On Wednesday, January 16, 2013, a Boeing 787 flight operated by ANA was forced to make an emergency landing at Takamatsu Airport due to a battery-related malfunction. We would like to once again express our deepest apologies for the considerable anxiety and inconvenience caused to the passengers aboard the flight and all parties concerned.
We would like to explain ANA’s comprehensive safety measures for batteries.
Explanation of a Passenger Aircraft’s Electrical System
- Engine Electric Generators - Main Power Source
- Operation of the computers, cabin lighting, in-flight entertainment systems, etc. of an aircraft all require electricity, which is normally generated by generators in the engines. The B787 is equipped with two generators in each engine, plus another two generators in the APU* which serve as a backup system, for a total of 6 onboard electric generators.
*Auxiliary Power Unit: This small jet engine is located at the rear of the aircraft and is mainly used to power aircraft systems when the aircraft is on the ground. On the B787, the APU is only used to provide electricity.
- Aircraft Batteries - Not Used in Normal Flight
- Passenger aircraft, including the B787, are generally equipped with two batteries, a Main Battery and an APU Battery. These batteries perform the roles shown below.
During normal flight situations, these two batteries are not used.
Outline of the battery-related investigation and technical solution development process.
- Expert Investigation Team
- In conjunction with the Japanese Ministry of Land, Infrastructure, Transport, and Tourism’s on-going investigation of the root cause of the battery malfunction, Boeing is also leading efforts to find technical solutions. Boeing formed a team which consisted of their own battery specialists as well as experts from the American automobile industry, battery manufacturers, academic institutions, etc. to thoroughly investigate the root cause of the battery malfunction. ANA also took part in the investigation.
- Identifying All Possibilities
- Boeing’s investigation team studied all possible causes of the battery malfunction and concluded that, since it did not originate from outside the battery (on the aircraft side), it had originated from within the battery system. It is believed that the malfunction was the result of the process below.
Boeing’s investigation team thus identified every possible cause that could trigger overheating of the battery cells. These causes can be classified into the following four categories.
- Creating the Solution
- While the root cause of the malfunction is being pinpointed, Boeing developed a set of comprehensive technical solutions which would cover all of the possible causes that were identified. Consequently, the battery system modification package includes solutions for all four groups of causes that were just mentioned.
- The triple-layered protection scheme not only prevents the initial cell from overheating, it also includes measures to prevent it from spreading in the first place, and isolate it if it occurs.
- More specifically, battery and charger modifications protect against the initiation and propagation of any malfunction, and a battery enclosure acts as a containment vessel for any effects of unforeseen malfunctions.
<Concept of Triple-Layered Protection >
- Details of the Modifications
- The three main points of the modifications are described below.
|To prevent battery overheating as well as propagation of heat to the surroundings in the event of overheating, the design and manufacturing processes were improved.
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|To decrease the burden on the battery, the battery charging method and the instruments used to monitor battery conditions have been improved.
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- In the event that a battery malfunction does occur, this newly installed battery enclosure would confine it within the battery. The metal enclosure prevents smoke, etc. from affecting other aircraft systems, thereby ensuring flight safety.
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- ANA’s Opinion
Regarding these modifications:
・ANA worked together with Boeing during the investigation and the modifications reflect our experience and knowledge as an airline.
・ANA also independently verified the modifications with over ten domestic battery, electronics, and material manufacturers, research organizations, etc. As a result, ANA determines that the modifications are sufficient to allow B787 operations to resume and provide safe service to our passengers.
In order to ensure the safety of our passengers, the following program was implemented after resumption of B787 passenger service.
- To confirm battery performance after the batteries have been in use for a specified period of time, the batteries will be removed and checked at designated intervals. This confirmation will be conducted in cooperation with Boeing and other manufacturers.
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- To maintain safety, battery performance is monitored during flight operations. ANA has implemented a system that alerts engineers on the ground as soon as any signs of irregularities are detected.
Information regarding the progress of the modifications and post-modification service results.
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- Is it safe to resume passenger service when the root cause of the malfunction has not yet been pinpointed?
Every conceivable cause which could lead to battery overheating was identified and the modifications include comprehensive solutions to cover all of them.
- What types of modifications are involved?
1) Battery Modifications: Prevention of battery overheating.
2) Charger Modifications: Improvement of the battery charging system.
3) Enclosure Installation: In the event a battery overheats, it will be contained within the enclosure.
- What is the process for confirming safety and implementing the modifications?
The modification program developed by Boeing is reviewed and approved by the Federal Aviation Administration(FAA) in the United States. The Japan Transport Safety Board then also review and approved this program. ANA will implement the required modifications in accordance with the modification program.
- Are the details of the modifications the same as other companies?
Yes. All airlines will follow the same modification order.
- What would happen if the battery becomes inoperable during a flight?
The two generators in each engine provide electricity during flight, so the safety of flight operations will not be affected even if battery system functions are lost.
- What about other malfunctions which ANA has reported in the past?
With regards to previously-reported malfunctions related to fuel leakage, oil leakage, brakes, cockpit glass, etc., modifications and inspection procedures are already in place.