Hi Jammed.
7 up seems a little bit high to me. I have flown many types of aircrafts from heavy to medium and as far as I remember a tipical setting for the TO is 3 to 4 degrees up.
The tilt is a reference to the horizon as it has been said here. It is like to say the angle of your neck and the horizon to scan for posible traffics. At the TO you will look up, at the cruise level straight and down for the descent.
Usually at FL280 must be scanning to the horizon, but I have found that setting very relative. At medium latitudes the more activity layer is from FL140 to FL210. As you goes to northern latitudes the atmosphere is compresed and as the radar antenna doesn't understand of FL but heights. Also depends on the diameter of your antenna. If I dont remember bad varies from 9 to 16 inches wide.
So the best rule is the rule of thumb. As you see the terrain echoes disappearing at the TO it is your setting. As you climb mantain the last ring (further from you) of the radar showing the terrain echoes varying the tilt setting as you climb or change the range of the scope, always to mantain the last ring with the terrain.
If that requires 7 degrees up or 17 down is strange but then you are sure you are scanning good.
Here you have the airbus document.
http://www.copac.es/direcciones/Segu...er%20radar.pdf Tailwinds
Edited to say... Consult with SNS3Guppy. He is (or was) a CB adict
