She crashed...

Weird birds here in Virginia...

Weird birds here in Virginia...

As I mentioned before, today was the maiden flight of the Ugly Duckling, the first drone that I've ever built (with some help).  Today also marked her third and final flight.  The good news is that the only thing that has to be replaced is the air frame.  All other components seem intact, though the receiver took a beating.

In other good news my son, who was watching, thought the crash was pretty awesome.

There were a lot of things that contributed to this crash and I'll detail what I know.  But first, maybe I should give some of the background.

About two weeks ago, I walked into a buddy's garage and saw a half-finished drone sitting on his shelf.  Turns out he had started the project three years ago but abandoned it two years ago due to lack of time.  I asked if I could take it over, he agreed, and I walked out with something in my hands I barely understood.

What followed was a solid two weeks of research and experimentation mixed with quite a few Amazon purchases.  Yesterday, we fully assembled the Ugly Duckling and today I took her up three times, the third of which she did not survive.

Who's parts are these, anyways?

So, these parts were second-hand to me.  But, uh, they were also partially second-hand to my buddy...

I know that the controller was second-hand and I think perhaps the flight control board was, as well.  He purchased the motors, ESCs and receiver.  The frame was a cheap $13 frame from eBay, which is part of the reason it didn't survive so long.

So, the first factor to all of this is that some unknown portion of the parts were second-hand with non-factory-default settings.

The Controller

The controller is a very nice, rather expensive and very capable Spektrum DX6i.  It is also solely Mode 1.  Mode 2 is what most folks in the US fly with and that is what I learned on.  Let's talk about the basics.

On any flight controller, there are two sticks, each of which moves up and down, and left and right (Oxford comma!).  On a quadcopter, these control:

  • Throttle:  How fast the rotors are spinning (consider this equivalent with speed, power and height)
  • Yaw:  Turning clockwise or counter-clockwise
  • Pitch:  Going forwards or backwards
  • Roll:  Going left or right (but not moving the nose of the quad)

In a Mode 2 controller, pitch and roll are on the right stick while throttle and yaw are on the left.  With a quad, at least so far in my experience, yaw is where things get tricky.  When you start playing with yaw, you end up changing the orientation of the quad and have to do some brain dancing in terms of your spatial relation to the quad.

In the Mode 2 setup, though, you can basically fly without yaw unless you need to.  So, you throttle the quad into the air and you can then move it in any direction with only the right stick using pitch (forward/back) and roll (left/right).

Now, of course I used yaw, but it wasn't strictly necessary.  I could kind of ignore it.

One last note, the stick that has throttle does not have a spring on the up/down portion.  This allows you to move the stick and set it, leaving it as it is, instead of having the stick auto-recenter.

In Mode 1, however, the setup is very different.  In Mode 1, the right stick controls throttle and roll, while the left stick controls pitch and yaw.  

My first two flights, I didn't know this.  I thought that Mode 1 was just the mirror of Mode 2.  So, as I took off, when I thought I was pulling the craft to the right, I was actually spinning it clockwise!  My first two flights were up and down, less than 20 feet traveled and probably no more than 20 feet in the air.  I wasn't confident.

On the third flight, though, I was more confident.  I gave it a lot more throttle and the quad darted forward and to the left.  I tried to correct for this with the appropriate stick movements, something that would have been without thought on a Mode 2 controller, but instead, I sent her hard right, then hard left, then upside down...  And, well, landing quads on their rotors from 30 feet is not well-advised.

However, this is not the whole story.

Unfamiliarity with the motors

 

I learned to fly on a Hubsan X4.  This is a tiny, tiny quad with tiny, tiny motors.  The Hubsan X4 is very spry for what it is, but if you want to go right, you throw the control full right.  If you want to go forward, you throw the control full forward.  There's just not a lot of headroom for max, if you will.

On the Ugly Duckling, my buddy had purchased 4 Angel A2212-9 motors.  Now, to put this in perspective, let's say that you had been drag racing with some kind of electric scooter and all of the sudden you sat down in a Ferrari and slammed the pedal to the floor.  My instincts to throw the sticks all the way over, while minimal at best on the Hubsan, were disastrous with the Ugly Duckling.  

All I really needed to do was twitch the controls!  As a result, I turned the quad over without even knowing I could do that.

The Kicker

After I collected everything, I went in to see if I had damaged any parts.  I did a quick receiver test and much to my horror I found out that pitch and roll were reversed.  I didn't have enough time with the quad to question it, but I kept pulling the pitch back and it kept going forward.  I thought I wasn't pulling hard enough, so I pulled back more.  What I was actually doing is sending the craft forward faster!  

Same thing with the roll.  I thought I was going right, but was actually going left...

Miscellaneous

There were also some funny artifacts with the board setup, but I'm not sure if this is an artifact of my testing, or some kind of weird motor config.

I'm still trying to diagnose what is reversing the pitch and roll.  It may be the controller, or it may be the flight board.  Not knowing if the flight board is second hand is not helping, so I'll likely do a factory reset.  I'm also going to try to convert the controller I have to Mode 2 some way.

But Wait...

Lest you think I took some dude's hobby project and slammed it into the ground from 30 feet, we decided yesterday to make a trade.  I gave him a MacBook Pro I had sitting around so he could learn iOS and I took the quad.

I am safely certain that, had I dropped the MacBook from 30 feet, it would be in worse shape.

I WIN!