# How does a standby ADI remain accurate when flying over the curved earth? [duplicate]

How does a standby attitude directional indicator remain accurate when flying for many hours over the curve of the earth? While maintaining level flight, wouldn’t the pilot see an apparent movement of the attitude indicator in relation to curvature he/she is flying over?

• Those answers don't address his specific question. The answer to his question is that "level" isn't level as in a constant plane through space. "Level" on earth is perpendicular to the center, or aligned with a spherical plane about the earth at the airplane's distance from the center. – John K Sep 5 '18 at 21:02
• @JohnK A gyroscopic AI has an erection mechanism, which continuously corrects the AI to be upright based on the local level, or downward acceleration vector. How does that not answer this? – TomMcW Sep 6 '18 at 17:50
• The explanation of the erection mechanism covered correcting for precession drift, and if you think it through it would also explain why the gyro doesn't remain on a constant plane but is continuously realigned toward the center of the earth but I don't think that aspect was explicitly covered in the answer. Maybe I missed it when I read them. – John K Sep 7 '18 at 1:07