What ignition system is approved for a Lycoming engine model 0-540-A4A5?

The correct answer identifies the Bendix magneto models S6LN-20 and S6LN-21 as the approved ignition system for the Lycoming engine model O-540-A4A5. This is accurate because the specifications and type of ignition systems approved for particular engine models are determined by the engine manufacturer and documented in the engine's maintenance manuals or service bulletins.

Bendix S6LN-20 and S6LN-21 magnetos are specifically designed for use with certain Lycoming engines, including the O-540-A4A5. These models provide the necessary performance and characteristics to meet the operational requirements of that engine.

Understanding the approved ignition systems is vital for compliance with regulations and for ensuring the reliable operation of the engine, as using an unapproved ignition system can lead to suboptimal performance or safety issues. Different magneto models have variations in specifications, such as timing, output, and installation features that align with the specific engine requirements. This makes it essential to select the correct models as specified by the manufacturer.