tandem-rotor helicopter (twin rotors mounted longitudinally)

dual rotors / twin rotors

twin rotors / dual rotors

tandem-rotor helicopter

engine mounted longitudinally

tandem-rotor system

lateral dual rotor system / side-by-side rotor helicopter

tandem charge

anti-tandem

dual-tandem landing gear

coaxial rotors

upper and lower coaxial rotors

tandem

wash from rotors

thrum of the engine (rotors etc.)

main-rotor head / main-rotor hub

main-rotor hub / main-rotor head

coaxial-rotor helicopter

single-rotor helicopter

side-by-side rotor helicopter

single rotor helicopter drone

air combat capable helicopter / air-to-air capable helicopter

ambulance helicopter / medical evacuation (MEDEVAC) helicopter

medical evacuation (MEDEVAC) helicopter / ambulance helicopter

twin

twin engine aircraft

twin-barrelled

twin-mount

twin detonating fuse

cam and twin lever

coupled twin engines

dual spacing of twin tires

twin-spool compressor