What happened
Between April 27 and April 29, 2019, a Cessna Citation CJ3+ (C525B) operated by a commercial operator experienced a series of navigation disruptions while operating within the Nicosia FIR, Cyprus.
During a flight from Poznań, Poland, to Larnaca, Cyprus, on April 27, the crew noted fluctuations in the GPS synthetic vision and several GPS switches, which caused the system to momentarily enter dead reckoning (DR) mode. While the approach to runway 04 was completed without further issues, two subsequent flights on April 29 experienced more severe disruptions.
On the flight from Larnaca to Linz, Austria, the crew lost all GPS indications, triggering terrain fail and ADS-B fail alerts. This loss of signal persisted for approximately 10 minutes until the aircraft reached flight level 400.
On the return leg from Linz to Larnaca, the crew observed fluctuations in the STAR arrival procedure. After passing the LCA VOR, the GPS signals were lost again, forcing the aircraft into dead reckoning mode. The crew performed an instrument approach for landing. During a turn toward the landing course in Larnaca, the GPS signal was restored, causing the Garmin map to jump approximately 2-3 nautical miles. The interference ceased during the final approach.
The investigation
The investigation, conducted by the operator, examined three consecutive flights where the crew reported significant GPS malfunctions. The investigation focused on the impact of signal loss on aircraft equipped with G1000/G3000 avionics, noting that such disruptions pose a significant risk to flight operations.
Findings
- The primary cause of the GPS signal loss was external interference with the GPS signal resulting from military activities being conducted in the aircraft's flight path.
- Atmospheric conditions had no impact on the occurrence.