DAVID GREENE, HOST:
Boeing and the Federal Aviation Authority are in for another day of tough questions, as the National Transportation Safety Board continues its probe of batteries on Boeing's 787 airliner. You might remember two severe battery failures prompted a worldwide grounding of the 787 fleet in January. While new batteries have just been approved and 787 flights will likely resume next month, there are ongoing questions about that original battery.
NPR's Wendy Kaufman reports.
WENDY KAUFMAN, BYLINE: The chairman of the NTSB, Deborah Hersman, made it clear that what she is looking for is lessons for the future, not just what went wrong here. And one of the biggest lessons from her perspective is testing, especially new technologies.
DEBORAH HERSMAN: There are always going to be challenges. What we want to make sure that we understand is what was known and how was that knowledge incorporated into the testing that was going on at the time.
KAUFMAN: Under sometimes intense questioning, Boeing officials acknowledged their risk assessment was too optimistic. They assumed the battery's design would result in only one severe failure every 10 million flight hours. But in fact there were two such failures in January. Boeing also acknowledged that their testing regime didn't always replicate what happens in the real world
Here's Boeing's Mike Sinnett, the chief project engineer on the 787.
MIKE SINNETT: We used what was the state of the art in the industry at the time for simulating a short-circuit of a cell. And that was using a nail penetration test. In retrospect, we don't feel that it was conservative enough.
KAUFMAN: The other focal point of the hearing was the standards and methods used by the FAA in approving the batteries. The NTSB is concerned that regulators relied too extensively on Boeing's own data and testing.
In a related matter, Steve Boyd of the FAA said the agency didn't feel the need to amend its certification standards even after an industry panel it was actively working with adopted more rigorous requirements.
STEVE BOYD: We think that's excellent when industry establishes a standard for themselves that exceeds the regulatory standards. But when it comes right down to it, we apply the regulatory standards as they appear in the special conditions.
KAUFMAN: Special conditions were the standards the FAA imposed on Boeing's batteries because the technology was still untested in commercial airplanes. The safety board will be asking a lot more questions about the certification process as the hearing continues today.
Wendy Kaufman, NPR News, Washington. Transcript provided by NPR, Copyright NPR.