Hi Ben;

I've done the field tests. No problem entering an outside loop inverted. A problem was only encountered at the bottom of an ordinary outside loop, when my low-wing, low-dihedral sport-aerobatic plane would stall and roll out of the maneuver, when I tried too tight a loop. No problem on big, easy outside loops.

The solution (suggested by a pylon-racer friend) was to mix in some flaps with elevator, so that up elevator causes down flaps and down elevator, "up" flaps, or spoilers. This worked great! Eliminated the problem entirely. Here is my analysis:

The highest loads encountered in an outside loop is when the aircraft is inverted at the bottom of the loop, since the loads resulting from the angular velocity are added to G. Also, the airfoil on my plane is only semi-symmetrical, and while it flies inverted quite well, it will stall at angles of attack that would be acceptable right-side-up.

So, when inverted, the down-elevator required to complete the loop causes the flaps (flaperons, in this case) to go "up," which is down, when inverted.

The extra curvature allows the inverted wing to accept the high angle of attack without stalling.