Bill,

I don’t know the technical answers of what you are asking.  I do know that in every case, and I have flown many ILS approaches, is that the TruTrac Sorcerer GPSV tracking driven from the Chelton follows almost identically to the needles.  The boxes are 250’ tall and 400’ wide  in the HITS.  The ILS needles place the course in the boxes, albeit sometimes not dead centered. 

 

My GUESS is that Chelton may be generating ILS data utilizing the WAAS enabled GPS information and feeding it to the Sorcerer and also for the HITS.  The needles are obviously driven from the Garmin 430 tuned to the ILS/GS.  I don’t believe that the GPS approach data is used by the Chelton when one has selected the ILS approach.  My belief is based on how the 2 tracks inbound correlate very closely—probably within about 50 feet of each other. 

 

I have found that the best/easiest way to fly the ILS is in GPSV mode on the Sorcerer with the ILS approach selected for the Chelton. 

 

 

 

Hi Carl,

Thanks for your lengthy response - some good info in there.

I think part of the original poster's question was whether there was a
problem if the Sorcerer seemed to be "flying the plane," but the HITS
was not centered during an ILS approach.

I have a concern that some people might get the idea that there is
"something wrong" when they are flying the ILS and the boxes are not
centered.

Since you own a Chelton and I do not, perhaps you would be willing to
clarify your remarks with the appropriate response on the forum (e.g.
"With the Chelton, the HITS is/is not perfectly aligned with the GPSS
approach, and does / does not appear when there is NO GPSS approach, but
may be considerably different than the ILS glide path
GPSS course and glidepath?>")?

I know for a fact that the ILS does not always align with a GPSS glide
path, so it seems VERY unlikely that flying an ILS will always put you
"in the center of the boxes." What I don't know is whether the Chelton
HITS follows the published GPSS approach (if there even is one), or
whether (as in some of the experimental models) it simply provides a 3
degree reference to the runway threshold irrespective of any approaches.

Cheers,

Bill Reister
Atlanta, GA


Carl Cadwell wrote:
> John and Bill,
> I have about 700 hours behind a triple display Chelton with a TruTrak
> Sorcerer autopilot.
> My experience is that I fly the approaches (ILS, VOR, GPS) with the
> Sorcerer in GPSV mode. The Chelton then drives the Sorcerer. Use the
> altitude select on the Chelton to track down to the altitudes that ATC
> gives you. When you level out at the approach altitude, turn off the
> altitude hold and the Chelton then feeds the data to the Sorcerer to fly
> the descents. The Chelton will display the approach altitude above the
> altitude strip on the right side. Note: if you are tracking on
> heading also turn off the heading. Both of these are turned off by
> pushing the prompts "LNAV" and "VNAV" in the upper left of the screen.
> Disengage the LNAV about 20 degrees before intercept as ATC is turning
> you to intercept the inbound course. Disengage the VNAV when you are
> ready to track vertically inbound.
>
> The Sorcerer then flies the approaches maintaining both vertical and
> horizontal axis. You must also dial in the ILS from the Garmin 430 or
> similar. Then set the OBS on the Chelton so the needles are
> appropriate. Do this when you first pick up the ATIS telling you what
> approach is being used. Also select the appropriate approach in the
> Chelton and Garmin 430 at this time.
>
> So let the GPSV mode in the Sorcerer fly the approaches and you verify
> everything is correct with the needles displayed on the Chelton. It
> will fly right down the boxes, perhaps not always exactly in the center,
> but right down the approach course. Said another way, you are flying
> WAAS enabled GPS for all approaches and verifying everything is a go
> using the ILS/VOR/GS needles. You have 2 systems that had better be
> displaying the same information.
>
> Note: I also have WAAS on the Chelton. The system is terrific.
>
> Carl Cadwell
> Formerly IVP with 1000 hours now an Epic with 700+ hours.
>
>
> John,
>
> Don't know Chelton specifically, but generally speaking the EFIS HITS
> approaches do NOT correspond exactly with the ILS or GPS glide paths -
> they are typically based on a synthetic approach to the approach end of
> the runway at a "standard" approach angle. Check your Chelton manuals
> to confirm this.
>
> In any event, the ONLY thing you should compare the approach to is the
> glide path / course needles. If they stay centered, the TT is doing it's
> job perfectly.
>
> Regards,
>
> Bill
>
>
> John Hafen wrote:
> Gents:
>
> In my IVP, I have a Trutrak Sorcerer Autopilot wired to a Chelton twin
> screen system.
>
> I shot a few GPS approaches today and everything seemed to work ok,
> except that the decent after the IAF seemed to lag behind the HITS green
> squares. The plane was going down, on the "glide slope" but not as
> aggressively as it should have. Kind of hanging out near the top, or
> slightly above the green boxes. It was a GPS approach that I initiated
> by hitting the GPSV button on the Sorcerer.
>
> I know that altitude transitions can be made by airspeed, vertical
> speed, or horizontal distance (VNAV). So if my descent was lagging, I
> wonder if I need to go into Pitch Setup mode and play with the vertical
> activity or vertical torque. Or some other parameter.
>
> Or is there a way to specify a certain airspeed or V-speed for the
> descent - or is it just supposed to center the boxes.
>
> I apologize for rambling a little here. I suppose my fundamental
> question is how to make the auto pilot fly the descent right in the
> middle of the green boxes...... What Am I Missing?
>
> Many thanks and Regards.
>
> John Hafen
> IVP N413AJ 175 hours
>

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