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Thrust Institute
how to time an aircraft magneto

Learn How to Time an Aircraft Magneto

In this article and video we’ll walk you through how to time an aircraft magneto to ensure your engine runs smoothly and safely. This process is key for proper ignition and overall performance.

Safety First

We always put safety at the top of our list when working on aircraft engines.

Before starting any magneto timing work, we take some key steps to keep everyone safe.

We make sure the ignition switch is turned off. This stops any accidental starts.

We also ground the P lead for extra safety.

Next, we take out all the spark plugs from the upper cylinders.

We disconnect all the ignition leads too. These steps prevent any surprise sparks while we work.

When we need to turn the engine, we do it carefully by hand using the propeller.

We never use the starter motor for this job. It’s safer to feel and control the movement ourselves.

Getting the Engine and Magneto Ready

Taking Out the Spark Plugs

As mentioned, we start by removing all the spark plugs from the upper cylinders. This step is crucial for the timing process. Make sure to handle the spark plugs carefully to avoid damage.

Unplugging the Ignition Leads

Next, we disconnect all the ignition leads. This is an important safety step. It prevents any accidental sparks while we’re working on the engine.

Turning the Engine to Its Highest Point

Now, we rotate the engine until the number one cylinder reaches its highest point. Here’s how we do it:

  1. Put your thumb over the spark plug hole of cylinder one.
  2. Turn the propeller slowly.
  3. Feel for pressure on your thumb.
  4. Listen for a specific sound – watch the video to hear it!
  5. Stop when you feel and hear these signs. That’s the top point.

Just remember to make sure the ignition switch is off and the P lead is grounded before you start.

how to time an aircraft magneto

Getting Ready for Magneto Timing

Installing the Timing Tool

We start by putting a timing synchronizer in place. This tool connects the engine ground to the Magneto condenser terminal. It’s a key piece of equipment for accurate timing.

Loosening the Magneto Bolts

Next, we slightly loosen the Magneto mounting bolts. This step allows us to rotate the Magneto during the timing process. We don’t want to remove the bolts completely, just enough to permit movement.

Adjusting the Mag’s Timing

Spotting the Left Mag

We start by finding the left magneto. It’s easy to spot – just look for the one labeled “left mag” on the engine. This is the only one we’ll be working on today, since our Piper Archer has an electronic ignition on the right side.

Moving the Mag into Place

Now comes the fun part!

We loosen the top and bottom nuts under the mag just a bit. This lets us turn it.

We slowly rotate the mag clockwise or counterclockwise until we hit 25° on the flywheel. Keep an eye out – the light will go off when we’re there.

Locking It Down and Double-Checking

Once we’re at 25°, it’s time to tighten things up.

We use a torque wrench set to 16 ft-lbs on those nuts we loosened earlier.

After that, we do one last check. The light should still go out at 25° if everything’s right.

Where to Find the Manual

We’ve shown you how to time an aircraft magneto on a Piper Archer. This process is key for keeping the engine running smoothly.

But don’t rely just on this video. Always check the plane’s maintenance manual for the full steps.

The manual has all the details you need to do the job right. It’s a must-read before you start any work on the plane.

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