FILE - In this Jan. 27, 2012, file photo, Boeing's newest aircraft, the Boeing 787, sits on the tarmac at Huntsville International Airport after a 3600-mile flight from Dublin, in Huntsville, Ala. Boeing executives insisted Wednesday, Jan. 9, 2013,  that its 787 Dreamliner is safe, and investors rallied behind the company. But federal investigators are probing a Monday, Jan 7, 2013 fire aboard an empty 787 in Boston, the latest glitch for a high-profile jet that has a lot riding on it, both for Boeing and its airline customers. (AP Photo/The Huntsville Times, Eric Schultz, File)

Photo: Eric Schultz

Boeing's troubled 787 Dreamliner is probably the most over-hyped airliner ever. Admittedly it is sleek, comfortable and fuel efficient, and airlines have rushed to order more than 800 of them. Boeing has delivered 50 but right now all Dreamliners are grounded because their powerful lithium-ion batteries catch fire.

The 787 began with a super-light plastic body, then marketing flacks wanted a swooping tail fin to make it look faster - shades of a 1960s Cadillac. When Boeing staged a spectacular rollout on July 8, 2007 - 7/8/7 in the US dating method - the plane was just an empty shell held together by far too few rivets, most of which were the wrong sort and had to be replaced.

During strength tests the wing cracked at far below design requirements.

Boeing redesigned and reinforced the wing structure but it delayed the aircraft by months. In all Boeing announced seven delays, each one touted as definitely the last. When the 787 eventually entered service in October 2011 it was three years late and had taken twice as long to create as Boeing's 747, 40 years earlier.

The 787 is a brave experiment which might yet succeed. To burn less fuel it is lightly built, more than of it half from fibre-reinforced plastic. FRP is not new, and Boeing first used FRP extensively for its 767 jetliner 30 years ago. Some of the structure was reinforced with Kevlar fibre, which worked well during tests but deteriorated quickly in service.

Boeing spent a fortune replacing Kevlar components on the 767, with no publicity and little risk to the public. Despite familiarity with designing FRP structures, Boeing and its subcontractors still ran into trouble with the 787. For instance, unlike metals that have strength in all directions, FRP is only strong along its fibres. So fibres must be meticulously placed to carry all loads, even quite light loads that are of no consequence to metals. Or the structure breaks, which is what happened when the 787's wing cracked.

Boeing also saved weight on the 787 by having lithium-ion batteries for back-up electrical power. It seems likely that Boeing made an even worse choice with lithium-ion on the 787 than it did with Kevlar on the 767.

Lithium-ion batteries are used by the million in tools, mobile phones and portable computers but occasionally they spontaneously catch fire. When they do their internal chemistry generates oxygen, which makes extinguishing the fire difficult. That's why these batteries are banned from checked bags for air travel. They are suspected of causing two freighter planes carrying cargoes of lithium-ion batteries to burn and crash.

The dangers of choosing lithium-ion batteries for the 787 were clearly understood by Boeing and its regulator, the US Federal Aviation Administration, but the weight saving was irresistible. In 2007 FAA carefully spelt out the dangers and set eight ''special certification conditions'' for their use; including:

■ Safe cell temperatures and pressures must be maintained during any foreseeable charging or discharging condition and during any failure of the charging or battery monitoring system.

■ Design of the lithium-ion batteries must preclude the occurrence of self-sustaining, uncontrolled increases in temperature or pressure.

■ No corrosive fluids or gases that could escape from any lithium-ion battery may damage surrounding structure or any adjacent systems, equipment, or electrical wiring

■ Each battery installation must have provisions to prevent any hazardous effect on structure or essential systems caused by the maximum amount of heat the battery can generate during a short-circuit.

Put simply, batteries must not burn, except possibly once or twice during the lifetime of the entire 787 fleet. If they do overheat or burn, any fire must be safely contained within their enclosures and any harmful fumes must be vented overboard. Apparently Boeing proved to FAA by analysis and tests that the batteries were safe and complied with all special conditions. This took years.

Two battery fires in January show the batteries do not meet certification requirements. Hence neither does the aircraft. One fire, on the ground at Boston airport, took an hour to extinguish. The other triggered an emergency landing in Japan. Either could have been fatal had the plane been over water, far from an airport. That is why regulators around the world have grounded the 787 and will not easily be persuaded of its safety a second time around.

The 787 is a masterpiece of delegation. Boeing went further than ever in delegating design responsibility to companies around the world. Mitsubishi Heavy Industries in Japan designed and builds most of the wing, though important parts come from Boeing's Aerostructures subsidiary in Melbourne. Also in Japan, Kawasaki builds large sections of fuselage with other parts made in Italy and the US.

The suspect batteries are made in Japan by GS Yuasa and their chargers by Securaplane, a US subsidiary of Britain's venerable Meggitt PLC. The system is integrated into the plane by French company Thales. Such divided responsibility makes a nightmare of sorting out contractual and technical blame for the failures. Fixing them will be equally fraught. Simply changing to a different type of battery is not an easy option because back-up electrical power is so critical and because the battery system is so deeply integrated into the plane.

The public might also be alarmed by how much of aircraft certification is delegated back to Boeing because FAA lacks the expertise and staff to do the job. Traditionally the maker of a new airliner negotiates certification rules with its regulator, and after agreed testing and analysis is done, it is often senior company engineers who judge whether compliance is proven. These engineers used to be known as ''designated engineering representatives'', appointed as representatives of the regulator in their particular field of expertise. DERs were proud of their status and took their responsibilities to the regulator and the public seriously. There were a few shameful abuses but generally the system worked.

Delegation went a stage further for the 787. FAA appointed Boeing as an ''organisation designation authorisation'' (ODA); Boeing essentially self-certifies its designs and design changes without direct oversight by FAA. It is a relatively new procedure and will be scrutinised if unsafe batteries did indeed slip through certification checks. Already, the US Senate commerce, science and transportation committee is calling for hearings into why FAA certified the 787 with lithium-ion batteries; a very good question.

Ironically, the only reason why Boeing can sustain the cost of Dreamliner delays and its grounding is because of profits from Boeing's cash cow, the 737 - a jetliner designed 50 years ago.

>> Martin Aubury is a retired aeronautical engineer. In the 1960s he worked at Boeing on design of the 747.