Your motor is also spinning when your prop isn’t (on the right one after the crash on the ground). Loose props could have done that too.
hmmm… i could be… but my air crash investigation 
after that accident, i found that the prop hole is burn because of friction… so there is a friction between prop and motor but u are right it’s loose but i’m not sure that’s prop is already loose before or after the first hit… but for sure next time i better check all the prop bolt before take off… thanks…
Just had the weirdest thing. Took the plane for a flight after a few weeks. Plane had flown fine the last time and hadn’t even been booted up since then.
Got an error that the trim values were lower than the minimum values and when I checked all 16 channels trim values were set at 874!?
How on earth does that happen? First time it’s booted in weeks and somehow all the trim values change?
Or is this just one of the idiosyncrasies of Ardupilot that we must accept?
Hi Graham,
I have seen that issue as well. When it was most prominent on my Tarot 680 Pro hexacopter, I replaced the old Pixhawk 1 with a Pixhawk v2.4.8 (also Version 1) and it went away. On other VTOLS, a re-boot can fix it or simply reloading your parameters from the PC file can fix it. If the plane was recently used, I did not have an issue.
I had some suspicions that my older Pixhawk 1 FCs were just losing their flash capability and I had other suspicions that it was an ArduPilot firmware issue across platforms (Plane, Copter, Rover, etc). I have not booted my VTOLs in months so it might make for an interesting weekend test. Although it is officially Spring here, the weather is still poor.
Cheers!
hmm… it make sense because i think i have experience this too… but after i load my last parameter it fix again…
Hey guys, here is some info on using Q_Autotune incase you want to interrogate the logs and find out what went wrong on the last flight. The first two went well but didn’t complete Pitch tuning. VTOL QuadPlane Tricopter Autotune - CRASH
Hi ovolkmann,
You may try posting your questions directly in the AUTOTUNE Blog here. I haven’t read any indication that AUTOTUNE has been successful on a tricopter or Numbus VTOL, nor can I find it in the Wiki. The quote below may be old but I haven’t seen anything that contradicts it. Perhaps you are the first to try it?
Hi Greg,
Yes, I do believe we are the first to do this q_autotune on a tilt-rotor platform. Today I’ll be running the YAW tuning after having repaired the nimbus. We’re doing this testing for two reasons, 1) To improve our VTOL flight characteristics and 2) to get the dev’s some data to analyze to further improve on the q_autotune protocol for tilt rotors. Hopefully they’ll get a chance to review the logs :). Will keep you updated if you are interested.
Yes, it is interesting for several reasons so please post your findings here as well. It is interesting because you are using a Nimbus. Also, it will be interesting to see if the Q_AUTOTUNE feature results in better performance than what others are currently seeing. I have suspicions that there may be expectations that a tricopter design with vectored yaw can perform as well as a true quadplane using 5 motors.
Cheers!
@GregCovey, I think that a true quadframe with 4 lifting and 1 forward vector motor is less sensitive to the hardware choices for tuning than a vectored yaw setup but I think that with the right components and settings one can get similar “copter” performance in both designs. That being said, the yaw axis is most likely the most difficult one to tune due to the difference between the width of the aircraft and the distance between the vector motors. Just got back to the office after completing the pitch and yaw tuning. Will put all the logs up soon. Did a test flight with the autotuned results and I’m not quite happy with the yaw still but pitch and roll seem great. Will share the post here shortly. Cheers!
Alright guys, here are logs and vids of all three axis Q_Autotune.
https://discuss.ardupilot.org/t/q-autotune-tricopter-tilt-rotor-results/40998
Remember to give your ESCs some time to cool off after each session, especially if you have thermal cut-off.
@GregCovey, can you confirm that the plane should be CG’d at 100mm from leading edge? Does the distance between the propeller to the CG make a difference to the fixed-wing portion of the flight?
Yes, 100mm from LE sounds right. We have seen various distances that the prop sticks out from the LE and have not heard of any negative comments. I would think it has minimal effect on forward flight.
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@GregCovey, we’ve had it at 85-87mm and even 120mm before. The plane seems to be very tolerant of poor CG for sure :-p. Thank you for confirming the 100mm from LE.
Hey guys,
Pulled off a nice 51 minute automatic flight today including VTOL Take-off and VTOL Landing. The flight was done at 16m/s and during the flight, it seemed that the plane was “hanging” on the nose with a 10-15 degree pitch up during the flight (which was done perpendicular to the wind). Now, I did CG the plane at 100m from leading edge which gave me a vast improvement on flight time however I am now thinking that perhaps the tail control surfaces are not properly setup due to this “hanging” phenomenon I noticed. Should the aircraft not maintain a level flight for the majority of a flight? I mean, it was very consistent. The flight prior to this one lasted 40 minutes and was at 18m/s and that behaviour was still there, just perhaps not as pronounced. Your input would be greatly appreciated!
I really don’t know much about the Nimbus but I can give you my advice from my background in aerospace engineering.
Should the aircraft not maintain a level flight for the majority of a flight?
Ideally, YES, but that will be case only if the wing is mounted at the right angle of incidence relative to the fuselage for the design AUW (with careful consideration for the tail mount angles too).
Let’s say an aircraft of weight W is designed with 0 degree wing angle of incidence, but the angle of attack (AoA) that is required to provide the lift required at level cruise condition (where lift = W) is 5 degrees. In such a design, the plane will cruise with the fuselage at an angle of say approx. 5 degrees to the horizontal (assuming that the tail and the fuselage doesn’t do any lifting, which may or may not be true). However, if the weight of the plane is increased, the angle that the fuselage makes with the horizontal will likely increase even more. Typically, you need the fuselage to be horizontal as you really dont want the fuselage of a conventional aircraft to generate excessive drag or any lift (because lift-induced drag increases). A fuselage pitch-up angle of 15 degrees at level cruise flight sounds a bit too high, as it’s quite close to typical wing stall angle. What was your AUW for this flight?
The flight prior to this one lasted 40 minutes and was at 18m/s and that behaviour was still there, just perhaps not as pronounced
The equation for the lift generated by the wing is: Lift = 0.5 x (lift coefficient) x (ambient air density) x (wing planform area) x (aircraft airspeed)^2
Since ambient air density at a given altitude is fixed by nature, and the wing planform area is fixed by the airframe you use, the aerodynamic lift generated by the wing at cruise condition can only be increased by either increasing your lift coefficient (by raising the AoA) or by increasing your cruise speed. So when you increased your cruise speed from 16m/s to 18m/s, the AoA doesn’t have to be as high, so the wing drops slightly. I hope that makes sense.
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Are you using SERVO_AUTO_TRIM? It should take care of leveling your plane in forward flight.
P.S. Love your flying area!
Thanks Greg! I’ll give SERVO_AUTO_TRIM a try. Any words of caution about using that feature?
Don’t let your jaw drop too far when you see your plane fly straight. 
I have been using it for years and never need to trim a plane…
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@Matt_C, Yeah, not too bad of a flying area but I miss mountains! lol Florida is just too flat for me. Yes, you see the V-map antenna attached to the top of the aircraft. The receiver itself is sitting in the nose. We love it, but since we make it, we are a little bias :-p. That being said, the results speak for themselves. I’ll try and get a log up for the flight here soon so that you can see what I am talking about but I will try the SERVO_AUTO_TRIM feature as recommended by @GregCovey