Just picked up an Aerobird (flame all you want ), charged the battery, and it's doing something odd.

The moment the motor starts to turn, there is a rather obvious noise, like a high-pitched hum, which doesn't waver, change pitch or anything until the motor is turned off. It continues even if the motor is stopped by hand with the throttle on. I'm thinking it's coming from the electronics, but don't know why the makers would put an annoying whistle on a "silent" plane.

Any ideas?

BTW, it's not a low battery warning. This occurs on 2 different batteries at full charge.

Could be you're hearing the switching frequency of the ESC. It's in the right frequency range to be audible if there's something resonating. On the other hand it's not really "normal" either.

Cliff

If the Aerobird is anything like its predecessors, there's nothing wrong with it, and no shame in owning one. It's more of a toy than a serious airplane, but it appears to do a good impression of a "real" 3-channel electric sailplane.

I suggest that if you think something is amis, you should contact Horizon Hobby technical support. All the information you require is to contact them is at http://www.horizonhobby.com, or http://www.hobbyzone.com. Horizon's tech support is very reasonable to deal with.