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Recip Ignition Sys
Reciprocating Engine Ignition Systems
| Question | Answer |
|---|---|
| During the four-stroke cycle, when does the ignition event occur? | Before top dead center on the compression stroke |
| Why are magnetos used in aircraft reciprocating engines? | The produce a hotter spark than a battery system |
| What is a low tension magneto system? | current at low voltage is delivered to transformer at or near the spark plug to produce a high voltage spark |
| What is a high tension magneto system? | A primary and secondary winding in the magneto produce high voltage which is sent to the spark plug |
| What are the four basic systems of the magneto? | Mechanical drive, Magnetic, Primary, and Secondary |
| What are the components in the primary circuit? | Primary winding in the coil, the breaker points, and the condenser or capacitor |
| What are the components in the secondary circuit? | Secondary windings, distributor and rotor, high-tension ignition leads, and the spark plugs |
| What are the function of the condenser/capacitor in the magneto primary circuit? | The condenser/capacitor prevents arcing between the contact points as they open by absorbing the "inertia" current induced in the primary coil, and minimize electromagnetic radiation . |
| Describe E-gap. | It is the number of degrees of rotation between the neutral position and the position where the contact points open. |
| What is the function of the distributor rotor? | It transmits the high-tension voltage to the different cylinder terminals on the distributor block. |
| What are the magneto pole shoes made of? | High grade soft iron |
| What opposes the magnetic field produced by the current flowing in the primary coil? | The magnetic field that caused it to flow |
| At what stage of the of magnet rotation in the magneto is the total magnetic flux the greatest? | After the magnet passes its neutral position |
| Why is a high magneto speed important? | At low speeds the high voltage spark necessary for ignition will not occur |
| Why is a dual magneto system used in aircraft reciprocating engines? | Safety because of redundancy, and quicker, more complete burning of the fuel-air mixture |
| What is meant by a magneto "coming-in speed"? | the specific rpm the magnet must turn in order to produce current in the primary circuit resulting in a high-tension output |
| At what stage of magneto rotation are the maximum number of lines of magnetic flux passing through the coil core? | When the magnet is in its full-register position |
| How will a broken or disconnected P-lead impact the magneto operation? | The magneto will be "hot" and the magneto will fire |
| What is the function of the impulse coupling? | momentary high rotation speed of the magneto and retards the spark during starting |
| What are the major parts of a spark plug? | The electrodes, the ceramic insulator, and the metal shell |
| Why are resistor-type spark plugs used in aircraft reciprocating engines? | the high current generated in the ignition system "after firing" can be reduced resulting in greater spark plug life |
| What is meant by spark plug reach? | The distance from the shell gasket to the end of the shell threads of the spark plug |
| What is meant by the heat range of spark plugs? | the ability of a spark plug to transfer heat from the firing end of the spark plug to the cylinder head of the engine |
| In a dual magneto, what are the common components share by each set of distributors? | The housing, the magnet, and the cam |
| What are two elements of magneto internal timing? | E-gap position aligned with contact point opening, and distributor timed to send voltage to the proper terminal |
| When checking the internal timing of a magneto, why is it important that the timing marks are aligned? | the magnets are in the E-gap position |
| At what point in the magneto operation is the current induced into the secondary winding? | When the primary circuit is interrupted |
| What components make up the magnetic system of the magneto? | Rotating magnet, pole shoes, pole shoe extensions, and coil core |
| Why is shielding used on spark plugs and ignition wires? | To prevent interference with radio reception |
| How is the electrical circuit form the spark plug back to the magneto completed? | grounding through the engine structure to the magneto |
| What is a common problem that occurs when using improper spark plug gapping procedures? | fracturing or breaking the spark plug ceramic insulator |
| What is the condition of the magneto primary circuit when the ignition switch is turned to the OFF position? | The primary circuits of both magnetos are grounded |
| The numbers appearing on the ignition distributor block indicate _______________________________. | the sparking order of the distributor |
| What type of aircraft reciprocating engines typically use hot spark plugs? | those with comparatively low operating temperatures |
| What will be the result of using an excessively hot spark plug? | Preignition |
| What should be done if new breaker points are installed in a magneto? | magneto internal timing and the magneto to engine timing |
| What would be the result of increasing the gap of the breaker points in a magneto? | The spark will occur early with less intensity |
| When will the voltage in the secondary winding of a magneto, installed on a normally operating engine, be at its highest value? | Just prior to spark plug firing |
| When the switch is off in a battery ignition system, the primary circuit is ______________ | opened |
| A defective primary capacitor in a magneto is indicated by ______________ | burned and pitted breaker points |
| The spark is produced in a magneto ignition system when the breaker points are ____________ | beginning to open |
| The purpose of staggered ignition is to compensate for ____________________ | diluted fuel/air mixture around the exhaust valve |
| In order to turn a magneto off, the primary circuit must be _______________ | grounded |
| When performing a magneto ground check on an engine, correct operation is indicated by __________________ | a slight drop in RPM |
Created by:
bgilbert