Originally Posted by Cpt Crash

The surging is probably the BEC kicking in. For some reason, your battery is not fully charged or it may be defective. If the battery is old, it may be beyond its service life.

I purchased a new 2100 mAh E-flite battery for my T-28 and took it out for a bit of flying. Did a quick flight of about 3 minutes just to see how things worked out, and then landed. Took off again, and on the first lap around the pattern as I buzzed by, I heard the surging of low power. Damn. Should have landed, but like a fool tried to go around and set up an approach. The power dropped, the BEC shut off the motor, and I glided in to a shrub. No damage. Turns out the "new" battery had sat on the shelf for too long. Fortunately, the good folks at the shop were only too happy to get me a fresh one, which performed as expected.