A magneto is a self-contained electrical generator that uses magnets to produce a high voltage current that fires the engine spark plugs. Because of their simple design, magnetos are compact, and because they require no external electrical source to operate, they are reliable. An aircraft magneto is comprised of a rotating magnet in close proximity to a high-output coil.
As the magnet spins, it generates electricity until it achieves a spike of 20, to 30, volts. When this voltage spike is achieved, a distributor carries the amplified current to the spark plug, which ignites the fuel-air mixture to fire the pistons.
Aircraft piston engines are designed with two independent ignition systems—that is to say, two spark plugs per cylinder. Likewise, there are two magnetos, left and right. The left aircraft magneto fires one plug per cylinder, while the right aircraft magneto fires the other. This redundant system ensures that the ignition will keep sparking even if one magneto fails. There are various types and brands of aircraft magnetos and choosing the right one for your aircraft application is important.
Currently these magnetos are manufactured by Champion Aerospace. The Slick Magneto line was acquired by Champion in s. Slick Magnetos offer a smaller and lighter design compared to other aircraft magnetos. The light weight of the part allows for easier installation of a Slick Magneto. The noise suppression of the magneto is also a feature that allows for the elimination of magneto filters on Slick Magnetos.
Parts for Slick magnetos are engineered for balanced wear which allows for predictable wear on the part and time for servicing. Another benefit of Slick Magnetos is the ease to keep up maintenance due to new parts used for servicing. All repair work for a Slick Magneto is to be completed in compliance with Champion manual L A dual magneto is an arrangement in which the left aircraft magneto and right aircraft magneto are contained in a single housing and operated by a single magnet rotor and engine drive.
Due to both magnetos being together there is significant reduction in weight and space taken up by a dual magneto as compared to single magnetos. Moreover, the single-housing design allows for more regular maintenance of the ignition system.
Dual magnetos were produced by Teledyne Continental Motors until October ofwhen the line was ended. There are two series of dual magnetos available, D and D, which differ mainly in the design of the housing.
Bendix single magnetos have been in continuous production by TCM since They are known for their light weight, compact design, reliability, and high output. There are multiple models of Bendix magnetos for different types of aircraft applications. The S series Bendix magneto can be impulse coupled or direct drive. This series will have a feed through capacitor that filters out radio noise from the magneto.
The S series Bendix magneto uses an ignition vibrator along with a retard breaker assembly to start the engine. The last series is the S These Bendix magnetos can be impulse coupled or use retard breaker contact assembly. This Bendix Magneto series is able to reach higher voltages to allow for higher altitude of flight. In aircraft engines, it is important to maintain an ignition system independent of the electrical system, so that the engine will continue to run in the event of alternator or battery malfunction.
Additionally, aircraft magnetos provide a compact and reliable means for igniting the spark plugs. No, the aircraft magneto ignition system is self-contained and independent from the aircraft electrical system.
In the event of an electrical failure, the mechanical aircraft magneto will continue to provide spark to the engine.
The aircraft magneto is a self-contained generator that consists of a magnet spinning in close proximity to a high-output coil.After talking to thousands of fellow homebuilders and giving many presentations at fly-ins around the country, I realized there was a need for information to design and build the newer, more complex electrical systems found in Experimental aircraft. This article is one in a series of excerpts from my new book entitled Aircraft Wiring Guide.
For more information visit www. Completing an electrical system is accomplished in five main steps. The most effort should be spent on the first step if you want to minimize issues later on. Following these steps will increase the likelihood of a trouble-free electrical system. It is recommended that you familiarize yourself with all five steps to better understand the scope of the project.
Step 1: Planning—Gather as much information as possible about the devices you want to install. Document and review all aspects of your electrical system. Step 2: Installation—Select and install wires and devices. Step 3: Configuration—Configure all of the avionics in the aircraft. Step 4: Ground Test—Test as much as possible on the ground to minimize surprises in the air.
Step 5: Flight Test—Test everything to its safe limits. Taking the time up front to carefully plan your electrical system will pay big dividends later on.
The electrical system on your aircraft can be thought of as having two major sections: primary power and secondary power. The primary power section is the backbone of the electrical system.
It includes the larger wires in the electrical system that tie together the battery, starter, alternator, and main power buses. It also includes the airframe, which is typically used as the ground.
The picture below shows a typical way to mount the contactors and alternator fuse.ATPL Training / AC Electrics #05 Alternators - Basic Alternators
In aircraft with aft-mounted batteries, the master contactor is located in the back near the battery, and the starter and fuses are located in the front on the firewall. The battery contactor also known as the master relay, master contactor, or master solenoid is a continuous-duty contactor and is essentially a big relay that allows a small amount of current to switch a large amount of current.
