What happened
On July 4, 2015, at approximately 12:15 PM, an MCR-ULC aircraft, registration HB-WBA, was performing a private VFR flight departing from Bad Ragaz. While the aircraft was in a climb phase near Maienfeld, the pilot observed a "low voltage" warning on the instrument panel. Shortly after this alert, the aircraft experienced a complete failure of the electrical system.
During the incident, the glider being towed successfully released from the aircraft, though the loss of electricity also caused the radio equipment to cease functioning. Following the electrical failure, the engine suffered an initial momentary drop in power, which quickly escalated into a total loss of engine performance. Realizing that returning to the airfield at Bad Ragaz was no longer possible, the pilot executed an emergency landing in a harvested field located roughly 2 km south of Maienfeld.
The investigation
The investigation focused on the sequence of technical failures that led to the loss of power. Investigators examined the state of the aircraft's electrical and propulsion systems following the event. Post-flight inspections revealed that the engine's loss of power was closely linked to the electrical malfunction. The investigation confirmed that the pilot's decision to land in the field prevented further escalation of the situation.
Findings
- The primary cause of the emergency was a total loss of engine power following an electrical system failure.
- The electrical failure began with a low voltage warning and progressed to a complete blackout of the onboard electrical network.
- The aircraft sustained no damage during the landing, and the pilot remained uninjured.
- Subsequent maintenance and inspections determined that the failure was attributed to a faulty regulator and a depleted battery, both of which were replaced.