From Wikipedia
[link]http://en.wikipedia.org/wiki/Park_flyer[/link]
The term park flyer denotes a class of small, primarily electric powered radio controlled aircraft, so named because their size enables some of them to be operated within the confines of a large public park. Some are slow and docile enough to fly within an enclosed area such as a gymnasium or even a living room[1]; while others require the open space needed for larger models due to size and/or speed.
The definition of Park Flyers means that they are electrics. If you move up to a glow powered plane, no matter how small, it's usually not considered a Park Flyer any longer. If you try to fly a small glow powered plane where Park Flyer's normally fly you may find that it's not as accepted, or allowed, as the electric planes are.
My 2 cents worth
Ken