Chapter 8 Section E - Electrical, Starting, and Ignition Systems
This set introduces the basic principles of aircraft ignition and electrical systems. It explains how generators convert mechanical to electrical energy through electromagnetic induction, the function of a point breaker in magnetos, and outlines the components of a typical battery ignition system, including the ignition switch, coil, breaker points, cam, capacitor, distributor, and spark plugs.
A generator converts mechanical energy into electrical energy by what method?
electromagnetic energy
Key Terms
A generator converts mechanical energy into electrical energy by what method?
electromagnetic energy
What devise is used to interrupt the primary in a magneto?
Point Breaker
A typical battery ignition system consists of what?
Ignition switch
Battery
ignition coil
set of breaker p...
In a battery ignition system, the battery supplies current to the primary winding of an ignition coil. What is an ignition coil?
A devise that steps up the voltage to the level necessary to create a spark in each cylinder.
Direct current (DC) from the battery is converted to pulsing DC by the opening and closing of breaker points connected in series with the primary winding.
What are breaker points?
Mechanical devises that consist of two electrical contacts that control when current flows through the primary winding. When the contacts close, th...
What is a capacitor?
A devise that momentarily stores electrical energy, prevents arcing across the points and increases the rate that the magnetic field in the primary...
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| Term | Definition |
|---|---|
A generator converts mechanical energy into electrical energy by what method? | electromagnetic energy |
What devise is used to interrupt the primary in a magneto? | Point Breaker |
A typical battery ignition system consists of what? | Ignition switch Battery ignition coil set of breaker points a cam compacitor distributor spark plugs |
In a battery ignition system, the battery supplies current to the primary winding of an ignition coil. What is an ignition coil? | A devise that steps up the voltage to the level necessary to create a spark in each cylinder. |
Direct current (DC) from the battery is converted to pulsing DC by the opening and closing of breaker points connected in series with the primary winding. What are breaker points? | Mechanical devises that consist of two electrical contacts that control when current flows through the primary winding. When the contacts close, the electrical circuit is complete and current flows through the primary winding. However, when the contacts open, the circuit is interrupted, and the magnetic field surrouding the primary winding collapses. As the magnetic field collapses, current is induced into the secondary winding |
What is a capacitor? | A devise that momentarily stores electrical energy, prevents arcing across the points and increases the rate that the magnetic field in the primary winding collapses. |
What is a cam? | A metal disk with two or more raised lobes, opens and closes the points |
When current is induced into the secondary winding, voltage is stepped up to the distributor. What is a distributor? | A distributor directs high voltage current produced by the ignition coil to the spark plugs. The distributor consists of a rotating finger and a distributor block. As it rotates, the finger distributes power from the coil to the contacts mounted in the distribution block. From there, the energy passes through an ignition lead to a spark plug. |
What is a magneto? What are it’s two classifications? | A permenent-magnet alternating current (AC) generator that use electromagnetic and induced current to develop a pulse of high voltage electricity to fire a spark plug. Magneto systems are classified as either high-tension or low-tension |
What components make up the high and low tension systems and what is the difference between the two? | Components include:
The difference between the two
|
The earliest high-tension systems experienced a problem called flashover. What is a flashover and what can it lead to? What two methods are use to prevent it? | A phenomenon at high altitude operations which causes the spark to jump to the wrong electrode. Flashover often leads to carbon tracking, which appears as fine pencil-like carbon trail inside the distributor. Two methods: Low tension ignition system and pressurize magneto |
A high tension system consists of what system and what three circuits? | A mechanical system magnetic circuit primary circuit secondary circuit |
What are the two types of cams that a high-tension magneto use? | Uncompensated cam Compensated cam |
What components make up a magnetic circuit? | Rotating permenant magnet pole shoes pole shoe extension coil core |
Rotating magnets are often made from something called alnico. What is alnico? | An alloy made of aluminum, iron, nickel, and cobalt |
