Aviation Lubrication Systems Chapter 9

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Questions and Answers

What is the primary purpose of the lubrication system in a turbine engine?

To increase fuel efficiency

To facilitate regular inspections of engine components

To provide lubrication and cooling for gears and bearings (correct)

To protect against electrical interference

Which characteristic is essential for aviation lubricants used in high altitude environments?

High conductivity to reduce heat

Thick viscosity for better cushioning

High volatility to enhance lubrication

Low evaporation rate (correct)

What is a significant drawback of the wet sump lubrication system?

It requires more maintenance than dry sump systems

It is more efficient than dry sump systems

It can facilitate overheating of engine components

It is heavier due to the oil contained within the engine (correct)

Which of the following is NOT a requirement for aviation lubricants?

Low flash point for safety Signup and view all the answers

In a dry sump lubrication system, what components manage the flow of oil?

Pressure and scavenging pumps Signup and view all the answers

What role does oil damping play in a lubrication system?

Reducing vibration Signup and view all the answers

Which oil system is most commonly used in modern turbine engines?

Dry Sump Lubrication System Signup and view all the answers

What issue can arise from the accumulation of metal particles in the lubrication system?

Potential damage to moving parts Signup and view all the answers

What role does the pressure relief valve play in a full flow oil system?

It returns excess oil to the tank when the pressure exceeds a set limit. Signup and view all the answers

Which component primarily functions to remove metal chips from oil in the system?

Magnetic chip detector Signup and view all the answers

What is the purpose of the deoiler in the oil system?

To remove oil mist from the breather air. Signup and view all the answers

How is the size of the pressure pump determined in a full flow oil system?

According to the flow rate required at maximum engine speed. Signup and view all the answers

What is the first step in the operation of the full flow lubricating system?

Oil is sent from the tank to the pressure stage. Signup and view all the answers

In which component is oil filtered before it is sent to the engine?

Main oil filter Signup and view all the answers

What happens when the oil pressure before the main filter exceeds the set pressure?

Oil is returned to the supply tank. Signup and view all the answers

Which component is responsible for distributing oil to the various parts of the engine after cooling?

Manifold Signup and view all the answers

What is the primary purpose of magnetic plugs or chip detectors in a lubrication system?

To collect ferrite debris and warn of impending bearing failures. Signup and view all the answers

Where are coarse strainers typically located in the lubrication system?

At the outlet of the oil tank or before the pumps. Signup and view all the answers

How can a 'pop up indicator' in a filter system assist maintenance?

It provides a visual warning of a partially blocked filter. Signup and view all the answers

What is a potential consequence of exceeding the contamination limits set by the manufacturer?

The engine may face an impending failure. Signup and view all the answers

Which type of oil is primarily used in modern gas turbine engines?

Synthetic oil, such as Mobil jet type II. Signup and view all the answers

What is the significance of a sight glass or gauge in the oil tank?

It allows for the monitoring of oil quantity. Signup and view all the answers

What warning typically indicates the need for immediate engine shutdown?

Low oil pressure warning signaled in red. Signup and view all the answers

What is one method of cleaning a cleanable filter mentioned in the content?

Implementing an electronic ultrasonic cleaning device. Signup and view all the answers

What is the primary function of the oil pump assembly in an engine?

To ensure consistent lubrication and pressure of oil throughout the engine Signup and view all the answers

How does a gear pump function to deliver oil?

It draws oil into the pump using intermeshing gears that transport oil between them Signup and view all the answers

What is the main purpose of the pressure relief valve system?

To limit the pressure in the oil feed line to prevent damage Signup and view all the answers

What distinguishes an air-cooled oil cooler from a fuel-cooled oil cooler?

Air-cooled systems utilize ambient temperature while fuel-cooled systems rely on fuel temperature Signup and view all the answers

In the context of oil pump operation, why is a weak shear neck not utilized?

Continuous oil supply is critical, requiring robust pump operation despite potential damage Signup and view all the answers

What is the role of the magnetic chip detector in an engine lubrication system?

To detect metal particles in the oil indicating wear or failure Signup and view all the answers

What is the primary purpose of incorporating a sight glass or dipstick in the lubrication system?

To allow operators to manually check the oil level Signup and view all the answers

How is heat transferred from the oil to fuel in a fuel-cooled oil cooler?

