The category "<rotary_aircraft_type-sing>" can be expressed as follows:

<rotary_aircraft_type-sing>

ah-64

black hawk

ch-47d

chinook

civilian chopper

civilian copter

civilian helicopter

civilian helo

cnn chopper

cnn copter

cnn helicopter

cnn helo

kiowa

neutral chopper

neutral copter

neutral helicopter

neutral helo

non-combatant copter

non-combatant helicopter

non-combatant helo

oh-58d

uh-60