Answers - Engine Cooling Systems

1. b
Many reciprocating engines utilize cylinder baffles to help direct cooling air into close contact with all cylinder parts.

2. b
In an augmenter system, engine exhaust gases are discharged into a stainless steel augmentor tube. The flow of high velocity exhaust gases within the tube creates an area of low pressure at the augmentor inlet that draws additional air from within the cowl into the augmentor tube where is it discharged overboard with the exhaust. This process increases the airflow over the engine and aids in cooling.

3. c
Cylinder deflectors and baffles are designed to force air over the cylinder cooling fins to ensure proper cooling. Therefore, if a cylinder baffle or deflector is damaged, it should be repaired as soon as possible to prevent a loss of cooling efficiency. Even a small amount of damage could cause a localized hot spot and an eventual engine malfunction.

4. b
Cracks in the cooling fins of a cylinder are allowed, provided they are within the manufacturer's allowable limits. To repair a cracked cooling fin, you should remove the damaged fin then contour file the affected area.

5. b
When performing repairs to a cylinder's cooling fins, the engine manufacturer's service or overhaul manual should be consulted to ensure the repair is within limits.

6. b
If a cooling fin is inadvertently bent on an aluminum cylinder head and no crack forms, the fin should be left alone. Aluminum cooling fins are very brittle, and any attempt to straighten them could cause them to crack or break.

7. c
On an air-cooled reciprocating engine, cooling fins are located on the cylinder head, cylinder barrel, and on the underside of the piston head.

8. c
Cowl flaps are typically located on the bottom of an engine cowl and provide a means of controlling the amount of air that exits the cowl which, in turn, controls the amount of air flowing around the cylinders. For example, opening the cowl flaps increases the air exit area which effectively increases the amount of air that can circulate over the cylinder fins. Furthermore, the outside airstream flowing over an opened cowl flap creates a low pressure area which further assists in removing heat from the engine compartment.

9. a
Cowl flaps are small doors at the rear of an engine cowling that are opened to vary the amount of cooling air that flows through the engine compartment. In normal cruise flight, the forward motion of the aircraft typically produces enough airflow over the engine that the cowl flaps can remain closed.

10. c
Cylinder baffles are sheet metal shields located in an engine compartment that channel air around the cylinders for cooling. If a small crack develops in a cylinder baffle it is acceptable to stopdrill the crack.

Answers for questions 11 to 32

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