Interseting that hoss brings up the Straight Down factor.

While the AMA has made passing reference to level flight for the 60mph cap,
in most cases where someone or something was hit by a RC plane,
the plane was either going in some degree of downward vector or just concluded a downward vector,
cause folks & things aint up in the air, we are on the ground and any plane that hits us has to be going from up in the air to down on the ground.

Will all colissions be at StraightDown?
Heck no.
Will the majority of collisions be in some degree of downward travel?
Obviously.

In measuring "incapable" does that mean terminal velocity under power, or wing shear?
Just asking because, like Hoss alluded to, Incapable has a very distinct meaning, and planes that can only go 60mph sustained level are very well capable of grossly exceeding that in even just a 45 dive.

But I've also seen GWS Tigermoths land with a negetive goundspeed in controlled foward flight.

We are dealing with the technologies of batteries; planes that go 55mph on a 3s 11.1v battery might go 70 on a 3s 11.1v battery <of higher C or mAH>. Voltage load drop is a fickle mistress, changing out the 3cell for another 3cell can require retesting.... which means will we have clubs retesting every flight, or having to hold the guys hand as he changes bateries to make sure the exact same componants are used every time?

But sometimes it is just obvious the plane dont exceed 60mph, thus is safe, like this [link=http://www.zagi.com/media/ZagiFixxWebClip1.wmv]PF manufacturer video[/link] <check the 25second mark [X(][:@]>