Hello, first post from me regarding a problem I witnessed yesteday with my sons F450.

I fly a Phantom 2 & my son & I built up an F450 from a kit purchased at the local model shop.  We've conducted several test flights on the 450, tested all radio functions and concluded that the model was flying properly. It's responsive, holds a stable hover and the return to home function works properly. Prior to take off after waiting for full GPS aquistion & home-lock my son armed the motors & took off.  Straight away the 450 began to drift slowly into the wind. he tried correcting the drift but the model gained approx 5 metres altitude & rolled to the left at a contant angle gaining a lot of speed in the first ten metres.  He activated the return home function but there was no response from the 450 which crashed, ending up inverted with the motors still running. I had to disconnect the battery to stop it. There was no damage apart from a little grass burn )

We bought the model with a Graupner radio as there were none of the DJI radio's available at the time.  All of the SW updates are in place & the GPS/compass antenna have been correctly configured in the XYZ axis. The compass was calibrated at home approx 3 miles from where we were flying at the time. We didn't carry out another compass calibration prior to this flight.

After a brief clean up we flew the model until the remaining batteries were used without any further issues.

Any help or info on why this could have happened would be greatfully received.

Thanks in advance.

Dave,

If the motors continued to spin with the throttle stick below 5% and the f450 upside down then the flight controller is bad..  So the question here is, where your throttle stick was when it was running upside down? If your tx or rx hiccuped somehow this could of also happend..  I would blame the control system before naza..  I have 2 f450's and 1 f550 all with naza-m v2 controllers and in over 2 yrs and at least 2000 15 to 20 minute flights I've never had any kind of problem with naza...  Knock on wood..

Also make sure the receiver fail safe is setup to send 50% throttle and return to home signals to naza in the event of tx signal loss..  

I had a friend bind his rx to his tx with 65% throttle and the elevator stick pushed all the way up and when is rx and tx lost sinal with each other his flamewheel started going higher and flew away on him because of where he accidentally set the receivers fail safe but he got lucky cuz of naza's advanced receiver protection and when naza seen the input signals  from his receiver not change for 20 seconds it put itself into Return to home  mode and came back and landed..  And that same thing could of happend to you except yours hit something as it was flying off which made the craft hit the ground..

The only way naza would let the motors run while the craft was upside down on the ground is if it was receiving a throttle input greater than 20%...  Now if the throttle was all the way down while the motors were running with the craft upside down then either the rx was sending a throttle signal to naza telling it the throttle was higher than 20% but if the rx was sending a throttle sinal telling naza it was under 20% then naza is bad which I doubt..  

Many thanks for your very detailed response.  I'm going to go over this with my lad & try to piece together exactly what position the controls were in during the crash sequence.

We've flown the F450 several times since the loss of control with no problems.

Many thanks, David.