It is the special transmission that converts engine horizontal motion to vertical rotation for the rotor
Helicopter blades operate from a transmission or gearbox immediately under the blades. They have to spin fast to give the helicopter lift. Once they are in the air the blades twist slightly to give forward motion.
gearbox
Question is not very clear. Most modern Helicopters are powered by turbo-jet engines that drive a transmission gearbox to turn the rotor blades. Jet engines have been attached to the tips of the main rotor blades. This design was used to turn the blades faster and have a smaller engine and gearbox. The forward velocity of a typical helicopter is limited by the tip speed of the rotor blades. The tip speed of the advancing blade is the sum of the airspeed of the helicopter and the speed of the blade. That is why helicopters are limited to ~150mph. If a jet engine was installed to push it faster, then either -A- the rotor blade would hit the sound barrier and become unstable or -B- the rotor blade would have to be stopped and the helicopter would have to fly using lift from a wing.
in the gearbox
i hate the word gearbox
gearbox!
A gearbox is another name for a transmission.
In the gearbox
A purple helicopter is a helicopter of the color purple. Really?
The 1997 Honda Civic gearbox has a fluid capacity of 4.8 quarts. You can check the gearbox fluid level with the gearbox dipstick.
Everybody I know says A helicopter.
behind the gearbox