MOD 4 Flashcards
DRIVE TRAIN
What is a Drive Shaft
drive shaft is one of the primary rotating components used to transmit power from one location to another
Supported Long Shafts
Some tail rotor drive shafts are single piece drive shaft. Typically made of aluminum, they are lightweight and can flex with the tail boom, ail Rotor Drive Shaft Hangar Bearings must support these drive shafts at regular intervals.
Unsupported Long shafts
Tail Rotor Drive Shafts that are unsupported are held at the forward and aft end of the drive shaft, with no supporting bearings in between. These are a simpler installation because of the lack of bearings, however the couplings need to be stronger to handle the additional weight and load
Segmented Shafts
A segmented shaft is a tail rotor drive shaft that is made up of short rigid sections.
Between each section will be some type of flexible or greased coupling.
Flexible Couplings
allow for movement between two parts. Flexible couplings have very strict damage limits. This is because the part is actually bending or deforming to work, therefore any defect could lead to a stress riser or failure point. Inspections of flexible couplings must be very detailed.
Types of flexing couplings
- the flex plate
- disk pack (Tomas coupling)
- Kamatics Ka flex
Greased Couplings
Under certain conditions a flexible coupling may not be able to provide the movement, or withstand the load required, so a greased coupling is used. These couplings are made up of an ,inner coupling and outer coupling. The parts are splined together and the gear teeth are curved (convex) to allow for movement between them. Once assembled, the inner and outer couplings are packed full of grease to provide lubrication between the steel parts as they move during rotation.
types of mast
- rotary
- stationary
Rotating mast
The mast of the helicopter must provide the support between the airframe and the main rotor. A rotating mast will be driven by the main gearbox and will drive the main rotor. Typically they are made of steel and are hollow.
Stationary Mast
Like a rotating mast, a stationary mast will support the flight loads of the helicopter however it will not drive the main rotor. A stationary mast is secured to the helicopter airframe or the main gearbox. A driveshaft will be inside mast to drive the main rotor.
Oil Cooler Blowers
Impellers are supported by bearings at either end. They tend to operate at high RPM so they are a balanced component, however some manufactures only require static balance.
Rotor Brakes
A rotor brake is used to slow or stop the rotor system after shutdown. Rotor brakes are spring loaded to the off position to keep the brake pads clear from the rotating surface.
Rotor brakes are either mechanically or ?
hydraulic operated. Those that use hydraulics will be totally separate from the helicopter flight control hydraulic systems.
Types of drive shafts
*segmented.
*one-piece or long shaft
– Supported (Bell 206)
– Unsupported (RHC)
Tail rotor driveshaft mounting
- Floating bushings
- Flexible or greased couplings
- Damper bearing (unsupported shaft only)
