Had my first Phantom fly-away experience today after dozens of successful flights without incident. That is a terrifying and somewhat traumatic experience to watch my $1000+ craft/camera fly off out of my sight (towards a park full of people!), with me standing there worrying what kind of damage/injury could occur when it lands/crashes, and wondering if I'll ever recover it, and if I do, what condition it would be in. Short story: I dId recover it (in the park), less than a quarter mile from takeoff point. No damage (to the Phantom, or any property) and no injuries. Seems to have done a controlled auto-land. Had some explaining/apologizing to do to the people in the park that it came down near, but definitely got lucky. I believe it was possibly due to FPV transmitter interference (new, more powerful transmitter), or interference from other rc pilots in the area. Flew again same day (FPV disconnected) without further incident. Long story: I've recently got into FPV, and prior to today I've been using a FatShark 250mW 5.8MHz transmitter with SpiroNET antenna. Yesterday I replaced the 250mW transmitter with the Immersion 600mW one, hoping to improve reception at the receiver (FatShark AttitudeSD outputting to a 6" LCD). The 600mW FPV transmitter definitely improved the video reception significantly. The FPV transmitter is mounted externally on the Phantom (via velcro, and zip-ties), behind a GoPro in the stock mount. Its antenna hangs down, extending out beyond the main body under the Phantom LED. Pretty standard mounting setup, from what I've seen in the forums. Below the FPV transmitter, I hang a Garmin GTU10 tracker (more zip-ties), because I've read too many tales of Phantom fly-aways, and wanted to be prepared. Other than the FPV, the tracker, and some CF props, it's a standard Phantom with latest firmware. Beautiful warm day, minimal wind. Flying around an old broken-up runway in a field next to a park. One or two other people around me with RC foam planes (also 2.4GHz). As a rule, we only fly over the empty field, and never over the park. We were on the 3rd of 5 batteries, with nothing unusual occurring on the first two flights. Third flight of the day, took off after GPS home locked (fast green blinks). Flying in GPS mode. All seemed ok. FPV was on (my son was watching). It was about 150 feet away, when I lost all control of the Phantom. As it flew past me, and headed out towards the park, I noticed that it had a flashing orange LED. That's not good. It happened so fast there wasn't much I could do. I first tried to switch to ATTI mode, assuming something had gone wrong with its GPS positioning. That didn't help. Then I powered off the Phantom transmitter, hoping to kick the Phantom into fail-safe home return, but that didn't help either. Next thing I know, it was just gone. Sinking feeling inside. I ran towards the park, in the direction it had last been heading, launching the Garmin tracker app on my iPhone as went, and waiting for it to update the tracker position information. Then my phone rings. Not a number I recognize. I answer. "Did you loose a drone?" goes the voice on the other end. That was fast. "Um…., yes", I replied, worried about what was coming next. (On the sides of my Phantom, I have printed labels in big lettering that say "If found please call, xxx-xxx-xxxx") Well, It did come down in the park, in a grassy area near the playground. It was laying upside down on the grass when I got there (the guy on the phone told me where it landed, so I never ended up using the Garmin tracker to find it). Because it was upside down, the props weren't spinning, but when I lifted the Phantom, the props started spinning (so the motors had never turned off). From what they told me (but it wasn't fully clear), it sounds like it might have auto-landed in a controlled fashion, then flipped on its back after landing (wasn't a fully level landing area). I don't think it flew far enough away to have landed due to low-battery, so it might have gone into fail-safe landing, but had bad GPS position info so it landed in the wrong place. Luckily, there was no damage to the Phantom, or to any other property, and it didn't hit anybody. If it was a controlled landing, those are usually slow enough (and the Phantom loud enough) that people around it were aware of its presence, and could avoid its slow decent. After some explaining and apologizing to the people who had seen it land, I took it back to where we had been flying, disconnected the FPV, and few two more batteries, (cautiously, low, and nearby) without further incident. So, now the post-mortem. Why me? No, just kidding. I'm fully aware of the possibility of fly-aways like this occurring, and always assumed it could happen to me too. I'd taken precautions (Garmin tracker, for example), but hadn't fully considered that if it did fly away, it would likely fly out out our large empty flying field, and towards a more populated area (park, shopping center, etc). Definitely going to reconsider where its safe to fly in the future. Going to need a wider safety area. From what I can tell, the only difference today from previous flying days is the new 5.8MHz 600mW FPV transmitter (instead of the older 250mW one). Could that have led to this fly-away? I though it was mounted far enough away from the GPS and NAZA antennas to not interfere, but perhaps that's not the case? Is there a safe way to use that transmitter on the Phantom? Or, maybe the new transmitter has nothing to do with it, and it's just coincidence that my first fly-away was on the same day I replaced the lower power FPV with the higher power one. There were one or two other people flying 2.4GHz planes in the area. I suppose there could have been extra interference with the NAZA communication because of that, but I think the FPV is a more likely cause. What do you all think? Interference? Bad day? Anyway, traumatic experience, yet lucky that we get to fly another day. Will rethink the FPV (especially the higher power transmitter), and be more caution in the future regarding how much space we require to fly.