Dette blir det diskusjon av: Skal et fly konstrueres slik at det har en svakhet som er kjent? Hvordan kan noe i det hele tatt sertifiseres etter "extremely remote" prinsippet når det ikke har fløyet 10 millioner timer? Er sertifisering egentlig et sjansespill?

The plan - a long-term solution, rather than a temporary fix - calls for revamping the aircraft's two lithium ion batteries to ensure that any short-circuiting that could lead to a fire won't spread from one battery cell to the others, officials said. That would be achieved by placing more robust ceramic insulation around each of the battery's eight cells. The aim is to contain not only the short-circuiting, but any thermal runaway, a chemical reaction that leads to progressively hotter temperatures.
The additional spacers will enlarge the battery, requiring a bigger battery box to hold the eight cells. That new box would also be more robust, with greater insulation along its sides to prevent any fire from escaping and damaging the rest of the plane, officials said
FAA approves Boeing plan to fix 787 Dreamliner’s fire-plagued batteries, requires testing
 

 
The FAA approved Boeing's plan to fix the 787 Dreamliner's batteries on March 12, 2013, with more testing required.

By Associated Press,

Published: March 12


WASHINGTON — A Boeing plan to redesign the 787 Dreamliner’s fire-plagued lithium-ion batteries won approval Tuesday from the Federal Aviation Administration, although officials gave no estimate for when the planes would be allowed to fly passengers again.
The plan includes changes to the internal battery components to minimize the possibility of short-circuiting, which can lead to overheating and cause a fire. Among the changes are better insulation of the battery’s eight cells and the addition of a new containment and venting system, the FAA said in a statement.

A series of tests, including flight tests, must be passed before the 787 can return to service. So far, flight tests of two 787s with prototypes of the new battery design have been approved, the agency said.
The plan is an outline for a recertification of the plane’s batteries, the FAA said. The 787 has two identical lithium-ion batteries, one of which is located toward the front of the plane and powers cockpit electrical systems, the other toward the rear and used to start an auxiliary power unit while the plane is on the ground, among other functions.

Every item that is part of an airplane, down to its nuts and bolts, must be certified as safe before FAA approves that type of plane as safe for flight.
The 787 fleet worldwide has been grounded by the FAA and civil aviation authorities in other countries since Jan. 16, following a battery fire on a Dreamliner parked in Boston and a smoking battery that led to the emergency landing of other 787 in Japan.

“This comprehensive series of tests will show us whether the proposed battery improvements will work as designed,” Transportation Secretary Ray LaHood said in a statement. “We won’t allow the plane to return to service unless we’re satisfied that the new design ensures the safety of the aircraft and its passengers.”

The cutting-edge airliner’s troubles have raised concerns that the FAA has ceded too much responsibility for evaluating the safety of new aircraft to manufacturers. To save manpower, the FAA designates employees at aircraft makers and their subcontractors to oversee the safety testing of new planes. Boeing’s battery testing concluded that short-circuiting wouldn’t lead to a fire and that the chance of a smoke event was one in every 10 million flight hours.

Instead, there were two battery failures when the entire fleet had clocked less than 52,000 flight hours.
The FAA’s approval of Boeing’s battery plan “is a critical and welcome milestone toward getting the fleet flying again and continuing to deliver on the promise of the 787,” Jim McNerney, the aircraft maker’s CEO, said in a statement.

The 787 is Boeing’s newest and most technologically advanced plane. Its grounding on Jan. 16, an enormous black eye for Boeing, marked the first time since 1979 that FAA had ordered every plane of a particular type to stay out of the air for safety reasons.
UBS analyst David Strauss estimated that the 787 will cost Boeing $6 billion this year. Besides the battery problems, the plane already costs more to build than it brings in from customers.