The FAA will publish a rule Friday mandating new safety design features for devices aboard Boeing’s 737 MAX jet that are powered by non-rechargeable lithium batteries. This follows a fire on a Boeing jet in 2013 caused by such a battery powering a small electronic device.
The Federal Aviation Administration (FAA) will publish a rule Friday mandating new safety design features for devices aboard Boeing’s forthcoming 737 MAX jet that are powered by non-rechargeable lithium batteries.
Known as a “Special Condition,” the rule requires Boeing to demonstrate during certification that any such battery aboard the 737 MAX will maintain safe temperatures and pressures under all foreseeable operating conditions — aiming “to eliminate the potential for uncontrolled failures.”
The rule also requires safety features — including sensors, warning systems and heat shields — designed to protect the airplane and its occupants if a battery does fail due to unforeseen circumstances.
The new requirements follow the July 2013 fire aboard a Ethiopian Airlines 787 Dreamliner jet parked at London’s Heathrow airport.
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That fire, which badly damaged the airplane but caused no injuries, was attributed to a short circuit that caused overheating of a lithium battery inside a small emergency locator beacon in the crown of the fuselage.
The beacon, designed to transmit location data to satellites in the event of a crash, was a standard electronic device installed on thousands of aircraft and was not specific to the 787.
Its non-rechargeable batteries have a different chemistry from the Dreamliner’s re-chargeable lithium ion main batteries that caused the grounding of the 787 fleet earlier in 2013. Boeing fixed the 787 main battery problem by encasing the two batteries in hefty steel boxes with titanium venting tubes that will carry any smoke, flames or flammable vapors outside the airplane.
However, the fire on the Ethiopian jet revealed the broader vulnerability of the world’s airline fleet to smaller non-rechargeable lithium batteries that power multiple devices on airplanes.
Besides locator beacons, such batteries are used in escape slides, cockpit voice recorders, flight deck displays, cabin entertainment systems, and cargo systems such as door controls.
The FAA Special Condition calls lithium batteries “significantly more susceptible to internal failures that can result in self-sustaining increases in temperature and pressure (i.e. thermal runaway)” than traditional non-lithium batteries.
The 737 MAX is currently in flight test and is due to enter service next year.
The FAA in April issued a similar Special Condition for Gulfstream’s G650 business jet, the first applied to non-rechargeable lithium batteries.