From reading some of these threads I am absolutely positive that you guys can help.
I am a RC plane nut. I practice mostly aerobatic sequences. One of the most important things about performing aerobatic maneuvers is that the plane be in a perfectly level attitude before the maneuver is performed. Its probably the most difficult aspect of aerobatics. The maneuvers themselves are basically easy to do. But to do them with good lines the wings must absolutely be level first. And from the ground flying determining if the wings are level is very difficult.

Here's what I would like to do. To help me with orientation I would like to install a tilt sensor of some sort accurate to 2-5 degrees at least that would light an LED light that is visible from the ground indicating when the wings are level. So, as I ready the plane for a maneuver I could glance at the area of the plane where the LED is to determine if it is level and if not correct for it. Even 3 LEDs would be great. One to indicate level and colored LEDs to indicate the need for left or right roll correction.

Soo...let's see what you guys got. I would need a walk through on what to purchase and how it should be wired as I have little to no electronics back round. Hope you guys are up to the challenge. The one who comes up with the most accurate, lightest weight , and least expensive solution to perform this task....gets.... Well nothing. A sincere thank you from yours truly.

Just to detect "roll" or "side to side". I would say it would have to detect or have resolution to 2 degrees or so. I have seen the mercury switches on youtube and it appears that they can be sticky. Must be due to the surface tension of a liquid. Most of the time I think I am getting to close to wings level flight by just sight. Probably with in 10 degrees of level. So it would have to probably be sensitive enough to detect correction from 10 to 0 degrees.

visiulize a tube with a slight bend shape with a metal ball inside.
the tube. to adjust amount of tilt (and help prevent vibrations and G's from affecting) just add more bend to the tube.
the tube also has contacts at both ends and in the middle to detect level.
using headphones instead of LEDs, have a small transmitter in the plane.
say the left earpiece beeps to detect tilt too much to the left, right= too much tilt to the right. beep in both = level.
could add a second set of beeps (different tone) for nose and tail level.
seeing LEDs more than 50 ft away unless you have lots of on board battery power, but even then if your LEDs are on not visiable unless your flying at night??
the tilt detection may be the most challenging
another thought perhaps is using flexable resistive strips that change resistance due to bending. utilize a PIC to decipher using ADC.
just a few ideas

I thought about the beep transmitter. That is a good point about be able to see the leds. My on board receiver system is using a 6V 2700mAh battery. I think a couple of high lumine LEDs should work and they won't be drawing much from the receiver battery because they will only be lit intermitantly. Actually, the deadzone line where the aircraft cannot pass is actually 100 ft from where I stand. I may have to range test a few high lumin LED's to see if I can actually see them.

I am familiar with the GY401. I have one on my heli. The gyroscope is going to hold a certain attitude and correct for it. It is a heading hold gyroscope. So if the wings were level the gyro would hold them their. I will have 2-3 seconds between manuevers to determine wings level and correct for it. Example: I will pull out of one check for wings level and then right into the next. I am glad I am getting some responses in this thread. Some great ideas to think about.