11.11 HYDRAULIC POWER Flashcards
(54 cards)
What is Hydrostatic pressure
Pressure produced by static build up in aircraft hydraulic system
What is hydrodynamic pressure
Pressure produced by moving liquids ideally with no friction
Explain open-centre
- series
- only operate 1 component at a time
- slower as pump
- selector valve for each system
Explain open-centre
- series
- only operate 1 component at a time
- slower as pumps Needs to supply high pressure (delay)
- selector valve for each system
Explain closed centre
- parallel connection
- multiple sub-systems can be used at one time
- Pressure build up if selector valve is neutral
- quicker response due to pressure build up
Explain viscosity
- Internal resistance to flow
- Viscosity increases as temperature decreases
Explain flash point
Temperature at which liquid gives off vapour in sufficient quantity to ignite momentarily
Explain Fire point
- temperature at which a substance gives off vapour in a sufficient quantity to ignite and continue to burn
3 types of hydraulic fluids
- minerals
- polyalphaolefins
- phosphate esters (skydrol)
What are the 2 classes of Phosphate Ester-based fluid (skydrol)?
- class 1 fluids are low density
- class 2 fluids are standard density
2 types of main servicing activities for hydraulic systems
- Reservoir filling
- Fluid sampling
What are the 2 ways reservoirs can be filled
- manually
- pressurised
Where is the hydraulic sampling valve located
- HP manifold of each hydraulic system
What are we looking for when carrying out a Hyrdraulic fluid sampling
- checks for water contamination
- reduction in fluid performance
How often is Hydraulic sampling scheduled
- every 1 year
- every 3000 flight hours
If hydraulic contamination is suspected what should be done
- fluid should be drained and replaced
- samples should be taken too
What is the function of the Hydraulic Reservoir
- storage
- replenishes fluid lost through leakage for operational needs
When are non-pressurised reservoirs used
- aircraft that do not fly at high altitudes
When are pressurised reservoirs used
- high altitude
- usually reservoirs located in non-pressurised areas like wheel wells
What is a pressure relief valve
- prevents excess pressure
How do you de-pressurise between the pump and the user?
- operate flight control to force fluid back to reservoir
What are the 2 servicing activities for hydraulic systems
- Reservoir filling
- Fluid sampling
Where is the Reservoir pressurisation module installed and what is its function
- Installed close to reservoir
- supplies aircraft bleed air to reservoirs
What are the 2 types of accumulators used on aircraft
- Spherical
- Cylindrical
