In an earlier post, I discussed the importance of having a redundant failsafe board so you can regain control in the advent (likelyhood!) of an autopilot failure. Basically, what that board does is sits in-between your autopilot, RC receiver and servos. You switch it between receiver and autopilot with a spare channels on your transmitter. If your autopilot fails, even if it loses all power, the failsafe board, which is independently powered, will allow you to switch control back to the RC system.
Here's a quick tutorial on the board we chose, an RxMux from Reactive Technologies:.
You'll need to do two bits of soldering first. The board doesn't come with connectors, so you've got to order those. It's a little funky, but the way to do that is to "build a part" at Smatec. The connectors you need are Samtec TSW-108-25-G-T-RA, and you just enter in the right numbers or letters in each data field, and it then confirms that this is a valid part and lets you order a sample for free! They sent me three of these right-angle connectors, which was just what I needed. Thanks Samtec! Once you get them you solder them on to the RxMux.
The second bit of soldering is that you've got to make a couple of female-to-female Y-cables. Simply take three of these cables and cut them in half, then resolder the wires, two connectors on one side, one on the other, with heatshrink tubing at each junction.
Then just plug it all together. The channels that don't go through your autopilot can go straight to Input A on the RxMux. The ones that do go through your autopilot will use the Y connectors, with one lead going to the RxMux and the other to the autopilot. And all the servo-out leads from your autopilot go to Input B on the RxMux. It's a lot of wires, but it's actually pretty straightforward. There's no configuration required of the RxMux--whatever RC channel you connect to the Channel 8 input of the RxMux's Input A is the switching channel, and it just transfers control of the servos from Input A to Input B and back again as desired.