3D Inverted Flying with a Quadcopter

Have you seen 3D RC Helicopter flying? Do you know that quadcopters can also fly inverted in 3D, by enabling your motors to rotate in both directions? Here SeekNDFPV shows you how he turned his mini quad into a 3D Aerobatics monster.

DISCLAIMER WARNING From SeekNDFPV:

I’m not an engineer but constantly changing the rotation direction of your motors during flight can’t be a good thing in the long run. Current draw goes up and down like a roller coaster, your motors could burn and eventually so can your ESC’s. I dropped rates but my motors still feel quite hot after a 3D session. Also, just because it’s possible doesn’t mean you should do it, which is exactly the reason why I immediately proceeded to do it!

Here is a demo video of the result:

What do you need to fly 3D with your quadcopter

  1. Reversible ESC’s that support bi-directional motor rotation
  2. Working with BLHeli
  3. Newer version of Betaflight (2.7 and above can certainly do it, I’m not sure if older version can do it too, I’m too lazy to check)
  4. A arm/disarm switch in your TX
  5. Balls of steel (most important of all)

Surprisingly the wonders of flying in 3D mode are quite well documented in Betaflight and it’s not that hard once you grasp the concept.

I’ll simplify the process in this tutorial, who really has time to read Github?

Configuring BLHeli

Connect your ESC’s to BLHeliSuite, either via flight controller pass through or using the one-wire method.

Remember to remove the props from your quad every time you connect the FC or ESC to your computer!

The settings you are looking for in BLHeli is Motor Direction. MAKE SURE YOUR ESC LETS YOU CHANGE IT TO “Bidirectional” FIRST! If not it probably means your ESC’s don’t support 3D mode.

bidirectional blheli 3d inverted flying

The settings I changed for each ESC were:

  1. Motor direction to Bidirectional
  2. PPM center throttle to 1500 ms
  3. PPM Min Throttle : 1040 ms (CHECK IF YOUR ESC ALLOWS FOR THESE VALUES)
  4. PPM Max Throttle : 1960 ms (CHECK IF YOUR ESC ALLOWS FOR THESE VALUES)
  5. Untick Programming by TX
  6. Motor timing to Medium

The rest leave to your liking.

Enable 3D in cleanflight configurator

This one is easy! Open cleanflight GUI and tick the 3D checkbox in the list of features.Also set the throttle deadband in 3D section.

3d_deadbandbetaflight cleanflight 3d inverted flying

I set mine to:

  • 3D low: 1425
  • 3D high: 1525
  • 3D neutral: 1500
  • 3D deadband throttle: 50

But you can adjust them to your liking.

In cleanflight you will also need to set a switch to arm/disarm (you can’t arm with low throttle+right yaw in 3D). It’s also important (but not mandatory) to set a switch to disable 3D mode.

Checking the motors and getting ready

  1. Remove your props, plug in a battery to your quad and connect it to cleanflight.
  2. Use the motor tabs to check if motor rotation is correct. You will see the motors sliders are already at the middle because of the 3D mode.
  3. If any of them are spinning the wrong way you will have to de-solder two of the motor wires and cross them. You can’t just change it in BLHeliSuite anymore, because the motor rotation settings has “bi-directional” selected remember?

I was using regular HQ 5×4.6 triblade durable props for testing, and they worked “fine”. However normal props are designed for 1 way rotation, and they perform less efficient (draw way more current) when spinning the opposite direction. So you’d probably be better off using some proper 3D propellers :)

Also, I had a better experience flying with the camera absolutely level to the frame, rather then angled.

You are ready to crash fly your quad now!

Some advice

Run a lipo or two first in regular mode (3D mode disabled). Use the 3D mode switch I mentioned before.

Once you are comfortable, you are now ready to activate 3D mode. While on the ground, set your throttle half way first before flipping the arm switch, and may god have mercy on your quad soul.

Go slowly and use the biggest open area you can find without any trees, people, vehicles around (100m2 felt small for me on my first go).

Run it upside down only for a few seconds until while you gain more confidence. It feels a bit like what you’d do when rolling half way and holding for a bit.

When you freak out (and you will), flip that disarm switch up. Your tendency will be to drop throttle all the way while flying, but instead this will invert your quad, sending it at full speed towards the ground or the sky, depending on which way your quad is facing.

Good luck and try not to hurt yourself, but if you do please record it on video.

Author : SeekND FPV

8 thoughts on “3D Inverted Flying with a Quadcopter

  1. MIchael

    Hi Oscar,

    stupid question – what does the motor do at exactly 50% throttle? Does it stop, or does it spin with positive min-throttle to ensure full airmode control? If it spins at min-throttle, how is the transition to reverse? Is there a reverse-min-throttle, so it will never spin less than min-throttle-RPM, no matter what direction?
    I am very very close to try on my Racer :-D

    Thanks,
    Michael

    Reply
  2. Mark Shaw

    What about micro quads with reversible motors? Are there any besides the nano qx 3D?

    Are there brushless escs for micro sized quads that can be programmed for bidirectional?

    Reply
  3. Chris H

    Is the only way to tell if the ESCs are reversable by setting them bi directional in BLHeli? Or is there a list of known reversable? (I just installed Little Bee Pros) also I reverse my motors in BLHeli to save resoldering two of them, will that be a problem if I want to try 3D?

    Also it might be helpful for some… When I was learning 3D on helicopters I set up a throttle curve in the TX that ensured bottom of the stick to mid stick was always centre pitch so flying in normal mode and 3D didn’t change the top half of the stick when I flicked the switch. It just enabled the reversed pitch which made transitions mid flight unnoticeable and it was easier to get used to the lower resolution and higher throttle stick position.

    Reply
  4. Bandook

    Awesome, didn’t realize it was this simple to configure. Is pitch also reversed when you are inverted?

    Reply
    1. Ari

      No, generally the motors simply start spinning in the opposite direction.

      There is one exception- Iirc it’s called ‘the Reaper’ and is the only collective pitch 3D quadcopter (that I’m aware of) that can do this.

      Reply

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