French aviation safety authority BEA has suggested that Embraer consider design changes to portions of the electrical system for its E-Jet regional jets, and that safety upgrades be made at Germany’s Nuremberg Airport.
The French authority made the request indirectly in comments on a draft final report released by the German Federal Bureau of Accident Investigation (BFU), which focused on a March 2013 incident involving an Air France Regional Embraer 170-100LR at the Nuremberg Airport. BEA was involved in the investigation, as the aircraft was registered in France and the airline is based there. BFU did not directly implement either recommendation in the final report, released this week.
The incident occurred when the aircraft arrived at the parking stand in Nuremberg, and the ground crew plugged in the external ground power connector to a receptacle on the underside of the fuselage to the left of the nose landing gear. The 77 passengers and four crewmembers had not yet deplaned when the pilots heard a “hissing sound” in the cockpit, followed by an electrical smell and smoke. The pilots called for the ground crew to push passenger stairs to the aircraft “as quickly as possible,” and for the passengers to “immediately disembark” using the stairs. The incident caused minor damage to the aircraft but no injuries.
Investigators found that the external side of the power receptacle was not damaged, but the internal portion was “covered by molten material.” Wire bundles, circuit breakers and the insulation above the receptacle were covered in soot. Analysis of the ground power unit showed that the system disengaged when a short circuit occurred in the aircraft. BFU noted that the cable lugs that connect the aircraft systems to the back of the power receptacle are covered by a plastic cap, but the cap has an opening of approximately 10 mm (0.4 in.) at the top.
Air France Regional inspected the receptacle area on 25 other E-Jets, finding “metal pieces”—including metal chips, washers, bolts “and the like”—in 13 of the aircraft, according to the report. Implied in the final report is that metal debris caused the short circuit. In September 2015, Embraer issued a service bulletin “which describes how the openings in the upper side of the external power receptacle covers can be closed to prevent short circuits by foreign objects,” the BFU said. Based on that response, the agency did not issue any safety recommendations.
BEA in its comments, however, asked for a safety recommendation “aimed at improving the design” of the plastic cap, as well as potential safety recommendations for operations at the airport. The final report did not include the connector design review, likely because Embraer had issued a service bulletin. It also did not include potential recommendations related to ground operations.
“The draft report does not mention that the cockpit voice recorder showed that the crew had difficulties contacting the ground personnel,” the BEA said. “When the pilots tried to get in contact with the ground staff, the ground power unit operator was no longer around and the stair drive apparently did not quickly understand the urgency of the situation.” BEA said the situation “made the decision to evacuate more difficult to take, as the actual situation around the aircraft was not properly reported to the crew.”
While the airline’s ground procedures require “systematic use of headsets” by the ground crew to contact the pilots, BEA said this was not done. “It is not known in this report if the ground staff at Nuremberg is trained about company procedures and standard practices,” BEA said.