The U.S. Federal Aviation Administration has approved Boeing’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 Boeing 787 flights, according to the manufacturer, but Boeing has not said yet how long it expects the process to take.
The FAA says the certification plan is the first step in the process to evaluate the 787’s return to flight and requires Boeing to conduct extensive testing and analysis to demonstrate compliance with applicable safety regulations and special conditions.
“Our top priority is the integrity of our products and the safety of the passengers and crews who fly on them,” says Jim McNerney, Boeing’ chairman, president and CEO.
“Our team has been working around the clock to understand the issues and develop a solution based on extensive analysis and testing following the events that occurred in January,” adds McNerney. “Today’s approval from the FAA is a critical and welcome milestone toward getting the fleet flying again and continuing to deliver on the promise of the 787.”
Ray Conner, president and chief executive officer of Boeing Commercial Airplanes, says the company’s focus has been on developing a permanent resolution to the battery issues which led to all 51 in-service Boeing 787s being grounded by the FAA on January 16.
The grounding followed two incidents in which a “thermal runaway” condition caused batteries in two Boeing 787-8 widebodies – a Japan Airlines aircraft on the ground at Boston on January 7 and an ANA 787 in-flight over Japan on January 16 – to emit dense smoke.
In the Japan Airlines incident, the aircraft’s auxiliary power unit battery – located midships in the aft electronics bay – also caught fire and it took firemen more than an hour and a half to put the fire out. One fireman was injured in the incident as molten material spat out from the battery and the fire caused damage to aircraft structures up to 20 inches away from the battery.
The ANA battery smoke incident – this time affecting the main battery, located in the forward electronics bay under the flight deck – required the pilots to make an emergency landing and order an emergency evacuation of the aircraft at Takamatsu. Japanese investigators subsequently found out the aircraft’s other battery (the APU battery) showed signs of damage as well.
“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,” says Conner.
“Our proposal includes three layers of improvements,” adds Conner. “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,” says Conner.
“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,” Conner says.
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, according to Boeing. The company says it will make additional details of the new design available in the days ahead.
Boeing made its certification plan proposal to the FAA in late February. Today the agency agreed that the proposed changes and the detailed test plans address the conditions that resulted in the suspension of 787 operations.
The FAA has also granted Boeing permission to begin what the agency calls “limited test flights” on two aircraft. The aircraft involved will be 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.
Boeing’s certification plan requires a series of tests which must be passed before the 787 could return to service, according to the FAA. The plan establishes specific pass/fail criteria, defines the parameters that should be measured, prescribes the test methodology and specifies the test set-up and design.
FAA engineers will be present for the testing and will be closely involved in all aspects of the process, the U.S. aviation regulator says. The manufacturer says it may schedule additional testing as needed.
Boeing’s 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 nine FAA “special conditions” developed specifically for lithium-ion battery certification in a commercial aircraft.
The company’s new battery-certification plan is also based on applicable lithium-ion battery certification guidelines published by the Radio Technical Commission on Aeronautics (RTCA), an advisory committee that provides recommendations on ways to meet regulatory requirements.
These RTCA guidelines were not available when the original 787 battery certification plan was developed, according to Boeing.
However, the RTCA guidelines were available well before the Boeing 787 was actually certificated under the FAA’s nine original “special conditions”. Additionally, some Boeing engineers sat on the RTCA sub-committee which developed the battery certification guidelines.
In the 787, Boeing uses lithium cobalt oxide chemistry, which offers a particularly high “energy density”, or ability to store electrical energy within a given battery volume. Lithium-ion batteries in laptop computers and cars typically use a different chemistry with a lower energy density, but are also known for their propensity to catch fire when over-charged or when their charges fall to a very low level.
“We have a great deal of confidence in our solution set and the process for certifying it,” adds Conner. “Before 787s return to commercial service, our customers and their passengers want assurance that the improvements being introduced will make this great airplane even better. That’s what this test program will do.”
The FAA says it will approve Boeing’s 787 battery redesign only if the company successfully completes all required tests and analysis to demonstrate the new design complies with FAA requirements.
Meanwhile, the FAA’s January 16, 2013 emergency airworthiness directive, which required operators to cease 787 operations temporarily, is still in effect. The FAA says it “is continuing its comprehensive review of the 787 design, production and manufacturing process”.