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Hi Guys

I recently built up my APM2.5 powered FPVManuals QAV500 frame with the following components:

• FM-4006-13 740kv Motors
• FPVManuals 30AMP SimonK Flashed ESCs
• APM2.5 with 3DR Ublox GPS and Telemetry
• Immersion EzOSD, 600mw Video Transmitter, FatShark CCD Killer FPV camera, 2000mah 3s battery - for FPV electronics
• 4000mah 4s Nano-tech battery - for main power

This is the first quad I have built using the Ardupilot APM2.5 (my other Quads use KK2 board or other proprietary board). Initially after building the QAV500 Quad, I did all the calibrations (compass, accel, radio ..etc). I have also programmed all the flight modes (6 modes - with a combination of a 2 position and 3 position switch on the Hitec Aurora 9) as well as setup failsafe when the transmitter is off. At first I was able to take off and fly the quad, although there was quite a bit of low speed oscillations on the motors. I started adjusting PID settings and tried to use other PID's from others with the same frame and similar motors, but only seemed to get worse (high speed osciallations) - even when lowering P rate.

I have subsequently reset the APM back to defaults and done the calibrations again, but I seem to have a very weird issue. After ARMing the quad, In Stablize mode, I add throttle to the minimum for the motors to spin (and I don't add any more throttle), but the motors slowly increase in throttle by itself and I have to cut throttle before it almost takes off. I tried to adjust the THR_MIN value to a lower or higher value than default, but doesn't seem to eliminate the "ghost" throttle increase.

I would really appreciate your input on what I can do from here, I've been very cautious to take this Quad for a proper maiden flight until I get this issue and the PID tuning sorted..