Despite its simplicity, the magneto timing synchronizer, commonly referred to as the magneto timing tool, can be one of the most frustrating tools for even the most experienced mechanic to use. The difficulty of using this tool can be baffling as the theory of operation is as simple as it gets. Connect a lead to the magneto ground point, connect a lead to the p-lead terminal, and as the magneto rotor shaft is turned, a light on the front of the tool will turn on and off as the contact points open and close.
All too frequently, however, a mechanic will struggle with timing a magneto, unable to get the tool to indicate that the contact points of one or both of the magnetos are opening. The typical action is to send the magneto back to Kelly for warranty inspection, only to be informed that the magneto contact points operated perfectly normally when checked on the bench.
This discussion will take a closer look at how the magneto timing light tool can contribute to false diagnosis of a magneto problem.
For the purposes of this topic, the Magneto Timing Synchronizer will be referred to as a Magneto Timing Tool. Of course, this tool has other names, ranging Buzz Box as a nod to the buzzing or whistling sound that backs up the on and off illumination of the timing lights, to other, very salty terms when struggling with the tool on a late Friday afternoon.
From the theory of operation standpoint, the magneto timing tool is not a continuity tester, at least in the conventional sense of how a continuity tester works. The principle of operation for a continuity tester is to introduce a voltage signal to a circuit. If the circuit is open, there will be no continuity and if the circuit is closed or complete, then there is continuity. If used on a magneto, the circuit is open when the contact points are closed, and the circuit is open when the contact points are open.
However, the slight introduction of a voltage is a theoretical safety issue as the voltage from a battery-operated continuity light or a multimeter can charge the electrical circuit and potentially enable it to discharge a spark. So, at some point in the past, a method to passively detect changes to the magnetic circuit of the magneto, or inductance of the magneto electrical circuit, was established to be the correct method. As such, all proper magneto timing tools are based on measuring induction, not continuity.
Inductive magneto timing tools are available in two different styles: mechanical contactor type or solid-state type. Both tools work to the same method of using lights and sound to signal contact point opening and closing, changing the indicating lights and sound based on changes to the magnetic density of the electrical circuit of the magneto.
The gold standard of the mechanical contactor type of magneto timing tool has been the Eastern Electronics E50. Hundreds of thousands of these tools have been produced, and it is virtually impossible to not find this tool in a well-equipped shop. The theory of operation is that the contactors are energized by the internal battery, and when connected to the magneto to detect the contact points are open, the indicator lights will turn ON, and the tone of the tool buzzer changes. The Eastern E50 does not have any instructions on the tool to indicate whether the indicator lights should be on or off when the points open, so the mechanic using the tool must confirm how the lights and buzzer actuate by grounding connecting the contact lead to ground to observe how the tool operates.
The solid-state magneto timing tool works in a similar way, except with no mechanical parts. The sensing of the magneto flux is accomplished strictly by electronics, no mechanical contactors are used. A big difference, though, is the lights turn OFF when the contact points open. The obvious initial concern is that the mechanic using either tool MUST know how it works. The solid-state units have instructions printed on the front that the lights will turn off, or be out when the contact points open.
The timing tool requires specific connections
Countless magnetos are incorrectly determined to be faulty due to the failure of the installer to connect the tool to the magneto correctly. Follow these simple connection rules and the magneto tool will work as required to time the magneto.
Slick magnetos: Connect the tool and use the fiber washer to prevent the tool lead from grounding and causing a false indication on the timing tool that the contact points are grounded and not opening.
The short cover magnetos that use a simple capacitor stud for the P-lead connection require the same fiber washer to ensure that the timing tool lead does not ground and send the wrong signal.
Inspect the magneto with the timing tool BEFORE installation
Step One: Confirm that the tool works before removing and installing magnetos. Low battery voltage, especially with the solid-state tool, can still illuminate the lights, but is likely to not be sufficient to provide enough voltage to sense the change of the magnetic circuit in the magneto. If the tool has not been used for several months, it is a sure bet that the batteries are weak and need to be replaced for accurate operation.
Step Two: Check the magneto for operation BEFORE installing on the engine!! With the magneto on the bench, connect the timing light and confirm that the timing lights illuminate correctly to show contact point opening or closing. In addition, the internal timing of the magneto can very easily be confirmed before installing on the engine.
