Hello,
I had a crash today with my Skyhunter running on 3DR Pixhawk with latest firmware 3.1.1.
I don't know why but after review of a tlog it seems I lost telemetry signal for a few seconds and then RTL mode switched over resulting in a crash because I was flying low and too close to the trees. But how is it possible that suddenly I had no telemetry signal when I was just 100-150m away ? I mean this is strange, my plane got destroyed badly and few months of work are gone apparently.. If someone could look into my logs, I'd appreciate it.
Thanks a lot !
Replies
After some tips from Andre-K, it appears that the problem in the drop of remote telemetry RSSI might have something to do with conductivity of the Kevlar-CF cloth or Aluminum tape.
This is the Kevlar-CF cloth I have attached on the body and added multiple epoxy layers : https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct...
The top layer is this Aluminum tape : https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct...
On top of that is the antenna in X configuration. Do you think I should remove something ? I mean I cannot remove the cloth anymore because I could destroy the body too. But do you think the aluminum tape has some conductivity too ?
And btw. do you know which antenna might be better for the 433 Mhz 3DR telemetry radio than those standard 2dbi whip ? Because I want to achieve long range telemetry and those whips loose signal after 1km easily.. If the CF cloth is taking the conductivity, I'll have to either place antenna on the wings (not preferred) and change the polarization to horizontal or buy new antenna. But which one ?
Michal, your RSSI is very low before taking off - around 100-115, maybe I'm spoilt with the RFD900 but we normally get about 200-217 RSSI before takeoff close to the GS.
I will check the radio tomorrow.. I'm using Graupner MX16, 2.4Ghz HOTT and GR16 receiver.
Sorry
Sorry for what ?
The rest of my sentence didn't show for some reason, I said "Sorry, I meant what were your telemetry radio's and frequency?"
433 Mhz 3DR radio set
Sorry for your loss, it's easy to lose telemetry if something was wrong like a wiring error or break or even antenna problems, terrain can also play a part. Low level behind trees can cause issues as I discovered once leading to a high speed terminal crash while flying FPV. It is critical, as you know to have all the auto modes (like RTL) tested repeatedly to make sure everything functions as it should. Even then things can go wrong, we lost a plane recently with all the failsafe's setup correctly, the Rx failsafe was set to go 950 on throttle but the mode switch set to it's default which unfortunately was 'manual'.
When I get a bit more time I'll have a look at your log or someone else will have a look too.
I'm using Graupner RC and it's hard for me to make proper failsafe setup with the Pixhawk. My only failsafe thus remains the GCS loss of telemetry signal for more than 10 sec, then RTL goes on. That is what happened to me now but it's a mystery why I lost the signal at all when I was in LOS range ? I can only guess: antenna positioned too low above the ground, notebook's USB power undervoltage (I can't believe), etc.. I was not flying behind trees, I believe the antenna was too low. But anyway I could not save the plane because I didn't know it lost the telemetry signal. So next time I will be more close to the notebook to hear the warnings..
Thanks anyway.
I thought that Throttle Failsafe will over-ride your mode, even if your failsafe also sets your mode to Manual. Have you tested to confirm this behavior? When I set up my failsafe, I'm always starting with the transmitter mode switch in Manual, and just set the throttle low and a little FPV camera tilt to show me the failsafe. I had successful failsafes doing this procedure.
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