Correcting Heading Indicator but not ADI???
 

Hi there!

as we all know you need to correct the indication of the heading indicator every 10 to 15 minutes. I understand that one, but why is there no need to adjust the Attitude Directional Indicator??

Because it adjusts itself. The gyro of the ADI, or Artificial Horizon as it is otherwise known, would topple over a period of time if it were not kept vertical to gravity.

In an air-driven AH, this is achieved by having a bottom-heavy gyro housing and by a system of air jets with doors which respond to gravity.

In the electric AH, it is achieved using mercury gravity switches and torque motors.

There is a bit of info on these instruments here: http://www.av8n.com/how/htm/motion.h...ro-instruments

Don't know it this helps with your question, the text is pretty technical. You'd better look for a book that has some diagrams showing the internals, that might better explain the principles!

The axis in which the gyro is in stalled has something to do with it as well. The Attitude gyro is installed vertically as opposed to longitudinally.

The link you showed me Jhieminga explained it very well.

thank you very much!