Op System: Win 10
FS Version: X-Plane 11.55r2
AIRAC Update No: 2107
Problem Details: The alignment on the GNS 430 GPS is not in line with the ILS for different airports. While this occurs with different smaller airports, I have replicated it, specifically, for ILS runway 15 in KTPL and ILS runway 19 in KACT. This was not case with runway 18L at KAUS or runway 07 at KSBA; the ILS and 430 GPS aligned well in those airports.
Op System: Win 10
On the X-Plane 530 on Cessna Skyhawk, I show LOC alignment at KTPL 15 and KACT 19.
Maybe provide screenshots showing behaviour using Guide to posting Screenshots.
Thank you, Ian, for your response and efforts. I returned to the ILS at KTPL 15 and was able reproduce the problem using the X-Plane 530 on the Cessna Skyhawk. Following are three jpeg pictures that illustrate the misalignment.
Figure 1 shows you an in-cockpit view with the GPS magnified. Here you will see that (A) the course-deviation indicator is aligned perfectly with the to/from flag. However, the (B) airplane is misaligned right of localizer as indicated in the map view and as evidenced by the (C) runway through the window.
The same is true in Figure 2. The (A) course-deviation indicator is aligned, but not the runway (C). What’s interesting in this picture is that it shows (B) the OBS indicating misalignment as well. Meaning that the OBS (HSI in the Mooney I normally fly in) shows the correct signal from the localizer, but this is not reflected in the CDI of the GPS.
Finally, Figure 3, shows an exterior view of the same thing, depicting the misalignment with runway which does not coincide with the aligned CDI on the 530.
Thank you, again, for your willingness to help.
the course deviation indicator on the GPS does not show the localizer, only the instrument in the panel does. If you are flying a localizer or ILS approach, you need to center the analogue CDI instrument in the panel, not the digital one on the GPS, as that one can’t receive the ILS.
As you can see, that digital CDI on the GPS is indicating a course to a waypoint that you have long since passed, as indicated by the to-from indicator pointing downwards instead of upwards.
Thank you, Phillip, for your help. I was activating the Vectors to Final but was entering the approach after the initial VTF point, which in the example above was MOODY. So the GPS was effectively reverse tracking. I did not notice the rear pointing (from) flag. I’ve experimented entering the approach further back before the initial point and the CDI appears to now be working. However, I do believe that the GNS 430/530 on x-plane is WAAS capable and thus receives both ILS localizer and glideslope signals. Thanks again.
WAAS has nothing to do with receiving the localizer and glideslope signal from the ground. That is a completely separate system, which is why you need to make sure the label above the CDI button reads “VLOC” and not “GPS” while you are flying an ILS approach. The GPS is merely along for the ride, but it is not generating the lateral and vertical offsets you see on the CDI and glideslope instrument.
WAAS enables an LPV approach at some airports, that is very much like ILS in that it often can go down to the same minima, but based on GPS and WAAS satellites alone, without the need for equipment at the airport. That kind of approach is as precise as an ILS, has lateral and vertical like an ILS but comes out of the GPS without tuning any ground stations. You can use the GPS in X-Plane to fly LPV approaches at airports where they are published, and for them you leave the CDI selector in GPS (and don’t switch to VLOC for the final approach). In that particular case, the digital CDI on the GPS will be exactly as precise an ILS localizer would be, but only for that particular type of approach.
Thanks, Phillip. Happy flying.
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