Insert the timing pin into the distributor gear in the hole that corresponds to magneto ROTATION, not the position on the engine. For example, the right position magneto on a Continental O-200 is LEFT rotation, so the timing pin is inserted into the L hole.
With the pin inserted, the rotor shaft can be moved very slightly. The timing light should turn on and off as the contact points open and close. If the pin has to be removed and the rotor shaft turned 90 degrees so the contact points open and close, then the internal timing is possibly incorrect. The magneto should not be installed until the internal timing is confirmed or corrected.
If the magneto passes the bench test, then it is ready to install.
Bendix Magnetos- 20/200/1200/Dual Magneto Series
Remove the vent plugs on the magneto to expose the red painted gear tooth.
Turn the rotor shaft so that the red painted gear tooth moves within the range of the vent plug hole. The timing light should turn on and off as the contact points open and close. If the rotor shaft is turned 90 degrees so the contact points open and close, and the red gear tooth is not visible in the vent plug hole, then the internal timing is possibly incorrect. The magneto should not be installed until the internal timing is confirmed or corrected.
If the magneto passes the bench test, then it is ready to install.
Final magneto installation and timing
Making a solid ground lead connection between the magnetos and the timing tool is critical. This is the single most often missed step when using timing light tools, and will invariably result in a false diagnosis of magneto timing or incorrect magneto to engine timing.
The magneto timing tool uses a very low voltage to power to power the tool to sense the changes to the magneto magnetic circuit. The ground path from the tool to the magneto has to be direct between the magneto and tool, and as short as possible. If the timing tool ground lead is connected to the engine, it is almost impossible for the tool circuit to complete the necessary ground path through the magneto to properly illuminate lights when the contact points open and close.
The best method to ensure a continuous ground path between BOTH magnetos and the timing tool is to connect an extra jumper lead. Connect the timing tool ground lead to the ground point on the primary magneto. Next, connect a jumper lead to run from the common connection of the timing tool ground on the primary magneto, to the ground point near the secondary magneto contact points. This extra lead provides for a solid ground path and will eliminate the majority of timing problems in which the contact points seem to not open or close as expected.
DO NOT CONNECT THE TIMING TOOL GROUND LEAD TO THE ENGINE OR AIRFRAME! The path to ground may not be connected if there is too much distance between the timing tool ground and the magneto ground.
That’s it for timing tool discussion, give the techniques discussed a try. If you have time, experiment with the tool to see where things can go wrong due to a mistake with a simple connection. As always, feel free to suggest a magneto topic for future discussions.
One of the most common inquiries we receive at Kelly Aero regards ignition harness applications. The basic engine application data is usually easy as most mechanics or owners will know that their airplane has a Lycoming or Continental engine installed, and perhaps they know whether Bendix or Slick magnetos are installed. However, that sort of general information is only partially useful. It is the very specific data on the configuration of the engine and magnetos that defines the correct features of the ignition harness.
So, what information or questions do you need to ask to determine the correct ignition harness for your engine?
#1 What is the engine model?
Invariably, the very first question asked by Kelly Aero Customer Service person is â€œWhat is the engine model?â€ Some customers may start the conversation with â€œI have a 4 cylinder Lycomingâ€ or maybe they know just part of the engine model or airframe, such as â€œLycoming O-320â€ or â€œa Continental 550 in a Cirrusâ€. The issue is that the very specific prefix, engine family and suffix will define the exact harness.
Continental tends to use simple one-letter designators for their engines: O-470-R, IO-550-N, for example. Lycoming uses a system with more numbers in the suffix: O-360-A4A, TIO-360-C1C6D which are good examples. However, the harness fit, lead length, and sometimes special features such as seals for pressurized magneto applications will be different.
The engine model can be found in the engine logbooks or in the Pilot Operating Handbook for the aircraft. The information is also on the engine data plate, but that is only visible when the engine is uncowled.
#2 What is the model number of magneto installed on the engine?
This is another item that requires some specific information. Many customers will say they need a new harness for their â€œâ€¦mags..â€ with no other details. The current production magnetos are generically referred to as Bendix or Slick, despite the fact that both the Bendix and Slick product lines have been sold by numerous companies. But, Bendix and Slick are the standards, but there are variations within the basic magnetos.
