Engine Cooling Systems
1. What is meant by pressure cooling of an aircraft engine? - Air cooling in which air is forced to flow
through baffles and cylinder fins by a pressure differential across the engine.
2. What is the purpose of an augmentor tube in the cooling system of an aircraft reciprocating engine? -
The augmentor tube uses the velocity of the exhaust gases to produce a low pressure on one side of the
engine that helps pull cooling air through it.
3. Where is the highest temperature located in a turbine engine? - At the inlet to the high-pressure
turbine.
4. How are the turbine inlet guide vanes and the first-stage turbine blades in some turbine engines
cooled? - High-pressure compressor bleed air flows through the hollow guide vanes and hollow turbine
blades.
5. Which side of an air-cooled engine cylinder has the greatest amount of cooling fins? - The side of the
cylinder in which the exhaust valve is located.
6. What should be done to repair a bent cooling fin in a cast aluminum cylinder head? - It is normally
best to leave a bent cast fin alone if it does not restrict the flow of air. Cast fins are brittle and could
break off.
7. What is used in a helicopter to increase the amount of cooling air that flows over the engine
cylinders? - A belt-driven fan.
8. What should be the position of the cowl flaps on a reciprocating engine when it is run on the ground?
- They should be wide open when operating the engine on the ground.
9. What is the function of the majority of the air that passes through a turbine engine? - Most of the air
is used for cooling.
10. How does metallic sodium in an exhaust valve aid in transferring heat? - The sodium melts when the
engine is running and it sloshes up and down as the valve operates. The sodium picks up heat from the
valve head and carries it into the stem so it can be transferred to the cylinder head and dissipated into
the air.
11. How is the structure around a turbine engine protected from excessive heat from the engine? - An
insulating blanket protects the structure from excessive heat.
12. What is the function of blast tubes that are installed in a pressure cooling system of a reciprocating
engine? - These blast tubes direct cooling air to the magnetos and the generator.
1. What is meant by pressure cooling of an aircraft engine? - Air cooling in which air is forced to flow
through baffles and cylinder fins by a pressure differential across the engine.
2. What is the purpose of an augmentor tube in the cooling system of an aircraft reciprocating engine? -
The augmentor tube uses the velocity of the exhaust gases to produce a low pressure on one side of the
engine that helps pull cooling air through it.
3. Where is the highest temperature located in a turbine engine? - At the inlet to the high-pressure
turbine.
4. How are the turbine inlet guide vanes and the first-stage turbine blades in some turbine engines
cooled? - High-pressure compressor bleed air flows through the hollow guide vanes and hollow turbine
blades.
5. Which side of an air-cooled engine cylinder has the greatest amount of cooling fins? - The side of the
cylinder in which the exhaust valve is located.
6. What should be done to repair a bent cooling fin in a cast aluminum cylinder head? - It is normally
best to leave a bent cast fin alone if it does not restrict the flow of air. Cast fins are brittle and could
break off.
7. What is used in a helicopter to increase the amount of cooling air that flows over the engine
cylinders? - A belt-driven fan.
8. What should be the position of the cowl flaps on a reciprocating engine when it is run on the ground?
- They should be wide open when operating the engine on the ground.
9. What is the function of the majority of the air that passes through a turbine engine? - Most of the air
is used for cooling.
10. How does metallic sodium in an exhaust valve aid in transferring heat? - The sodium melts when the
engine is running and it sloshes up and down as the valve operates. The sodium picks up heat from the
valve head and carries it into the stem so it can be transferred to the cylinder head and dissipated into
the air.
11. How is the structure around a turbine engine protected from excessive heat from the engine? - An
insulating blanket protects the structure from excessive heat.
12. What is the function of blast tubes that are installed in a pressure cooling system of a reciprocating
engine? - These blast tubes direct cooling air to the magnetos and the generator.
