COOLING SYSTEMS

Question 1

what effect does excessive heat have on reciprocating engines

Answer 1

it shortens the life of the engine parts changes the behavior of combustion and impairs lubrication

Question 2

what is the purpose of cooling fins

Answer 2

they provide a larger cooling surface area for removing heat from the cylinder heads of air-cooled reciprocating engines air flow around the cooling fans transfers the heat from the cylinder heads into the air

Question 3

what are the reasons for using engine cowlings baffles and cowl air seals

Answer 3

the cowling performs two main functions it streamlines the engine area to reduce drag and is used together with the baffles and cowl air seals to direct airflow over the cylinders for cooling

Question 4

what is the purpose of cowl flaps and how are they operated

Answer 4

they are used to control the amount of airflow through the cowling they are either mechanically electrically or hydraulically operated

Question 5

how does an augmented cooling system work

Answer 5

an outer tube placed over the existing exhaust gas creates a venturi effect that draws more airflow over the engine thus providing additional cooling

Question 6

where should cowl flaps be positioned for ground operations

Answer 6

fully open

Question 7

what type of power is used to operate cowl flaps

Answer 7

manual hydraulic or electrical

Question 8

what should be done when cooling fin damage is discovered

Answer 8

depending on the scope of the damage some cooling fins may be repaired subject to the manufacturer’s overhaul and repair limitations if an excessive amount of cooling fin is broken off the cylinder should be replaced

Question 9

why is cowl flap adjustment important

Answer 9

the movement must be within tolerances to keep cylinder head temperatures within allowable limits

Question 10

how are turbine engines cooled

Answer 10

they are cooled by air passing through the engine about 75 percent of the air passing through the engine is used for cooling which leaves only about 25 percent for combustion this air is used to cool the combustion chamber and turbine

Question 11

in a turbine engine where does bleed air come from that is used to cool bearings in other parts

Answer 11

the engine compressor

Question 12

what is the relationship between turbine engine upward temperature limits and power produced

Answer 12

the higher the combustion temperatures that an engine can withstand without damage the more power it is capable of producing

Question 13

what is the approximate percentage of air passing through a turbine engine that is used for cooling rather than combustion

Answer 13

approximately 75 percent

Question 14

what can be done to effectively allow higher gas temperatures in the turbine section of some engines

Answer 14

compressor bleed air ducted through hollow sections in the turbine inlet guide vanes and first stage rotor blades can lower temperatures enough to prevent heat damage