FLYING ILS with AFS AP

Today I flew an ILS with the AP. It had about a 20 kt crosswind from the left. The autopilot wasn't able to compensate for the cross wind and my deviation bar remained off to the windward side yet when i flew a gps approach to the opposite runway with the same cross wind(from the right) my course was right on. Is there something different how the AP handles an ILS approach?
Alan

Yes, the GPS approach is a lot easier to control. With a GPS approach we always know where the plane I and how far away from center it is. The CDI needle on a gps approach is actually a distance. On a ILS the CDI needle is just a deflection and it gets a lot more sensitive as you get closer, it makes it difficult to control the gain for the control loop.

You should try increasing the LOC gain on the EFIS to make it follow it bettter.

Quote:

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Originally Posted by Rob Hickman

Yes, the GPS approach is a lot easier to control. With a GPS approach we always know where the plane I and how far away from center it is. The CDI needle on a gps approach is actually a distance. On a ILS the CDI needle is just a deflection and it gets a lot more sensitive as you get closer, it makes it difficult to control the gain for the control loop.

You should try increasing the LOC gain on the EFIS to make it follow it bettter.

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Rob,
My current setting is .50. What number to you suggest?
Alan

just keep increasing it until it gets jumpy, .7 ?

will try it.
Alan