Chapter 12: Lubrication and Cooling Systems

Flashcards covering lubrication and cooling systems concepts from the video notes.

What is the key component in an aircraft lubrication system?

Oil.

Besides lubricating, what are the other roles of oil in an aircraft engine?

It carries away heat and foreign material (dirt), and it seals between the cylinder walls and the piston to prevent the fuel–air mixture from entering the crankcase.

What does viscosity refer to in engine oil?

How easily the oil will flow at a specific temperature.

How does high temperature affect oil viscosity?

High temperatures make oil less viscous (it flows more easily).

How does low temperature affect oil viscosity?

Low temperatures make oil more viscous (it flows more slowly).

What are the two main oil types used in piston-engine aircraft?

Mineral oil and ashless dispersant (AD) oil.

Why is mineral oil not normally used long-term in aircraft engines?

It tends to form residue and carbon deposits at high temperatures and is less effective at lubricating and cooling.

What does 'break in the engine' mean in the context of oil?

Conditioning a new or overhauled engine, usually for the first ~50 hours.

What is ashless dispersant (AD) oil?

A petroleum-based oil with additives that reduce deposits and help clean the engine by loosening debris and carrying it to the oil filter.

How are oil viscosity ratings indicated in aviation?

By SAE rating and the commercial aviation oil number (usually double the SAE rating; e.g., SAE 50 = 100 grade).

Why might an engine operating in cold climates require lower-viscosity oil?

To ensure the oil flows adequately when cold.

Why might an engine in warm climates require higher-viscosity oil?

To maintain adequate lubrication as oil thins with higher temperatures.

What is a multi-viscosity oil example mentioned in the notes?

SAE 20-50, which acts like SAE 20 when cold and SAE 50 when hot.

Which handbook should pilots consult to ensure the correct oil type and amount?

Pilot Operating Handbook.

What are the two main lubrication system types?

Wet sump and dry sump.

Where is oil stored in a wet sump system?

At the bottom of the engine, in the sump.

What happens to oil in a dry sump system?

A scavenger pump moves oil from the bottom to a separate storage tank, keeping the bottom dry.

Which aircraft typically use wet sump vs dry sump systems?

Most small aircraft use wet sump; aerobatic aircraft use dry sump.

Name the main components in an oil system.

Engine-driven oil pump, oil filter, oil cooler, pressure relief valve, and screens.

What is the function of an oil cooler?

To remove heat from the oil; the oil may bypass the cooler if it is already cool.

What is the purpose of oil screens and oil filters?

Screens remove larger contaminants; oil filters remove finer material; a bypass valve allows oil to skip the filter if clogged.

What does the oil pressure relief valve do?

Regulates oil pressure by returning excess oil to the sump when pressure is too high.

How are oil pressure and oil temperature gauges typically indicated in the cockpit?

Oil pressure is shown in psi with green (normal) and red (min/max); oil temperature also has green and red indicators.

What might low oil pressure indicate and what should you do?

Engine may not have enough oil due to a blockage or seal failure; divert to the nearest aerodrome, keep power settings low, and be prepared for possible engine failure.

What might high oil pressure indicate and what should you do?

Pressure-relief valve not working; risk to the oil system; operate at lower power and land at the nearest suitable aerodrome.

What does fluctuating oil pressure suggest and how should you respond?

Could be due to a faulty bypass or relief valve; if within green range, not a major concern; if out of limits, treat as out-of-limits.

What could cause high oil temperature with normal oil pressure?

Hot day or high-power operation; reduce power and level the aircraft; if temperature does not drop, there may be too little oil circulating; divert.

What is air cooling and its main limitation?

Using outside air to cool the engine by directing it around hot parts; less effective at providing even cooling, especially at high power/low airspeed.

What are cowl flaps and when are they used?

Hinged covers on the engine cowling used to increase cooling by allowing more hot air to escape; opened during takeoff/climb, closed during cruise/descent (not all aircraft have them).

What is shock cooling?

Damaging rapid cooling of a hot engine, common in high-speed descents; can cause engine damage.

What is liquid cooling and its trade-offs compared to air cooling?

Circulates coolant around the outside of cylinders and through a radiator; provides more even cooling but is heavier, more complex, and less common in small aircraft.

Why is monitoring engine cooling important for pilots?

Early intervention can prevent overheating-related problems and engine damage.