15.10 Lubrication systems Flashcards
(26 cards)
Whats the difference between wet and dry sump lubrication systems?
Oil is stored inside the engine casing in a wet sump
Oil is stored in an external tank for a dry sump system
How is oil circulated in a lubrication system?
By pressure and scavenge pumps.
What is a full flow system?
The oil pressure varies with N2 rotor speed and temperature. No regulation.
Whats a constant pressure system?
Uses a regulating valve to maintain consistent pressure across all speeds/ temps
What are the advantages and disadvantages of a full flow lubrication system?
✅ Simple, no maintenance adjustments.
❌ High pressure at high speeds.
❌ Oil temp can rise after power reduction.
What are the advantages and disadvantages of a constant pressure system?
✅ Consistent oil pressure.
❌ More complex system.
Which lubrication subsystem stores and delivers oil?
Oil reservoir and supply system
Which subsystem returns oil back to the tank?
Scavenge system
Which subsystem regulates air pressure and vents oil vapour?
vent/ breather system
Which subsystem monitors oil temp, pressure. quantity and condition?
Monitoring system
What pressure does the lubrication system oil tank maintain and how?
~4 psi pressure via check relief valve (for pump inlet)
Whats the oil tank made of?
Aluminium alloy, silicone-coated for fire resistance
What spills the oil safely?
Scupper drains
What removes air from returning oil?
Dearator tray
What is the oil flow path?
Oil tank → pump → pressure filter → oil coolers → bearings/gearboxes → scavenge pumps → oil tank
Whats the two types of oil pumps?
Gear pump - most common
Gerotor pump - smooth flow, compact
What does the bypass valve do?
Skips cooler when oil is cold or cooler is blocked
What is the thermostatic bypass valve?
Bypasses cooler when oil is too cold, once the oil has heated up it routes it through the cooler to ensure it’s at the correct temp
Where is the bypass valve?
in the oil filters and screens
Where are the last chance filters?
upstream of bearings
What is the main oil cooler in jets?
Fuel- cooled
What oil cooler is used in turboprops & APUs?
Air cooled
Whats the cold tank system?
There’s a cooler in the scavenge line (before oil returns to the tank)
Cool oil in the tank
Whats the hot tank system?
Oil from the tank goes directly tothe cooler
cooled oil goes to the bearings/ gearboxes
Scavenge pumps return hot oil directly back to the tank
