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Real GPS Outage

One has only to monitor the GPS NOTAMs to conclude that our near-100 percent confidence in GPS is misplaced. Here’s a story of a real GPS outage.

No GPS position
Gemini Sparkle

Key Takeaways:

  • A localized GPS outage at an airport was traced to two re-radiating GPS antenna systems in a nearby maintenance hangar that were inadvertently interfering with external signals.
  • The incident highlights the critical need for pilots to maintain proficiency in non-GPS navigation (e.g., VHF nav or "green needles") and always verify GPS integrity before flight.
  • The author advises against the trend of eliminating VHF navigation systems during modern panel upgrades, considering it unsafe for aircraft regularly flying in Instrument Meteorological Conditions (IMC).
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Routinely, my two GPS navigators will lock onto GPS satellites within a few minutes once powered up. But not this time. Both indicated LOI (loss of integrity), implying that the GPS satellites were insufficient. This was confirmed when no satellites appeared on the GPS Status pages. With the failure in two separate units, a failure in the airplane was unlikely. I suspected some systemic GPS problem.

Curiouser and Curiouser

Once I taxied perhaps 100 yards beyond the FBO, the satellites came alive one-by-one. Since I remain well practiced in VHF nav, and it was a local flight, I continued.

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