I am dumb struck!!
I have a Bixler 1 and have been flying it for three to four months with no problems at all.
Have a bigger motor in and FPV gear on it. Last Thursday went to fly and something very strange happened. The Bixler nose-dived on its own, in stabilize mode. I did manage to save the bird, but 1 min later it did it again. But this time I could not save it as it was too low. I also did not have any telemetry connected.
Rebuilt it and went to the field Saturday morning. This time I had telemetry connected. I took her up and flew in manual mode for 3min, then switched to stab. It was not even 1min and it happened again. Saved her but the second time I could not. Crashed again !! I was busy turning (with the ail and elev) the nose just went down uncontrollably. I looked at the tlogs with Graham Dyer, what we could see is that the vcc was not very consistent at the time of the crash. Tlog attached named Saturday.
Rebuilt the Bixler AGAIN !! I swapped the ESC too and reloaded the APM firmware (v2.68). Calibrated everything and tested it on the table. Sunday morning went out to the field. Once again took her up in manual and flew around for a while. Switched to stab and it went well for a couple of min’s. Then it happened again. Nose down 100% and whatever I did, did not help. CRASH NUMBER THREE !!!
We looked at the tlog and the power this time was 100%. But at the point of the crash there was nearly no input from ch2 but 100% output on ch2. Tlog is attached below, named Sunday
Rebuilt Bixler AGAIN !!!! Took out the APM 2 and swapped it for another one I had in my quadcopter. I went this morning and flew the Bixler again. It was much better but found something interesting, when I bank full ail the Bixler will tip over and dive, but this time it recovered after a second or two. Still very stressful to see. I tested this a couple of times, it loses control but gets it back again. Still not 100%.
Thursday I flew with 2.66 the rest was done with 2.68. I also loaded the default bixler.para from this site every time.
Please can someone look at the tlogs and give me some advice.
Replies
It happens to me too.
One day everething goes more than awesome and the next day everething goes wrong... I lost 3 airplanes with reliability issues.
I was working for hours triying to find what goes wrong...
I was thinking in a Manual mode board that act as a bypass to have a real manual mode. because in my case the APM reinitializing is a recurrent cause of problems. and almost everytime ends in a crash.
Im having this exact same problem on my Skywalker 1900. Flew awsome for the past week and havent made any changes. Now all of a sudden, today I am getting the exact same symptoms as you descrobe above. I crashed once this morning, rebuilt and tested again this evening and crashed again. The plane has had it, but I would like to know why this happened.
I figured it out just by looking at the pics. It's because it's green. Problem solved everyone go about your business, nothing to see here! Kidding. Sorry for your loss hope you figure it out.
This thread is a great read. I just want to add that it is important to remember that even the best autopilot is not some magic box that will prevent any kind of airplane crash. Basic principles like weight restrictions, proper center of gravity and trust vectors still has to be correct. Or simply put, if you have a hard time flying the plane in manual, sooner or later it will probably crash in auto also.
If anyone wants to see the trouser changing stall/spin/crash, attached is a Google Earth "Tour" of it. You'll need the latest version of Google Earth to view it (v7+) - (I didn't know GE could do this, thanks to Vince for mentioning it)
(@Khairul, yours looks like a stall and spin too right at the end of the flight.)
Bixler stall, spin and crash.kmz
Hi Louis,
My team and i have been experiencing the same issue.
I posted previously in the Arduplane User Group:
http://www.diydrones.com/group/apmusergroup/forum/topics/apm-2-5-on...
Today we just had another crash and its already about 7 crashes due to the same issue and 3 planes are somewhere in the forest which we are yet to locate. 2 Skywalker Condor and 1 Bixler. All with APM 2.5
The issue remains even after updating to 2.68 fresh clean firmware without any modifications.
We are using Ublox GPS and 3dr Radios, Futaba radio systems. And its always the same characteristics, Throttle will power up more than what it should in Auto and a gradual nose down..sometimes im able to recover in stabilize or manual but most times no. It happens randoom, sometimes at the start of auto mission, sometimes middle or at the end. Past few days we stressed test tour plane and covered total flying time equivalent of 200km and all was fine and we thought problem was solve. But today this crash happened again.
I read people here talking about tip stall but our crashes all happen on a straight path.
Lousi, do share which GPS and electronics were on your Bixler?
My TLOGS and KML from today are attached.
Cheers,
Khairul
2012-12-12 12-46-32.tlog
2012-12-12 12-46-32.tlog.kmz
@ Vince, LOL !!
At least someone had a thrill, I still want to cry. LOL !!!
Here are the tlogs from yesterday’s flying with Graham. If someone want to look at the controlled tip/stall and spin.
Graham made the Bixler stall to see what it does, and there it happened, stall and death spin. But guys I have to say seeing a Master like Graham handling that plane in the air is amazing!! He made it stall and spin and never lost control, I would have made it a grass dart!! Vince you are not the only one that have to change the trousers.
Thanks again Master Graham!!
@ Andrew, thank you very much for all your insight, as Graham said it was spot on.
We did two flights, one with the rudder as Graham said and one without rudder, belowe are the two tlogs. Look at the time, first with rudder, second without.
2012-12-11 16-57-31.tlog
2012-12-11 18-31-06.tlog
Louis, I just converted your Saturday file into a KML and did a ‘first person view’ on google earth. From being ‘inside’ the plane it just looks identical to a classic tip stall/spin. Will have to change my trousers now.
Ok we've just got back from some testing. Louis' Bixler does have a very aggressive tip stall due to excess weight and probably wing damage/roughness/sharp leading tip edges which results in normally a fast right-hand spin. This could happen in level flight or in a turn. The non-recovery thereafter was exacerbated by fairly large control surface movements and coupled aileron/rudder (from the default Bixler parameters) causing a recurring violent flick into an opposite spin and dive. I could recover everytime if I had height and switched out of Stabilize. (Wings level and pull out once speed returned to normal)
We then disabled the CA/R, turned down the throws and found that the APM would recover by itself 50% of the time in Stabilize as long as the spin did not reached more than 3/4 to a full turn. If it went into a deep spin then only switching to manual would allow a recovery.
During the spin the APM didn't seem to "sense" that it was rolling and diving aggressively and thus did not attempt to return to level flight.
The stall and resulting spin actually occured in FBW-A mode aswell but recovery by itself then seemed to be easier and quicker, probably because the APM was not allowing such aggressive control surface movements.
Louis has the log files which I'm sure he'll post here if anyone wants to look at them.
Thanks again Tridge for your insight!
I wonder if it is not happening because the plane is not moving ?
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