The generic Bendix magneto models fall into the following categories:
20/25/200 Series: Most commonly, all of the compact size Bendix magnetos are referred to as the â€œ20 Seriesâ€ even though there are variations within the basic 20 Series of the 25 and 200 models. The 20 series are offered in 4 and 6 cylinder versions, but this will be defined by the engine model as the 360 Series Lycoming is always four cylinder and an IO-520 Continental will always be six cylinder, and so on.
1200 Series:Â the 1200 Series is identified by its large size, and offered in 4 and 6 cylinder versions.Â The difference between the 20 Series and 1200 Series is that the distributor blocks are much different in size and the ignition harnesses are not interchangeable.Â
Slick 4300/6300 Series: The Slick magnetos have more rounded features, and a data plate riveted to the side of the magneto, as opposed to the Bendix method of affixing the data plate to the top of the magneto. The Slick harness cap is perfectly round and held to the magneto with three screws. Typically, the Slick ignition harnesses will have a label that denotes the left or right harness part number, and that can be useful in determining the Kelly harness part number.
#3 What size are the spark plugs- 5/8â€ or 3/4â€? Or maybe asked as Small Barrel or Big Barrel plugs?
Historically, this detail trips up most private owners who are trying to buy parts for their airplanes. The spark plug nuts must match the type of spark plug and mistakes made at the time of order will invariably result in buying the incorrect harness.
There are two types of spark plugs: SMALL barrel 5/8-24 or BIG barrel 3/4-20. The numbers refer to the diameter and thread pitch at the top of the spark plug:
Another easy way to determine spark plug nut size is to use a wrench on the flats of the plug. BUT, be careful, as the correct wrench size can be interpreted for the wrong spark plug and harness nut size. A 3/4â€ wrench does not remove a 3/4-20 nut! Use the illustration below for guidance, but a 3/4â€ wrench is used to remove a 5/8-24 nut and a 7/8â€ wrench is used to remove a 3/4-20 nut.
#4 Straight or Elbow leads?
Virtually all modern engine installations use the straight lead, identified by a wire captured in a simple assembly just the small ferrule nut and the larger spark plug nut. A formed tube that guides the wire into the spark plug nut supports the elbow lead.
Straight leads are the industry standard, but Kelly offers the elbow lead for owners who prefer the extra support that the elbow provides. Some aircraft, especially radial engine airplanes and helicopters, prefer to use the elbow harness for extra protection in the slipstream. Current production airplanes with enclosed cowlings make the elbow redundant as the wire is protected within the cowling.
#5 Time to Order
Now that all of the information for engine, magnetos, and spark plug size is known, the Kelly Ignition Harness Application Chart can be used to find the correct harness. On the Internet, navigate to www.KellyAero.com and click on the Support tab, and then Application Chart
The Ignition Harness Application Chart will open and looks like this:
The chart is easy to use, the engine OEM and Models are listed on the left, and magnetos and spark plug sizes are listed along the top. The letter â€œXâ€™ denotes the column with the applicable magneto and the two far-right columns show the Kelly Ignition Harness part number. As a lookup tip, most of the Kelly harnesses use part numbers similar to the Slick part numbers. Kelly replaces the Slick â€œMâ€ prefix with the â€œKA1â€ prefix. In the example above, KA12772 is a replacement for the M2772 ignition harness.
Here are some examples of what it looks like to find common ignition harnesses:
Lycoming IO-360-A1A, Bendix 20 Series magnetos, 5/8â€-24 spark plugs: Harness is a Kelly KA12364, or a KA2364E if the elbows are required.
#6 Half Ignition Harnesses
Sometimes customers will require just a Left Hand or Right Hand side of the ignition harness, just for one magneto. Bendix and Slick use unique part numbers for the Complete, Left Hand and Right Hand harnesses, Kelly Aero uses a simplified system of simply adding an â€œLHâ€ or â€œRHâ€ to the basic part number of the harness. A very important note to identify Left and Right: All Left and Right references are from the pilotâ€™s perspective, looking forward through the propeller. The wrong way to determine left and right is to reference left and right from the propeller, looking back at the tail of the airplane.
