“This comprehensive series of tests will show us whether the proposed battery improvements will work as designed,” says U.S. Transportation Secretary Ray LaHood. “We won't allow the plane to return to service unless we're satisfied that the new design ensures the safety of the aircraft and its passengers.” FAA Administrator Michael Huerta adds the agency is “confident the plan . . . includes all the right elements to conduct a comprehensive evaluation of the battery system redesign.”
The plan lays out a series of pass-fail criteria, and “defines the parameters that should be measured, prescribes the test methodology and specifies the test setup and design. FAA engineers will be present for the testing and will be closely involved in all aspects of the process,” the FAA adds.
Flight tests of the prototype revised battery containment system will be conducted using Line No. 86, an aircraft designated for LOT Polish Airlines. Aviation Week was the first to report this same aircraft being previously used for ground tests of the battery system in mid-February (AW&ST Feb. 18, p. 32). The modified battery has also been installed in test aircraft ZA005, though Boeing says this is to allow testing to resume of the planned General Electric GEnx performance improvement package (PIP) II engine upgrade. The FAA says flight tests will validate instrumentation for the battery and testing its enclosure in addition to improvements for other systems.
Explaining the triple-layered safety improvements in the revised battery system, Boeing's Conner says the design will prevent faults from occurring and “isolate any that do.” It also incorporates enhanced production, operating and testing processes. “In the unlikely event of a battery failure, we've introduced a new enclosure system that will keep any level of battery overheating from affecting the airplane or being noticed by passengers,” he adds.
Boeing says the enhanced production and testing processes include “more stringent screening of battery cells prior to battery assembly.” Operational improvements also focus on tightening of the battery system's voltage range. This addresses another finding of the NTSB interim report that the battery did not behave as either Boeing or the system subcontractor Thales indicated. In particular, the battery's power discharge was “not at the constant rate described by the Boeing or Thales documents and included large changes and reversals of power within short periods of time,” it notes.
Operators and lessors express encouragement at the FAA's approval of Boeing's fix. Speaking at the Istat Americas 2013 conference in Florida, Air Lease Corp. Chairman and Chief Executive Steven Udvar-Hazy said the move is “. . . positive. Customers are looking forward to getting it back in the air and certainly this is a good step forward. I'm happy the FAA is taking a constructive role with Boeing in moving this forward.”