By circulating oil around heated fuel tubes without mixing Signup and view all the answers

Study Notes

Chapter 9: Lubrication

This chapter discusses lubrication systems in jet engines, referencing Rolls Royce 1996
Introduction
- Facts on lubrication systems
- Requirement of lubrication systems
- Types of oil systems
- Operation of oil systems
- Components of oil systems
- Important facts on oil systems
- Recap

Introduction Lubrication System

The lubrication system is needed for lubrication and cooling of parts like gears, bearings, and splines
The system must collect foreign matter—if left in a tank, housing, or gearbox—and protect components made from non-corrosion resistant materials without significant deterioration

Purpose of Turbine Engine Lubrication

Lubrication reduces friction and wear
Cleaning removes metal particles to prevent further damage
Cooling prevents material degradation and seizure
Oil damping reduces vibration

Requirements of Aviation Lubricants

Low volatility reduces evaporation at high altitude
Anti-forming characteristics ensure positive lubrication
High flash point minimizes ignition risk
Wide temperature range ensures proper operation across various temperatures
Excellent film strength ensures cohesion and adhesion, while a high viscosity index ensures viscosity retention during heating

Types of Oil System

Discusses various types of oil systems, likely including wet sump and dry sump. (Further detailed information about these follows)

Wet Sump Lubrication System

The oldest design, rarely used in modern engines
Oil is contained within an engine sump, submerging lubricated parts in oil

Dry Sump Lubrication System

Used in most modern turbine engines
Consists of pressure system to deliver oil, scavenge pumps to return it, and a breather vent
Oil is delivered to parts by a pressure pump and returned by scavenge pumps

A Full Flow Type Oil System (Dry Sump)

Achieves desired oil flow rates based on maximum RPM
Excess oil returns to the supply pump via a pressure relief valve
Pump size is determined by maximum engine speed requirements

Operation of Oil System

Overall view of a full flow lubricating system, including components like oil pumps, filters, sensors, tanks and more.
Operation (Supply): Oil flows through filters to a heat exchanger, then to a cooler, and across a manifold to various engine parts. If pressure is too high a relief valve returns it to the tank.
Operation (Scavenge Line): Oil is removed from components, then through a filter, then through a sensor and into the tank.
Operation (Breather Line): Oil mist is removed from the breather air, which is vented overboard.

Components of Oil System

Details of common components:
- Oil Tank
- Pressure & Scavenge Pumps
- Pressure Relief Valves
- Fuel Oil Heat Exchanger / Oil Cooler
- Air Oil Heat Exchanger
- Deoiler / Centrifugal Breather
- Magnetic Chip Detectors
- Filters

1. Oil Tank

Typically mounted on the engine or in the external gearbox
Provisions for draining and replenishment
Sight glass or dipstick for manually checking oil level

2. Oil Pump Assembly/Oil Pump

Gear pumps: Pair of meshing steel gears in an aluminum casing, used for delivering oil under pressure and/or returning oil to the sump
Other pumps: Vane type, etc
Oil pumps are crucial for efficient engine operation
Pump drive shafts don't have weak shear points; ensuring continuous oil supply, regardless of damage.
Supply and scavenge pumps are often integrated within an assembly

3. Pressure Relief Valve System

Controls oil flow to bearing chambers by limiting pressure
Uses a spring-loaded valve to return excess oil to the tank or pump inlet, when pressure exceeds a predetermined design value

4. Fuel-cooled Oil Cooler / Air-cooled Oil Cooler

Transfers heat from oil to fuel / air to reduce oil temperature
Multiple tubes carry fuel alongside oil streams directed by baffle plates
Uses either fuel or air as a cooling medium

5. Air/Oil Heat Exchanger

Facilitates heat transfer between oil and air

6. Centrifugal Breather

Removes oil mist from breather air through centrifugal force

7. Magnetic Chip Detector

Catches ferrous metal particles to prevent bearing damage
Using magnetic plugs, or chip detectors,
Designed for removal during inspection for condition monitoring purposes.

8. Filter

Prevents foreign matter from circulating through the system
Coarse strainers at oil tank output or prior to oil pump inlets prevent damage
Fine pressure filters catch very small particles that could block oil jets.

8. Electronic Cleaning of a Cleanable Filter

Traditional solvent cleaning is still frequently used.

Important Facts on Oil System

Most modern turbine engines use synthetic oils (e.g., Mobil jet type II oil, Exxon 2380)
Oil tanks are typically checked 10 minutes after shutdown
Oil levels are tracked on sight glasses, gauges or LED screens
Specific values of low oil pressure / high temperature trigger an immediate engine shutdown

Recap

Covers the need for lubrication, the basic principles/purposes of engine lubrication,
distinctions between wet and dry sump systems, hot oil tank full flow diagram with component operations,
critical facts concerning oil systems that cause engine shutdowns

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Description

This quiz covers Chapter 9 on lubrication systems in jet engines, focusing on their importance, types, and operational aspects, referencing Rolls Royce 1996. Learn key facts about the requirements and components of aviation lubrication to enhance engine performance and reliability.