Sorry to hear you lost your quad, that sucks man. I just had the same thing happen to me. Flew it for a few mins testing loiter and RTL, all worked perfectly. Then I disarmed and disconnected the battery to mess with the cheap hobby king wing cam. Powered it back on waited a few mins just to make sure of a good gps lock (all the lights indicated it was so) then took off, first I switched to loiter and it started to head off so I switched to RTL and then it really took off heading to who knows where so I quickly switched back to stabilize mode and tried to bring it down gently. No such luck, since I couldn't see it clearly it went down a bit too fast and hit a chain link fence 150 yards away. I was able to retrieve it with just one broken prop. Going to put my info on it now per Richard Boyhan's suggestion. At least I got some good crash video lol.
My guess is that your barometer was not properly shielded from air currents from your props. If you are moving air and creating a positive pressure on the barometer then the same pressure reading you had on the ground with throttle at zero might be read at a much higher altitude!
Check out this user's experience: http://diydrones.com/profiles/blogs/important-note-for-apm-2-5-user...
Hey Mike Pursifull,
You stated: "Willie: I disagree. I believe your issue was caused by another problem. Namely, that you did not carefully read the manual before attempting to fly."
In stead of being opinionated, obnoxious, and rude, offer some good direction. Not all of us are good as YOU!!
Just a thought? Could the fact that the telemetry antenna was not fitted cause a brownout? If it is not there it will suck a load more power... As the problem certainly sounds like a brownout to me?
What did I not read in the manual?