Observer/Ranger Quadplane


Here is a short build log showing the work required to convert my Quanum Observer to VTOL Quadplane. The mods are done in such a way that the Quadplane can be reverted to pure fixed wing in around 10mins for ultra long duration flight (+-80mins on 15AH packs) and when a landing strip is available.

Total weight added for Quadplane is 1,320g but only 270g of this is permanent (ie. fixed items such as carbon spars in the wings, mounting legs, wiring in the wings, glue, etc). Total all-up weight in Quadplane mode is around 4,800g (including camera and gimbal).

Specs as follows:
Frame size 1070mm (measured diagonal)
T-Motor MT4006 740KV
T-Motor Air 40A ESC
T-Motor carbon props 14 x 4.8
4S 10,000mAh
Pixhawk flight controller, running firmware version 3.6.0 with Quadplane support.

I've done some hover tests and transition flight will hopefully happen soon.Here is a video to show the stabilized footage I was getting before converting to Quadplane:

Thanks to all for the great work being done in this community, particularly Tridge! 




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  • Here's a demo video of some test flights from last week:

  • Hoping someone with QuadPlane experience can take a look at my logs before I try transition? I have uploaded the .bin files to Dropbox here:

    (dropbox account is not needed to retrieve)

    I'm interested to hear anyone's thoughts on the gain settings. Q_A_RAT_RLL_P and Q_A_RAT_PIT_P are at the recommended values of 0.25 for this flight.

    I have dialled down Q_A_ACCEL_R_MAX and Q_A_ACCEL_P_MAX to 7,500 which seems to have softened the responsiveness in Qstabilize and Qhover modes slightly (it was far too sensitive before). Can someone comment on the default values for these parameters when Quadplane is enabled? The 110,000 value equates to 3 full rolls per sec (it's in centidegrees)?


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  • @ Jacques

    The main reason for the motor/rotor brake is to stop it interfering and creating both lift and drag in flight. There's also the possibility of the quad motors/rotors creating voltage spikes/interference from freewheeling in the "wind" in forward flight, that can lead to ESC failure because typically FETs are voltage sensitive. Spinning low kV motors at high RPM could produce voltages over the FET rating. You should be ok, but I'd recommend using an ESC with brake to improve performance and reliability anyway. FBW_MIN should be good at 15 I think, without knowing the airframe myself. Let us know how you go! Quadplanes are pretty awesome to fly around! ;-)


    @ Kevin

    We've been having a series of issues with the ESC's we've been testing as well. In particular BLHeli versions seems to be giving us setup headaches atm. I presume you have done a radio calibration on the PXH, are engaging the safety switch on the PXH and are using the throttle down/right yaw to arm, and have the ground signal wire of the ESCs connected to the PXH? Let me know your config a bit more and I might be able to help.

  • @JB: Regarding vibrations: for my initial hover tests, I have some cross bracing (fishing trace wire) going diagonally from motor to motor and passing under the fuse. This gives the wing significant torsional rigidity. The spars I added (see 3rd photo) are 8 x 8 carbon box section spanning from boom to boom, which gave the wings a lot more strength, but they can still be twisted slightly if I left the plane by holding 2 diagonal motors. They may be fine and I'll try some tests without the wire soon.

    Regarding airspeed setup, I have increased FBW_MIN from 12 (which was the sweet spot before the QP conversion) to 15. Hopefully this will cover the additional weight but I may push that a little to start with, as you suggest.

    Unfortunately I don't think there's a brake option on the ESCs I'm using so they will be freewheeling. Is it a known issue that this can reduce ESC life?



  • Yes, and I would definitely recommend it for any plane and particularly quadplane to ensure smooth transition. I have mine in a 3D printed holder, as per the photo.3702256574?profile=original

  • Just a quick question re quadplane setup.

    Do you have to have an airspeed sensor?



  • Developer

    this looks like a very nice build!

  • Looks good. I like that it is dis-mountable and your CF components build. I think we'll see many more reconfigurable quadplanes in the future that are quad (with pusher prop), plane and quadplane in one.

    I was wondering how it goes with vibration in the quad motor mounts in this configuration? Our second prototype had the same configuration using CF rods suspended from the wings, but we found that the combined length of the wing and CF rod, especially the front quad motors (which need to be well forwards to maintain CoG) would have excessive vibrations at full throttle. Our solution was to use spars running across the fuselage instead, which removed the problem entirely, and also simplified and shortened the wiring and setup considerably. One can also shorten the arm length as typically roll authority is not an issue with a quadplane, unlike yaw, so it's possible to have the motors closer to the fuselage. There is of course a question of aerodynamics with the full CF tube exposed to airflow, this can be mitigated by using CF flat bar or streamlining the rod. 

    BTW just a tip which might be obvious on transitioning when you get to it: If you make the ARSPD_FBW_MIN higher and the Q_TRANSITION_MS longer than required the quad will remain on until it achieves sustainable forward winged flight. You can then dial it back from there once you have more confidence in the transition performance. Also preferably use the motor brake on your ESC to avoid the quad motors from auto-rotating in flight, which will produce drag and can sometimes lead to premature ESC failure.

    Regards JB 

    Complete Parameter List — Plane documentation
  • Developer

    That is a really nice build.

  • Great work Jacques. I was looking at the Ranger as well for this. I have a few Bixler's i am playing with but I think I will need a bigger plane. Look forward to see your flight times with a VTOL take and landing. 

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