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 Post subject: KAP 140 autopilot FAQ
PostPosted: Wed Sep 04, 2013 10:54 am 
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We have spent great deal of time implementing (and testing) the KAP 140 autopilot, so that it operates just like the real unit. Because of that, it behaves differently than stock FSX autopilot you may be used to. It has some unique "features" that may surprise even real pilots who are not familiar with this system. Here are some most common questions that we've seen:

1. I can't engage Autopilot using the key in the VC.

You have to press it and hold it for at least 250 milliseconds. Safety feature of the real unit.



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?



3. When I press ALT button the altitude window does not update.

This is just how the real one works.



4. The autopilot does not intercept selected altitude.

If the altitude is not armed (ALT ARM displayed in the lower row), then the autopilot will continue the climb/descend.



5. When I change the selected altitude, the autopilot does not climb/descend.

If you are in the ALT hold mode, you have to exit it first (by pressing the ALT button), then set your desired vertical speed using UP/DOWN buttons. Oh, and don't forget to check, that the new altitude is ARMed. :)



6. The autopilot has intercepted the altitude, but it's off by couple hundred feet.

The autopilot has separate barometric pressure entry, it's not connected to the altimeter on the main panel. Press the BARO button and set the correct pressure there.



7. I see some vertical oscillations in ALT/VS.

The autopilot does not have vertical gyro, meaning that it does not know the aircraft's pitch. The only source of reference for elevator control is Vertical Speed gauge, which is relatively imprecise and slow to react. You may experience some oscillations, especially with aft cg, although we have tried to minimize those.



8. REV mode does not work.

To follow a backcourse approach, you have to set the HDG bug to the ILS localizer direction, not to the direction you want to fly (reverse). For example if the runway ILS is 120 degrees and you want to fly backcourse (300 degrees) you have to set the HDG bug to 120 degrees.

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Last edited by some1 - A2A on Tue Sep 17, 2013 2:22 pm, edited 1 time in total.

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PostPosted: Fri Sep 06, 2013 11:43 pm 
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I did have one issue not mentioned in the FAQ.

I could not get the vertical speed to work. I tried adjusting it many times,
but it just would not give me an option for changing the vertical speed.

This is what I tried:

Setting Altitude (5000 ft) and pressing Alt
" " " " " and Arm

Pressing the Vertical speed Up/Down buttons (no effect)
Turning off Alt/Arm, dialing in 5000 ft, then pressing Up/Down (no effect)
Turning on Alt and repeating (no effect)
Turning on Arm and Alt off (no effect)
Turning Alt on and Arm on (no effect with vertical speed buttons on all of these tries).

Since I've not seen this issue elsewhere, I'm guessing the methods I tried were wrong, so
would like to see this added to the FAQ. I read through the manual to try to find info on it,
but couldn't seem to find it. Time for a reread I think.

Neon

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PostPosted: Sat Sep 07, 2013 2:08 am 
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When you engage the autopilot, it starts in VS mode with your current vertical speed as reference, you can try to press up/down buttons then to check if VS mode operates correctly on your machine.

To intercept altitude:
1. Set the desired altitude using knobs.
2. Verify that ALT ARM is displayed in the lower row.
3. If the ALT mode is displayed as active (upper row), change to VS by pressing ALT button
4. Enter desired vertical speed using UP/DOWN buttons.

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PostPosted: Sat Sep 07, 2013 5:31 am 
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And if all else fails, check the 172 manual. There are links to manuals for the real world counterparts that are quite informative.


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PostPosted: Sun Sep 08, 2013 12:58 am 
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some1 - A2A wrote:

2. VOR / Localizer tracking does not work correctly
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?


May I ask some1 why A2A used this heading indicator system rather than using an HSI? My guess
is this type is usual in trainers whereas HSI is not. I don't know, but I am rather curious as to
why A2A chose not to use an HSI. Also I'm curious if at some time in the future there maybe
an option to use an HSI (either as add-on purchase or just an patch)?

Neon

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PostPosted: Sun Sep 08, 2013 1:18 am 
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Neon wrote:

May I ask some1 why A2A used this heading indicator system rather than using an HSI?

If if I may answer on Some1's behalf, it's because the 172R didn't come from the factory equipped with an HSI. In my personal experience, none of the 172s I flew came equipped with them. This is generally an upgrade you would see a private owner potentially do.

