Left of course on ILS... because...

[ryanbatc]

I didn't set HDG bug to FAC? I guess I'm a little confused with the KAP140 manual.

Here's an example, tell me if I'm doing it wrong. The ILS is Ry 27, FAC 270. I'm being vectored to FAC, and the controller says I'm 5 miles from the FAF, turn right heading 240, maintain 3200 until est on loc cleared ils ry 27 apch. I set the heading bug to 240, and then select APR on the AP. The HDG flashes at me... am I to now turn my HDG bug to 270? And it needs that to compute the turn or what?

Here's another approach (KSNA ILS 19R) I did tonite on Pilot Edge (amazing service by the way highly recommended http://www.pilotedge.net/ )
I was left of course the entire approach. I intercept the FAC at around 100 kts... not too fast by any means.

[CAPFlyer]

The HDG flashing is a reminder only. When flying on autopilot, you're supposed to match the HDG bug to the heading being flown so if your NAV/GPS capture fails for whatever reason, the airplane won't make a sudden turn.

As far as being left of centerline, I'm not sure on that because your VOR1 is reading correctly. Did you try to do a rudder turn and see if it took you back to the left of course?

I'll admit, after my own experience with the KAP140, I don't let it do much more than hold the plane on course and altitude after I've gotten established in cruise, so I can't compare its performance in sim to the real thing beyond any deviation from what you want it to do probably isn't too far off actual operation of the thing.

[ryanbatc]

Ok so the HDG bug should be set to the final appch course just in case the AP is not correctly flying the LOC or VOR course, and the pilot needs to quickly switch back to HDG mode?

I didn't check rudder I'll try that next time but it was significantly off course as you can see in that approach at KSNA.

If the real one is this bad (it very well may be as some GA AP's are), I guess, in this case I'd prefer A2A make it work how FSXers would want or expect it to. I mean for me, I'd like the APR mode to work in the sim. What I'm saying is... Even if the real unit doesn't fly approaches so well I'd hope the FSX version would.

[CAPFlyer]

As for the rudder, I'm not suggesting that there was rudder input that was causing the problem. My suggestion was to test if it was something with the AP itself or something else (like scenery, FSX, FSUIPC, or Squawkbox). As the KAP140 is a 2-axis autopilot, you can still "steer" the plane without having to disengage the autopilot by using the rudder. What I want you to try is setup on an approach like the one above where you're established with the AP engaged and "tracking" to the left or right of course. Then use the rudder to try and "force" the AP to intercept the localizer and report what happens. This will help determine if the AP thinks it's on the localizer (if it returns to the original course after you release the rudder input) or if it simply wasn't actually captured (if it accepts the heading change and properly intercepts the course).

Also, I wasn't being serious about A2A perfectly modelling the inconsistencies of the real autopilot. That's why I put the smiley face at the end of the statement. However, I have personal experience of flying in an acquaintance's Cessna 310 with a brand-new S-Tec autopilot installed and it doing the same thing but to the right. On his plane it was because the signal being sent out by the HSI wasn't strong enough for the AP to realize it was paralleling the intended track. He had to install a separate mini-VOR/GPS indicator for the autopilot to receive its signal from as a new HSI would have been way too expensive.

[some1 - A2A]

Ryan, the procedures to perform ILS approach are described in details in the Bendix manuals, I know you love those

Basically for all modes that involve the use of CDI (NAV/APR/REV) you HAVE to set the HDG bug to match OBS setting (NAV) or ILS course. This is because the HDG bug is the only source of plane heading AND course reference. The autopilot doesn't get that signal from the OBS gauge.

So if you are flying ILS approach at 250 deg, but you have your heading bug at 330, the autopilot will think that the ILS course is 330, but will still try to match the CDI which is set for 250 deg. This will cause completely erratic behavior. To my knowledge, we are the only ones that modelled it in FSX.

This is how the real autopilot operates and it can confuse even real pilots: http://www.pprune.org/archive/index.php/t-486606.html
It's a limitation of an KAP autopilot coupled with simple directional gyro. If we had HSI installed, it would work more like the other autopilots you are used to.

As a side note, there is a bug in REV mode, this will be fixed in a update.

[ryanbatc]

Mike this time I did RTFM... As I wrote in my initial post I was confused about the KAP140 operation. I read the NOTE at the bottom of page 20 and it says what you wrote. I just wanted to make sure that's what it really said. Thanks for confirming it.