Servers by jDrones

FireFLY6 VTOL with APM Plane

(David) #92

Greg, thanks for taking a look. By controlled flight I mean the FF6 responding to inputs from the RC. Seconds after the transition to FBWB or A, the plane rapidly rolled off and started to spiral to the deck.


(David) #93


Again, thanks for all your help.

As requested here are the deflection measurements of the elevron control surfaces. I’ll only list the right side as the left are the same.

In manual, centered stick, approximately .5 inches up. It was trimmed to this position per manufacturer’s recommendation, found here. This manual is for the DIY FF6. So it’s possbile these aren’t applicable to this model.
manual, full right stick 1 inch up
manual, full left stick .5 inch down, a full inch from the neutral position.

All measurements are from the top of the foam on the wing to the top of the foam on the elevron.

Please let me know if you need anything else.



(David) #94

I am wondering if the elevron neutral position is causing the wing to stall as it transistions to plane causing all the inexplicable graphs.

(Greg Covey) #95


I would like to check the flight controller compensation in FBWA mode. Also, I recommend that your next flight attempt use FBWA with 2/3 to 3/4 throttle during the transition into the wind. Using FBWA, you can control altitude with either throttle or elevator sticks or both. In this manner, if the plane starts going higher, you can control it back to the desired altitude. Also, transitioning back to hover modes should also be done into the wind. By using 66%-75% throttle during the transition to forward flight into the wind, the plane will be virtually stall-proof.

From the Elevon Planes section of the Wiki, in the Servo Reversal section, verify correct movement for an elevon plane using the table. This is done in Manual Mode.

Next, in the Confirm Servo Reversal section, switch the plane to FBWA mode and with the transmitter sticks centered move the plane per the table and verify correct movement.

(David) #96

Thanks Greg, all the control surfaces are moving in the correct directions in all modes. Not sure why my ff6 is having such a hard time and yours and Tridge’s are transitioning without problem. I did increase Q_TILT_RATE_DN to 30 instead of your 20. Based on my assesment of the logs, the plane is stable through the transition to Q_tilt_max.

I suspect the wing is stalling because the nose is being held up with excessive upward elevron.

(David) #97

This is the graph I used to conclude the airplane is stalling. I think we have insufficent airspeed for a nose level pitch attitude, causing the wing to stall. Starts with a little roll and side slip then off to the races.

Other interpretations happily welcome

(David) #98

Another day in the field: four flights, three failed transistions, and finally our first sucessful transistion to plane and back to copter.

Prior to going to the field I physically changed the deflection of the elevons so they were aligned with the airfoil of the wing. The gross adjustment was done with changing the linkage and the last 1/8" was done with servo1/2 trim values - both were modified by 10, one positive, one negative consistent with one servo being reversed.

We climbed to a safe altitude and attempted a transition. The FF6 accelerated but wobbled out of control. She recovered well and we tried it again using FBWB with the same result. Excited we made it further down the transition, we speculated that it needed to transistion to plane quicker. To do this we set ARSPD_FBW_MIN to 12. Repeated the above with futher progress, but she still wobbled out of control.

We landed the FF6 and set ARSPD_FBW_MIN to 10. From the graph above I was fairly confident the stall speed of the FF6 is right around 8m/s. So we tried it again with success. The transition wasn’t graceful and appeared to be on the edge of controlled flight but she made it through to plane.

Once we were in plane the airplane flew ok. I was mostly turning right. When I attemped to roll to the left the airplane began to wobble, so I continued the turn to the right and having enough fun for the day, transitioned back to copter and landed. I don’t remember much about the transistion to copter.

Upon landing I noticed both elevons were deflected up approximately 1/4 of inch from the position I set. Looks like servo_auto_trim reset the trim value by about 10 PWM. Also, the logs reveal a fair amout of altitude fluctuations due to ptich changes. I don’t remember much from school but this looks like a classic phogoid. Not sure if we can dampen that with PIDs.

Overall I am very pleased with how the drone is flying in copter. Great lateral control, great yaw control (perhaps too much) and fair pitch control.

Definitely need some help figuring out how to tune up plane.

Here is the log file from today’s flight.

I love this community and grateful to all those that helped make this happen. I look forward to making the FF6 better with your input and recommendations.



(David) #99

Another day in the field with mixed results. Multiple transition attempts with two successes.

The test plan today was to improve the transition from VTOL to plane and once in plane do an autotune…never got to the autotune.

