What happened
On June 22, 2016, at 11:13 UTC, a Liberty XL2, registration SP-TZC, was participating in a five-aircraft formation flight for instructor training near the HOTEL1 waypoint in the Rzeszów (EPRZ) control zone. The flight was operating under Visual Meteorological Conditions (VMC) approximately 30 minutes after departing from Jasionka (EPRJ) at an altitude of 2,500 feet.
During the flight, the aircraft experienced a momentary loss of engine power accompanied by several cockpit warning messages, specifically EBAT FAIL, POWER FAIL, and ALT FAIL, indicating malfunctions in the engine and alternator systems. The pilot immediately terminated the training mission and declared an emergency, requesting landing permission for runway 27 at EPRZ. At the time of the request, a Lufthansa CRJ7 was operating on runway 27 at EPRZ; that aircraft departed shortly after the SP-TZC pilot reported the technical issues.
Two minutes after the initial declaration, the pilot of SP-TZC informed the controller that the situation had stabilized and requested a diversion to land at the original departure airfield, EPRJ, on runway 26L. The aircraft landed safely at EPRJ without further incident.
The investigation
The investigation focused on the electrical system malfunctions reported during the flight. Technical personnel from the operator, OKL Politechniki Rzeszowskiej, conducted inspections of the aircraft following the event. The examination revealed that the alternator housing had become loose, leading to physical contact with an "AUX" terminal. This contact created a short circuit within the aircraft's electrical system.
Findings
- The primary cause of the technical malfunction was a loose alternator housing.
- This looseness caused the housing to contact an auxiliary terminal, resulting in an electrical short circuit.
- The short circuit triggered the engine power fluctuations and the subsequent cockpit warnings (EBAT, POWER, and ALT FAIL).