As U.S. National Transportation Safety Board investigators continued their painstaking examination of the lithium-ion battery that caught fire on February 7 in a Japan Airlines Boeing 787, the airplane’s manufacturer projected a business-as-usual posture during its fourth-quarter earnings call last Wednesday. Boeing chief executive Jim McNerney reiterated the company’s intention to maintain 787 production at five per month until mid-year, when plans still call for an increase to seven a month and, finally, to ten per month by the end of the year. McNerney repeatedly said he didn’t want to comment on “hypotheticals” when asked about the potential effect of a long-term grounding of the fleet.
Although he acknowledged that the rate of battery replacement in the field had proved “slightly higher” than predicted, McNerney characterized all the cases as routine. “I don’t have an exact number on how many batteries have been replaced, but what I do know is batteries are replaced on our airplanes every day…every type of battery, including these batteries,” said McNerney. “What we do know is the replacement cycle that we’ve been experiencing there has been for maintenance reasons. There hasn't been an incident that we’re aware of where a battery has been replaced due to any kind of safety concerns.”
The question arose after several press outlets last week raised concern about the rate of battery replacement in the 787. The U.S. National Transportation Safety Board has since confirmed that its investigation includes an analysis of records documenting the cause of earlier battery replacements.
A spokesperson from Japan’s All Nippon Airways told AIN that the airline had to replace 10 batteries before the latest failure prompted the grounding of the world fleet, but that none of the cases resulted in a flight delay or cancellation or required reporting to regulatory authorities. Half of the cases involved a drop in “capacity” of the main battery, according to the spokesperson. The other five involved a battery charger malfunction, a standby power malfunction, an APU starting problem, a power supply failure and a main battery warning message. JAL also confirmed “a few cases” but wouldn’t specify their cause.
ANA reported last week that the cost of the 459 flight cancellations the groundings forced during the month of January totaled some $1.4 billion yen ($15.4 million) in lost revenue.
Meanwhile, examination and testing of an exemplar battery got under way last week at the Carderock Division of the Naval Surface Warfare Center laboratories in West Bethesda, Maryland. The tests, which consisted of electrical measurements, mass measurements and infrared thermal imaging of each battery cell, uncovered no anomalies. On Friday investigators began conducting CT scanning to examine the cells’ internal condition.
At the same time, another investigative group continued to interpret data from the two digital flight data recorders on the JAL aircraft and examine recorded signals to determine if they might yield more information about the performance of the battery and the operation of the charging system. This week, the NTSB battery testing team plans to start a non-invasive “soft short” test of all cells of the exemplar battery in an effort to detect any high-resistance, small or “soft” shorts within a cell. The NTSB also plans to send an investigator to France with the airplane’s battery contactor, which connects a wiring bundle to the battery, for examination at its manufacturer, Thales.