GNSS Interference

Question 1

What are the implications of deselecting GNSS?

Answer 1

Only aircraft position impacted, not surveillance equipment (TAWS or ADS-B).
Full capabilities not recoverable when GPS signal restored.

Question 2

Will GPS PRIMARY LOST be displayed as soon as GPS data is lost or incorrect?

Answer 2

No, the FMGS enters coasting mode and uses IRS data for position. “GPS PRIMARY” remains displayed as long as horizontal integrity is within the threshold.

Question 3

Where can we find the airways PBN requirements?

Answer 3

By long pressing the airway on LIFO En-route map, then selecting info button.

Question 4

What to do after suspected GNSS interference?

Answer 4

• ASR
• MOC

Question 5

What are the impacts of erroneous timing data?

Answer 5

Lost CPDLC, ADS-C, erroneous FMS time and Fuel predictions.

Question 6

What are the impacts of erroneous vertical GPS data?

Answer 6

Wrong predictive GPWS warnings and cautions and DBUS (Backup Speed Scale).

Question 7

What are the implications of erroneous lateral GPS data?

Answer 7

• Incorrect ADS-B transmission
• Terrain Display Shift (not Map shift)

Question 8

What to do before TO if GPS PRIMARY not available?

Answer 8

TO from full length of enter TO shift on PERF TO page as per TO SHIFT shown at bottom right of FS+.

Question 9

For how long does the clock INT keeps ATC Datalink capabilities after correct GPS synchronisation?

Answer 9

24h

Question 10

What to refer to in case of suspected GNSS interference?

Answer 10

FCOM PRO-NOR-SUP-GPS INT for course of action and PRO-SPO-51 PBN Management of degraded navigation for the according RNP requirements of the airway.