Optimal Cruise Trim Setting

[201er]

What is the ideal place to be able to set the trim during cruise for minimal elevator/stabilizer drag for cruise? Approximately where would this be on the trim indicator (takeoff, full down, etc)? One thing I don't understand is how people are recommending back CG when it is foreward trim (relative to takeoff setting) that we are using to keep the plane level during cruise.

Lastly I've noticed that the elevator can be up or down on the ground depending on the trim setting, I was wondering if it stays rigitdly in that position during cruise or if that pressure is offset by moving air? Because it seems impractical to have the entire elevator move during trimming operations if you are going to move the stabilizer too.

[jetdriven]

Ideal trim is whatever it takes to maintain level flight. The further aft the CG is the less drag you are going to have, I think right until you get to the aft limit.  The elevator trails in cruise flight. Those springs act on it when sitting still. The 231 elevator is full down on the ground, so is an A36 Bonanza.  Different systems though.  Even with a middle CG, the elevator is deflected downward and the counterweights stick up above the stab.  At about 190 MPH IAS, our trim is almost to the complete forward limit.

[Immelman]

The whole issue of CG vs. speed has to do with how a (conventional) airplane is balanced along its lateral axis. The CG - to inculde the aft limit, should be forward of the wing's forward-most center of lift. To counteract this, the horizontal stabilizer is used to create down-force. This down-force has induced drag of its own, and creates more work (i.e. higher angle of attack necessary) for the wing to overcome the additional 'weight'.

With an aft CG, less tail downforce is required to achieve this balance, and thus, nose down trim (which as we know in a Mooney, pivots the whole tail section) should reduce the horizontal stabilizers angle of incidence, and angle of attack.

Now with all that said. I, *personally* have not seen a substantial difference in cruise speed with the CG aft vs. forward in my Mooney. I also think its worth highlighting that an aft CG tends to make the airplane less stable and controllable going into a stall. I say this as a reminder to load our airplanes within limits (it is relatively easy to get out of allowable CG range aft with people in the back seat), and not be tempted by the lure of an extra half-knot of speed to err on the side of tossing heavy luggage aft.