AIM 1-1-13

Users of the National Airspace System (NAS) can render valuable assistance in the early correction of NAVAID malfunctions or GNSS problems and are encouraged to report their observations of undesirable avionics performance. Although NAVAIDs are monitored by electronic detectors, adverse effects of electronic interference, new obstructions, or changes in terrain near the NAVAID can exist without detection by the ground monitors. Some of the characteristics of malfunction or deteriorating performance which should be reported are: erratic course or bearing indications; intermittent, or full, flag alarm; garbled, missing or obviously improper coded identification; poor quality communications reception; or, in the case of frequency interference, an audible hum or tone accompanying radio communications or NAVAID identification. GNSS problems are often characterized by navigation degradation or service loss indications. For instance, pilots conducting operations in areas where there is GNSS interference may be unable to use GPS for navigation, and ADS-B may be unavailable for surveillance. Radio frequency interference may affect both navigation for the pilot and surveillance by the air traffic controller. Depending on the equipment and integration, either an advisory light or message may alert the pilot. Air traffic controllers monitoring ADS-B reports may stop receiving ADS-B position messages and associated aircraft tracks.

Malfunctioning, faulty, inappropriately installed, operated, or modified GPS re-radiator systems, intended to be used for aircraft maintenance activities, have resulted in unintentional disruption of aviation GPS receivers. This type of disruption could result in unflagged, erroneous position-information output to primary flight displays/indicators and to other aircraft and air traffic control systems. Since Receiver Autonomous Integrity Monitoring (RAIM) is only partially effective against this type of disruption (effectively a “signal spoofing”), the pilot may not be aware of any erroneous navigation indications; ATC may be the only means available to identify these disruptions and detect unexpected aircraft positions while monitoring aircraft for IFR separation.

Pilots encountering navigation error events should transition to another source of navigation and request amended clearances from ATC as necessary.

Pilots are encouraged to submit detailed reports of NAVAID or GPS anomaly as soon as practical. Pilot reports of navigation error events should contain the following information: Date and time the anomaly was observed, and NAVAID ID (or GPS).

Location of the aircraft at the time the anomaly started and ended (e.g., latitude/longitude or bearing/distance from a reference point),

Heading, altitude, type of aircraft (make/model/call sign),

Type of avionics/receivers in use (e.g., make/model/software series or version),

Number of satellites being tracked, if applicable,

Description of the position/navigation/timing anomaly observed, and duration of the event,

Consequences/operational impact(s) of the NAVAID or GPS anomaly,

Actions taken to mitigate the anomaly and/or remedy provided by the ATC facility,

Post flight pilot/maintenance actions taken.

Pilots operating an aircraft in controlled airspace under IFR shall comply with CFR § 91.187 and promptly report as soon as practical to ATC any malfunctions of navigational equipment occurring in flight; pilots should submit initial reports: Immediately, by radio to the controlling ATC facility or FSS.

By telephone to the nearest ATC facility controlling the airspace where the disruption was experienced.

Additionally, GPS problems should be reported, post flight, byInternet via the GPS Anomaly Reporting Form at http://www.faa.gov/air_traffic/nas/gps_reports/ .

To minimize ATC workload, GPS anomalies associated with known testing NOTAMs should NOT be reported in-flight to ATC in detail; EXCEPT when: GPS degradation is experienced outside the NOTAMed area,

Pilot observes any unexpected consequences (e.g., equipment failure, suspected spoofing, failure of unexpected aircraft systems, such as TAWS).