3D Robotics

Airbus Cargo Drone using Dronecode/PX4 stack

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From the Local Motors blog, a report from the first bench testing of the 1/4 scale prototype of the Airbus Cargo Drone Challenge winner, which will debut at the Commercial UAV Expo in Las Vegas next month. That's me at right (with safety glasses)

Two months ago our co-creation community was drawing sketches on napkins to determine wing taper ratios and materials for what would ultimately become a finished cargo drone. The build has now progressed to the point that Local Motors and Airbus engineers have completed scale models and experimental test flights.

The nose cone, fuselage, tail boom and several other parts of the full-scale Zelator-28 are nearing completion.

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The experimental quarter-scale model took flight this past weekend in Henderson, Nev. Local Motors engineers and Jon Daniels of Praxis Aerospace Concepts International (PACI) teamed with Chris Anderson of 3D Robotics (3DR) on the integration and demonstration of his flight control system for vertical take-off and transitional forward flight, known as PX4. Anderson’s flight system served as an interface for the motors, speed controllers and servomechanisms.


The test model completed a hover and touchdown, but a few mechanical issues prevented forward flight. The experiment was very beneficial to the build team, however, as it helped identify potential failure modes before stepping up to the full scale aircraft.

“They are simple fixes for the most part. There was a hardware conflict with the servos and an issue with the motor pods in the quarter-scale model,” said Local Motors engineer Alex Palmer.  “[The quarter-scale model] has a different attachment design than the full scale so that issue will resolve itself.”

The team is now focused on completing two full-scale models of the Zelator-28 that should be ready for flight testing in the next two weeks. Airbus engineers are planning to join the team for the first flights of the prototype. There are still active discussions on the project page for the co-creation community to provide ideas and feedback pertaining to wing design and the landing gear. Make your mark on the present and future of unmanned aerial vehicles by getting in on the discussion.

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  • Of course we realize this is a 1/4 scale model.  However, mass does scale linearly.  The question is, how did you get that far along on the 1/4 scale model, with the battery under the wing, instead of in the nose?  You've now got the battery suspended in front of the nose cone on two sticks, fastened with tape, and the sticks zip-tied to ribs in the frame.  This leads to a credibility problem.

    It's also interesting, that apparently the team has now recognized the problem with mass distribution of the original design.  And the control surface problem. And the gull wing problem. And the wing thickness problem.  And the landing gear problem...  all problems highlighted by the community but ignored during the judging stage.  And so, you are now fixing these problems, taking the design further and further away from the original design, which begs the question, why did the winning design win?  Because it was pretty.  Not because it was a sound engineering design.  Which, is what our complaint was from the beginning.  This was a rendering project, not an engineering project.  And the winner won, presumably because he was the best at 3DS-Max, not because he was good at CAD.

    The other attributes you wish to test, props windmilling and tail geometry, do NOT scale well, and the 1/4 scale test won't do you much good.  And neither will the control system.  When you try the full scale, then you will realize all the problems with PX4 flight stack.  I just helped somebody get a very large quad-plane flying (>50lbs), and the algorithms  needed to do it are not available from PX4. You can't PID-bang an aircraft of that size into flying properly.  The underlying controller design needs to be sound.  And PX4 doesn't have it.  Maybe you should look before you go too far down this road.

    I anxiously await to see how you will build a battery pack in a pyramidal shape to fit in that nose-cone.

    The Zelator won because it was a pretty rendering.  But the finished product will look nothing like the original design, because it was pure science-fiction.  The entire process is an insult to people who put real effort into their designs.

  • 3D Robotics

    You guys crack me up. You do realize that this is the 1/4 scale airframe geometry test platform, not that actual thing, right? And that the actual thing has a massive battery in the front that that's optimized for the nose cone, as opposed to the hobby batteries we were using for this one?

    The point of this exercise was just to distribute the components in approximately the same geometry so that when we do take it outside we can see if there's any weird coupling issues Airbus needs to incorporate in the design, such as the horizontal props windmillling in forward motion despite braking, or whether the tail geometry needs to be tweaked. 

    Gary is right, BTW. This is a Las Vegas engineering company that is doing the airframe prototypes and creating the fiberglass molds. The Airbus engineers don't kick in until the next phase of full-scale testing.

  • imho according to empennage distance to the cg, the control surface is ugly but have to be that way to get a effective moment. 

  • Well, the good news is, I see they have added elevator control surfaces.  Another problem that was highlighted by the community post-award.  But man, the included-angle of those "horizontal" stabilizers is insane.  Down elevator they will just act like a massive air-brake.


  • I know those guys aren't Airbus engineers, but the design was supposedly vetted by them. And I quote:

    There are two possibilities: either 1) you guys are right and all the Airbus team are idiots, or 2) there was a lot more documentation for each project that is not available to public yet. 

    As a judge who has seen all that additional documentation, I can give you a hint as to which of these is more likely. 

    And now we see the battery suspended on sticks ahead of the nose-cone, because they didn't even apply the sniff-test before building this thing.

    Here's where it was highlighted 3 months ago:


  • Moderator

    It is not Airbus engineers and it was just a best 3D rendering competition with little to no thought of the real world. Nice use of a felt tip pen on the control surfaces.

  • Remember when I said that the vehicle design was implausible because the designer completely neglected to consider the center of gravity.  And Chris responded that "surely you're not suggesting that you know more than the Airbus engineers" or something like that.

    Have to wonder how they got as far as they did with all those brains in the room....  Look at the story told by this series of images.

    I think this is after they finally realized they had a problem, and trying to think about what to do.  The man on the left has some carbon fiber sticks and is in deep thought.  "What can I do with these?"


    In this one, the plane is sitting on a standard CG measurement device.  "Hmmm... I guess the battery can't go there after all."


    Voila!  CG problem fixed!  Battery mounted on carbon fiber sticks, rammed through the fuselage, suspended ahead of the nose-cone.  That'll mess up the pretty styling of the original designer!

    3702312585?profile=originalt's going to take a while with engineering judgement like this.  How could anybody not see this problem coming before they got to this stage?  It boggles the mind.

  • Well... It is very optimistic to call it a flight test!! xDDDDD

    Anyway it is great to see it!

  • Developer

    you can watch it fly here ACDC Quarter Scale Test Flight 10-08-16.mp4

  • Well Chris is the head of Dronecode and Dronecode owns PX4 so it's not that far from the truth that it his flight system.

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