Boeing received approval from the US Federal Aviation Administration (FAA) of the company’s plan to test and certify improvements to the 787’s battery system. Successful completion of each step within the plan will result in the FAA’s approval to resume commercial 787 flights. (Earlier post.)
Working with internal and external experts in battery technology, we have proposed a comprehensive set of solutions designed to significantly minimize the potential for battery failure while ensuring that no battery event affects the continued safe operation of the airplane.
Our proposal includes three layers of improvements. First, we’ve improved design features of the battery to prevent faults from occurring and to isolate any that do. Second, we’ve enhanced production, operating and testing processes to ensure the highest levels of quality and performance of the battery and its components. Third, 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.—Ray Conner, president and CEO of Boeing Commercial Airplanes
Design feature improvements for the battery include the addition of new thermal and electrical insulation materials and other changes. The enhanced production and testing processes include more stringent screening of battery cells prior to battery assembly. Operational improvements focus on tightening of the system’s voltage range. A key feature of the new enclosure is that it ensures that no fire can develop in the enclosure or in the battery. Additional details of the new design will be provided by Boeing in the days ahead.
Boeing made its certification plan proposal to the FAA in late February.
The FAA also granted Boeing permission to begin flight test activities on two airplanes: line number 86, which will conduct tests to demonstrate that the comprehensive set of solutions work as intended in flight and on the ground; and ZA005, which is scheduled to conduct engine improvement tests unrelated to the battery issue. Additional testing may be scheduled as needed.
The certification plan calls for a series of tests that show how the improved battery system will perform in normal and abnormal conditions. The test plans were written based on the FAA’s standards as well as applicable guidelines published by the Radio Technical Commission on Aeronautics (RTCA), an advisory committee that provides recommendations on ways to meet regulatory requirements. The RTCA guidelines were not available when the original 787 battery certification plan was developed.
NTSB investigation. The National Transportation Safety Board investigation into the cause of the APU battery fire on the 787 at Logan Airport on 7 January continues. NTSB issued an Interim Factual Report on 7 March, without drawing any conclusions or recommendations.
In addition to the ongoing investigation of the battery, NTSB is also continuing to review the design, testing, certification, and manufacturing processes for the 787 lithium-ion battery system.
During the 787 certification process, Boeing performed a safety assessment (known as functional hazard assessment) to determine the potential hazards that various failure conditions of electrical system components could introduce to the airplane and its occupants. Boeing also determined that the probability that a battery could vent was once in every 10 million flight hours. As of January 16, 2013, the in-service 787 fleet had accumulated less than 52,000 flight hours, and during this period two events involving smoke emission from a 787 battery (the BOS event and a second event in Japan being investigated by the Japan Transport Safety Board) had occurred on two different 787 airplanes.—NTSB Interim Report
The NTSB public docket for this incident, DCA13IA037, can be accessed at the NTSB’s website.