...t&icao=LOWITerrain on the east side prevents a GS all the way to the airport. For the LLZ to be even seen by avionics it must be offset to the side of the runway since obstacles do not allow it to be seen from the runway center line (extended). Note that the last stage horizontal path is curved and visual for runway alignment. The vertical path also varies along the approach somewhat and is not a constant.On the links above look at the various charts individually for both visual, LLZ/DME, and RNAV (GPS). None have raw data (glideslope) information and depend on database altitude information in the avionics database for the vertical path whether A/P coupled or controlled by the pilot. There is no glideslope to the runway surface for this curved approach. Note that the EAST LLZ chart is arrival from the EAST therefore to runway 26 and the WEST chart is a west arrival to runway 8. Just a little bit confusing.Also of interest these same localizers are departure aids as well.I suggest the offered airport chart bundled download.This is one of the most challenging airports to arrive and depart from and aircraft performance by type and weight restrictions are in place due to steep approaches and steep departures required and tight obstacle clearance to the sides.

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Thanks for the replies. I'll certainly have a look at the charts.In FS9 at least, I'd have thought that a straight approach was preferable to the offset - the terrain isn't too hard to navigate I found - I just flew an Embraer 145 there from EDDF - though for some reason, although it latched on to the localiser OK, it wouldn't capture the GS at all, even though I could see it moving down on the instruments, so I switched off the AP and landed manually. All went fine. This time round anyway!I flew into real world LOWI last year - or I was supposed to: we couldn't have been more than 100' off the ground when there was a huge roar of engines and back we went up into the clouds. The pilot said that flurries of snow obscured his view of the runway at the crucial moment. We circled for 15 minutes, then he gave up and we had to land in Munich. Which meant a long delay and then a coach .... We took off from Innsbruck on the return, and I took a long video of the take off from my window - we used Rwy 8, then doubled back pretty much 180 degs. back over the town. Makes a nice film - maybe I should post it somewhere...OK, enough of that. Back to the real world of FS9 (?) - I'll certainly have another go very soon, and have a look at those charts in the interim.Thanks again,Martin

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Snip-------Terrain on the east side prevents a GS all the way to the airport. For the LLZ to be even seen by avionics it must be offset to the side of the runway since obstacles do not allow it to be seen from the runway center line (extended). Note that the last stage horizontal path is curved and visual for runway alignment. The vertical path also varies along the approach somewhat and is not a constant.On the links above look at the various charts individually for both visual, LLZ/DME, and RNAV (GPS). None have raw data (glideslope) information and depend on database altitude information in the avionics database for the vertical path whether A/P coupled or controlled by the pilot. There is no glideslope to the runway surface for this curved approach. Note that the EAST LLZ chart is arrival from the EAST therefore to runway 26 and the WEST chart is a west arrival to runway 8. Just a little bit confusing.
RonI might be misunderstanding some of the GS statements The current Jeppesen charts (and what FS9/FSX loads into the database) show the Glide Slope (GS) for Rwy 26. The Glide Slope antenna can be seen with Google Earth positioned at the touchdown point of the runway. However since the Glide Slope can only be used on a portion of the Localizer, the Approach is a Localizer/DME instead of a ILS. The Approach could qualify as a LDA (greater then 3 degree LOC offset) but the non-precision GS makes it more of a Localizer/DME. The GS is 3.80 (same that FS9 and FSX uses) or LOC Desent gradient of 6.7 percent. The 3.8 Degree GS indication is only available from the D18.2 OEV and the MDA for runway 26. Many confuse Glide Slope (GS) with Glide Path (GP) which are very different. It is hard to capture the GS at 18.2 OEV while maintaining 9500 ft. The Pilot must have the plane in the slot and confiqured properly (real world and FS9/FSX) so a safty of margin is maintained as we fly a correct slotted glide path on the glide slope.jim

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I am looking at a Jepp chart now that came with an Aerosoft/Sim Wings FS9 collection (GAP 1) and it is a bit clearer than the link I posted. This shows the GS as you state from OEV 17.2 transitioning to visual at about OEV 3.8 MAP just past the RUM inner marker (First time I've noted a marker beacon with a Morse code ID "._." for R(um) .). This time I looked at the AFCAD with the Navaids enabled in the view showing the GS transmitter and also their properties.My error on the East Approach.

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snip----just past the RUM inner marker (First time I've noted a marker beacon with a Morse code ID "._." for R(um) .). This time I looked at the AFCAD with the Navaids enabled in the view showing the GS transmitter and also their properties.
The RUM Terminal Waypoint has the marker. I add and set it as a middle marker in FS2004 (FSX already has it). The marker is for both visual transitions for the Loc 26 and the Loc 08 approach.jim

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