Hi,
I’m having the problem that my KAP 140 + G1000 combo doesn’t intercept NAV courses.. HDG mode works fine but when I push on NAV it just says “NAV arm” but the plane doesn’t even move in the direction of the magenta line nor does the “NAV arm” ever switches to NAV – it always remains in HDG or ROL – depending on what you’ve had selected previously.
I’ve got a diagnostic cable and I’ve checked the error logs – nothing is in there and everything else works fine as well, I’m unsure if maybe GPS must be aligned in order to start working again ? In the Installation – Installation Offset menu there are several options to align the Autopilot, Heading Datum, Course datum etc.. Anyone got a procedure how to typically align the options ? Simply set a GPS Target somewhere, turn the plane until the Target is at the 000 Heading and then press enter while in the setting mode ?
Thanks for any tips.
First off, just to make sure… You are aware that the A/P will intercept the NAV course on the heading you have selected? It will not turn towards the magenta line “by itself” until it is only a few dots off and only at that point will the ARM indication go off.
If you have a valid CDI indication on the G1000, then NAV should work. If you suspect the GPS, start by selecting VOR navigation on the G1000 and see if you have the same problem. If you do, then I would suspect the cabling between the KAP140 and the G1000.
Airborne_Again wrote:
You are aware that the A/P will intercept the NAV course on the heading you have selected? It will not turn towards the magenta line “by itself” until it is only a few dots off and only at that point will the ARM indication go off.
You’re wrong here, at least in my case (DA42, G1000, KAP140) or I didn’t correctly understand the case you described. If you fly in HDG mode and e.g. select “Direct” to some point in FPL, magenta line will point in direction of chosen point. If you switch AP at that moment to NAV, the aircraft will turn to heading shown by magenta line and then will slowly change the heading for wind correction if any. On the other hand if you have magenta line pointing somewhere and you were flying in HDG mode for some time and then hit NAV, the interception heading depends on your actual heading and difference between it and actual magenta line track.
Hmm… This is confusing..
Let’s say i’m flying on HDG mode and I’m holding of 120 degrees. Then I create a “direct to” GPS target to an airport at lets say heading 090 and got my magenta line pointing towards 090 – I push “NAV” mode on the KAP 140 and I expect it to turn to the left and say “NAV arm” until it has successfully intercepted that course and from that point follows it.
It works exactly this way when I dial in a VOR and select a radial on it by pushing CDI until I’ve got the green line and then using the Course Knob for the radial…
Weird…
OneEightyTwoTango wrote:
Let’s say i’m flying on HDG mode and I’m holding of 120 degrees. Then I create a “direct to” GPS target to an airport at lets say heading 090 and got my magenta line pointing towards 090 – I push “NAV” mode on the KAP 140 and I expect it to turn to the left and say “NAV arm” until it has successfully intercepted that course and from that point follows it.
That’s how it should work if everything is OK.
Yes that what I expect as well.
Any avionics guy here who can point me towards the procedure I need for aligning it ? I’ve got the diagnostic cable and can access the menu, I just don’t want to break anything and rather have some information before aligning…
Emir wrote:
You’re wrong here, at least in my case (DA42, G1000, KAP140) or I didn’t correctly understand the case you described. If you fly in HDG mode and e.g. select “Direct” to some point in FPL, magenta line will point in direction of chosen point. If you switch AP at that moment to NAV, the aircraft will turn to heading shown by magenta line and then will slowly change the heading for wind correction if any. On the other hand if you have magenta line pointing somewhere and you were flying in HDG mode for some time and then hit NAV, the interception heading depends on your actual heading and difference between it and actual magenta line track.
I’m right and so are you as we’re talking about different cases. 
In his first post, OneEightyTwoTango talked about intercepting NAV courses and turning towards the magenta line. You are talking about a case where you are already on the magenta line – i.e. you don’t need to intercept, just turn to follow it.
On the other hand if you have magenta line pointing somewhere and you were flying in HDG mode for some time and then hit NAV, the interception heading depends on your actual heading and difference between it and actual magenta line track.
According to both the KAP140 Pilot’s Guide, the POH for the Cessna 172 with G1000+KAP140 and my experience, the interception heading will be exactly what the heading bug says and is unrelated to the difference between it and NAV track.
OneEightyTwoTango wrote:
Any avionics guy here who can point me towards the procedure I need for aligning it ? I’ve got the diagnostic cable and can access the menu, I just don’t want to break anything and rather have some information before aligning…
I very much doubt if GPS alignment has anything to do with your problem. Is the EHSI on the PFD is showing correct indications? If so, then the GPS should work correctly and your problem is caused by something else.
OneEightyTwoTango wrote:
Let’s say i’m flying on HDG mode and I’m holding of 120 degrees. Then I create a “direct to” GPS target to an airport at lets say heading 090 and got my magenta line pointing towards 090
What does your EHSI show at this point?
I push “NAV” mode on the KAP 140 and I expect it to turn to the left and say “NAV arm” until it has successfully intercepted that course and from that point follows it. It works exactly this way when I dial in a VOR and select a radial on it by pushing CDI until I’ve got the green line and then using the Course Knob for the radial…
So the problem is apparently GPS-related. It could also be a problem with the roll steering. When you are using GPS navigation, the G1000 is using roll steering to control the A/P.
