I use to fly this plane. It flyes pretty good, it is not perfect as the others, but neither a bad tuned plane.
I had a problem during yet another AUTO-takeoff. It went wrong.
I shaked it, motor spoon, i hand launch it as usual, it goes straight for 10/15 meters without climbing and suddenly dove in to the ground with a hard pitch down.
Zero wind condition.
I like to have a look at logs. I can say there have been an issue with airspeed. What is happening?
I wouldn’t expect it to dive so hard because of airspeed.
Did i touch radio sticks and interfere with autotakeoff?
Shortly after take off there was an elevator stick input demanding full pitch up, 55deg. The plane tried to get there and was moving the elevons, at times, full deflection.
I’m just wondering if that so soon out of the throw, the plane wasn’t stable enough yet to manage the demand for full nose up pitch and stopping the roll at the same time. The mixer is at 0.5, so the pitch and roll demands can only control half the elevon throw and maybe that just wasn’t enough.
I am checking the sensor right now.
It shows values oscillating between 4 and 10 km/h on the desk. I would say it is ok.
If i blow, speed goes up. That is ok too…
I use matek ASPD-4525 digital sensor.
I can see, on the graph, airspeed going the opposite of GS. What if the sensor has excanged dinamic and static pressure ports? I dind’t swap the tubes since first use. Maybe on startup it does some kind of calibration (or other things)?
I guess it depends on the sensor you’re using but all the ones I’ve used in the past determined the pressure differential in the calibration. So as long as you didn’t change anything it should be okay. Any chance you pinched a tube when you closed it up to launch it?
In your ARSP_OPTIONS you have Speed Mismatch Disable set. You might want to turn that off so Speed Mismatch works.
I would say no to the pinched tube option. But i will consider this.
Sure i touched the stick.
Sure there was a problem with airspeed reading.
I changed arming check to 1 on all my planes.
I than enabled speed mismatch.
Next time i will check airspeed sensor reading before takeoff with ground station connected.
Thank you Allister, you always help! Appreciate it.
Edit: Previous flight same day, airspeed reading is ok. I assume something went wrong during initial calibration. Still not sure if it caused the crash or if it was me
I am playing with tube ARSPD_TUBE_ORDR.
I use to leave it auto, but if i change between normal or swapped than i can se the speed going up with correct tube order or going to zero with wrong order.
I will now keep it to manual setting. I suspect something happened during startup calibration.
The cover doesn’t need to seal tight, it just needs to keep any wind or breeze out. I used to use the case from a busted ball point pen. The Gen 1 Wingtra came with a glass tube that always made me think of a guitar slide. It was deliberately too big and loose fitting so if somebody left it on it would fall off after take off.
On both my airplane, i can confirm that using the slightly loose cap on the pitot tube during calibration, will give a big chance of error on the tube ordering from autopilot. This will lead to the air-speed going low as fast as you fly. Tecs will than pitch and terrain could be a problem.
I did’t use to use the cap, but with wind i did. Than the problems above…
I confirm using manual tube ordering is a working solution for me.
