Originally Posted by
jim billings
How do I measure the wing incidence? Is the reference a line from the lead edge through the wing to the trail edge? This assumes a line from the furthest point forward on the lead edge to the center of the trail edge. In that case, there is an obvious angle between that line and the bottom surface of a flat bottom wing or a semi symmetrical wing. This means the bottom surface of the wing would be pointed down if the line were used as "level". That seems contradictory. I don't want to be argumentative or take over this thread with my problems, so if there is a book (if there is such a thing as a book, anymore) that could guide me, please let me know. And thank all who have replied to my question. You are greatly appreciated.
Level would actually be the Datum line in which all of the elements of the aircraft are placed. This is a straight line running the length of the fuselage. This line is what is used to measure the rigging (incidences of the airplane).
For instance -2 degrees of engine thrust is relative to the datum, + 2 degrees of wing incidence is measured from the datum, and so on.
So, it just so happens that most modern IMAC type aerobatic planes have the datum line parallel with the top of the fuselage hatch.
I think that you may be over thinking this though. Just "Eye" level your plane before initiating your gyro, and that should be close enough.