An aircraft RPM censor is one of the most important instruments inside of an aircraft. This specific instrument measures the RPM of the Bendix in the Magneto, or the Bendix inside the Slick Magneto. More recently, they have been used in the Dual Magneto, but this is not a popular application.
The Bendix Magneto can easily be repaired if something goes wrong with it. Typically, you can tell there is something wrong with the Magento by the report sent back from the sensor. Since aircraft is not a popular focus of manufacturers, the most popular options are made by J.P. Instruments.
What Does the Magneto Run Off of?
The Magneto does not run off of the aircraft’s battery. Instead, the power to the magneto comes from the spark plugs, which work like a miniature generator. The Bendix Magneto acts as a small generator would, but inside of the aircraft. It also serves as a transformer, a breaker switch, and a distributor guide, which provides a high amount of power back to the spark plugs.
The RPMs are relayed into the cockpit and read by a sensor. The pilot is able to gauge the function of the components it is attached to, to ensure that the aircraft is operating normally.
Why Do You Need an RPM Sensor?
The RPM sensor inside of the aircraft is essential to the safety of flying your plane. Any sudden drop in RPMs on the sensor Fuel Gauges can alert the pilot of a significant problem or deficiency with the spark plugs of the craft.
Generally, the magneto wears equivalent to the rate of the point faces. The system was designed this way so that the pilot can monitor the wear of the components and ensures that all aspects of the plane are functioning on the same timing structure. If there is a fluctuation in the RPM sensor, this could mean that there is significant wear to the components that could result in equipment failure.
The pilot can also tell if the cam follower has adequate lubrication by monitoring the RPM sensor. They will have warning before the aircraft engine develops delayed timing, or if the fuel is not being burned properly.
When to Replace the RPM Sensor
If you notice any deviation in the RPM reading, you should first have all of the components connected to it checked. Some of them may need to be replaced. If you have replaced all of the parts that are associated with the RPM Sensor, and it is still providing a fluctuating reading, you should probably replace the RPM Sensor.
Replacing the sensor is a lot easier than you may think. All you have to do is remove the vent plug from the magneto plug. Insert the right aircraft flight instruments (which will vary depending on your specific aircraft). Feed the wiring bundle toward the firewall, but do not detach it. Make sure you have enough slack in the wiring bundle and plug the connector according to the package instructions.