XAircraft WTF just happened?

[mediaguru]

I can barely breath. I did an evening flight with my T960, just like I do every evening. This time though I was quite high. I was flying in ATT mode when all the lights on the bird went dark and I could see it free falling. The first thing I could think of was to jam it into GPS mode. When I did that the lights came back on and I could hear it rev up the motors higher than I have ever heard. It put on the air brakes and somehow leveled itself off. In looking at the logs, the thing dropped from 222 meters up to 88 before I gained control. It was literally falling from the sky. I just did the math. 450 feet it dropped in about 10 seconds.

I thought it was a total power outage but that would mean the log would cut off at that point. You can see in the log below the event takes place at about 260 seconds.

At 230 seconds I got a notice that RSS level was critical. So I started bringing it closer. You can see that it went into safe mode for what appears to be a couple of seconds. At 257 seconds it goes into manual mode. I did NOT switch to manual mode. I never fly in manual. Not sure about my skills yet. Two seconds into manual mode it dropped.

http://log.xaircraft.com/report.htm#2014_08_25_195607.750_66.1.05.52

I'm still a bit shaken, and I brought her in fine and was so nervous when I landed that I tipped the bird over, luckily in long grass.

A quick exam of the frame shows nothing loose. The G forces rotated the gimbal 45 degrees. The camera was in photo mode, or I'd watch and listen to the video to get a better idea what happened.

I suspect it is possible that the lights were always on, but when it was dropping I could not see them. But that would be pretty unlikely. It was literally falling to its death until I somehow saved it.

Thoughts?

UPDATE: Just looked at some of the photos. One was snapped which tells a lot. The camera was pointing straight down at the ground, as well as the front right arm. The front was pitched beyond 90 degrees downward at the time the photo was taken. The LED lights were ON.

 

[X650Mouse]

An observation! if you look at the first log you will note that at approx 1.22 into the flight your throttle was at 50% and did not advance from there, that would have put SX into an altitude hold mode with ATT and GPS but probably would not be enough thrust in manual to maintain positive flight.

The key time in the flight log is 258.814 if you look at each major log at that time stamp you will see the events unfold.

I am not saying you did this but I have been guilty on 2 flights of going into manual when I thought it was Attitude hold mode, the results were my first aircraft is at the bottom of a lake the second crash was on soft sand. I completed my 400th flight 2 days ago but still live in fear of doing that again because if you don't know and try to fly manual with only 1 stick it is crash time.

I don't know why you throttle was at 50% but either the radio was playing up or something else caused it.

X

 

[mediaguru]

Yes I held the altitude in GPS and/or ATT mode, and was rotating the bird taking night photos of the city. It was dark and I was flipping the switch on my TX to either shoot photos or shoot video. I suppose it is possible that I bumped the switch into manual mode, but I would have had to bump it toward me, which is not really likely as that switch is back right on the TX. The photo/video switch is front right, so not too far from the GPS/Manual switch. The log says I went into manual mode so that is what the SX saw regardless. I'm quite amazed the bird leveled itself when I hit gps mode. I can see some motors cranked up to 100% while a couple of others were at 11%. I can't imagine the G forces at that point and surprised the arms didn't snap or the gimbal didn't fly off.

If I were to assume I hit manual by accident, I have to say I'm impressed the SX was able to recover during that fall. Fortunately I had room to spare due to being so high.

 

[Ronan]

I'v accidentally flipped the manual switch on mine too (neck strap pushed it down into manual mode when i was adjusting the strap to be higher on my neck)... man my heart sank when i saw it free fall... quickly flipped to GPS and it leveled itself.

They REALLY fall quickly too, it's scary. Maybe someone has a recommendation for which switch to have as GPS/ATTI/M on remotes, to minimize accidentally switching to different modes.

Tarot T810/T960 has a good design/build. You are right when they get hit with a good amount of G's when something like this happen!

