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Special Report: Defusing 787 crisis

A team of experts dealing with the space station, rockets, satellites, planes and automobiles as well as 500 of Boeing’s own engineers expended 200,000 hours of analysis and tests to find a solution to the Dreamliner’s baffling battery issue. Chief project engineer Mike Sinnett dissects the problem and outlines a comprehensive plan to refloat the great plane

The common man’s understanding of Murphy’s Law is that the epigram “Anything that can go wrong, will go wrong” is a way of life or a grand excuse for mismanagement. It’s more than a coincidence that the law has its origin in the aerospace industry and still relevant over 60 years later.

When new measurement devices developed by Edward Murphy failed to perform during a rocket sled test, the eponymous engineer apparently blamed the fiasco on his assistant, saying: “If that guy has any way of making a mistake, he will.”

It wouldn’t be an exaggeration to say it’s the modern synthesis of Murphy’s Law that keeps thousands of aeroplanes cruising across the skies safely.

Asked later how come there was no casualty during the failed rocket sled test, Dr John Stapp, a US Air Force colonel who worked with Murphy, reportedly said it was because they always took Murphy’s Law into consideration. What he meant was it’s extremely important to consider all possible things that could go wrong before doing a test and act to counter them.

Boeing seems to have weaved the same adage into its design philosophy. Outlining a fix centred on a new design for the lithium-ion battery system that has layers of safeguards to prevent overheating, Mike Sinnett, vice-president and chief project engineer of the 787 programme, said in a webcast from Tokyo that Boeing engineers design areoplanes with two things in mind: Design to prevent failures and design in protections in the rare event a failure occurs. The goal, he said, is to ensure that no single failure will prevent safe operations and put the airplane at risk.

“We have been making safe planes for almost 100 years and because of this history and experience, we have the benefit of lessons learnt and applying those lessons to new designs, so that each new plane we design is better and safer than any new airplane that has gone before it,” he added.

Boeing’s Dreamliner fleet was grounded by the US Federal Aviation Administration and its counterparts in other nations in January following a battery fire in a 787 parked in Boston and an overheated battery that led to an emergency landing of another 787 in Takamatsu, western Japan.

Though it has not pinpointed the cause of battery overheating, Boeing said it was confident that the grounded jets would take to the skies within weeks after the safety fix.

The 787 chief project engineer denied the battery malfunctioning had put the airplanes at risk at any point in time.

Explaining the roles batteries play, Sinnett said they only provide a back-up support function in flights. A plane’s electrical system produces, controls and distributes power to onboard systems during flight. Similar to the electrical system in a house where wires carry electricity from the circuit box to appliances and lights, on an airplane the electrical system carries power to all the other systems that need it — the hydraulic system, flight deck displays, flight controls, in-flight entertainment etc.

Boeing explains that while residential power is made elsewhere by a utility provider and fed into a house, the airplane generates its own electricity in flight. It does not fly on battery power — it uses generators to make the power it needs.

According to Boeing, on a traditional aeroplane, power is extracted from the engines in two ways: Engine-driven generators which power the electrical system; and the bleeder system that diverts hot, high-energy air from the engines into the pneumatic system.

Engines have generators, which spin when the former run to produce electrical power. The pneumatic system, or the a “bleed-air” system, bleeds air off the engines to power other systems.

The Dreamliner is called a more-electric jet because it uses electricity, not pneumatics, to power aeroplane systems and relies on electricity more than any other Boeing airplane.

“Instead of using bleeders to power other systems, we use electric power. In the 787 we do this with two generators on each engine. These four generators in combination can produce one megawatt of electrical power. However, we have been able to demonstrate continued flight safety with only single generator operating,” Sinnett explained.

In addition to these four primary generators, the auxiliary power unit also has two generators associated with it. “If any of the primary generators were to fail, the auxiliary unit can be started and their generators can be brought on line to provide filling power,” Sinnett said.

“If in the very unlikely event of all four generators were to fail and the auxiliary power unit generators were also to fail, we have a device called RAM air turbine which deploys to supply back-up electrical power.”

So the only job the battery does in any of these is to keep the displays blinking when the plane transitions to the RAM air turbine.

“We do not need the main battery in flight for safety. We do not need the auxiliary power unit battery in flight for safety. They only provide strictly back-up functions — powering up airplanes on the ground, providing braking power and providing power for the navigations lights on the ground when the airplane is being towed and providing power to start the auxiliary unit,” Sinnett added.

He said the system has been extensively tested both on the ground and in flight with test crews making 5.5 hours of flights on one engine with five of six generators turned off.

Talking about the controversy that the Dreamliner’s lithium-ion battery has sparked, the Boeing executive said any design decision on an aeroplane is the result of a series of a complex trades. “We look at things like maintenance costs, operational costs, weight, volume etc. When we considered lithium-ion battery technology for the 787, it was already a matured technology being used in many applications, including aerospace.”

Sinnett defended the battery maker saying GS Yuasa had significant experience in the field. He said the lithium-ion battery provides benefits in lots of ways — high power on the ground for support functions, light weight and quick to charge.

“It also got a better shell life. It does not discharge on its own while sitting on a shelf, which means the airline costs for using this battery are less than what will be otherwise,” the chief engineer added.

“We never put a technology on an airplane unless it earned its way on, and the lithium-ion battery clearly did that.”

Sinnett said Boeing works hard to make sure the system it designs does not fail. “In the very next step we assume that it will fail and we provide sufficient redundancy capability to take over the system if it fails.”

