What happened
On March 13, 2013, an Embraer ERJ 170-100 LR operated by a French airline arrived at Nuremberg Airport. The flight, carrying 77 passengers and four crew members, proceeded without incident until the aircraft reached its parking position. Shortly after the aircraft was connected to ground power, a hissing sound was heard, and the ground power unit automatically shut down.
Following the shutdown, an electrical odor and visible smoke appeared in the cockpit. The pilot immediately instructed ground personnel to bring passenger stairs to the aircraft and directed the passengers to evacuate the aircraft via the normal stairs. There were no injuries resulting from the event, though the aircraft sustained minor damage.
The investigation
The BFU examined the aircraft's external power connection, located on the underside of the fuselage near the nose gear. The investigation included an analysis of the aircraft's voice data recorders, which confirmed that no unusual events occurred during the flight prior to landing.
Investigators inspected the external power connection components, including the bolts, cable lugs, and nuts for the AC phases. The ground power unit used during the incident was also tested by the airport's maintenance workshop. Additionally, the airline conducted a fleet-wide inspection of 25 Embraer jets to check for foreign object debris (FOD) under the external power connection covers.
Findings
While the exterior of the external power connection showed no damage, the interior of the connection was covered in melted material. The connection cables and the circuit breakers located above the connection were blackened by soot, and the insulation on the surrounding conduits had sustained heat damage. Specifically, the bolts, cable lugs, and nuts for the AC phase connections had melted.
Testing of the ground power unit revealed no defects, and the unit had shut down due to a "generator short circuit" error. This indicated that the short circuit originated within the aircraft. The airline's fleet inspection revealed that in 13 of the 25 inspected aircraft, metal debris—such as metal shavings, washers, and screws—was found under the connection covers. These findings suggest that foreign objects entered the connection through openings in the protective cover, leading to the electrical malfunction.