Here is an example: A Lycoming O-360-A4A, Slick magneto installed on the left position, 5/8â€-24 spark plugs. The complete ignition harness is a KA14004, so to order just the Left side, order a KA14004LH.
That is it for the Ignition Harness selection discussion. If you have any questions, call Kelly Sales, Product Support, or send an e-mail to us through the website link: https://kellyaero.com/about/contact-us/
Kelly Aero receives calls daily from customers in need of product support to select a Kelly product or technical assistance after the product has been installed. Due to our long industry experience at Kelly Aero, the vast majority of calls are routine, and we can quickly provide an answer to any question asked to us. However, calls get a bit complicated when the first several minutes are spent trying to determine what the topic is when a customer calls. All too often, customers start their phone call with a vague request of “I have a Lycoming engine and I need a harness” or “…the magneto on my engine isn’t working…” While all conversations have to start somewhere, the reality is that some conversations stop as quickly as they start. The information provided by the customer is missing too many important details or the customer simply does not know the details. It can be frustrating to a customer who is in a rush or in the middle of working to solve a problem when the conversation with Kelly becomes a game of 20 Questions. Unfortunately, this game of 20 Question is particularly frustrating for both sides on a busy Friday afternoon when an airplane needs to fly on Saturday morning. Just like how a pilot completes a checklist before the airplane is ready to fly, customers and mechanics can complete a simple checklist of items prior to calling that will the customer to ask the right questions quickly, and the Kelly Aero representative to provide an accurate answer.
What is the engine make and model you are working on? Invariably, the Kelly Aero Product Support person will need the following specific information:
Which company manufactured the engine? Is it Continental, Lycoming, Superior, Franklin, etc.? As a note to this comment: The name of company who overhauled the engine is not useless, but also not particularly useful. Starting the conversation with “I have an engine overhauled by Empire Engines” is good to know, but does not really provide any magneto information. What is useful is the specific original manufacturer of the engine, such as Continental or Lycoming.
What is the complete engine designation? Ok, you know that you have a “four cylinder Lycoming” or a “550 Continental” but specific details are critical. For example, the magnetos used on a TSIO-550-K are much different in configuration and troubleshooting than the magnetos installed on an IO-550-A. Provide as much exact information as possible including the prefix, engine number and suffix, such as O- 320-D2J, O-470-R, TSIO-550-C. Additionally, some of the Kelly Aero Technical reps are experienced A&P mechanics with deep knowledge of specific engine and airframe applications. If a customer calls in with what seems to be a magneto operation issue, a bit of discussion may lead to other known areas of concern unique to specific engine models. What is make and model of magneto? Simply referring to a magneto “a Kelly mag” or maybe as a “Bendix” or “Slick” usually is too broad of a description. No surprise, but Kelly will need the exact magneto part number details to put the known service history or troubleshooting techniques into perspective.
Is the OEM manufacturer of the magneto Bendix or Slick? While Kelly takes it as a compliment when a customer says, “it’s a Kelly Aero mag”. While Kelly is an OEM for replacement parts, we are also a service provider to overhaul OEM magnetos. The magneto data plate may be labeled with Kelly Aero, but the magneto it is attached to is Bendix or Slick magneto, but overhauled by Kelly Aero.
