What happened
On September 22, 2022, a Piper PA32RT-300 (registration OY-GVD) was conducting a local VFR flight from Roskilde (EKRK) when the pilot experienced intermittent failures of the aircraft's communication and navigation equipment. During the flight over South Zealand, the pilot observed sparks and the development of smoke within the cabin.
As the situation progressed, the pilot attempted to toggle both avionics master switches repeatedly in an effort to resolve the issue, but the electrical malfunction persisted. While the smoke did not significantly obstruct visibility, the pilot reported the situation to Copenhagen Information and sought guidance for an emergency landing. After evaluating nearby options, the pilot determined that available fields were too short and elected to climb to 3,000 feet to proceed toward the Køge VFR report point. During this period, the pilot used a mobile phone to message the aircraft owners to request that they contact Roskilde Tower to advise of the intended flight path.
The pilot eventually returned to Roskilde, where emergency vehicles were already on standby. The aircraft landed safely on runway 2/21 without further incident.
The investigation
The Danish Accident Investigation Board examined the aircraft's electrical systems and the pilot's emergency response. A subsequent inspection at a maintenance facility revealed that one of the two avionics master switches had become charred and sooty due to an internal failure. The second switch remained intact.
The investigation also reviewed the operational procedures regarding the use of the two parallel-connected switches. While maintenance recommendations suggested keeping one switch off to mitigate risks, the aircraft owners had been operating with both switches turned on. Additionally, the investigation looked into the pilot's use of emergency checklists during the high-stress event.
Findings
- An internal failure in one of the avionics master switches caused the sparks and smoke in the cabin.
- The pilot was distracted by the unfolding emergency and did not utilize the aircraft's emergency checklist, which could have helped structure the decision-making process and reduce stress.
- There was a discrepancy between the maintenance-recommended procedure for the master switches and the actual operational practice of the aircraft owners.