G1000 KAP 140 NAV to APR transition question

[Rich]

My KAP 140 never makes std rate turns (usually 60-70% of std) ...

Same with mine, but it's because of the turn coordinator. In my plane the TC is not a blind model so if I manually make standard rate turns as indicated it takes about 2:40 to complete a 360-deg circuit. And the KAP140 does this faithfully as well, with the TC blithely indicating standard rate. It's always been this way. I don't know the possibility of getting the TC properly calibrated. In any case it hasn't caused me enough grief in the real world to obsess over it. I haven't had the kinds of problems discussed here. Of course, in my plane the AP is controlled by the KI525/GNS530W, not a G1000, so it may be there is some difference in the corrective signals being sent to the AP.

[40flyer]

I’ve had my hidden TC checked twice, both before and after it was overhauled. It puts out the appropriate signal for a 3 degree per second Turn. Nevertheless, when the KAP140 is in HDG, NAV or APR mode, the turn is less than std rate, about 60-70% of std rate. The KAP140 has been checked good so I am having the roll servo checked at my next annual.

I flew several different RNAV approaches this morning and got the autopilot disconnect every time at the IF/IAF, the first waypoint on the FAC. Just reengage APR mode and all is well.

[Rich]

The TC is a feedback instrument, not a control input. There is nothing that sends a signal to the TC that says" initiate a standard rate turn", at which time it controls the A/P. Instead, based on the reaction of the gyro/spring calibration to the motion of the airplane and the signal resultant to the A/P, it's telling the A/P "all is good - the plane is doing what you want", when the plane is not in fact doing so. The sole input to the TC is the actual motion of the plane.

In my case of a non-hidden device, the little airplane dealy shows a two-minute turn when the airplane is not, in fact turning at 3-deg/sec. This is true whether the A/P is making the turn (in which case both the display and the electronic feedback signal are incorrect, though consistent with each other) or with the A/P off I manually make the turn (manual control based on the display alone), in which case the feedback circuit and A/P are irrelevant and the display is still wrong. So it's the T/C.

[Rich]

When my GNS units were converted (swapped, essentially) to WAAS units, the interconnection to the AP was supposed to have been configured to require a specific manual confirmation at the FAF that the AP was to fly the approach. Mine was not so configured and just seamlessly grabs onto the GS and down we go. I somehow neglected to bring this to the attention of the installer Anyway, I'm supposed to have a behavior somewhat similar to the undesirable G1000 behavior I see in this thread. So maybe there is a similar kind of thing in the G1000 - just supposin'

[Keith M]

After this discussion on standard rate turns, I decided to check the behavior of my G1000/KAP140 today. It took 2:37 to turn right 360 degrees and 2:55 to turn left. Not sure if I there's anything that needs to be done to address this, or if I just have to live with it.

[carym]

After this discussion on standard rate turns, I decided to check the behavior of my G1000/KAP140 today. It took 2:37 to turn right 360 degrees and 2:55 to turn left. Not sure if I there's anything that needs to be done to address this, or if I just have to live with it.

Time goes slowly when you're having fun! You are clearly enjoying your left turns more than your right turns.