A succession of problems has plagued Boeing's 787 Dreamliner, but investigators are now most concerned about incidents involving overheating of lithium-ion batteries.
Federal Aviation Administration (FAA) officials grounded Boeing's high-tech Dreamliner after battery electrolytes reportedly leaked from a lithium-ion battery onboard an All Nippon Airways flight on Wednesday. The liquid reportedly traveled through an electrical room floor to the outside of the aircraft, leaving burn marks around damaged areas.
The latest incident followed on the heels of two battery-related problems encountered on Japan Airlines flights and another on a United flight earlier this month. Those incidents happened in parallel with multiple other episodes, including two fuel leaks. Since July, the 787 has also encountered a damaged cockpit window, an oil leak, and two cracked engines, according to multiple news reports.
Auxiliary power batteries onboard a Japan Airlines Dreamliner 787 caught fire at Boston's Logan Airport on January 7. The battery was taken back to the National Transportation Safety Board's Materials Laboratory in Washington for further examination. (Source: NTSB)
Aviation experts said most of the problems are unrelated. "I tend not to believe that there's a single root cause behind all of this," David Freiwald, an assistant professor of aerospace at Embry-Riddle Aeronautical University, told Design News. "Any new system has teething or growing pains. A few issues are to be expected."
The incidents did motivate aviation authorities around the world to order stoppage of Boeing 787 flights, however. The FAA also announced it will work with Boeing engineers to conduct a comprehensive review of the 787's design and manufacture, with an emphasis on the aircraft's electrical power and distribution systems.
On its website, Boeing emphasized the safety of its new aircraft, releasing a statement saying, "The airplane has logged 50,000 hours of flight and there are more than 150 flights occurring daily. Its service is on par with the industry's best-ever introduction into service -- the Boeing 777. Like the 777, at 15 months of service, we are seeing the 787's fleet wide dispatch reliability well above 90 percent."
Most of the concern around the 787 involves the use of lithium-ion batteries. The 787 is the first commercial aircraft to employ them. Its electrical architecture also operates at a higher voltages than predecessors, experts told us. "In terms of the ancillary systems, almost everything on the 787 is electrical," Freiwald said. "Most aircraft systems operate at 115V AC, whereas this is a 230V system. It's a pretty substantial amount of power and current."
Freiwald added that the lithium-ion batteries are used for auxiliary power back-up. In the past, he said, commercial airliners have typically used nickel-cadmium chemistries.
Battery experts told Design News that the choice of a lithium-ion chemistry shouldn't be a problem, but it does call for tighter control. "Lithium-ion is a pretty energetic material," Eric Dietz, a professor of computer and information science at Purdue University, told us. "You've got oxidation and reduction reactions happening in close proximity to one another, so it's important to maintain engineering control around the battery."
max take off weight of 787-9 is 251 metric tons (modification for long distanses 15700km), total force from engines 64.4tons
amazingly 787-3 (not in production) has near 170 tons weight and flight distance 5500km, total engine force 48 tons - look like very different plain, but with same design & engines.
Seems like the batteries are the culprit, but as of now no one knows why. They've x-rayed the batteries, put them through CT scans, disassembled them and checked the associated wiring bundles and battery management circuit boards. As of now, regulators have said that overcharging doesn't seem to be the issue, but we don't know much more than that. We'll have more coverage on this coming up.
@Ervin- I'm a pilot and engineer, and your aerdynamic theory is more or less correct. As you state, planes don't fly by converting PE to KE by falling. But without gravity there won't be a lift vector; a subtle but important distinction. BTW an airliner is a surprisingly efficient glider...I'd guess a 20:1 glide ratio is typical.
Airflow over the top contour of the wing is critical while the underside of the wing less so. (Next time you see a plane, look at the designed-in smoothness of the top of the wing compared to the bottom). Frost, insect contamination, or a paint step can drastically or completely destroy lift if it "trips" the laminar flow over the top of the wing. So will going too fast if airflow over the top of the wing accelerates to supersonic, called a "Mach stall". (The 777 and other newer planes use a "supercritical" airfoil that allows it).
