Readback: January 2020

Your shop gave you bad advice. Garmin says that the frequencies are sufficiently different, even counting various harmonics, that interference wouldnt be an inherent problem. They do, though, recommend a minimum of two feet between a GPS antenna and any strong transmitter. There are few, if any, airframes where it would be impossible to get at least that. If your tech, however, has seen that problem, its likely due to other factors, like poor antenna grounding, poor connections, bad wiring, etc., but not antenna proximity unless they were right next to each other.

Key Takeaways:

• A normal 3-degree glidepath corresponds to a 1:20 descent angle, correcting a previous article's misstatement.
• ADS-B Out antenna diversity is generally safe for small aircraft; reported jamming concerns are usually due to installation factors like poor grounding or proximity, not inherent frequency interference.
• LPV approaches are classified as "Approaches with Vertical Guidance" (APV) by ICAO (not true precision), but are credited as precision approaches for FAA checkride and IPC testing purposes.
• Garmin resolved an issue where G1000 navigators omitted some approaches by correcting erroneous Visual Descent Angle (VDA) coding in the navigation database, effective from Cycle 1912.

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