An All Nippon Airways Boeing 787 experienced a minor electrical fault during a recent proving flight, but the cause was traced to an insufficiently turned nut in an electrical panel.
During a proving flight on 4 May on the Tokyo Haneda-Chitose route, the flightcrew of aircraft registration JA809A observed five advisory messages about an error in an electrical distribution panel located in the aircraft's aft power bay, says an ANA spokeswoman.
Only a pilot and co-pilot were aboard the aircraft.
The flightcrew continued to Chitose and landed safely at 16:15 local time. Upon examination, it was revealed that a nut used to secure the panel had been insufficiently tightened, thus causing heat and turning part of the panel black.
Both the nut and electrical panel were replaced by 7 May, and the aircraft returned to Tokyo Haneda on another proving flight with a new crew.
ANA is conducting 230 proving flights with the 787 to ensure crew proficiency in the type before it re-enters revenue service with the carrier on 1 June.
The world's 787 fleet was grounded in January after separate battery fires aboard a Japan Airlines 787 on the ground at Boston Logan airport and aboard an ANA 787 that resulted in an emergency landing. Boeing's modified battery and containment system has been installed on 15 to 16 of ANA's 17 787s, says the spokeswoman.
The carrier also received its 18th 787 in the week ended 19 May.