співісні утримувальні гвинти
dual rotors / twin rotors
twin rotors / dual rotors
upper and lower coaxial rotors
tandem-rotor helicopter (twin rotors mounted longitudinally)
wash from rotors
thrum of the engine (rotors etc.)
coaxial-rotor helicopter
hollow shaft (of lower coaxial shaft)
through shaft (of upper coaxial rotor)
coaxial machine gun
coaxial mounting
coaxial