What happened
On 12 December 2012, an Airbus A319-112, registration HB-IPX, was operating a scheduled commercial flight, LX 1250, from Zurich to Stockholm Arlanda. During the flight, the aircraft experienced a series of electrical disturbances. The sequence began with a brief voltage drop in a sub-busbar, which triggered the activation of the essential transformer rectifier.
As the flight progressed, the aircraft's electrical configuration fluctuated significantly. Between 13:13 and 13:30 UTC, the battery bus was repeatedly supplied by alternating transformer rectifiers, resulting in intermittent cockpit alerts regarding the brake system, blower, and extract fan. By 13:34 UTC, transformer rectifier 1 had switched off, forcing the aircraft to rely on transformer rectifier 2. Despite this change, multiple voltage drops continued to affect the primary DC bus and battery bus.
At 13:57 UTC, a circuit breaker tripped automatically, de-energizing a specific bus and causing the failure of various systems, including cockpit temperature controls and control panel lighting. During the descent and subsequent landing at Stockholm, the crew noted that the engine 1 anti-ice panel light failed to illuminate and the left engine thrust reverser did not function.
The investigation
The Swiss Transportation Safety Investigation Board (STSB) examined the aircraft's electrical power supply system, including the transformer rectifiers, circuit breakers, and the electronic instrument system. Investigators analyzed flight data recorder information and the post-flight report from the aircraft's centralized fault display system. Physical inspections were conducted on suspected loose connections, but no irregularities were found in the inspected areas.