Boeing is also using the 787 downtime to develop, test and certify a series of other systems improvements to areas that proved troublesome during the aircraft's initial service period. The work included testing a revised power panel design, an improved engine anti-ice system and upgrades to the back-up standby instrument displays and crew information system (CIS), a Honeywell-developed aircraft health-monitoring feature that forms part of the 787's central maintenance computer.
Boeing says that, following FAA clearance to resume test flights, it has been conducting “routine test flights designed to address some of the component reliability projects we have been working. One such flight last week was to conduct testing to address some of the power panel improvements we have been working. We are always working to improve component reliability, and a new airplane program always has some start up issues. This work never stopped. In fact, during the return to flight work we're doing with the airlines, we will be addressing several improvements that should help further improve the 787's overall reliability and performance, including screening of power panels and several other activities.”
Ground tests of new software for the aircraft's power electronics cooling system (PECS) were also undertaken. The PECS dissipates the heat created by the large, high-voltage motor controllers that condition the variable-frequency power generated by the engines and auxiliary power unit (APU) for use by aircraft systems. Although portions of the large motor power system are energized by the APU battery, the changes are related to the overall electrical system upgrades rather than being associated with the battery modification.
The power panel was the source of early in-service issues with the 787, at least one of which on an ANA aircraft in April was traced to a short circuit in one of the units. Power panel malfunctions were also behind a string of events in December that triggered error messages indicating failures of the aircraft's starter-generators.