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namida

IAN with offset LOC

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* Wrong title, sorry. it's VOR. During VOR/DME offset approach (app course is different to runway heading) with FAC & G/P armed,is it normal FAC tries to capture Dashed Runway Centerline rather than LNAV course andG/P deviation is based on 3.0 degrees for E/D instead VNAV path? (rather higher than VNAV path)I read the whole FCOM and Training documents but could missed some conditions or characteristics of IAN. When I turn into Dashed runway line, it captures FAC as expected and also G/P does. 88AQ.jpegin this image, RWY HDG is 239, VOR/DME CRS is 245. RKTU, VOR DME Rwy24R.(Both FD on, both Nav tuned to correct VOR, both CRS set to approach course.(245)) I'm very happy IAN has been implemented in NGX but still need more stuty. rolleyes.gif edit : ↓ I think G/P follows G/P angle wrote above RWxx column in LEGS page, and also G/P follows it's HDG of RWxx.88Gf.jpeg


Peter Chang

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As I understand it lateral deviation should be from LNAV path to MAP and vertical deviation should be from VNAV path to MAP. Reference FCOM Vol 2 11.31.38. I tried IAN only once or twice so far though, certainly need to look into it myself. sig.gif

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Guys, There's a bit of an issue with this IAN stuff that is (once again) due to the limitations of FS navdata. In real life, the FAC and G/P values are coded into the procedure in the navdata - Navigraph's data doesn't support this, so we came up with a workaround basically. I will have to verify with Vangelis what FAC does, but I know for G/P it calculates the angle based on the runway to the first altitude restriction on the approach. It always shoots for a 3 degree G/P if possible in the case of a "soft" restriction, and it will not exceed the published allowable G/P limits from the FCOM (something like 2.79 to 3.77 degrees). By the way - did you guys realize you can do "hybrid" approaches where the roll mode is VOR/LOC and the pitch mode is G/P? This might work better for you in these cases. It's only going to go to FAC if you press approach and are not in VOR/LOC mode or there's no valid radio navaid tuned. If you tune a VOR or a LOC and press VOR/LOC, it'll capture that first and then you can get G/P by pressing APP. You'll then have VOR/LOC | G/P in the FMA. San Diego's famous LOC 27 approach works really well for this for example.


Ryan Maziarz
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Thank you very much Ryan, I'll use that hybrid procedure. It makes me exciting, too!Anyway, I'm satisfied with current status but wish it would be implemented with full availability and can be used as it's original purpose. edit :

If you tune a VOR or a LOC and press VOR/LOC, it'll capture that first and then you can get G/P by pressing APP.
I tried this hybrid procedure but pressing APP also steals VOR and became FAC if offset not so far.. sad.pngEngaging LNAV again makes LNAV and FAC armed, as airplane come closer to E/D, it steals again.. (doesn't matter because a/p disconnecting..)

Peter Chang

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Is it also normal that changing the CRS setting on a LOC (!) approach would make the plane turn?? Remember, a LOC has a fixed course, actually it shouldn't really matter what your CRS/OBS is set to, same as ILS... We're not flying radials here. sig.gif

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