Quill gearboxes are common in helicopters due to their relatively light weight caused by the hollow nature of quills. These assemblies allow different gear ratios, which let a helicopter change gears without switching through multiple gears.
Besides being light and strong, quill gearbox assemblies are also smaller than many other types of gear housings. This is because the quills are not only hollow, they are also smaller than most shafts connected to gears.
Helicopter gearboxes in general must be very rigid in construction, otherwise they will produce excessive vibration. Gearboxes need regular pre-flight inspection.
