Definition
Notices to Air Missions that report the operational status of the GPS satellite constellation, including scheduled satellite outages, unscheduled outages, and degraded service that may affect the availability or integrity of GPS-based navigation. Pilots planning IFR flight using GPS are required to check these notices before departure to confirm that the satellites needed for the route and approach will be usable.
Plain English
Official notices that tell pilots when GPS satellites will be out of service or working poorly, so they know whether they can rely on GPS for the flight they are planning.
Context Anchor
Seen during IFR preflight planning when checking notices before using GPS for en route navigation, an arrival, or an instrument approach.
Derivation
NOTAM stands for Notice to Air Missions (formerly Notice to Airmen). GPS NOTAMs are simply the subset of these notices that deal specifically with the Global Positioning System.
Why Pilots Care
GPS NOTAMs can reveal when satellite coverage is degraded, forcing a pilot to use an alternate navigation method or delay a flight to avoid loss of required navigation performance.
Intuition Check
Do not assume GPS will always warn you about every planned GPS problem in the area. GPS NOTAMs are part of the preflight check before relying on GPS, especially for IFR flight.
Example Sentence 1
During preflight, the pilot checked GPS NOTAMs and found a scheduled satellite outage that would affect the RNAV approach at the destination.
Example Sentence 2
A GPS NOTAM warned of reduced satellite coverage over the destination area, so the crew prepared to use VOR backup navigation.