By Stuart Burns
As time goes by, the pain for Boeing only gets worse as all 50 Dreamliner 787s remain grounded around the world.
The grounding is said to be costing Boeing $50 million a week, so the incentive to find a quick fix must be almost irresistible. According to wired.com, Boeing is expected to propose a short-term fix for the battery problem as early as this week, said to focus on a heavy-duty containment box to replace the relatively simple box now used to hold the lithium-ion cells in each of two electrical bays in the airplane.
The box is expected to be constructed out of titanium and have a vent to the outside in the case of smoke and particulate emissions, i.e. if it catches fire while in flight.
No mention is made at this stage what would power the aircraft if its batteries became inoperative in the event of a “contained” fire. The 787 is the most wired commercial aircraft in history, supplanting traditional hydraulic controls with electrical.
Nor has much mention been made of the rationale that says it’s ok to propose a solution where an onboard fire is a tolerable situation, even if it is contained within a strong box. Surely the FAA would never allow an airline to design a system like that on a new build, so why would it be acceptable as a “short-term” (read: months) measure simply for commercial expediency?
So far the airline has refrained from adopting the use of nickel cadmium as Airbus has decided to do in the new A350 XWB due to enter service next year. Airbus had been developing lithium ion batteries with a French battery maker, but has switched back to NiCd, a decision probably not unassociated with Boeing’s problems.
Perversely, according to Wikipedia, lithium-ion batteries containing more than 25 grams (0.88 oz) equivalent lithium content (ELC) are forbidden in air travel.
Passengers are not allowed to carry more than a certain concentration in their carry-on baggage and only in checked baggage if it is in its original packing – i.e. largely discharged.
Apparently this restriction is due to the possibility of batteries short-circuiting and causing a fire, yet the FAA gave approval for Boeing to use the technology as the primary electrical store on the 787 in far higher densities than passengers are allowed.
The Dreamliner is the first plane in the world to use the lithium-ion batteries, which are lighter, hold more power and recharge more quickly, but have been known for years to be prone to overheating and even catching fire under a variety of conditions including over-charging, shock and short-circuiting.
Technologies do appear to exist that greatly reduce the volatility of the lithium-ion battery and, of course, the use of nickel cadmium is always an option, although it has a weight implication as larger battery packs are required to achieve the same storage. Not only that, but changes to the re-charging, monitoring and control systems would be required, which cumulatively make a move to NiCd very costly both for Boeing and the airlines operating the 787.
The problem will get solved, but judging by some of the blog traffic out there, many from an engineering background are questioning the use of these batteries in the first place – and what is viewed by some as the too-close relationship between the aircraft maker and the FAA leading to a less than 100% satisfactory solution from a safety point of view.