Discussions

A couple days ago we were talking about redundancy and reliability in the APM:Plane 2.74 thread. I have been thinking about how to add more redundancy without adding too much complexity and cost. I have been thinking about how to safely guide a plane after a total APM failure. This requires not giving the APM control of every servo, and hooking one of two elevator servos and the rudder servo directly to the receiver which is powered by a different source. This means that during autoflight, the APM will have to be tuned to make do with only half an elevator and no rudder. I believe that is totally doable, but not a very elegant solution. So then i was thinking how to backup the control of a servo so that it could still be utilized if the APM was dead.

Is it possible to simply Y-splice a servo signal line between the APM and the Rx so both had simutaneous control? So during auto flight the servo would be getting signals from the APM unless the pilot moved the sticks, then there would be two different signals being sent to the sevo at the same time. I wonder what a servo would do? Would it freak out and jitter, or would it simply react to the sum of the signals and behave sort of like the Stick_Mixing parameter?

I know this is a ridiculous idea, so feel free to ridicule it. Perhaps there is a more elegant way of sharing a servo for redundancy. Ideally the APM would have a true RX pass through that would function with no power. I don't know if such a device could be created as a stand alone unit, or if there could be a software solution.

Redundant system integration is the key to our success in the eyes of the FAA, so it is a conversation worth keeping active.