Dreamliners safely back in service

Dreamliner cokpite showing instruments

Image credit: Brandrodungswanderfeldhackbau [shifting cultivation] October 2007

The Dreamliner’s battery enclosures have been redesigned.  The first first commercial flight took place from Addis Ababa in Ethiopia to Nairobi, Kenya on 27 April, and normal operations are resuming as aircraft are put back into service after approved modifications have been made.

The batteries are now contained in a fireproof steel box with a chimney that vents outside the aircraft.  That’s what you get for an extra 200,000 hours of engineers’ time.

The actual root cause of the problems previously experienced “may never be determined” but some 80 battery-related technical features have been upgraded.

Why try a new battery design

The Lithium-ion batteries on the 787 are characterised by being able to provide a large amount of electrical power in a short period of time.  They are about the size of a car battery and are much lighter than older types of battery.

By way of comparison, the 787’s batteries provide up to 150A of current and weigh 29kg (excluding the new modifications), whereas the older battery design used on the Boeing 777 weighs 49kg and provides just 16A of current.

What are the batteries used for?

There are two identical lithium batteries carried on the Dreamliner.  The one in the middle of the craft is used to start a small turbine at the tail of the aircraft, the Auxiliary Power Unit (APU).  And it powers the navigation lights.  The APU, in turn, provides the power (1100 shaft horsepower) needed to start the main engines.

The battery in the forward electrical bay, under the main cabin floor,  powers certain accessories when the aircraft is on the ground, and powers various electrical systems prior to the APU starting up.

All craft being modified

Ten teams of engineers, averaging 30 per team, are converting the 50 Dreamliners already delivered so they can be returned to service.  The modifications are scheduled to be completed mid-May.  The first commercial flights have resumed without incident.

The modifications are also being applied to aircraft that have been built but not delivered.  All deliveries scheduled for 2013 are expected to be delivered by the end of the year.

No problems have been experienced with craft that have been modified and returned to service.

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