"I have duplicated this on the bench and yep RTL without GPS. Interesting point Paul.
So what will the AP do with the aircraft if it does not know where it is? but chases are of having NO GPS in flight is very slim."

"This is helpful to know. the sensor I am using is the 3DR digital. 
Perhaps the warning / error is caused by too big a change in the sensor between samples.

Thanks Anthony.

I see many other posts from people asking about this but no explanation as…"

"Is this in Autotune mode or FBW?
If this is Autotune at first you will see no response, then a little response and will gradually build up as you manipulate the stick.

For auto tune, take off with PLENTY of room to fly in a state line upon entering…"

"Desired Roll is what the Flight controller wants the copter to do. 
Roll is what the copter is actually doing.

If there is a discrepancy between the two (amusing the PID are correct and the copter power to weight ratio is OK), this indicated there…"

"Are you using a satellite connected directly to the AP?
if so what satellite are you using? (OrangeRx, Spektrum:- DSM2, DSMX)
Which AP are you using?"

"OK here is one for you.
I have just been out testing a rig that is sealed. It is actually at positive pressure as there is a powerful fan sucking air in. the air intake is higher then the venting. 

It dawned on me just now. It held altitude well! …"

"OK I see a few people have watched the video.

So, because the body is enclosed there is no air flow internally. The ESC start over-heating and drop the power to the motors.
I can ASSURE you if this was a DJI FC the rig would have been lost. The Dji…"

"A good new year to you all.
Now a little challenge. I have replicated the above issue and after watching back video and logs have solved it.
I post a little video for you to watch. i have overlaid the motor outputs and at some points the inputs.
I…"

"Ah that makes sense."

"I see throughout the flight ChOut 1,2,7 and 8 are much higher then the others.  These are all CW blades. When the rig droops it is spinning CW. With all the CW blades high the copter should if anything spin CCW. 
So there MUST be a failure in one of…"

"Still, I bereave you have spotted an issue. Interesting the ESC's UBEC on Ch7 is used as a backup power for the FC. i wonder if something odd happened causing the UBEC to shut down, this would kill the ESC. 

There is a drop from 5.17 to 5 V around…"

"Andre, thanks for your reply. Please note this in an H frame not a X frame. The COG is dead center.
Also during the flight the rig had to sit at an angle most of the time as it was fighting 45mph wind. From memory when hovering it sat about 20 deg…"