Part I of this post is here.
When I reconfigured my Spektrum AR636A and reloaded code to make it into (essentially) a standard AR636 receiver and used it as a non-AS3X model by setting all the gains to zero… all was well. But when I then decided to add back in some AS3X functionality in certain flight modes I overlooked one important plot point. Luckily while reading some forum posts on the subject of the Timber in general one comment about reversing the servo direction got me thinking. So I ran up to the shop and checked and guess what? My elevator and aileron were responding exactly the opposite of what I would want when I tested the AS3X reaction to uncommanded roll and pitch movements!! This could have been disastrous had I flown in this mode.
Here’s the problem. When I went back to what I’m calling “standard” receiver mode with no gains so no AS3X functionality at all, I decided to treat this just like every other receiver. I relied on my transmitter to make all servo adjustments including centering, movement direction and speed, expo etc…. That’s great in standard mode. The problem comes when I decided to re-institute a switchable AS3X mode. With the servos all set to standard (not reversed) and the servos reversed as needed (Aileron and Elevator) in the transmitter the stick command work fine. But, when the AS3X is on and sees an un-commanded pitch change it command the elevator in the opposite direction. Unfortunately since it does not know the transmitter is acting in reverse it command what it thinks is the opposite direction from the pitch but (the way these servos are connected and linkage attached) is simply more of the same!! This would result in a sudden increase in whatever uncommanded pitch occurred. I’m guessing the plane would try to loop… continuously. For the ailerons a constant roll would likely have occurred and in my case both would have happened and things might have gotten ugly from there. Of course I could have overridden those command but as soon as I neutralized the sticks it would have just reoccurred and we would have been off to the races again.
Honestly my only shot to control the plane might have been if I could have reached the switch to shut off the AS3X function in time. Since this likely would have occurred quickly after launch… I imagine there would have been some unscheduled contact with the earth and a lot of cursing and gnashing of teeth!
Lucky for me I have been reading a lot of posts and so this came to mind before an ugly incident forced me to learn the hard way! So lessons…
- When working with the AS3X receivers, servo reversing is best done “on board”
- Make sure you have a known good working flight mode to use when changing these things. Take off in that mode and test up high in the air so you have time to switch back to the known good mode if anything seems amiss.
- Don’t trust anything you read or are told if the person telling you has not flight tested his tweek/update or whatever!
OK, so quit wasting your time reading on line and go fly!! 🙂