Two days after a fire forced the grounding of the 787 test fleet, a power control panel, responsible for distributing electrical power generated by the aircraft's left engine, is at the center of the investigation.
Program and supplier sources confirm the panel, known as P100, caught fire as ZA002 was passing through 1000ft during its final approach into Laredo, Texas on Tuesday.
Boeing declined to comment prior to publication to this report, but later confirmed the P100 panel was significantly damaged by the fire.
Boeing says: "We have determined that a failure in the P100 panel led to a fire involving an insulation blanket. The insulation self-extinguished once the fault in the P100 panel cleared. The P100 panel on ZA002 has been removed and a replacement unit is being shipped to Laredo. The insulation material near the unit also has been removed."
The P100 panel sits on the left side of the aft electrical equipment (EE) bay, and is part of a highly-integrated electrical system that receives 235v ac power from the left engine's twin 250 kVA engine generators for distribution throughout the aircraft.
An identical P200 panel performs the same tasks for the right engine's generators.
The 787 more-electric systems architecture is driven by up to one megawatt of electricity from the two 250 kVA variable frequency starter generators (VFSG) on each of the 787's twin General Electric GEnx-1B or Rolls-Royce Trent 1000 engines. ZA002 is powered by Trent 1000 engines.
The P100 panel is home to seven main components supplied by Hamilton Sundstrand, including those that are responsible for commanding loads on and off to various systems depending on the need on board the aircraft, as well as components that replace thermal circuit breakers, which provide overload and fault protection.
Further complicating ZA002's return to testing is the damage sustained during the fire, which included dripping of molten metal onto the system wiring and internal fuselage structure, which program sources say is driving Boeing's inspection of the area surrounding the P100 panel to "determine if other repairs will be necessary."
"As part of our investigation," says Boeing, "We will conduct a detailed inspection of the panel and insulation material to determine if they enhance our understanding of the incident."
"In addition, we are determining the appropriate steps required to return the rest of the flight test fleet to flying status."
Boeing is continuing to investigate the fire and determine any impact to "the overall program schedule" as it reviews data collected from the incident.