For critical systems, Boeing provides additional layers of functionalities. For e.g. the pilot of the plane needs critical flight data in order to do his job of aviating, navigating and communicating. This information is presented to the pilot on a display in his primary field of view. A computer generates the images that go to the display.

“And if that computer fails, we automatically switch to another computer that provides the same information to the pilot on the same primary display. And if the display itself were to fail, the format automatically transitions to the display right next to one that has failed. And if all of that fails, the co-pilot has the same information with the same source of redundancy. And if all those fail, we have an independent back-up standby flight display that provides the same information to both the captain and the co-pilot in their primary field of view,” the chief project engineer said.

The engineer said in both incidents involving the Dreamliner — at Takamatsu in Japan and Logan International Airport in Boston — no significant flight structure was damaged. Denying reports that there were flames, explosions and fires in the incidents leading to the grounding of the Dreamliner fleet worldwide, Sinnett said the factual report mentioned only two small three-inch flames on the front of the battery box on the connector. “There were no flames inside the battery. And in the Takamatsu event, there was no flame at all.”

So what went wrong with the lithium-ion battery? The cells vented. Venting is a protective measure that has been designed in. If something happens inside the battery cell and it begins the process of failing, pressure and heat can build up inside the cell.

“We vent that cell to keep that pressure from building up too high and to keep the temperature down. This is what happened in the Takamatsu and Logan incidents. A cell vented and the heat from that venting cell propagated to other cells and they vented as well. Again, this is a protective mechanism that has been designed into the batteries themselves. When they vent, they vent vaporised electrolyte which to you and I looks like smoke. But it’s not the product of combustion. It’s not the result of a fire. It’s the intentional venting of a cell to relieve temperature and pressure,” Sinnett clarified.

“It’s true that venting propagated from one cell to another but that is not the same as a fire spreading throughout the battery. In neither event was there a fire inside the blue box of that battery.”

He said after the battery failed, the planes responded exactly as it has been designed and intended. In the Takamatsu incident, after the battery vented, the flight crew got the notification that there’s a battery problem in the electronics bay where the cell venting. The smoke detection system detected the vented electrolyte. It came through the flight notification that something has been detected, and then it automatically reconfigured the airflow.

“So the airflow containing the electrolyte went overboard half of the airplane — but not to the cabin, not to the flight deck and not to any areas of the airplane where it could be unsafe. The crew was able to follow their non-normal checklist, divert the plane and perform a safe and normal landing. So when the battery failed, the damage was limited to its functions and immediate areas, but the airplane was never at risk,” Sinnett argued.

While what happened inside the battery has been referred to as thermal runaway, Sinnett said the definition covers a variety of situations. “What we worry about from a thermal runaway perspective is a vent involving so much energy heat and flame that could put the plane at risk. But that was not the case in the Logan and Takamatsu events.”

He said the only mechanism that could lead to thermal runaway at the battery and the airplane level is overcharging. “But our system has four layers of protection against overcharging. Two of the layers are in the battery and two in the battery charger. Going by the flight data recorder prior to these events, Boeing is confident about the protection against overcharging,” he added.

After 200,000 hours of engineering-design analysis and tests after the incidents, a team including 500 of Boeing’s own engineers and experts responsible for the space station, rockets and satellites and people from other airplane programmes, automobile industry, national laboratories, government organisations and universities has come out with a comprehensive plan to help address the battery problem.

The comprehensive 787 solution package will add several layers of additional safety features to the lithium-ion batteries. New enclosures for the batteries are also being built and will be installed in planes in the weeks ahead, Boeing said. The enhancements to the battery system address causal factors identified by the Boeing technical team as possible causes of battery failure.

Sinnett said the first layer of improvements is taking place during the manufacture of the batteries in Japan. Boeing has teamed with Thales, the provider of the integrated power conversion system, and battery maker GS Yuasa to develop and institute enhanced production standards and tests to further reduce any possibility for variation in the production of the individual cells as well as the overall battery.

Four new or revised tests have been added to screen cell production. Each cell will go through more rigorous testing in the month following its manufacture, including a 14-day test during which readings of discharge rates are being taken every hour, Boeing said.

The partners have also decided to narrow the acceptable level of charge for the battery, both lowering the highest charge allowed and raising the lower level allowed for discharge. The battery charger will also be adapted to soften the charging cycle to put less stress on the battery during charging. To better insulate each of the cells in the battery from one another and from the battery box, two kinds of insulation will be added.

A set of changes is being made to the battery case that contains the cells and the battery management unit. Boeing said small holes at the bottom will allow moisture to drain away from the battery and larger holes on the sides will allow a failed battery to vent with less impact to other parts of the battery.

The battery case will sit in a new enclosure made of stainless steel. This enclosure will isolate the battery from the rest of the equipment in the electronic equipment bays. It will ensure there can be no fire inside the enclosure, thus adding another layer of protection to the battery system. The enclosure features a direct vent to carry battery vapors outside the airplane.

Addressing the webcast, Boeing Commercial Airplanes president and CEO Ray Conner affirmed the 787 is a great plane. “The efficiency, capability and comfort it brings are unmatched and we will continue to provide tremendous benefits for decades to come to our airline customers and to the flying public,” he added.

Having said that, one is reminded of another of Murphy’s Law: If everything seems to be going well, you have obviously overlooked something. The baffling battery issue was probably a blessing in disguise, serving a reminder to the aviation industry that when it comes to the safety of aeroplanes, no stone should be left unturned.

suresh@khaleejtimes.com