"The thinner the air the faster you need to go to maintain the same amount of lift"..this is called Indicated Airspeed and True Airspeed. For a constant amount of lift, IAS will be the same at sea level or 40,000 feet. As the term implies, it's the number of air molecules the plane encouters per unit of time. That produces a ram pressure that the pilot sees on the airspeed indicator. But, in thinner air the plane can go faster before it encounters the same ram pressure and drag. IAS to TAS is a pretty complicated equation. A 767 at cruise altitude may have a TAS of 500 knots (= groundspeed with no wind) while IAS is 325 knots.
Airliners are one of the most high-tech machines you will encounter in daily life. It's amazing they perform so reliably and safely. The 4th anniversary of US passenger airlines being fatality-free is a few weeks away. About 3 billion people carried on 40 million flights!
JAXA, Japan's space agency, as well as US federal investigators are planning on testing the battery type from this incident. Any news beyond "we are going to test" yet?
@Jennifer Campbell: Yes, I remember reading about the 787 in Design News back when I was in college. It was called the 7E7 then, and it was supposed to be the next big thing. Over the past few years, the news has been a lot less positive.
Another major aerospace project that got lots of "gee-whiz" press around that time, the Joint Strike Fighter, has also met with lots of delays, cost overruns, and technical problems. Now it seems more and more likely that the Department of Defense will pull the plug on the whole program.
Speaking as an outsider: what's going on with the U.S. aerospace industry? Are we just not capable of executing these kinds of big projects anymore? Are the projects just too big these days (the mutually-conflicting requirements for the Joint Strike Fighter come to mind)? Or has the development process always been this messy?
Given that the highest-profile civilian and military aircraft projects of the last decade have wound up scandalously late, over-budget, over-weight, and full of bugs, it almost seems like there is a systemic problem in the industry. But maybe this is just "normal," and I shouldn't have been naive enough to believe the hype in the first place. Or maybe things aren't as bad as they seem.
Any industry insiders care to weigh in on this quesion?
Design News has been covering the Dreamliner for so long - it's actually a bit sad to see it come to this. The plane seems to be falling apart at the seams.
Chuck, can you give us any insight into what Boeing's next step might be? They emphasize the safety of the aircraft, but, at the end of the day, it's been grounded by the FAA ...
You are right I was thinking more in line with 777 and 787 since they are still flying.
Some basic info on how a plane flies. This is a physicist's view (so most likely incorrect). You transfer enough kinetic energy to potential energy (exhaust of the engine is kinetic, plane flying is potential energy) and the object flies. The reason the object flies is because the air flowing around the wing provides lift hence the plane does not convert the potential energy to kinetic by falling. The downside and the reason engines need to remain on during flight is drag on the plane. Drag (air friction) slows down the plane converting some of the potential energy into heat. The engine has to burn fuel and input more energy into the system to insure we don't loose enough potential energy to loose altitude. As far as thin or thick air that only effects drag and efficiency of the airplane. The thinner the air the faster you need to go to maintain the same amount of lift or more wing span (seeing that wingspan is fixed we tend to make airplanes go faster). Also keep in mind that these engines output 240-330 kN of force. That force is enough to suspend 60 tons of mass. Now yes an airplane is far greater than 60 tons I think Dreamliner tops at 500. Keep in mind that we only have to defeat drag to make it fly we don't have to supply enough force to lift it straight up.
This is a very interesting article. Great information Charles. I'm sure a company such as Boeing has a procedure similar to FEMA (Failure Mode Effect Analysis ). I would love to see the failure mode "tree" for the lithium-ion battery application. Of course, the FEMA does NOT take the place of testing, bench and flight but it can be an indicator of "things to come" realtive to failure. In looking at the possible failure modes, severity, probability and detctability are given a number to quantify and pritorize each possible occurance. From these multiples, rankings of high, moderate and low are addressed. I have not idea if Boeing does this but if so, it would be very interesting to see.
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