During yesterday’s successful transition, I observed lots of tail wagging as the FF6 transitioned from VTOL to plane. So today’s goal was to reduce this by changing Q_tilt_max and q_tilt_rate_dn. Really didn’t find a combination that worked as desired. Perhaps I need to adjust some other parameters. What I did conclude is the only way to successfully transition is to have forward airspeed in copter prior to starting the transition. Maybe this will alway be necessary but with AVA I could transition from a level hover to plane without touching the throttle or forward velocity. I’d like to find the right combination of variables to do the same with plane.

When I did get to plane, it flew poorly. The goal was to do an autotune to tune it up. But everytime I tried to turn left the airplane refused to comply. The elevons are trimmed the same and have equal throw and the plane is weighted symmetrically along the longitudinal axis so I am puzzled by this behavior.

Upon landing after the second flight, I observed considerable vibration as I approached touch down. It look like the airplane was bouncing up and down a few inches. I looked at z vibes and the looked ok. But I did note divergence in PIQP. I haven’t observed this behavior on previous flights.

Any insight is apprecated. Here is the log from the flight.



(Greg Covey) #100

My second flight of the FireFLY6 using APM Plane v3.8.2 was as good as the maiden flight. Transitions seemed flawless and I had better turning capability than when using AvA because it can be set to the user’s needs.

I took off and landed in our tiny mowed opening surrounded by hazards. Once airborne, I had a large wild field to fly over. Landing can be tricky when the wind is blowing because the take-off and approach are from the same direction. Other than a little prop turbulence during my descent, the flight was great!

(David) #101


Looks great, thanks for posting. Are you using the same parameters you previously posted? Not sure why yours is flying so well and mine struggles with the transition and flies poorly in plane. Doesn’t seem like it should change much with a 6s power supply

(Greg Covey) #102


Yes, I using the GregsFF6wAPM_Hover4.param file from post 1.

One way around your brick wall may be to re-install the AvA firmware and re-test. It will be easy and quick as you only need to change the tilt servo cable.

(David) #103

Really frustrated.

Went through the entire set up process again: reset elevrons to factory default 5/8in up, recalibrated compass. recalibrated accelerometers and compared my parameters to Tridges and Gregs. Everything checks. Went to the field. No luck. 4 transition attempts, 4 failures. I don’t know what’s different about my set up. Probably a bit heavier with the 6s batteries but other than that should be really similar to Tridges and Gregs FireFly. Not sure where to go from here.

Here is the latest log file.

Thank you,

(Greg Covey) #104


Are you using two 6s packs in parallel or two 3s packs in series?

Has this setup previously worked using AvA?

(David) #105

Two 6s packs in parallel. Yes, this set up worked in AVA. Flew is at least a dozens times with AvA. The AvA transitions were beautiful. And it flew well otherwise. This was a fully assembled FF6 Pro.

We had repreated issues with their camera trigger and want to use VP-Systems CAMRemote. Howver, I can’t do that with with AvA. They either removed or hid the ability to remap ports. And they are triggering with I2C instead of with an aux port. The original plan was to continue to use AvA with CAMRemote, but that is not an option.



(Greg Covey) #106

It seems that one option could be to use AvA with just a simple camera timer setting; like an auto trigger every 3-5 seconds.

The FF6 Planner doesn’t give you the options as Mission Planner does to set the output. They use a standard relay output on Aux6 to trigger the camera. I never had an issue with my S100 cameras running CHDK with the MobileXcopter trigger for Cannon and Pixhawk. You can, however, set the duration in the parameters via Cam_Duration (normally set to 10 or 1 second duration). Most cameras need to use the relay trigger board that I used.

(David) #107

Thanks Greg. They are no longer using AUX6 for the trigger. For reasons, I don’t understand they are using I2C for the trigger and RCTM, which is another heartburn with AVA. I want to use my own GNSS card, not their L1 only solution.

If I could manipulate AvA to control trigger, camera feedback and RCTM, I’d probably stick wiith it… but I want the control afforded with Aurduplane and full up mission planner.

I am hopeful we can get this working with APM.


(tridge) #108

Hi David,
I spent some time reviewing your most recent logs this morning. My apologies that it has taken me this long to get to it.
The most useful log was 2017-10-12 14-04-04.bin as that is the only one that has an extended period of fixed wing flight as far as I can see (it is in FBWB mode).
For that particular flight can you tell me what the elevator neutral trim was? Was it 5/8 inch up? The reason I ask is that in that flight the average elevator was up about 50% from neutral. That would normally imply a very nose heavy plane. Can you also remember what CoG position you had for that particular flight?
So if I was looking at this log in isolation, without knowing that the FF6 already flies well, I’d be telling the user the following:

