OK, lets put this to bed. I used to work as an aircraft instrument technician! I pulled hundreds of artificial horizons apart, overhauled them, and recalibrated them, I would like a $ for everyone I have done mostly military aircraft, fighter bombers and fighter jets. I can ell you for a fact there are NO digital or electronic components, which automatically adjust for the curvature of the earth . The primary force used for obtaining a TRUE horizontal artificial plan is, centrifugal force through the use of gyroscopes’. If you do not have an independent reference of you’r plain of travel from visual observation on an aircraft, all hell will break loose in a short time. Also, centrifugal force is constant and infinite, provided spin is maintained, a kind of unseen spirit level,; once set you cannot adjust it’s orientation regards perfect horizontal/true horizontal or you will instantly obtain FALSE readings which equal aircraft accidents all over the place !! You can adjust what the pilot sees or believes is the true horizontal, but as said, if you do this, you end up with real big problems in bad weather. Just look up the films (DIE HARD 2) That’s how they crashed a plane, by adjusting the correct settings to be false, the pilots thought they were X 1000 ft higher than they were. But the Gyroscope would still have read perfect horizontal, they just adjusted what the pilots saw!, which was wrong !