Coupled ILS - initial overshoot

[swatson999]

This might be related to my autopilot tuning, which I intend to do again, but just a question...Shooting coupled ILS approaches this evening, it appeared that the VNAV function kicked in at the point the ILS glideslope was precisely "on", followed by a bit of overshoot before it started nosing over to track the GS. After that, it was rock steady once it was on GS (I reduced power to maintain 110 KIAS or so at the point it captured the GS).

Is this normal? Do others see the same thing? It went about 1/2 to 1 dot above GS, then within about 10-20 seconds was back on GS.

All in all, very impressive performance, but just wondering either my technique or further tuning would improve the initial capture rates.
TIA!

 

[krw5927]

The RV12 may be quite different, but I find my fixed-pitch RV9A is so slick that I cannot start down the glideslope AND lose airspeed at the same time. So my procedure is to slow to 75 KIAS before the FAF, deploy half to full flaps, and let the autopilot capture and fly the ILS with me on the throttle to control airspeed. I don't see any over/undershoot this way.

 

[swatson999]

Yeah, I'm slowing to around 100 kts just after the IAF, then managing airspeed with throttle on the ILS...I suspect this is more of an A/P tuning issue.