I just did a quick demo video to show Arducopter 3.0.1 flying a large electric heli.  This is my new GreyHawk Maxi development frame.  Loosely based on TRex 550 mechanics, stretched to 700 size, and with a direct drive tail rotor motor.  The DD Tail gets rid of a lot of unreliable, noisy, vibrating geartrain.  The heli is very smooth and you can hear the blades instead of gears screaming.  In person, it's actually eerily quiet, if there's a wind out, you can barely hear it from a few hundred feet away.

This video is pretty tame.  But I wanted to show how stable the and precise Arducopter can be.  Normally I shoot test video in worst-case conditions, but most marketing videos are done to show perfect performance, so here you go.

This is only my 4th flight on this new heli, and I'm still getting it dialed in.  Alt Hold has absolutely no problem at all with the Asymmetric rotor blades.

This video is also the first appearance of the DD Motor control feature which should be coming out with 3.1.  The motor control for the tail motor comes out of Ch7.  The setpoint can be changed in MP, independently of the main motor setpoint. And it can be started before the main motor, or held on after the main motor is off (auto-gyro flight).  One very nice feature of this system is that you can have different flight modes on the main rotor, low speed and high speed, but the tail motor retains a set speed, even with a very low main rotor speed, so you retain tail authority.

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Comment by Gary McCray on July 28, 2013 at 9:33pm

Very Nice Robert,

Certainly one of the least frightening examples of this size of copter.

When my friend Oliver is flying one of his big Helis I always position myself well and directly behind him and he is a good pilot.

I know your's isn't intrinsically any safer, but at least it doesn't sound like its waiting for a chance to hunt you down and chop you into little bits.

And it is nice to see 3.1.x performing so well on a trad heli.

I'm going to recommend to Oliver he look at your video too.

Comment by Mark Harrison on July 28, 2013 at 10:19pm

Nicely Done!

What do you think is the smallest size heli that will be practical to control with APM?

Comment by Oliver on July 28, 2013 at 10:59pm

Nifty, Robert! Don't you love that "real" helicopter sound from those big blades? So, is that DD tail your own work? What sort of motor?

Comment by Gary Mortimer on July 29, 2013 at 1:43am

This might be a silly question but does the disc get in the way of GPS signals much?

Comment by R. D. Starwalt on July 29, 2013 at 5:05am

Well done RL! Thank you for the peek.

The DD tail has a separate ESC then?


Comment by Randy on July 29, 2013 at 5:48am

I've put an APM2.0 on a Trex250.  I flew it once or twice but the code was not as good then (by a long shot) and I moved over to multicopters soon after.

Comment by Rob_Lefebvre on July 29, 2013 at 6:35am

Mark, I'm not sure if there's a smallest size that APM will *control*, the limitation is actually more about the mounting.  Heli frames are very small, and cramped already as they tend to be made just big enough to house the components they are designed for.  Adding something like the APM usually requires some kind of subframe, especially on the smaller machines.  You can see that in Randy's picture, I have something like that on my 450 as well.  All of this extra mass starts to affect them, and the smaller the machine, the worse it is.  

Personally, I think even a 450 is a bit smallish.  A 500 would be just big enough.

Oliver, yes, the DD Tail is my work, though I got some inspiration from a few others.  The motor is an SK3 4250 350KV.  I needed an ultra-low KV motor to be able to run on 8S with a sane RPM.  Even with that, the tail ESC is running with a governor setting of 50%.  The motor is probably larger than it needs to be.  In the future, I want to do some power studies and see if I can use a smaller low-KV multi-rotor type motor.  

Having the motor out back really affects the CG, and ONLY makes sense if you're building a UAV system with a plan to have a payload on the front.  I'll eventually have a heavy camera and gimbal on the front.  As it is now, I've got 1.5 lbs of ballast on the nose!

Yeah... 1.5 lbs of ballast. Plus a Contour camera.

Ultimately, I'd like to move the tail servo right to the back as well.  

Gary, it doesn't seem to affect it.  We used to think it would, and placed the GPS WAY at the back near the tail motor.  But at some point I started putting it up front and found it just didn't matter.

Doug, yes, the tail has it's own ESC.  So this thing has a YEP 120A and 80A ESC.  I'd like to shrink the size of the tail drive system, but not having any data to start with I did the "go big or go home" approach. ;)

Comment by Josh Potter on July 29, 2013 at 1:19pm

Does the DD tail work out of the box with the APM or did you code that in?  What are the benefits of a DD tail these days (besides no need for a drive system)?  I've a few helis with them but there were small indoor size helis.

Comment by Euan Ramsay on July 29, 2013 at 1:52pm

There may be a grammar thing going on in your vid btw.

When the british say "the neighbours are not out", it means they are in their homes of gardens. Less than ideal when testing a big heli with new code...

However, I suspect you mean they are "not outside", so they are inside, and thus this is a safe test. Am I right?

Sorry to be pedantic...flight itself looks nice and smooth!

Comment by Euan Ramsay on July 29, 2013 at 1:53pm

homes *or gardens...doh.


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