RE: Electric helicopter motor vs electric airplane motor
The Kv parameter of a motor indicates the RPMs it will produce with a given voltage. A motor with Kv=3000 will turn approximately 3000 RPMs per volt, or 36,000 RPMs on a 12V pack. The higher the Kv, the higher the RPMs. You must also remember that high Kv motors have very little torque, and can only spin small props directly. If you over prop any motor, it will draw more current than it can handle, and you will fry the motor (and possibly your ESC and battery pack). Motors aren't really made specially for airplanes vs. helicopters. The higher Kv motors require gearboxes on planes to spin the prop, and require more down-gearing for helis. Lower Kv motors, such as outrunner motors, can direct drive props on airplanes, and require less down-gearing for helis.