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PostPosted: Sun Sep 08, 2013 1:39 am 
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HSI was an option, but pretty expensive one, so very few c172s out there have it installed.

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PostPosted: Sun Sep 08, 2013 1:44 am 
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some1 - A2A wrote:
HSI was an option, but pretty expensive one, so very few c172s out there have it installed.

Learn something new every day! I wasn't aware Cessna offered that option. Never saw a single Cessna at any FBO I trained at who had one. Just goes to prove what happens when you "assume." Thanks for the tidbit!

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PostPosted: Sun Sep 08, 2013 2:32 am 
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I've been flyng a lot in the Legacy which had a HSI and a DG and I used to fly using VOR only with those two gauges. When I first flew the C172R I noticed I had used the HSI most often as the main instrument and only used the DG for triangulation (for instance following the radial on the HSI and only use the DG to check when I was at a certain radial). So during my first two flights I sometimes made mistakes like flying in the almost wrong direction. With the A2A 172 I check the FSX map after the flight to see how I have flown: the red line went all over the place! But I got used to it quite quickly and my last flights done with VOR only (as usual for me) showed pretty straight lines, even when there wasn't a VOR (or NDB) on the airfield itself.

So all in all I already got used to not having an HSI. Once you 'get' the DG's, they are just as easy to follow. (And in fact, it's more fun too!) :wink: So I like it that A2A kept the 172 realistic in this regard!

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PostPosted: Tue Sep 10, 2013 3:25 pm 
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I'd like to add one point to the original FAQ list. Suggested text:

----
9. The first press of the UP/DN buttons already changes the VS value.

According to the KAP 140 manual, "if VS mode is active, the initial [UP/DN] button stroke will bring up the commanded vertical speed in the display. Subsequent immediate button strokes will [then change the commanded vertical speed]"
This will be fixed in the next update. :wink:
----

Ok, probably a not-so-frequent question, but with the level of quality that A2A is aiming for (and generally achieving!), this may be of interest.

Cheers,
Bernhard


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PostPosted: Wed Sep 11, 2013 12:06 am 
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Lol, good find :)

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PostPosted: Sun Sep 15, 2013 11:15 am 
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Hey guys,

I don't want to start a new thread with this, as it might be a really dumb question xD

Is there any way to shut the autopilot off? I don't mean to disengage it, but shutting it completely off. Every time I engage the battery switch, the AP is doing a system check and is on. And every time I'm flying around, the damn altitude alert is beeping and beeping and beeping and... as soon a I get to the +/-1000ft before reaching the set alt setting in the AP... (??)

Or if not, is there any way to shut that beep off? ^^

Yep... dumb question xD

Greets,
Marc :D

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PostPosted: Sun Sep 15, 2013 11:22 am 
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1. You can't turn it off.

2. To avoid the beeping give the alt knob a whirl to an altitude you aren't (or won't get) close to! If I have used the ALT function of the AP and I don't need it anymore, I always turn it up to a few 1000 feet.

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PostPosted: Sun Sep 15, 2013 1:45 pm 
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J van E wrote:
1. You can't turn it off.

2. To avoid the beeping give the alt knob a whirl to an altitude you aren't (or won't get) close to! If I have used the ALT function of the AP and I don't need it anymore, I always turn it up to a few 1000 feet.



probably not a proper real world manner, but a good solution :D

thanks ^^

Greets
Marc

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PostPosted: Mon Sep 16, 2013 5:35 pm 
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If I am flying with the RXP GNS in GPS mode and the autopilot in NAV mode,
and push APR, the autopilot goes to HDG mode - only a second push of APR
gets me to approach mode.

Secondly, with an LPV approach, the autopilot does not capture the glideslope,
but holds altitude, when in APR mode.

Edit: I am aware that the basic KAP140 does not capture LPV glideslope (only ILS),
but later KAP140 models do... so please can you upgrade your installed KAP140 to WAAS
capability? This would make sense with a WAAS equipped GNS530 in the panel.. :-)

Quoting from a RW KAP140 guide:

"NAV/APCH Modes

... In NAV mode, the autopilot will track whatever the CDI is set to, whether it be GPS, VOR, LOC, or ADF (if the airplane is equipped). In approach mode, the sensitivity of the autopilot is increased, so it holds to tighter tolerances. It also will track the glide slope on an ILS approach in APCH mode (as well as the glide slope on a WAAS approach, if equipped)."

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