  • its quite nose heavy. Move the batteries to shift the CoG by an inch.
  • the fixed wing gains are far too low.
    What doesn’t make sense for me is that Greg and I don’t see what you’re seeing. Has the airframe really changed that much between models?
    On the gains, my normal advice based on this log would be:
  • increase PTCH2SRV_P from 1.1 to 2.0
  • increase PTCH2SRV_D from 0.02 to 0.1
  • increase PTCH2SRV_I from 0.5 to 1.0
  • increase RLL2SRV_P from 1.0 to 1.5
  • increase RLL2SRV_I from 0.3 to 0.6
  • increase RLL2SRV_D from 0.02 to 0.1
    these are really large gain increases, but the log shows lots of control lag, so clearly the gains are far too low.
    The good news is that you have good recovery, so you could try these updated gains with relatively low risk.
    The other part of the log that is puzzling is the transition. It is really horrible. I think you should slow down the forward transitions by reducing Q_TILT_RATE_DN from 30 to 15. You’ll still be able to recover just as fast as Q_TILT_RATE_UP will still be 40, but it should allow the system to remain more stable in transition.
    I’d also recommend reducing Q_TILT_MAX from 45 to 30. That will keep the rotors more upright until you have gained some more speed. I think that 30 will be enough for it to get to transition speed, but if not then try 35.
    I’d also again recommend using FBWA for your test transitions.
    I must admit however that I am really puzzled by your results. If we don’t succeed with this approach then what I think we’d have to do next is fly AvA on this exact airframe and get a log of it flying well so I can do a comparison.
    Cheers, Tridge

(Greg Covey) #109

David revealed that he is using the Pro model which is very similar to the DIY25 model except that it uses two 6s 5200mAh packs or twice the weigh of our battery packs. Other than that, the main power system difference from our working DIY15 models is the motor Kv for 6s.

(David) #110

Well it all came to a dramtic end today. Ironically, I went to the field confident that it was going to fly well. I found serveral problems in my set up that were likely the source of the problems. The vertical tilt was off about 3 degrees. Not a big deal but was causing the FF6 to move forward when it should be stationary. The horizontal tilt was about 7 degrees over rotated, past the intended thrust line. I believe this was causing the apparent heavy nose. There was a 5 degree difference between the left and right forward motor mounts. This was exacerbated by the tail engine assembly being canted 3 degrees right. Combined, I think this is why in airplane mode it only turned right.

I fixed all of these and confidently drove to the field, thinking it would surely fly.

With multiple attempts, I still couldn’t get it to transition. Slower was definitly better, but it wasn’t getting to the transition speed at q_tilt_max 40 (this was after I tried Tridge’s 30 and 35 degree recommendations). I think I needed to set q_tilt_max to 50. However, I had a dramatic and catastrophic crash prior to continued expermentation.

After reviewing the damage and impact area my working hypothsis is a propeller came loose. I double checked the writing was up on all propellers and tightened them, at least I thoguht I did. My habit is to grab the propeller and the rotor on the engine and spin until tight. I swear I did this on all six motors, but the crash site says otherwise. The tell tale sign was finding an unbroken propeller about 30 ft from the crash site. The threads on the engine and in the prop appear intact, with no indications of being torn off.

Continuing to speculate, I think the loss of the propeller induced a violent roll, ejecting one of the batteries and then the other, leading to a powerless and uncontrollable airplane accelerating toward the deck. The FF6 impacted the ground nearly vertical, nose first, crumbling the fuselage. It was hard to watch, knowing I couldn’t do anythign to prevent the inevitiable.

I am reminded of the old ABC Sport’s slogan: “The Thrill of Victory or The Agony of Defeat.”

I am grateful to Tridge for all the time and effort he contributed to my endevor. I am dissappointed I crashed it. I really thought I was close and I think I was.

This expereince has reaffirmed our commitment to Ardupilot and this fantastic community. Thank you for the great work.

Lastly, we are in the market for a durable, Pixhawk controlled VTOL airplane that is well-tested and ready to go. lt needs to cover at least 500 acres in one flight and be able to carry a sony A6000 or equvialent weight payload. Suggestions?


(tridge) #111

I’m so sorry you lost the airframe!
I am still puzzled by the flight results from earlier flights. The motor tilt could explain part of it (especially apparent “nose heavy”, I really should have thought about thrust alignment to explain that).
I’m curios about the motor mounts - you describe a screw thread? Mine is a pure friction fit. If it is a screw thread, is it self-tighening?
You may remember that I lost a prop in flight too - the top rear prop. The plane did turn almost upside down when I lost it, then recovered and continued to fly to land normally. After that I used some locktite on the shafts to prevent it happening again. Strangely enough, another club member found my lost prop on the weekend.

that does make prop-loss in flight pretty likely, yes. If you’d like me to look at the log as well I’d be happy to. Only if you want to.
Condolences on your loss!