What happened
On May 26, 2019, a student pilot conducting a training flight under a structured training program departed for a mission involving several flight segments. While cruising at 3,000 ft near Opatów, the pilot observed that the fuel gauges were providing inaccurate readings, indicating significantly less fuel than was actually on board.
In response to the fuel gauge discrepancy, the pilot decided to terminate the planned route to EPCD and instead diverted toward the airfield in Stalowa Wola (EP/EPST). During the diversion, the pilot noted erroneous oil temperature readings. Additionally, the Garmin G 500 display and the radio equipment began displaying an "External power lost" message. Although a low voltage warning light illuminated, the pilot did not notice the corresponding discharge indication on the ammeter. The aircraft landed safely at the airfield at 13:30 UTC without further incident. Following the flight, a mechanic confirmed that the battery had been discharged.
The investigation
The investigation focused on the electrical system performance and the pilot's monitoring of the cockpit instruments. The investigation established that the battery had depleted during the flight due to a failure to maintain proper charging.
Findings
- The primary cause of the incident was the failure to engage the alternator (ALT) switch during the pre-taxi checks.
- The pilot failed to notice the low voltage warning light and the ammeter discharge indication during the flight.
- Following the event, the operator replaced the battery and verified that the alternator and all electrical components, including fuel and oil gauges, were functioning correctly.
- As a preventive measure, the training organization decided to remove the specific procedure of testing the alternator by switching it off and on during the pre-taxi phase from their Standard Operating Procedures (SOP).