This contactor is switched with a wire that comes from the master switch in the cockpit. The starter contactor allows the small starter switch in the cockpit to switch several hundred amps that are drawn by the engine starter.
The bus bars are copper strips that connect the contactors together electrically. Cable can be used as well, but tends to be more work to build and install. The ANL fuse is a specific type of fuse used to protect the main bus from any problems with the alternator or cable running to the alternator.
This is an area where you want to keep things simple. Install a single bus, single battery, single alternator system in your aircraft and add to it as needed, noting the following:. It is not meant for starting the engine. Some avionics include their own backup battery system, or you can install a third-party backup battery system.
The reason is because you can fly indefinitely on a backup alternator, but a second battery has limited life.Home Capabilities Facility Troubleshooting Contact. DC charging systems can be identified as type "A" or "B" circuit. It is necessary for the technician to determine which system they have in order to properly troubleshoot. The "A" type system controls the output by regulating the field circuit to ground. The "B" type system controls the output by regulating the battery to field.
All Delco Remy aircraft generator charging systems are "A" circuit therefore their regulator controls how much ground is placed on the generator field circuit.
This was originally accomplished by a vibrating point system in the voltage regulator. The more the points were vibrating toward the closed position the more output. The further apart the points were during the vibrating function the less the output.
Most general aviation alternators are "B" circuit. In order for them to output current from the alternator, battery must be applied to the field. The more battery to the field the higher the output. The regulator is then assigned the task of controlling the amount of battery to field. There are some general aviation charging systems that are "A" circuit or field to ground.
These can readily be identified if the voltage regulator part number has "VSF" at the front of a four digit number. When this regulator is used the alternator will not have one of the two field terminals attached to ground. The "VSF" series regulators control field to ground in order to control alternator output.
The reason it is important for the technician to determine whether the system is "A" or "B" circuit is so they can proceed to diagnose the charging system. A common method used is called the "full field" test.
This test is used by technicians to determine if the alternator or generator is functioning. Since the regulator controls how much battery or ground is applied to the field circuit the "full field" test requires bypassing the regulator. This is done by jumping full battery or full ground to the generator or the alternator field post.
This causes the alternator or generator to charge at full output when rotated. The aircraft engine will be used to rotate the alternator or generator similar to using a test bench.
Since this is being done on the aircraft caution must be taken to not damage anything in the electrical system. You will, for a very short period of time, be raising the system voltage.
All other electrical devices should be in the off position while performing this test. Only about 4 to 6 seconds is needed to perform the "full field" test. When the "full field" test is being done on an aircraft with a Delco Remy generator system the technician will need one jumper and a DC voltmeter.
Remove both the armature and field wire from the generator. Tape the wire ends for protection. Connect a jumper from the field post to airframe ground. Connect your voltmeter from the armature post to airframe ground. Start the engine and gradually bring the rpm up from idle to approximately rpm.
The voltage on the armature post should follow the throttle.Light aircraft typically have a relatively simple electrical system because simple aircraft generally require less redundancy and less complexity than larger transport category aircraft.
On most light aircraft, there is only one electrical system powered by the engine-driven alternator or generator. The aircraft battery is used for emergency power and engine starting. Electrical power is typically distributed through one or more common points known as an electrical bus or bus bar. Almost all electrical circuits must be protected from faults that can occur in the system.
Faults are commonly known as opens or shorts. An open circuit is an electrical fault that occurs when a circuit becomes disconnected. A short circuit is an electrical fault that occurs when one or more circuits create an unwanted connection. The most dangerous short circuit occurs when a positive wire creates an unwanted connection to a negative connection or ground.
This is typically called a short to ground. There are two ways to protect electrical systems from faults: mechanically and electrically. Mechanically, wires and components are protected from abrasion and excess wear through proper installation and by adding protective covers and shields. Electrically, wires can be protected using circuit breakers and fuses.
The circuit breakers protect each system in the event of a short circuit. It should be noted that fuses can be used instead of circuit breakers. Fuses are typically found on older aircraft. A circuit breaker panel from a light aircraft is shown in Figure 1. Figure 1. Light aircraft circuit breaker panel. The aircraft battery and battery circuit is used to supply power for engine starting and to provide a secondary power supply in the event of an alternator or generator failure.
A schematic of a typical battery circuit is shown in Figure 2. This diagram shows the relationship of the starter and external power circuits. The bold lines found on the diagram represent large wire see the wire leaving the battery positive connectionwhich is used in the battery circuit due to the heavy current provided through these wires.
