What happened
On April 16, 2015, a flight crew performing an air ambulance mission from Przylądek (EPZG) to Warsaw Chopin Airport (EPWA) experienced multiple instrument malfunctions during descent into the Warsaw TMA. The crew observed several warnings on their flight instruments, including FD warnings on the left EADI, HDG1 warnings on the and left EHSI, a HDG warning on the center MFD, and red flags on the right RMI and right ADI (COMPUTER). Following the Quick Reference Handbook (QRH) procedures, the crew switched the HDG selector on the EFIS panel from NORM to XSIDE. This action cleared the warnings on the left EADI, left EHSI, MFD, and right ADI, allowing the crew to proceed with an ILS approach to runway 33 and land safely.
Following the initial event, the Piaggio P180 Avanti I was grounded for maintenance. Although technicians performed cleaning and functional tests on the autopilot and gyroscope connection systems which initially passed, a second incident occurred on April 20, 2015. During the before-taxi checklist after engine start, the pilot identified new HDG red flags on the ADI, MFD, and RMI 2, accompanied by an FMS message indicating an EFIS#1 HDG failure. The aircraft was again removed from service.
The investigation
The investigation focused on the recurring instrument failures and the subsequent maintenance actions. Technical personnel at the Warsaw-Okęcie maintenance facility performed a thorough inspection of the flight instrument systems. Following the second occurrence, technicians replaced the Primary DGS Directional Gyro, which is the main gyroscopic platform for the aircraft's heading indication system.
Findings
- The primary cause of the instrument malfunctions was a failure of the main gyroscopic platform within the heading indication system.
- The initial maintenance attempt, which involved cleaning and testing connections, did not resolve the underlying hardware defect.