Recip Technology: Rotax Engines

Understanding and troubleshooting


AMT: As for ignition?

Vogel: Ignition problems will show up either in the mag check or at shutdown. If the engine won’t start, the problem is almost certainly not the ignition. The ignition system on this engine is dual, independent, redundant, and solid-state. The only moving part is the flywheel. The probability that both systems would fail at the same time in the same mode is extremely remote.

The major components of the ignition system — with the exception of the modules themselves — have resistance values that are published in the Heavy Maintenance manual. This provides one way to check for the health of those components. Beyond that, troubleshooting of this system is a little too complex to attempt a description in a magazine article, but suffice it to say that with complete parallel systems, it’s fairly convenient to troubleshoot by switching connections in different places to work the gremlin into a corner.

A word of caution: Do not treat this ignition like the magneto on a Briggs & Stratton. Putting a screwdriver in a spark plug cap and holding it next to the block to check for spark is dangerous — not to you, to the ignition module. Many people have started off thinking they had an ignition problem when none existed — until their troubleshooting technique resulted in one, a $1,100 one.

AMT: Please walk me through the process for resolving these problems.

Vogel: Carburetion problems are almost always a cleanliness issue. Often people will be struggling with issues and call us for help. After finding out how old the carburetors are, or how long it’s been since they’ve had any scheduled maintenance, we suggest that the carburetors be rebuilt and taken back to their original configuration so we can eliminate the obvious before continuing to troubleshoot. As you might expect, after the rebuild the carburetors are reinstalled and synchronized — and the problems are gone.

If the problem persists, there are other adjustments available, but you’ll want to consult with someone who possesses a lot of experience with these engines before toying with them.

Kickbacks: Replacement of the sprag is a heavy maintenance repair item. That means it should only be done by a facility that has the specialized tools and training to accomplish the task. In the vast majority of installations this means the engine must come out of the airplane. Now you know why we urge people to take care of starting problems before they get to the point of damaging the sprag.

One of the key ways to avoid doing this damage is to get a Soft Start module installed in one of the ignition circuits. Experience from the field indicates that even if the airplane has one of these other problems, the Soft Start may make up for it.

When it comes to ignition, the most frequent problem — when one shows up — is the wiring. Once it’s been located it is easily repaired — unless the break occurs very close to where the wire disappears into the component. Once the wire is repaired, take another look at the way the installation is done. If the connectors are not secured, they could be flopping around due to engine vibration and/or wind buffeting, and be the source of the wire failure. Make sure you secure the connectors — securing wire bundles next to the connectors will only make matters worse.

If troubleshooting indicates one of the actual components is the problem, replacement is the corrective step. All the components, as we said earlier, are solid state. There is no such thing as opening them up and repairing them.

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