Boeing engineers repairing the Ethiopian Airlines 787-8 stranded at London Heathrow Airport for five months since it was badly damaged by an emergency beacon fire have replaced a large section of the upper fuselage structure and refitted the tail unit as part of efforts to return the aircraft to service early next year.

The fire, which started July 12 in one of the 787’s Honeywell-made Rescu 406AFN emergency locator transmitters (ELTs) while parked between flights, scorched the crown of the fuselage forward of the tail fin leading edge and caused major smoke damage to the interior. Cabin linings, panels and furnishings were ruined while water and other agents used by fire fighters are also believed to have caused significant damage to the interior and systems of the aft lower lobe.

Boeing, which declines to comment on details of the repair, is understood to be around 60% of the way through the recovery process.

The fin originally was removed to enable a large area of the Section 47 crown to be cut out and replaced with a new section. This unit is normally integrated with the rest of the aircraft as a one-piece barrel structure combined with the aft-most Section 48. However, for the Ethiopian repair task, Boeing opted to insert a new composite crown section.

It is thought the replacement section included the integrated co-bonded stringers which form part of the standard barrel unit. The repair also is likely to include the addition of ribs that will be integrated on site.

As well as the major structural repair—one of the largest and most significant ever undertaken on a composite fuselage primary structure—the refurbishment also is believed to involve complete replacement of the interior paneling, sidewalls, overhead fixtures, lining, seats and other fittings.

The full repair, including interior fittings and all inflight entertainment and other cabin systems, is expected to be completed in-situ at Heathrow, rather than involving a two-stage process in which the aircraft would have been made airworthy for a ferry flight to another maintenance facility.

The 787 is fitted with two ELTs located in the main passenger cabin: one in front of the forward lavatory, which is aft of the flight deck bulkhead, and a second in the aft cabin, above the galley outboard storage area. The units contain an internal electronics box and external antenna and are powered by five lithium-based battery cells that are chemically different from the lithium-cobalt batteries used in the main and auxiliary power unit batteries that caused a fleet grounding earlier this year.