52 RCACS Ground School Engines PO 407 EO 4 “Fuel Problems, Ignition, and Basic Electrical System”

Introduction Teaching Points Teaching Points Problems with the Fuel System Problems with the Fuel System Ignition System Ignition System Ignition Timing Ignition Timing Components of the Electrical System Components of the Electrical System Review Review Reference: Reference: FTGU Chapter 3 FTGU Chapter 3 Section B Page 61 Section B Page 61 Section E Pages Section E Pages Section G pages Section G pages 71-72

Problems with the Fuel System DETONATION: DETONATION: Rapid and violent burning of fuel (explosion). Causes overheating and damage to metal of the engine. Rapid and violent burning of fuel (explosion). Causes overheating and damage to metal of the engine. SIGNS: SIGNS: rapid rise in cylinder head temperature and pressure. rapid rise in cylinder head temperature and pressure. CAUSES: CAUSES: incorrect fuel incorrect fuel overheating (lack of airflow) overheating (lack of airflow) too lean a mixture too lean a mixture SOLUTION: SOLUTION: make the mixture richer make the mixture richer

Problems with the Fuel System PRE-IGNITION: PRE-IGNITION: Premature burning of fuel in cylinders Premature burning of fuel in cylinders Can cause serious damage. Can cause serious damage. CAUSES: CAUSES: Glowing carbon particles, otherwise known as "local hot spots“ Glowing carbon particles, otherwise known as "local hot spots“ Preignition and Detonation Preignition and Detonation VAPOUR LOCK: VAPOUR LOCK: High atmospheric temperatures vaporize liquid fuel inside the fuel lines, blocking normal flow. High atmospheric temperatures vaporize liquid fuel inside the fuel lines, blocking normal flow.

Ignition System Supplies a spark to ignite the fuel/air mixture in the cylinders Supplies a spark to ignite the fuel/air mixture in the cylinders Consists of: Consists of: Two Magnetos Two Magnetos Two Spark Plugs per Cylinder Two Spark Plugs per Cylinder Ignition Leads Ignition Leads Magneto Switch Magneto Switch

Ignition System Magneto Magneto The magneto does three things: The magneto does three things: Generates a low Tension current Generates a low Tension current Transforms this to high tension current Transforms this to high tension current Sends it, through the distributor to the spark plugs Sends it, through the distributor to the spark plugs Dual Ignition Dual Ignition An aircraft engine has two magnetos. An aircraft engine has two magnetos. Each magneto is connected to one spark plug per cylinder. Each magneto is connected to one spark plug per cylinder. Therefore, there are two spark plugs in each cylinder. Therefore, there are two spark plugs in each cylinder.

Ignition System DUAL IGNITION IS NECESSARY FOR: DUAL IGNITION IS NECESSARY FOR: SAFETY : SAFETY : if one system fails, you have a back up. if one system fails, you have a back up. if one magneto fails, there will only be a 3% drop in power. if one magneto fails, there will only be a 3% drop in power. PERFORMANCE : PERFORMANCE : more complete combustion. more complete combustion. MAGNETO SWITCH MAGNETO SWITCH Lets the engine run on either one, both or no (turned off) magneto. Lets the engine run on either one, both or no (turned off) magneto. To check magnetos, the switch should be switched to: To check magnetos, the switch should be switched to: BOTH--RIGHT--BOTH--LEFT--BOTH BOTH--RIGHT--BOTH--LEFT--BOTH SHIELDING SHIELDING Parts and wires of ignition system are surrounded with a metal covering. This prevents interference with the radio. Parts and wires of ignition system are surrounded with a metal covering. This prevents interference with the radio.

Ignition Timing Timing the Magnetos to fire the spark plugs at the right time Timing the Magnetos to fire the spark plugs at the right time Advanced or early firing of the spark plugs Advanced or early firing of the spark plugs results in a loss of power results in a loss of power Overheating which can cause detonation or Pre-Ignition Overheating which can cause detonation or Pre-Ignition Piston Burning Piston Burning Scored cylinders or broken rings Scored cylinders or broken rings Magneto timing should be checked every 100 operating hours. Magneto timing should be checked every 100 operating hours.

Components of the Electrical System Battery: Battery: Stores electrical energy required to start engine. Stores electrical energy required to start engine. Master switch: Master switch: Overall on/off switch for the electrical system. Overall on/off switch for the electrical system. Starter motor: Starter motor: Turns engine over. Receive current from battery. Turns engine over. Receive current from battery. Generator/alternator: Generator/alternator: Supplies current to system. Recharges batteries. Supplies current to system. Recharges batteries.

Components of the Electrical System Voltage regulator: Voltage regulator: Prevents system from being overloaded and the battery from overcharging. Prevents system from being overloaded and the battery from overcharging. Bus bar: Bus bar: Receive current and distributes it to the various circuits. Receive current and distributes it to the various circuits. Circuit breaker: Circuit breaker: Prevents damage from overload. Prevents damage from overload. Ammeter/voltmeter: Ammeter/voltmeter: Indicates current, voltage storage and drain of the system. Indicates current, voltage storage and drain of the system. Generator warning light: Generator warning light: Indicates generator failure. Indicates generator failure.

Cessna Instrument Panel Cessna 150 Cockpit and Startup

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