What it is the magneto model series? Bendix makes the 20 series, 1200 series, and Dual D2000 and D3000 series magneto. Slick mags will be either a 4300 or a 6300 series. Drilling deeper, the part number of the magneto is critical as this identifies the configuration of the magneto. As an example, the Bendix 20 Series 10-51360-37 and the 10-500514-1 are approved for the same engine applications, but very different in the details of how the magnetos are mounted to the engine and how the ignition switch p-lead attaches. But, these seemingly small details can add a lot of time and expense to an otherwise simple installation if a mechanic has to alter a P-lead or order different mounting clamps and gaskets. What is the magneto serial number? The new data plate that Kelly Aero affixes to all Bendix and Slick overhauled magnetos has lots of information that the Kelly Aero product support representative will need to know. Most important will be the serial numbers stamped on the data plate. The Kelly Aero data plate will display both the OEM issued serial number and the Kelly Aero issued serial number. The OEM serial number is important to track any OEM specific service issues or compliance to OEM Service Bulletins. The Kelly Aero assigned serial number links the overhaul of the magneto to records maintained by the Kelly Aero Repair Station quality management records. The Kelly Aero serial number is required to confirm compliance to Airworthiness Directives, certain manufacturer Service Bulletins and the general timeframe when the magneto was serviced. When was the magneto installed? Calendar date and hours, please… Hours of operation and calendar time are two different ways to measure time in service for magnetos, and each tells a story independently, and together to put the magneto service history into perspective. For example, calendar time frames the reference for the type of parts or service issues known to be in effect during a particular year or month. Hours in service provides a view of how quickly, or slowly, hours were accrued on the magneto. The relationship of calendar time and hours is very important for the Kelly Aero product support specialist to assist with customer questions. For example, a customer may comment that they have a question regarding a magneto with 100 hours. However, was that 100 hours accrued over two months or ten years? Low magneto time is one story, but low magneto time over many years tells a different story. Harness Nuts and Spark Plug Type. Let’s have this discussion again…and again…and again… Search through Kelly Aero ignition system articles and ignition harness selection has been a topic more than once. Ignition harnesses have a few options and do required the buyer to do some homework as part of the selection process. Virtually all customers are able to determine which custom fit harness is required for their engine using Kelly’s Ignition Harness Application Data by clicking on this link: http://kellyaerospace.com/wp-content/uploads/2019/08/Aircraft-Harness-Application.pdf.
But, there are also many, many times that customers, typically private owners who are learning the process to buy their own parts, who need a bit of guidance on selecting between ignition harnesses that fit Bendix or Slick magnetos. As always, the most confusing part is the difference between 5/8-24 or 3/4-20 spark plug nut connections. Sorting out the difference between spark plug nut sizes is usually the substance of most phone calls. The 5/8” and 3/4” refers to the diameter and thread pitch of the spark plug barrel, not the wrench used to remove the nuts. The easy way to determine nut size follows:
A 3/4” wrench is used to remove 5/8”-24 spark plug nuts used on REM style spark plugs
A 7/8” wrench is used to remove 3/4”-20 spark plug nuts used on RHM style spark plugs Who is asking the question: an A&P mechanic….or an Owner? Let’s be realistic: Aircraft owners are more deeply involved in the maintenance process of their airplanes than ever before. Owners provide important operational information used by mechanics and product support representatives. Owners research and purchase parts used on their airplanes, consulting their mechanic, parts supplier, and manufacturer sales and support teams. Internet owners groups can be useful, but very often lead to some good answers. The same groups also generate answers that may not be completely accurate or even completely incorrect. Ultimately, owners are going to have to spend their hard earned money and the educated owner is motivated to do research on the products that they own or want to buy. By no means does this imply that Kelly Aero does not want to talk to aircraft owners. In fact, we encourage and support aircraft owners to contact us to work through product selection or product operation questions. But, calls can become frustrating when the owner is speaking in terms which are not aligned with standard industry terminology used by trained mechanics. Additionally, Kelly Aero product support answers may overwhelm an untrained caller with all sorts of terms and references that will make no sense. It usually require a lot of repetitive discussion to explain terms and concepts that are easily understood, with no further explanation, by an A&P mechanic. From the technical support perspective, Kelly Aero can be less technical, use or explain more of the specific terms that an owner may not understand. In effect, Kelly Aero can tailor our conversation with the customer to speak with terminology useful to the caller. The end result is a much better experience for both the customer and the Kelly Product Support representative. Kelly Product Support does not replace required reading material! When working on a critical process, such as ordering internal components to the magneto, completing magneto assembly, or performing magneto to engine timing, the Kelly Product Support Representative will ask, “Do you have a manual?” To be blunt, working on a magneto is not the same set of skills as required to change the light bulb inside your refrigerator. The magneto and ignition harness are components critical to the safe operation of the engine. It only makes sense that anyone who plans to or is working on an item critical to safe operation would have a set of instructions in their hands. It is reasonable and obvious that a properly rated individual should have access to and use the service manual. Nevertheless, it is also a good idea
for an educated owner to read the service manual to have an idea of the work required for a particular component. While Kelly Aero is eager to assist our customers, discussions with a Kelly Product Support Representatives do not replace the need- or FAA requirement- to have a service manual for the component that will be serviced. Copyright laws restrict Kelly Aero from sending copies of OEM service manuals to customers, but Kelly can distribute our own documents freely. A brief note regarding Kelly Aero manuals: Keep checking the Kelly Aero web page during 2021! We are working on new product application manuals, product service manuals, and supplementary Service Letters to make it easy for users of Kelly Aero products to service all of the parts and assemblies that we manufacture. Are you ready to make the call? Get your notes ready and give Kelly Aero a call at 334-286-8551!
