It's a nightmare isnt it? I put a very similar post on here a few months back.. .My advice is to sit down with your notes, and make headings to break down its operation.. .Cover firstly the 2 systems-stable platform and strapdown.Into these then cover the operation of each what really makes it work. In a stable platform its accelerometers and rate integrating gyros, in a strapdown it's ring laser gyros and accelerometers.. .Its important that you always remember that even if the aircraft is stationary the platform is is moving to remain fixed in azimuth to account for earth rotation. With the aircraft moving it then has to account for aircraft movement and transport wander. This really applies to the gyros wether it be ring laser or RI gyros.. .The accelerometers need to sense only aircraft acceleration. To do this it has to remove accelerations caused by centripetal force, and coriolis effect.. .Schuler tuning ensures that the platform correctly follows the curvature of the earth in relation to horizontal. To do this it oscillates at a period of 84.4 minutes to correct errors, and these are bounded errors.. .On your breakdown then put key points for what it requires in a working environment in particular what it requires at startup, and how by using gyro compassing it aligns itself in azimuth.. .Lastly you must be able to caculate its error rate. This is a fairly simple calculation that will be explained in your notes.. .I just didn't get it at all until i broke it down like this.. .Hope this helps !! Best of luck <img border="0" title="" alt="[Razz]" src="tongue.gif" />