Hi Guys,

I just started using this plane and I have a problem with the autopilot and ILS. When I select approach hold, the localiser is captured but the plane goes up and down and does not maintain the glideslope. 

Do you fly level before capturing the ILS from below? (i.e. no slam dunk approach)

What was your indicated airspeed? Maybe reduce power, use flaps.

Also try applying the small change listed on http://flysimware.com/website/Cessna441.html:

Change elevator_trim_limit in aircraft.cfg to 20.0 (I think the original value is 15.0)