What happened
On April 12, 2018, at approximately 13:59 UTC, a serious operational disturbance occurred at Graz Airport (LOWG) involving two aircraft. A Piper PA-28R-201 (Arrow III) was conducting a VFR flight from Vöslau (LOAV) to Klagenfurt (LOWK) with two non-flying passengers. Shortly after departure, the aircraft encountered turbulence that caused a navigation tablet to fall to the floor. During this incident, the pilot inadvertently toggled the alternator switch to the off position.
As the flight progressed, the aircraft experienced a total electrical failure. This failure resulted in a loss of radio communication with Air Traffic Control. Unable to maintain contact, the pilot elected to perform a precautionary landing at Graz Airport. At the same time, a Bombardier CRJ900 was on its final approach to runway 17C. The Piper landed on runway 35C, which was the active runway for the CRJ900's approach. To prevent a collision, air traffic controllers immediately instructed the crew of the CRJ900 to execute a go-around. The airliner subsequently completed a second approach to runway 35C without further incident.
The investigation
The Austrian Federal Safety Investigation Board (SUB) examined the sequence of events, including the flight paths, weather conditions, and the technical status of both aircraft. The investigation reviewed the pilot's flight planning, which utilized a private software rather than the standard ACG Homebriefing system. The investigators also analyzed the impact of the electrical failure on communication and the subsequent actions taken by the tower controllers to manage the conflict between the two aircraft.