auto pilot ground system test B737-800
 

here in my hands i have page 4.10.20 on which i find under the "autopilot disengage light"... illuminated red....

steady for any of the following conditions....stabilizer out of trim below 800 ft RA on dual channel approach...ALT ACQ mode inhibited during A/P go around if stabilizer not trimmed for single A/P operation...disengage light test switch held in position 2...

all of which i understand and have seen for years but next is one i have never seen and cannot find any other reference in same operations manual...

"automatic ground system test fail."

does anyone out there know what this refers to? we have never seen it before, but will be the first to admit that i have missed things before.

any help will be greatly appreciated.

cheers and best rear guards;

applicable as well for the classics 4.10.17 ops man. vol. II
I believe it is a grd system test done by maintenance. Steady red illumination of the light meaning failure of the test.

Steady Red A/P Warning Light will come on...
...
- the airplane is on the ground and the FCC fails the power up test
...
- the light will also come on if the DFCS is in BITE or if the other FCC part number is invalid.