I have a Tarot 650 Sport quadcopter that I built. It uses an APM flight controller and is powered by four MN3220 T-Motors, which require 6S power.I have flown this several times, but recently made a few mods/adjustments, including adding 15"x5 carbon fiber props. I wanted to test it's flight endurance, using a 6000 mAH lipo, so I charged the battery pack and took it out to the field for a timed flight.
My plan was to start the stopwatch as I took off, retract the landing gear and put the aircraft in Circle mode and have it fly continuously in circles until the voltage failsafe was tripped and it returned to land. As soon as I put the aircraft in Circle mode, the motors behaved oddly - surging and dropping off; the aircraft wobbled a bit. I was soo spooked that I lowered the landing gear and took over manually. In a hover, everything seemed to be okay, so I put it back in Circle mode. The behavior returned, though not as bad - I let it continue flying in circles until the Failsafe was tripped and it returned and landed - the motors seemed fine during the landing sequence.
I had another quad, a modified Parallax Elev-8 that was similarly equipped; during a flight, it suddenly wobbled and essentially fell out of the sky, crashing and destroying the aircraft. I never figured out what happened and I'm afraid of repeating this with the Tarot.
Does anyone have any ideas what could be going on?