US regulators have issued the special conditions for approving lithium-ion battery installation on the Airbus A350-900.
The US FAA’s conditions have been developed to take account of the possible use of lithium batteries on the type, and follow similar requirements laid down for the Boeing 787 – although the FAA has amended the details in places.
Airbus had initially opted for lithium batteries to power certain electrical systems on the A350 but switched to conventional nickel-cadmium after battery-related incidents on the 787 sparked safety concerns.
The special conditions are necessary because airworthiness regulations do not contain adequate standards for certain aspects of modern aircraft design, including the use of lithium-ion batteries.
“Lithium-ion batteries and battery systems have new hazards that were not contemplated when the existing regulations were issued,” says the FAA.
While its conditions for the A350 are broadly similar to those issued for the 787 in 2007, there are some notable updates.
The FAA says the instructions for continued airworthiness must contain maintenance requires assuring that the batteries are “sufficiently charged”, retaining enough charge to ensure the cells will not be damaged.
“A battery cell may be damaged by lowering the charge below a point where the battery experiences a reduction in the ability to charge and retain a full charge,” it states. “This reduction would be greater than the reduction that may result from normal operational degradation.”
It adds that precautions should be included in these instructions to prevent mishandling of the batteries which could result in short-circuit or other unintentional impact damage.