The rotating magnet in a magneto turns between two pole shoes. To complete a circuit, each pole shoe is joined at one end to the magneto coil core. What are the pole shoes and coil core constructed from? | Laminated layers of high-grade soft iron to: reduce eddy currents keeps magneto cooler boosts efficiency the high permeability of the soft iron enables flux lines to pass through easily |
When a pair of poles aligns with the shoes, lines of flux flow through the coil core. This position is known as what? What degree angle is this? | Full register position In this position the magnetic field is strongest and the density of flux lines is greatest This would either be the 0 degree or 180 degree position when the current flow is changing direction |
As a magnet rotates beyond full register, the magnetic field slowly collapses until no lines of flux pass through the coil core. What is this position called? What angle is this? | Neutral position In this position the magnetic field is weakest. This would be be either the 90 or 270 degree position |
What is a E-Gap and why does it occur? | Efficiency Gap The specific number of degrees the rotating magnet is beyond the neutral position. The magnetic circuit is designed to hold the flux in the core at the highest possiable value until the rotating magnet reaches its neutral position. After the magnet rotates beyond neutral, a magnetic field of opposite polarity begins to build. At this point, the greatest magnetic stress exists. This is the E-gap angle. |
What components make up the primary electrical circuit in a magneto? | Primary winding of an insulated magneto coil set of breaker points capacitor |
At the E-gap position, opening the breaker points will do what? | Interrupt current flow in the primary circuit and induces current into the secondary coil |
What is the purpose of the secondary circuit? What components make up this circuit? | Produces the high-voltage energy required to cause a spark. Components:
|
What is the purpose of the carbon brush? | Directs current that is coming from the secondary winding to the distributor rotor. It is mounted in the center of the distributor rotor. From the distributor rotor, current passes to the distributor block through a distributor finger. |
What is the purpose of the conductive arm? | A.K.A distributor finger, it passes the electrodes for each spark plug in the distributor block as it rotates. |
During normal operation, whenever the rotating magnet is in an E-Gap position, what else is happening in the distribution block and why? | The distribution finger is aligns with an electrode on the distributor block to deliver a high voltage pulse. |
What is the cause of the current flow in the primary winding? | The continuous expansion and collapses of a magnetic field due to the rotation of the magnet. |
At what speed does the distributor rotor in a magneto rotate? What formula is used? | 1/2 the engine crankshaft speed but depends on the number of cylinders and the number of poles on the rotating magnet cylinders / (#poles)2 |
What is arching and why is it an issue? How does a capacitor (condensor) resolve this issue? | Arching is the gap between the two breaker points. It is an issue because as the points begin to seperate, the electrical resistance between the two points produces enough heat to ionize the air, now allowing current to travel through the air, and can get hot enough to weld the two point together. By installing an compacitor in parallel with the breaker points, as the breaker points begin to open, the compasitor absorbs the electrons and prevents the arching from occuring |
What happen when the ignition switch is in the OFF position? | Because the ignition switch is wired in parallel with the breaker points, switching it to OFF shorts the breaker points and grounds the primary coil, preventing the magnetic field in the primary winding from collapsing and inducing current into the second winding. Basically, both P-Leads are grounded |
What connects the ignition switch to the primary circuit? | P-Lead When the P-Leads are open, it is called "open". When the P-Lead is closed, it is called "shorted to ground. |
How is a magneto check performed? | Set engine between 1500 and 1700 RPM Move switch from BOTH to LEFT - This causes the right magneto to become grounded and a slight drop in RPM Return to BOTH Move switch from BOTH to RIGHT - This causes the left magneto to become grounded and a slight drop in RPM Return to BOTH If at anytime the RPM drops to zero, there is a short between the magneto and the ignition switch |
What do you do to time a magneto? | Put the magneto in a neutral position |
What is responsible for the magneto's high starting rotational speed located at the base of the magneto? | Impulse Coupling |
What is the cam made from in a slick magneto? What about a Bendis magneto? | Slick magneto cam - made from plastic Bendix magneto cam - made from steel |
What would cause the breaker points in a magneto to be pitted? | The compasitor has failed |
