Wild ride in APR mode?

[rc flyer]

Got her last night and put about 3 hrs on the Hobbs . She's a delight as expected . Took her up to about 6K and did some spins, and just flew around playing with the AP. Decided to do an approach to an ILS on the way back in. I intercepted the localizer at about a 45 degree angle and the AP overshot and over corrected and started such a wild zigzag ride that I had to disconnect and land manually. Not knowing the characteristics of this AP, I decided maybe it was not designed to handle that big of an angle so I tried again just slightly off course on the intercept. It was better but still seemed to over correct too much and this time it also had trouble staying on the glide slope. I don't think I'm doing anything wrong but maybe someone can plaese explain whats going on ????? Meanwhile I'll have a read on the AP manual

Thanks
Steve

[rc flyer]

Hmmmm...went to the manual and clicked on the link for the AP manual and it showed nothing unusual about APR mode. Sooo......has no one else noticed this??? I tried 3 different airport ILS approaches and all were the same. Went as far as getting stabilized with needles centered before engaging APR and it still wouldn't follow glideslope. It overshoots badly and the roller coaster ride starts . Must be something on my end because this would have been picked up for sure in beta as it's pretty severe. Been lurking over on AVSIM and see Scott and the boys are busy with other more "pressing" or "clicking" issues BTW I did see that at least one other person has problems with the localizer.

Steve

[SanderK]

Did you match the heading bug on your directional gyro to the OBS-setting?

[rc flyer]

Did you match the heading bug on your directional gyro to the OBS-setting?

No, but I don't think you have to. The OBS is set to the runway heading and HDG mode should disengage when the LOC is captured. Anyway that's what the AP manual says. Thanks for the reply BTW.

Steve

[craftsman]

I have the rxpGNS530 installed, it is on com2 and nav2. GPS turned off. Read entire autopilot manual about 3 times. I was doing the ILS approach runway 7 KSBA Santa Barbara California, it ran the opposite direction. Tried to intercept at a very small angle, same as you. The heading seems to Auto find the course to a point but is a bit erratic. I am using the ELITE avionics panel. I have done this approach in Carenado, Realair, etc.. on and on for over 10 years. Up-down side to side?????What a ride. Don't know.

[rc flyer]

I have the rxpGNS530 installed, it is on com2 and nav2. GPS turned off. Read entire autopilot manual about 3 times. I was doing the ILS approach runway 7 KSBA Santa Barbara California, it ran the opposite direction. Tried to intercept at a very small angle, same as you. The heading seems to Auto find the course to a point but is a bit erratic. I am using the ELITE avionics panel. I have done this approach in Carenado, Realair, etc.. on and on for over 10 years. Up-down side to side?????What a ride. Don't know.

AH, so I'm not crazy after all (at least not about this). Was beginning to wonder there Thanks craftsman, I'm sure the boys will get it fixed then.

Steve

EDIT: Well maybe I am crazy after all. Just realized I'm post all this in the wrong forum . Just saw the TECHNICAL section and found the answer in the FAQ

2. VOR / Localizer tracking does not work correctly

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. The flashing HDG after you arm one of those modes is a reminder for that.
For example if you are following VOR radial 250, but you have your heading bug at 330, the autopilot will think that the desired course is 330, but will still try to match the CDI which is set for radial 250. This will cause completely erratic behavior.
It's a limitation of an KAP autopilot coupled with simple directional gyro. If we had a HSI installed, it would work more like the other autopilots you are used to. But that would be boring, wouldn't it?

Have to say though that's a new one on me!!! SanderK, you were right, thanks again.

[craftsman]

Last night I did approaches at KSBA Santa Barbara Rwy 7 coming from the North GVO and coming up from the south to intercept the localizer. Page 67, paragraph 4.

4. Now you have reset the heading bug to 103°
and made a 180° turn to this heading. This
103° heading will intercept the front course of
058°. You must now select the approach mode
by depressing the APR button on the KAP 140.
* The HDG annunciation will flash for five seconds
then extinguish. While the HDG annunciation
is flashing, move the heading bug to the
front course 058°. Since the 45° intercept is
103°, the aircraft will not turn until the front course is captured.

The difference is you really have to WORK the hdg bug ALOT. We are used to just setting up a gps approach, when we are established put it on heading, kick back drink some coffee and wallah, it picks up the localizer for a nice smooth ILS approach.
After deciding to lose some sleep I started to get the knack of it. Not sure if it is NOT a little buggish or it is just very different from what we are used to. Approaches that are TIGHT.
Got to admit it was getting to be .........a much less ......easily anticipated approach and started to be what it is, Different.
But I was enjoying the new challenge.

[J van E]

The difference is you really have to WORK the hdg bug ALOT. We are used to just setting up a gps approach, when we are established put it on heading, kick back drink some coffee and wallah, it picks up the localizer for a nice smooth ILS approach.

Not sure if it is NOT a little buggish or it is just very different from what we are used to.

Well, this simply is how the real thing works, so yes, it is different and a lot more work but that's all part of the fun!

[CYQG87]

With that information in mind, what's the point in using NAV setting? Just thinking if you have to set the heading to the OBS setting why not just tune the OBS and change heading? Is there some aspect in the NAV setting I am not understanding?


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[J van E]

With that information in mind, what's the point in using NAV setting? Just thinking if you have to set the heading to the OBS setting why not just tune the OBS and change heading? Is there some aspect in the NAV setting I am not understanding?


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One thing I can think of: with NAV you can INTERCEPT a radial automatically and precisely. With Heading you can't. Well, you can do it MANUALLY of course, but with NAV you can approach a radial at a certain angle and then NAV will make sure you will nicely and precisely intercept it.

[CYQG87]

Good point, aspects I will have to try, using vor to vor mainly when I fly as my flight plan setting I get spoiled I guess with not having to intercept radials. That being said I am slowly ever so slowly building a chart data base from navigraph for flying with real world navigation not just the default flight planner ( I use fsb for liner flying)


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[some1 - A2A]

NAV will also keep you on track in windy conditions automatically. In HDG, you constantly have to monitor CDI deviation and adjust heading if the wind pushes you off track.