Motor order and first flight

Hello everyone,

My son and I just built a qav250 with the pixhawk using the qbrain esc and finally got it off the ground. But things did not go well.

When buiding the quad, we setup the motor order per the diagram: … s-pixhawk/

in the quadX layout resulted in the quad wanting to flip upside down. After reading that the flipping issues was likely a motor order issue, I tried different sequences. What I found one that finally got the quad into the air, and it was:


Where 2 is the front left, 1 is front right, 3 is rear left, and 4 is rear right from the back to front perspective.

In this configuration, the quad lifted off but was going forward pretty fast. I was able to get this a bit better than allowing more than a few seconds of flight with positioning the battery further toward the rear and adjusting the trims on the radio.

This got the quad about 5 feet off the ground and for a short time relatively controllable. Then the quad decided all on its own to shoot up to about 20 feet, hover for a bit then drive itself nose first into the ground. This snapped off a couple of the screws on the front standoffs, dinged up the props, and ruined a couple cables, yet everything else seems to have survived okay. When it took off on its own, the quad did not respond to any radio controls.

I am a bit gun shy now about flying it again until I have a better understanding about what is going on. I have to order some new cables to get if flyable again but since the motor order does not match up the prescribed sequence, I am wondering what has gone wrong.

Any advice/ideas would be much appreciated.

It almost always helps to include the .bin file to get any useful response.

When you tried the suggested Quad X layout did you insure that all the motors were rotating in the correct direction for their locations?

I looked at the .bin files an not really sure which one corresponds to the event. So once I get it running again, will get that data.

As for motor rotations, I have the motors rotating per the initial layout plan 3,1,2,4 and I am not certain if the motors direction and props need to be switched out with the 2,1,3,4 layout. All props are generating thrust in the proper direction but not certain if I need to make adjustments due to the different motor layout. … ads_PH.jpg

Since motors 2 and 3 are swapped, should the rotation and props be switched?

The direction the props turn, is always same for a given location, front left, front right, rear left, rear right, regardless of the numbering.

The leading edge (high side) swings in toward the center line. On the front the leading edges move towards the back as they rotate. On the rear they move toward the front as the rotate.

So you need three things right.

  1. The right motor # in the correct location.
  2. The correct rotation direction of each motor for its location.
  3. The correct prop, CW or CCW on each motor based on its location and direction of rotation.

If any one of those are wrong you won’t stay in the air long, if you even get off the ground.

If #s 2 and 3 above are correct but #1 isn’t you may get airborne but then any directional command (from either the (FC or TX) will lead to undesired movement/crash.