(under subclass 4) Aeronautical machines sustained by the downward thrust developed by flapping or reciprocating blades attached to the machines. These blades may also be the propelling agents.
(1) Note. For machines having fixed sustaining airfoils as well as beating wings, see this class, subclass 11.
(2) Note. For lighter-than-air craft sustained also by beating wings, see this class, subclass 28.
(3) Note. For beating wings, per se, see this class, subclass 72.
