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0 votes
asked by (12 points)
edited by

Any known bug with X-plane 11, and the default Cessna 172 autopilot not tracking ILS approaches correctly?

1 Answer

+1 vote
answered by (19.3k points)
Near the end of the beta period, the C172's autopilot behavior was changed. It's now supposed to be more like the real world AP, but it means it has to be set up a bit differently than it was for many years.

It's been updated to :

HDG with GPSS: This setting is new as of X-Plane 11. The autopilot takes the course to intercept in VOR nav/LOC app mode from the heading bug when tracking a VOR radial or localizer. It is important that the pilot always sets the heading bug to the desired front course, otherwise the autopilot cannot intercept and track a radial or localizer. Tracking and coupling works when the correct front course is selected using the heading bug. Dual-mode intercepts to VOR radials and localizers are not possible with that type of autopilot. However, when the navigation source is the GPS, the autopilot gets GPS steering (GPSS) information and thus works with  turn anticipation and can also fly DME arcs or fixed-radius RNAV legs. The S-Tec Fivty-Five autopilot works like this when installed in an airplane which does not have an HSI.
commented by (13 points)

Hi jroberts,
Your answer is from Apr 5.
Today Aug 6 the problem seems to be corrected. I think it's important to provide this information.
I've just performed an automatic ILS approach, using the Cessna 172 default (S-TEC like AP), I intentionally set a course 90º offset of the LOC final approach course, used an interception vector of 40º (HDG mode) and armed APR. In spite of the windy conditions, intercepted the localizer a little slowly but acceptable and maintained a good wind correction along all the descent.
It behaved like a real LOC, which just detects relative positions to the center line and knows nothing about radials.
About the GS I cannot say the same. It started the descent too early and came slightly bellow the glide path all the time. I suspect it needs an adjustment...
Just to clarify, my IAS was never too low.
Best regards