I've just lost my second UAV to Lake Erie. What's going on?!? It has a bit of history as a ship graveyard, but I haven't heard any Bermuda Triangle like stories along the lines of what I'm experiencing.
First time I took a DJI hex up and got it about 50 yards over the water and it started dropping and would not respond to transmitter. Even though I used a battery from my 'charged' LiPo bag, I chalked it up to pilot error for not doing a voltage check before take off.
This time, I was going up w/ my Y6 (pixhawk) and had 16.4 volts on my 4 cell. I got about the same distance over the water and kerplunk, same thing happened. It just dropped w/ no response to transmitter. No low voltage alarm. This was actually the second flight for this mission. First one out was no problem. Brought it back, swapped out batteries and disaster that second time.
I have never had that response or experience any of the many times I've flown over land. Would there even be anything salvageable other than maybe the frame if I could recover it? I'm thinking not, and it's why I never went diving for the first one down.
- Possibly hanging up my Tx after this
(discussion category chosen for humor. I need that at this point)
Replies
I had a parallel topic going over on the Flite Test forums and one of the members linked me to this page on Throttle Failsafe;
http://copter.ardupilot.com/wiki/throttle-failsafe/
At the very end of page is what I'm now leaning towards as the cause of my catastrophe.
Operation of failsafe using a Spektrum Satellite receiver
"When using a Spektrum Satellite receiver with Pixhawk, the failsafe will trigger after receiving no data from the satellite receiver for two seconds, and not immediately when the transmitter is turned off. This behavior is due to the satellite receiver being directly connected to Pixhawk without connecting to the main receiver."
That's exactly how I was setup. I had also configured some channel mixing to get more modes out of my switches which may have contributed to the mishap. And, I'm positive, I never altered my throttle failsafe mode, so what I likely saw happen before my eyes was an auto Land working as it was designed, just at the worst location possible.
I wish I could say I learned a lesson by getting to what I think is root cause, but that Pixhawk+Tx config is far beyond what I would normally think to check and likely won't have that combination again. So, chalk this up as an expensive lesson mistake accident freak accident I guess.
sorry for you loss, you should find a recent discussion thread named "Naza Fly Away" - you can find more info and a link about the problems DJI users experience, or meet people in denial that will convince you that it was your fail, because DJI is reliable
- then you can believe one side or the other based on your own experience :)
Thanks Andre. I'm leaning towards RF interference being a possible cause. Although, it really doesn't explain the sudden drop from the sky. If it lost communication with the transmitter I would expect a different reaction.
most full spectrum frequency hopping 2.4ghz systems are hard to even jam, unless using a very wideband jammer.
Not even half-decent systems accept frames with bad checksum. (unless you used some old analog TX, the digital systems verify a data packed before accepting it and outputting its data to PPM, PWM, or SBUS.)
Yes, it did feel like a stretch to blame it on RF interference, especially the way it responded. But immediately dropping w/ no alarm on what should have been plenty of battery left made me wonder. Lake Erie, where this happened, does have some fairly populated metro areas on its shores. I had thoughts that all the radio activity taking place and easily traveling over the surface of water at greater distances may have played a part. I'll never know I guess.
flying over water is not a problem. I live on an island, and regularly fly mapping/photo missions near and over fjords. flying 600m-1Km over sea to get photos of populated areas is not uncommon.
It's a pity the log in inaccessible - it's most likely fine - most SD cards handle water very well.