The aircraft RPM Sensors we refer to in this article are the ones used to measure RPM of the Bendix Magneto or the Slick Magnetos. There's also the Dual Magneto but the popular ones in use are the Bendix Magnetos and the Slick Magnetos.

1. Use Of Aircraft RPM Sensors
The aircraft RPM Sensors we refer to in this article are the ones
used to measure RPM of the Bendix Magneto
or the Slick Magnetos. There's also the Dual
Magneto but the popular ones in use are the
Bendix Magnetos and the Slick Magnetos.
The Bendix Magneto is easily overhauled and
therefore extremely cost effective. Companies
such as J.P. Instruments manufacturers

2. highly accurate aircraft RPM sensors for both - Bendix Magnetos
and Slick Magnetos.
For the uninitiated, rather than rely on the aircraft battery, the
power to the spark plugs comes from the magneto – think of it as a
mini power generator. The Bendix Magneto is a small generator
with a transformer, breaker switch and a distributor to guide the
high voltage to the spark plugs.
A power generator obviously means there is a rotating magnet
inside the generator. It is important that this magnet rotate within
the prescribed range and to confirm this, you
need the aircraft RPM Sensor which is a small
cylindrical device that plugs into the magneto
and provides a feedback to the RMP display
unit in the cockpit.
Why Aircraft RPM Sensor is a big deal
A sudden RPM drop could indicate a serious problem with the
spark plug. The magneto cam follower (or cam in the case of Slick
magneto) generally wears at the same rate as the point faces. This
intentional design feature ensures that the magnetos internal
timing are at the correct angular opening point for long periods of
time.
If there is inadequate lubrication of cam follower (or cam), it will
result in accelerated wear leading to a domino effect inside your
aircraft engine. To start with, it results in late engine timing i.e. a

3. late spark which in turn reduces the sustainable RPM which in turn
means fuel is not burned properly and there is a energy kick-back
to the piston. Energy burned in the exhaust system results in
abnormally high EGT. This is why it is important that the aircraft
RPM always be within specified limits and to ensure this is so, your
aircraft needs an accurate RPM sensor.
Replacing your RPM Sensor is easy
Attaching a new RPM sensor is easy; just remove the vent plug from
the port on the magneto that covers the portion of the magneto that
contains the rotating magnet.
Next, you insert the correct
Aircraft Flight Instruments
(depending on whether your
aircraft has the Dual, Bendix or
Slick Magneto) into the vent port
and tighten.
Route the wiring bundle back
towards the firewall taking care
to not attach the bundle directly
to the ignition, harness or
magneto p-leads. Ensure there is
sufficient slack. Plug in the
connector or connect the wires to
the corresponding colour wires in the instrument harness.