52 RCACS Ground School Engines PO 407 EO 5 “The Propeller and Engine Instruments”

Introduction Teaching Points Teaching Points The Propeller The Propeller Types of propellers Types of propellers Propeller Control Systems Propeller Control Systems The Propeller Pitch Settings The Propeller Pitch Settings Basic Engine Instruments Basic Engine Instruments Review Review Reference: Reference: FTGU Chapter 3 FTGU Chapter 3 Section H Pages Section H Pages Section I Pages Section I Pages 75-79

The Propeller The function of the propeller The function of the propeller Convert the turning of the crankshaft into thrust. Convert the turning of the crankshaft into thrust. As the propeller extends from the hub it twists. As the propeller extends from the hub it twists. Because the tip of the propeller travels at a faster speed than the hub, this twist provides uniform thrust along the length of the propeller Because the tip of the propeller travels at a faster speed than the hub, this twist provides uniform thrust along the length of the propeller Some propellers have the ability to vary their pitch. Some propellers have the ability to vary their pitch.

The Propeller Pitch Pitch Coarse Pitch: Coarse Pitch: Blades have a large angle of attack Blades have a large angle of attack (takes a large "bite of air“). (takes a large "bite of air“). Provides greater power (more forward motion) per crankshaft revolution. Provides greater power (more forward motion) per crankshaft revolution. Good cruise performance and better fuel economy. Good cruise performance and better fuel economy. Fine Pitch: Fine Pitch: Blades have a small angle of attack Blades have a small angle of attack (takes a small "bite of air"). (takes a small "bite of air"). Produces a higher blade RPM which results in greater forward pull. Produces a higher blade RPM which results in greater forward pull. Used for take-off and climb. Used for take-off and climb.

Types of propellers Fixed: Fixed: Constant angle of attack. Constant angle of attack. No pitch setting control. No pitch setting control. Pitch angle is chosen to provide good climb and cruise Pitch angle is chosen to provide good climb and cruise Adjustable Pitch: Adjustable Pitch: Pitch can be adjusted on the ground. Pitch can be adjusted on the ground. Controllable Pitch: Controllable Pitch: Pitch can be adjusted in flight by the pilot. Pitch can be adjusted in flight by the pilot. Constant Speed: Constant Speed: Engine speed is set and blades automatically adjust to keep speed constant. Engine speed is set and blades automatically adjust to keep speed constant. Controlled by the throttle. Controlled by the throttle.

Propeller Control Systems Mechanical: Mechanical: Hand controlled by linkage. Hand controlled by linkage. Hydraulic: Hydraulic: A fluid under pressure pushes or pulls on a cam that uses gears to turn the propellers. A fluid under pressure pushes or pulls on a cam that uses gears to turn the propellers. Electric: Electric: Operated by an electric motor Operated by an electric motor

The Propeller Pitch Settings Feathering Feathering This is turning the propeller to an extreme coarse pitch. This is turning the propeller to an extreme coarse pitch. Used in the event of an engine failure to stop the propeller from "wind milling", as this can damage the engine. Used in the event of an engine failure to stop the propeller from "wind milling", as this can damage the engine. Thrust Reversing Thrust Reversing Done by changing the pitch past the feathered position. Done by changing the pitch past the feathered position. Thrust now works in the reverse direction. Thrust now works in the reverse direction. Used to slow down the a/c after it has landed and to maneuver the a/c on the ground. Used to slow down the a/c after it has landed and to maneuver the a/c on the ground.

Basic Engine Instruments The basic instruments are perhaps the simplest yet most important. The basic instruments are perhaps the simplest yet most important. These gauges monitor essential components of the engine. These gauges monitor essential components of the engine. Oil Pressure Gauge Oil Pressure Gauge Monitors oil pressure supplied by the oil pump low pressure (low in oil) and high pressure. Monitors oil pressure supplied by the oil pump low pressure (low in oil) and high pressure. Oil Temperature Gauge Oil Temperature Gauge Monitors temperature of oil. Monitors temperature of oil. Oil temperature and pressure are related, but it should be remembered that oil acts as a coolant as well as a lubricant. Oil temperature and pressure are related, but it should be remembered that oil acts as a coolant as well as a lubricant. Carburetor Air Temperature Gauge Carburetor Air Temperature Gauge Enables the pilot to monitor the temperature of intake air or air/fuel mixture in the carburetor. Enables the pilot to monitor the temperature of intake air or air/fuel mixture in the carburetor. If icing condition exists, the carburetor heat control unit can be activated by the pilot. If icing condition exists, the carburetor heat control unit can be activated by the pilot.

Basic Engine Instruments Tachometer Tachometer Monitors the number of revolutions per minute the engine crankshaft is turning. On a/c with fixed or controlled pitch propellers, RPM is controlled by the throttle. Monitors the number of revolutions per minute the engine crankshaft is turning. On a/c with fixed or controlled pitch propellers, RPM is controlled by the throttle. Cylinder Head Temperature Gauge Cylinder Head Temperature Gauge Records the temperature of one or more of the engines cylinder heads. Records the temperature of one or more of the engines cylinder heads. Manifold Pressure Gauge Manifold Pressure Gauge Monitors engine power controlled by throttle. Usually beside the tachometer because both indicate engine power output. A drop in manifold pressure usually indicates carburetor icing. Monitors engine power controlled by throttle. Usually beside the tachometer because both indicate engine power output. A drop in manifold pressure usually indicates carburetor icing.

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