On a couple of occasions I have seen coupled autopilots initiate an uncommanded climb towards the glideslope (ie you are cleared for the procedure at a level, establish on the localiser and then the a/p climbs above the level towards the GS.)
Of course, whenever this has happened I have immediately disengaged the autopilot and flown manually; thus I have never seen how it would develop.
Does anyone know whether these experiences are:
My old S-TEC 60-2 would do that if I manually forced the approach mode. It was documented but with this autopilot I had my “WTF is it doing now” moments on pretty much every flight.
How did you “manually force it”?
I have never seen this with the KFC225 but have seen it turn onto a false localiser if I pressed the APR button (normally from HDG mode) much too early; say 10nm from the localiser. So now I set up the GPS in OBS mode to show the ILS lateral path, for my guidance, and press APR when only a few nm away.
But intercepting a glideslope too early and climbing up to it is just bizzare. I’d say it is a defective system.
Does the same aircraft fly any ILS correctly?
How did you “manually force it”?
Just press the GS button, if it is within reach, the S-TEC will capture it like a madman, stalling or overspeeding your airplane.
Just press the GS button, if it is within reach, the S-TEC will capture it like a madman, stalling or overspeeding your airplane.
I think you meant to say, press the ALT button, there is no GS button on the Stec 60-2.
My old S-TEC 60-2 would do that if I manually forced the approach mode. It was documented but with this autopilot I had my “WTF is it doing now” moments on pretty much every flight.
You hurt my autopilot’s feelings. It told me it was dirt simple to use. 
Yes, ALT on the 60-2. I had the 60 PSS before where the button is called GS.
You hurt my autopilot’s feelings. It told me it was dirt simple to use.
We had our regular disagreements and eventually it got fed up with me and tried to kill me which I thought was really mean. So I killed it and keep it as a trophy on my cupboard.
My experience of this behaviour has been when the time to intercept the GS has been very soon after intercepting the localiser/centreline (I can’t actually remember whether this was on ILS or LNAV, or if that makes a difference.
If we were talking about LNAV/VNAV or LPV would that change the answer?
Just press the GS button, if it is within reach, the S-TEC will capture it like a madman, stalling or overspeeding your airplane.
Huh? My Sys 60 PSS enters GS capture mode when I press GS (ALT illuminated, GS blinking). It only starts to track the GS once the needle crosses the center line, at which point ALT goes dark and GS stops blinking.
If we were talking about LNAV/VNAV or LPV would that change the answer?
It depends on how fancy your setup is. In mine, it won’t. The autopilots only see the “needle deviation” signal and have absolutely no clue which receiver drives the needle.
If we were talking about LNAV/VNAV
Do you perhaps mean LNAV+V ?
In light GA, one has only GPS/LNAV, GPS/LNAV+V (the “advisory glideslope”), GPS/LPV – AFAIK.
That said, not having a “W” box I have no idea how one configures one of those to capture the advisory glideslope…
