I have been running and testing my APM 2.5 for about 4 weeks now. I have had some learning curves when it comes to stable flying, given the quad would dip and lower it self when locked in Alt Hold. It has all been minor adjustments but I had not turned on any fail safes what so ever. I do have a power module but for low alt flight testing I didn't see a need for it.
I am running on a 6CH radio. SW-A 0 setting in its natural start up state puts the quad in stabilize of course. The PWM is 0-1230. When SW-A is switched to 1. It sets the flight mode to 6. I have flight mode 6 set for loiter with a PWM of 1750+ I have found flying while locked into loiter mode it handles like a dream. (Again talking low level flight, maybe 25 ft from the ground.) My SW-B when switched into the 1 position triggers flight mode 2 RTL with a PWM of 1231-1360. I have tested this a few times. I will take it out of loiter mode, and flip the RTL switch. The quad gains up in ALT, gets its orientation and comes home. So far this has worked the best for me when flying.
Now for the heart attack.
I set the battery fail safes. I wanted to start going a bit higher and wanted to make sure that if power level ran low I had enough time to get it to return to launch. I set the power level to 10.1 (I am running a 3300 mha battery with 4 1000 kv motors, 40 amp esc's, a video TX, a 3DR radio and a OSD. and of course the APM and external GPS module.) The pwm on the fail safe is 1200. This week when I was flying and testing everything was going well. I brought the quad back to me under manual control and attempted to land it. As it touched the ground and i powered down the throttle the props started to stop but then sped up. It lifted up off the ground and headed north. I had no control over it what so ever. Not in stabilize, loiter, or RTL. Nothing worked. Suddenly it shot straight up into the sky. All I could see of it is a black dot it was so high. Once up there, it just sat. I tried everything to get some control of it, but nothing I did made any difference. At this point, my heart is racing due to the fact I am in a urban area. Was terrified it was going to take off or fall out of the sky or both. It sat as if in loiter mode above me, and after about 3 min, it started descending and after a few prayers to any God that was listening at the moment, it landed it self in front of me.
I would really appreciate some help in troubling shooting exactly the cause of this. I am guessing its in my FS and the PWM of 1200 being the problem, although, anytime I have ever done any kind of RTL it never travels to the height it did when control was lost. So I am suspect of it being a true RTL override but could be wrong. I will leave it here for now, and wait for more experienced APM engineers out there to weigh in .
Thanks for reading.
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