Long flight Autopilot issue

[N4GIX]

Bert, the "Low Fuel" indicators should illuminate whenever the main (tip) tank fuel level(s) fall below 10 gallons.

Edit.... I just tested and they DO work.. indeed.

The lights will remind you to switch to the aux tanks, but keep in mind you still have 18 or so gallons of usable fuel in the mains if needed.

[ThomasAH]

The lights will remind you to switch to the aux tanks, but keep in mind you still have 18 or so gallons of usable fuel in the mains if needed.

And I guess you should use the main tanks for landing as they can provide fuel even if the fuel pump fails, unlike the aux tanks.

[fppilot]

Good catch. I completed a long flight yesterday from Bloomington, Indiana, to Austin, Tx. Flight time 5.2 hours. Used the RXP GTN 750/650 combination along with the Weather Radar. I also in this case had no autopilot issues. I routinely burn mains down to around 25% of their capacity, switch to aux tanks, burn them down to 25% of their capacity, then back to mains. I was cruising at 12,000 burning just under 70 lbs/hr (per engine) and had almost an hour's fuel in reserve upon landing. So I have not tested the warning system.

The issues I have with the autopilot all come when I use a GNS 530/430 combination, and the timing of the issue has been consistent.

It sure sounds like to me the problem is with the GNS 530/430, doesn't it?

It appears to be within the combination of the aircraft model and the GPS. Repeatable. Difficult to isolate so no conclusion yet. The behavior is by the autopilot. The cause is undetermined. The 530 has been the primary GPS coupled to the AP. I have a long flight scheduled for Monday and may use just a 430 and see what transpires.