 

[mediaguru]

I'v accidentally flipped the manual switch on mine too (neck strap pushed it down into manual mode when i was adjusting the strap to be higher on my neck)... man my heart sank when i saw it free fall... quickly flipped to GPS and it leveled itself.

They REALLY fall quickly too, it's scary. Maybe someone has a recommendation for which switch to have as GPS/ATTI/M on remotes, to minimize accidentally switching to different modes.

Tarot T810/T960 has a good design/build. You are right when they get hit with a good amount of G's when something like this happen!

I don't plan any time soon to fly in manual mode at all. I wonder about perhaps programming the GPS/ATT/Manual switch to only be GPS/ATT? That way I could never accidentally hit manual, like I apparently did.

 

[mediaguru]

I suppose it would be a good plan to add some audio to my Taranis for mode switch as well. That way I can hear her voice say "Manual Mode" if it does get switched...

 

[andrewrob]

I don't plan any time soon to fly in manual mode at all. I wonder about perhaps programming the GPS/ATT/Manual switch to only be GPS/ATT? That way I could never accidentally hit manual, like I apparently did.

I think this is the best bet. Used to do this with the Wookong M and after doing a calibration (where you have to flick manual/atti/gps 10 times whilst on the ground then turn the UAV laterally and horizontally to calibrate the compass) we'd tune out manual mode so the 3 way switch would go Atti/GPS/Fail safe.

Was wondering if there is a way on the Taranis to use another switch to adjust the limits or centre point on the mode switch to "lock" and "unlock" manual mode effectively.

 

[Ronan]

I would never take manual out since it has saved some people when the FC goes haywire and you have to bring it in manual. I know people have done it for the DJI FC's, i don't know about xAircraft.

 

[X650Mouse]

I suppose it would be a good plan to add some audio to my Taranis for mode switch as well. That way I can hear her voice say "Manual Mode" if it does get switched...

Change the extension from PDF to WAV, this is for Taranis

X

 

[Motopreserve]

Glad to hear you made it land safe. That's a wild ride for sure.

As as has been mentioned, I think having manual available to is is more safe then loosing it altogether. I have the taranis set up with voice alerts for all the flight modes. It's definitely comforting.

 

[dazzab]

222 meters high? What were you doing up there? I'm surprised you could even see it.

 

[Ronan]

222 meters high? What were you doing up there? I'm surprised you could even see it.

Didn't the media tell you? At that height, not only you can spy on the neighbors daughter sunbathing int he backyard, you can see the one's of the neighboring cities and states too!

 

[mediaguru]

Didn't the media tell you? At that height, not only you can spy on the neighbors daughter sunbathing int he backyard, you can see the one's of the neighboring cities and states too!

That flight was a learning experience to say the least. I should NOT have been that high, though had I been half as high my bird would have been destroyed since I would not have had time to recover the flight. I've never flown that high. It was an evening flight and with the LED's I put on the bird for LOS flying it looks much closer in the dark than it really is from both a horizontal and vertical standpoint. I need FPV gear and altitude telemetry stat. I was not only far higher than I thought I was, I was also much farther away than I thought. All bad bad bad.

I have flown twice since then and not managed to go into manual by accident. Much more conservative, only 30 meters high and perhaps 100 meters down line.

 

[andrewrob]

I suppose it would be a good plan to add some audio to my Taranis for mode switch as well. That way I can hear her voice say "Manual Mode" if it does get switched...

Think I've found a way to get the best combination of having manual mode as an emergency backup but not activating accidentally.

I've set the "SE" 3 way switch as my flight mode switch and set to go Fail safe > Atti > GPS but I've set a logical switch function that activates manual mode only if "SE" is in the up position and "SB" in the down position, when this combination happens it activates two special functions.
Special function one: adjusts the trim on the flight mode channel to put it in the manual mode section in Super X or DJI or whatever you're using

Special function 2 plays the audio track that I've recorded that says "manual mode"