Magneto technology is some of the oldest and most trusted in the aviation industry! However, what happens when a pilot has magneto failure? When one magneto fails, there are a few things a pilot might notice. First, there will be a decrease in engine power, but the engine will remain running thanks to the second system being independent of the first. Second, sometimes a magneto can malfunction in its failure to ignite the spark plugs, or the internal timing may malfunction. In this instance, the pilot will notice the engine beginning to run rough and will need to switch to the remaining magneto and see if that clears the problem. Even though an engine will continue to run with the loss of one magneto, there are several problems with having a magneto failure mid-flight. With the loss of one magneto comes the security of redundancy. They are a vital piece of equipment, and there is a reason that aircraft are built with two. Additionally, the loss of engine power can be potentially problematic, though in most cases does not pose a serious threat to the safety of pilots and guests.
Even in the case of magneto failure, only a very few accidents are a direct result of magneto failure, according to statistics provided by the National Transportation Safety Board. NRSB reports 16 recorded cases of aviation accidents due to magneto failure, with two of those sixteen being fatal. Most of these failures were listed as being caused by a lack of maintenance or non-compliance with servicing and inspections.
With attention to detail and a history of reliability, Kelly Aero has made sure that the magnetos produced are dependable and safe. Our products are designed and engineered using in-house resources, with additional tooling and manufacturing for aftermarket magnetos occurring at our facilities. We offer an FAA and PMA approved quality system, which is readily available with low wait times. We both meet and exceed the standard industry testing with our own set of criteria for the product, whether it be the full system or a replacement part. We want to work with customers to ensure the delivery of a product that is first and foremost high quality and reliable, and that meets their needs.
Montgomery, Alabama. March 1, 2021 – Kelly Aerospace Energy Systems LLC, an industry leader in general aviation ignition systems, has announced today that the company will begin operating under a new name and will be known as Kelly Aero LLC, effective immediately. This rebranding strategy consolidates our company name while encompassing our 37-year history in general aviation. The company’s ownership, location, and staff have not changed. Company President, Jeffrey Kelly stated “This rebrand of our company gives us a modern streamlined brand while paying homage to our strong family commitment to aviation. Our core values and commitment to deliver premium quality and value to our customers will continue to hallmark to our success.”
For more information about the name change or to learn more about Kelly Aero LLC please visit: www.KellyAero.com.
About Kelly Aero LLC Kelly Aero LLC is an industry leader with over 37 years of manufacturing and overhauling products for general aviation. Kelly Aero’s facility, located in Montgomery, Alabama, is not only an FAA-approved repair station that overhauls general aviation magnetos, but it is also an FAA MIDO approved Production Approval Holder, with an FAA & OEM approved quality system.
Montgomery, Alabama. March 1, 2021 – Kelly Aerospace Energy Systems LLC, an industry leader in general aviation ignition systems, has announced today that the company will begin operating under a new name and will be known as Kelly Aero LLC, effective immediately. This rebranding strategy consolidates our company name while encompassing our 37 year history in general aviation. The company’s ownership, location and staff have not changed.
Company President, Jeffrey Kelly stated “This rebrand of our company gives us a modern streamlined brand while paying homage to our strong family commitment to aviation. Our core values and commitment to deliver premium quality and value to our customers will continue to be hallmarks to our success.”
For more information about the name change or to learn more about Kelly Aero LLC please visit: www.KellyAero.com.
About Kelly Aero LLC
Kelly Aero LLC is an industry leader with over 37 years of manufacturing and overhauling products for general aviation. Kelly Aero’s facility, located in Montgomery, Alabama, is not only an FAA-approved repair station that overhauls general aviation magnetos, but it is also an FAA MIDO-approved Production Approval Holder, with an FAA & OEM approved quality system.