What happened
On December 23, 2019, a privately owned Embraer ERJ190-100ECJ, registered B-3203, was performing a final approach to Runway 01R at New Chitose Airport. The flight, which included 19 passengers and five crewmembers, was operating with one display unit already inoperative under the Minimum Equipment List.
During the approach, at an altitude of approximately 1,260 feet, the aircraft's Engine Integrated Drive Generator 2 (IDG2) tripped off. The crew elected to continue the approach as the remaining generator was functioning normally. However, roughly 94 seconds later, while at a pressure altitude of approximately 240 feet, the Engine Integrated Drive Generator 1 (IDG1) also tripped off. This secondary failure resulted in the loss of both main AC power supplies.
As a consequence, the indications on all cockpit display units temporarily vanished, and an "ELEC EMERGENCY" warning was issued. The Ram Air Turbine (RAT) automatically deployed to provide emergency power, and standby instruments remained functional. Despite the loss of critical systems—including the autobrakes, nose wheel steering, and engine reversers—the captain successfully landed the aircraft. The crew used manual braking to decelerate and vacated the runway via a high-speed taxiway.
The investigation
The Japan Transport Safety Board (JTSB) examined the electrical power supply systems, including the Integrated Drive Generators (IDGs), Generator Control Units (GCUs), and the emergency power architecture. The investigation also reviewed the aircraft's flight data records and the status of applicable Service Bulletins (SBs).
Investigators found that while the aircraft's batteries and the RAT were functioning correctly to maintain essential instruments, the flight data recorder (CVFDR) had ceased recording during the power loss. This was attributed to a wiring configuration where the data communication channel was not connected to the battery-backed essential bus. Furthermore, the investigation looked into why the GCUs failed to maintain stable power distribution during the approach.
Findings
- The primary cause of the incident was the sequential loss of both main power supply systems. The first failure occurred when the GCU2 erroneously detected an overfrequency condition, causing IDG2 to trip. This was followed by the IDG1 tripping due to a false undervoltage detection by GCU1.
- The failure to incorporate existing Service Bulletins (SBs) for the GCUs contributed to the incident, as the unmodified units were susceptible to these false electrical detections.
- The loss of main power caused the temporary disappearance of all primary display units and rendered several landing systems, such as spoilers and autobrakes, inoperative.
- The flight data recorder stopped recording because its communication channel lacked a connection to the essential DC bus powered by the aircraft batteries.
- The crew's ability to land safely was aided by the fact that the captain had previously undergone simulation training for landing in power-loss scenarios.