According to the AMA it's:
Park flyer models will weigh 2
pounds or less and be incapable
of reaching speeds greater than 60
mph. They must be electric or rubber
powered, or of any similar quiet means
of propulsion. Models should be
remotely controlled or flown with a
control line, remain within the pilot’s
line of sight at all times, and always be
flown safely by the operator.
A Park Flyer site can be either an
outdoor or an indoor venue. When
Park Flyer Definition
flying at sites specifically designed
for Park Flyers, the pilot will keep the
model within the established flight
boundaries of the field. Members need
to take into consideration several
factors, including piloting ability,
weight, size, and speed of the Park
Flyer model, to determine if a Park Flyer
site is an appropriate venue for flying
a particular model. The test should be,
“Can I fly this model safely and quietly
at this flying site?”
I started out park flying behind my yard, then had an incident involving a window....
I really do not recommend parkflying until you have had some instruction at a model club, or unless you have are really big (1500m X x 1500m +) park as a beginner.
I do fly in that field again, but now only my pusher prop flying wings or multiplex easystar fly there.