My FMS Skytrainer is "barking "

[Prowler901]

I have an FMS Skytrainer that is a few months old. I love the plane. But it has recently developed a strange issue. After a few minutes flying it starts to "bark". The sound seems to be at regular intervals. Then the plane loses power. I can still control it, but there is no motor power. I've been lucky to get it down in one piece. The batteries I'm using are new Admirals and fleshly charged. I can normally get 8 minutes flights. But this happens after about 3 minutes now. I've run it up on a test stand, but it won't do it there. Could this be a sign that the ESC is going bad?

[xviper]

I doubt it's the ESC. They either work or they don't - it's an electronic device, no moving parts. Also, they don't make noise. What they do is make the motor make the noise. I think it could be a motor bearing or a motor magnet that's loose. Run it on the ground at about the same throttle as when you're flying but be careful to guard the propeller so nobody gets in its way. Secure the plane properly. I'd normally suggest you take the prop off but I think you need the load to duplicate what might be happening. When it begins to "bark", run it for a bit longer, then shut it down, disconnect the battery and carefully feel the motor for excessive heat. Don't burn yourself. If it's really hot, then it's something in the motor. Try turning it by hand to see if it's stiff or hard to turn or makes any noises. You should know what it feels like to turn it when it's NOT barking. It wouldn't hurt to feel the ESC. If it's just warm, it's likely OK. If it's the motor, best option is to buy a new motor. They shouldn't be too expensive.

[fhhuber]

Could be arcing between motor phases at the bullets, since there is typically a gap in the insulation there.
Has it been more humid lately? That makes the arc jump more easily.

A few other possibilities but I'd start there.

[Prowler901]

Thanks for the suggestions, guys. I'll take a closer look at the motor.