Because batteries can supply large current flows, a battery is typically connected to the system through an electrical solenoid. A battery master switch on the flight deck is used to control the solenoid. For general purposes, an aircraft technician may consider the terms relay, solenoid, and contactor synonymous.DC alternators like generators change mechanical energy into electrical energy by the process of electromagnetic induction.
In general, DC alternators are lighter and more efficient than DC generators. DC alternators and their related controls are found on modern, light, piston-engine aircraft. The alternator is mounted in the engine compartment driven by a v-belt, or drive gear mechanism, which receives power from the aircraft engine. DC Alternators. DC alternators contain two major components: the armature winding and the field winding. The field winding which produces a magnetic field rotates inside the armature and, using the process of electromagnetic induction, the armature produces a voltage.
This voltage produced by the armature is fed to the aircraft electrical bus and produces a current to power the electrical loads. Figure 2 shows a basic diagram of a typical alternator. The armature used in DC alternators actually contains three coils of wire.
Each coil receives current as the magnetic field rotates inside the armature. The resulting output voltage consists of three distinct AC sine waves, as shown in Figure 3. The armature winding is known as a threephase armature, named after the three different voltage waveforms produced.
Figure 4 shows the two common methods used to connect the three phase armature windings: the delta winding and the Y winding. For all practical purposes, the two windings produce the same results in aircraft DC alternators. Since the three-phase voltage produced by the alternators armature is AC, it is not compatible with typical DC electrical loads and must be rectified changed to DC. Therefore, the armature output current is sent through a rectifier assembly that changes the three-phase AC to DC.
Figure 5. Relatively smooth ripple DC. The invention of the diode has made the development of the alternator possible.
The rectifier assembly is comprised of six diodes. This rectifier assembly replaces the commutator and brushes found on DC generators and helps to make the alternator more efficient.
Figure 6 shows the inside of a typical alternator; the armature assembly is located on the outer edges of the alternator and the diodes are mounted to the case. The field winding, shown in Figure 7, is mounted to a rotor shaft so it can spin inside of the armature assembly. Figure 7.
Small Single Engine Aircraft Electrical System
Alternator field winding. The field winding must receive current from an aircraft battery in order to produce an electromagnet. Since the field rotates, a set of brushes must be used to send power to the rotating field.
Two slip rings are mounted to the rotor and connect the field winding to electrical contacts called brushes.
Since the brushes carry relatively low current, the brushes of an alternator are typically smaller than those found inside a DC generator. The alternator case holds the alternator components inside a compact housing that mounts to the engine.
Aircraft alternators either produce a nominal volt output or a volt output. Common alternators for light aircraft range in output form60— amps. Voltage regulators for DC alternators are similar to those found on DC generators.
The general concepts are the same in that adjusting alternator field current controls alternator output. Regulators for most DC alternators are either the vibrating-relay type or solid-state regulators, which are found on most modern aircraft. Vibrating-relay regulators are similar to those discussed in the section on generator regulators.Username or Email Address. Remember Me.
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I can fly with confidence now that I have their products. Thomas Mosby.Still, all of us can benefit from fundamental systems knowledge, especially when it comes to telling your mechanic about a problem so that he or she can better understand it and work more efficiently to troubleshoot and repair that problem.
Some of these systems are easier to understand than others, but one system that has many owners flummoxed is the electrical system. All airplanes have them and they are independent of the electrical system. I once lost an alternator and finished a flight by flying a Grumman Tiger like a Piper Cub for miles. Piece of cake—it called for different skills, but it was cool!
But if you have a starter, and if you have a radio, then you will need an electrical system on board. This discussion will tell you how an aircraft electrical system works, not why. Our electrical systems are pretty simple. We use DC power in our airplanes and, for that matter, most other vehicles as opposed to AC which we use in our houses. The main components of our system are a battery, an alternator or generator, a master solenoid, a master switch, a buss bar, wire, switches and, finally, the appliances.
Older aircraft were built with generators that produced DC current. Generators suffered from high weight, unreliability, and their output was directly tied to the RPMs of the engine. At idle or low RPM, demand on the battery could cause it to run out of power.
Alternators were simpler, lighter, cheaper, and much more dependable. They create AC current that is rectified into DC. In fact, Plane Power www. The volt systems use even lighter wiring and lighting, and appliances are designed differently so nothing is interchangeable. The power source in our airplanes is the battery. Most batteries are lead acid; though lithium and nickel cadmium batteries are becoming more popular.
Plane Power Alternator Wiring Diagram Sample
The positive side of the battery cathode is connected directly to the master solenoid and the alternator. The negative side anode of the battery is connected to the airframe and engine. Located strategically, solenoids can save a lot of wire weight.