Odd RTL behavior

Hi all!

New to multirotors and Ardupilot. I’ve been testing my new quad the past few days and have noticed some very unexpected behavior from RTL. 9 times out of 10, it does what you would expect, heads back to the launch point and lands.

However, twice now RTL has gone very wrong on me. Both times it headed back toward the launch point, but then rather than landing, it throttled up and began flying in an outward spiral pattern, increasing speed as it goes. Efforts to regain control were ineffective, although I could see some slight changes in the copter’s behavior, so I’m pretty sure it was getting signal from the TX. On the second occurence, though, I turned off my RTL switch and attempted to engage LOITER mode, but I’m not seeing these events in the logs. On the second occurence the copter was nearing the edge of my flying area, had a tree not saved my butt I would have likely been on the hook for some very expensive damages.

So, I have a couple of questions:

1.) What sensors, settings, etc… should I be looking at to prevent this in the future? (this is an APM 2.5 with the 3DR gps module. GPS module does not have a magnetometer, so using the APM 2.5 onboard compass.)

2.) Does anybody have a switch that they configure as a “Panic button”? I had configured a switch for RTL with that purpose in mind, but after watching how it behaves, and one very near miss, I don’t think it’s the best choice anymore. Perhaps loiter?

What surprised me was that when auto-navigating, the quad apparently behaves like an airplane, moving in the “forward” direction and banking to make turns. Obviously an airplane needs to do that, but it seems like there should be a way for a craft that’s capable of hovering and/or moving in any arbitrary direction should simply head in a straight line to its next waypoint.

Anyway… Thoughts? Suggestions? I do enjoy using the automated flight features of this code and don’t want to stick to 100% manual control, but at this point I’m skittish about activating them until I get a better understanding of them.

I found out about AMA during some of my searching today, and will be joining that organization to gain access to a couple of flying fields nearby, but before I get back in the air I’d like to solidify my understanding of how some of the APM code functions.

Thanks all!

If your auto mode (auto, RTL, Loiter, Position Hold) is not working or going astray then switching to different auto is not going to help.
Stabilise is your way out of this situation for nearly all occasions.

The compass seems to be culprit for these events, I have had a few myself.

What firmware are you running?

Have you calibrated the compass and done the ‘compassmot’ if you are running 3.01.

Ive noticed odd RTL behavior also. And definatly can relate to the need for a Panic or MANUAL OVERRIDE switch!

While flying in stabalize mode my SAT Count dropped to 0 for a few seconds putting my Quad (Arducopter 3.x / APM2.5 ) immediately into land mode. A couple seconds later the satcount jumps to 7 again but APM will not switch back to last state and remains in LAND mode! I have control over everything but throttle and I need to think really quick and finding a place to land Thick bush, sand box, or pile of rocks usually…

Also Attempts to Disarm (left gimbal Down and to right) are unsuccessful while in LAND MODE. :confused:
Props will continue to spin untill APM believe land mode is complete our Im able to get my hands in between the props to disconnect the battery.

In stabilize mode, the APM does not go into failsafe land due to GPS loss. Only due to low bat. if enabled. And it’s possible to switch modes away from failsafe land. You have to switch to anything else and then back to stabilize.

I think I would investigate that 7 to 0 event as well on the GPS count sounds like something is loose or power is an issue.

Hrrm loosing power is a good point I didnt think about.
I havnt noticed it on the bench but maybe in the air under load something is happening.

ITS a NEO brand GPS with the larger ceramic antena on it…
Is there a Telemetry check I can monitor for the status of the GPS itself?