ADS-B Shenanigans?

Thank you for printing in Augusts magazine the short letter I wrote, highlighting an issue I encountered just south of the Albany, N.Y., Class C airspace-a Cub showing an ADS-B altitude of 500 feet below sea level. (By the way, I passed the same Cub today at very close range. This time he wasnt showing up at all on ADS-B). In your response, you asked readers to report other anomalies, so heres one from a week or so ago.

Editorial Staff

Tuesday, October 01, 2019 at 12:00 AM ET

Verified

Key Takeaways:

A reader reported multiple recurring ADS-B data anomalies, including an aircraft showing 500 feet below sea level and another reporting over 1000 knots groundspeed, leading to speculation that a local ground station might be misinterpreting the data; the magazine encouraged other readers to report similar "ADS-B shenanigans."
Another reader introduced "POH Performance" apps that calculate and adjust aircraft takeoff and landing distances for sloped runways, based on historical flight test data, providing conservative estimates, and are available for free with published source code.

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Thank you for printing in August’s magazine the short letter I wrote, highlighting an issue I encountered just south of the Albany, N.Y., Class C airspace—a Cub showing an ADS-B altitude of 500 feet below sea level. (By the way, I passed the same Cub today at very close range. This time he wasn’t showing up at all on ADS-B). In your response, you asked readers to report other anomalies, so here’s one from a week or so ago.

I was in nearly the exact same location as I was for the prior report when my ADS-B In/Out transceiver, a Garmin GTX 345, highlighted an aircraft passing low overhead at a speed of 1033 knots. I eagerly acquired it visually, assuming it was a UFO. (There has been a spike in UFO sightings recently—I was hoping to report the first one with ADS-B compliance!)