ORIGINAL: speedracerntrixie

The CG gremlins are at it again LOL. As I stated previously CG is very often mis understood. Most of us are taught that a nose heavy airplane is more stable. My instructor made sure I learned that. For years I would set up my airplanes slightly nose heavy and fought them just like everyone else. mention the words '' Tail heavy '' and see the fear in peoples eyes.

The truth is that a nose heavy airplane will just never trim correctly. It will constantly experience pitch trim changes with airspeed changes. The reason for this is that you must carry some up elevator trim to compensate. This trim will become more and less effective with airspeed changes. For a trainer this can be a good thing for a while. When the student gets into trouble the airplane will have some self righting tendancies. For doing aerobatics, it would be a disaster. The airplane would fly strait and level at one airspeed but would pull to the canopy on uplines and knife edge. For a pylon airplane it would require more elevator travel for tight turns which would kill airspeed and could cause a high speed snap. In all cases a nose heavy airplane will need to be landed slightly faster.

There are many viable tests to determine the optimum CG. The first step is to make sure all your incidences are correct then plug the numbers into the CG calculator to get a safe starting point. During the maiden take note if you have to give up trim or not. Usually you will have to do this. That up trim is telling you that the airplane is either nose heavy or out of alignment. Thats why it is important to measure and adjust the angles first. For an aerobatic airplane putting the airplane into a knife edge is a good check. With proper CG the airplane will want to pull to the landing gear slightly. I will employ a mix to compensate the final 3% or so. On my pylon airplanes to get a 30 ft radius turn at 130+ MPH requires only 3/16'' of elevator travel do to a slighly aft CG position and like I said earlier allows them to slow down nicely for landings.