When is a coil able to store energy? | A coil stores energy in a electromagnetic field when current is increasing and returns the energy when the current is decreasing |
When does a compacitor (condensor) store energy? | It stores energy in a electrostatic field when voltage is increasing, and returns the voltage is decreasing |
What is the difference between a step up and step down transformer? | Step up - Heavy guage fewer turns in primary with many finer turns in secondary. Step down - Many finer turns in primary with fewer heavy guage turns in secondary |
What are the two types of step up transformers? | Self Induction Mutual Induction (This is the type our step-up transformer uses) |
What are some ways that current can be lost? | ddie current - caused by flux reversal Copper - if the wire is made from copper, a voltage is dropped every 1,000 feet Hystersis - Heat lost |
What can be done to make lines of flix stronger? | Faster rotation speed Add more poles |
Define retentivity, reluctance, and permeanbility. | Retentivity - Duration an object remains magnetized after removed from an magnetic field Permeanbility - How easily an object becomes magnetized Reluctance - resistance or opposition to the lines of flux |
What are the laws of magnets? | Lines of flux travel from North to South Lines of flux never intersect Cannot be stopped Opposites attract and likes repel |
What are the characteristics of permanet magnets vs. temporary magnets? | Permanent magnets
Temporary magnets - (the complete opposite) |
What is amp ratio? | The ratio between the # of turn in the primary vs the secondary |
The rotational speed necessary for a magneto to fire a spark plug is known as what? | Coming-in speed |
Because the ignition event normally occurs before top dead center of the compression stroke, normal ignition timing can cause an engine to kick back during start. To prevent this, some magnetos use a set of _____to delay the spark during engine starting. | Retard breaker points |
This item is widely used to augment low speed ignition from magnetos. It is wound up by the magneto drive gear and then released, providing a momentary increase in rotational speed while delaying the spark. What is it? What is the name of the three components? | Impulse Couplings
|
What is an induction vibrator? | An ignition booster that supplies pulsing direct current (DC) to the primary winding of a maneto coil, inducing current into the secondary winding. |
The wire that connects the ignition switch and the primary circuit is called what? | P-Lead |
NAme two types of starting aids | Impulse Coupling
Induction Vibrator or Shower of Sparks
|
What is kickback? | The tendency for the engine to rotate in the opposite direction |
What would be the difference and the cause between slow and fast RPM drops during magneto checks? | Slow RPM drop - Faulty timing Fast RPM drop - Bad plugs or bad leads |
What is the engine procedure to clean foul spark plugs with carbon build-up due to a rich fuel/air mixture? |
|
Name three methods to destroy magnetism | Heat Shock reverse megnetism |
What are we basically doing when we internally time a magneto? | Putting the rotor in a neutral posion |
If there is no RPM drop during during a magneto check, what could be the problem? | P-lead is not grounded and open |
What is another name for a broken P-Lead? | Hot Mag |
Where do we find information regarding engine timing? | Engine's data plate |
How would you know if a bendix magneto is in the neutral position? | A red mark would appear in the chanfer tube |
What can cause magneto timing to change? | Cam Breaker points |
In a bendix magneto, what is used to open and close the breaker points? | Cam follower The cam rides the cam follower which opens and closes the breaker points |
In a bendix magneto, what can change the timer? | Were of the cam follower
Were of the breaker points
|
What is used to verify timing on a slick and bendix magneto? | Slick - Timing light Bendix - red chafer tube |
If a set of points are badly pitted, what may be the cause? | The capacitor is faulty |
What is used to check the strength of a magnet? | Magnetometer |
What is the primary difference in the internal timing procedure of a typical Slick magneto nad a Bendix? | With bendix, you must adjust and set the points before you join the case halves and a slick magneto uses a timing pin or e-gap guage to lock the magnet in place |
What is the difference between synchronized and staggered ignition timing? | Synchronized ignition timing - fires both spark plugs in each cylinder at the same time Staggered ignition timing - fires the two spark plugs in each cylinder at slightly different times. |
What is used to accurately identify that the piston is top dead center? What is the alternative? | Timing plug & Propeller protractor Time-Rite indicator can be used as an alternate |
Where are the timing reference marks located on Lycoming engines vs Teledyne Continental Motors engines | Lycoming - front side of flywheel TCM engines - on the propeller mounting flange or an internal gear. |