PC12 GS ILS Approach

[vincentrouleau 71]

I have been trying integration on the RXP 750 doing ILS Approaches in CYUL ILS24R. Using the A2A 182 , the autopilot stays perfectly on the GS. But for is Carenado PC12, the autopilot seems to follow a perfect offset above the GS. See the offset that it perfecly follows all the way down the runway.

 

https://imgshare.io/image/ppXOFw

 

What am I doing wrong?

[vincentrouleau 71]

@Bert Pieke I know you use the Pilatus PC-1, may iI pick your brains? Does the autopilot follow the glideslope when in VLOC on an ILS? Thanks

[Bert Pieke 7,584]

52 minutes ago, vincentrouleau said:

@Bert Pieke I know you use the Pilatus PC-1, may iI pick your brains? Does the autopilot follow the glideslope when in VLOC on an ILS? Thanks

PC12,  I believe so.  Try landing with flaps 2, instead of 4.. (!)

I typically fly RNAV approaches in GPS mode..

Edited February 3, 2021 by Bert Pieke

[vincentrouleau 71]

I was going waaay to fast. Really need to keep the AOA indicator at 0. Funny thing that the FD needle does not point to reach the glidepath. If the AOA is a bit off, the GS will be off. Thanks

[C2615 319]

It's just the PC12's AP are too bad to caputure G/S properlly, nothing wrong with GTN750.

It's very laggy on initial GS capture, simular to the buggy IAS mode, it'll "reset" to 0 pitch before starting to follow the GS, if you are on flaps30, in most condition it'll pitch up initially, thus make it high.

And after offseted too much, the G/S will inactivate as shown on your picture as a white G/S, rather than green. So it now will not even try to capture the GS, just keep what attitude it have.

I tried to adjust the autopilot parameter in aircraft.cfg but it still doesn't work...

Maybe Bert could do something in autopilot's gaugues to bring some inprovment? 🥺

[Bert Pieke 7,584]

13 hours ago, C2615 said:

Maybe Bert could do something in autopilot's gaugues to bring some inprovment?

I believe the previous post nailed it... slow down and use less flaps. 😉

[RXP 2,336]

Another explanation could have been the PC12 EFIS displaying a linear deviation whereas the RXP GTN is outputting an angular deviation. In this case, you'd probably notice the needle offset from the center reducing as you'd be also reducing the distance to the TD point.

[vincentrouleau 71]

I've reflown the approach at ~60 knots, where the AOA is centered. The autopilot followed the glideslope with no problem. So I was going to fast. But I find funny that the flight director would not point to the flight path angle that would send me back to the glideslope. The FD kept me higher. I mean, why would the autopilot would keep me at a constant offset above the glideslope because I was going too fast?

Edited February 9, 2021 by vincentrouleau

[C2615 319]

7 hours ago, vincentrouleau said:

 I mean, why would the autopilot would keep me at a constant offset above the glideslope because I was going too fast?

You noticed the G/S is white, rather than green, that means it's NOT in glide slope mode anymore. Basicly you over shoot it, offset too much, and AFDS just quit.

The AFDS in this condition should only keep atitude, rather than chase GS.

 On 2/8/2021 at 2:34 AM, Bert Pieke said:

I believe the previous post nailed it... slow down and use less flaps. 😉

I'm still in my Boeing habit, Flaps15, and drop Flaps 30/40 upon G/S capture... that might be the problem too.

Edited February 10, 2021 by C2615