Boeing, General Electric and US officials are investigating after the engine on a new 787 Dreamliner spewed metal and started a grass fire during pre-flight testing.

The US Federal Aviation Administration has ordered checks on Boeing's new 787 Dreamliners after the discovery of fuel leaks. Photo: AFP

The US Federal Aviation Administration confirmed Wednesday it is requiring inspection of Boeing's new 787 Dreamliners after the discovery of fuel leaks traced to a manufacturing flaw at Boeing plants.

A safety order mandated inspection of fuel line couplings in the engine pylons to make sure the couplings are correctly assembled and installed, the FAA said.

The order "makes mandatory inspections already recommended by Boeing," the company said on Tuesday.

A view of the business class cabin of the Boeing 787 Dreamliner during a demonstration flight. Click for more photos

The Dreamliner's dream tour

A view of the business class cabin of the Boeing 787 Dreamliner during a demonstration flight. Photo: Reuters

Separately, a brand new United Airlines 787 Dreamliner with 184 people aboard was forced to make an emergency landing in New Orleans on Tuesday after a generator failed on a flight from Houston, Texas, to Newark, New Jersey.

The issues constituted a twin blow to Boeing, which was dogged by production problems that delayed delivery of the 787 for 3-1/2 years.

The 787 is the first airliner with a composite-plastic fuselage and wings, instead of aluminum.

United, the only US operator, flies three 787s. Another 33 are in service with foreign operators, the FAA said in an emailed statement.

The fuel leaks were due to the improper assembly of the couplings at the Boeing factories, it said.

The 787-8 has one rigid coupling and one flexible coupling per engine for a total of four couplings per airplane.

The safety order, known as an airworthiness directive, requires operators to inspect for correctly installed lockwires on the engine fuel line couplings within seven days of its publication.

Within 21 days, operators must inspect the couplings to verify they have been assembled correctly.

Boeing said on Tuesday that improperly installed fuel line connectors could lead to fuel leaks, loss of engine power or fire. But it said there were "multiple layers of systems to ensure none of those things happen".

Boeing advised airlines flying the 787 to make inspections last month, and it said about half of the 33 jets in service have already been inspected.

The biggest 787 customer so far is Japan's All Nippon Airways, which was the launch customer and has 16 of the jets. Qantas cancelled an order for 35 Dreamliners in August, but will still receive 15 next year to be assigned to Jetstar.

There was no fire and no sign of electrical arcing during the incident on board the United flight, Lori Gunter, a spokeswoman for Chicago-based Boeing, said in a statement.

The generator breakdown wasn't related to a 2010 short circuit and fire caused by debris in an electrical panel during a test flight, said two people familiar with the matter who weren't authorised to speak publicly.

The Dreamliner has an all-electric flight system that saves on fuel by not diverting air from the engines for power, instead using five times as much electricity as older jets. United hasn't determined why the generator, one of six on the 787, failed, said Christen David, a spokeswoman.

"It's certainly very important," Peter Arment, a Sterne, Agee & Leach analyst, said of the electrical issue. "We need to see any of the issues resolved in a fast timeline so it doesn't affect production. It's probably fairly isolated and the computer data should be able to ferret out what happened."

After the 2010 fire, engineers rewrote software to improve power distribution and altered the design of the panel, which is made by United Technologies's Hamilton Sundstrand Unit. That incident grounded the entire 787 test fleet for six weeks.

United is viewing the incident as a "single aircraft situation" and isn't inspecting its other Dreamliners, David said. The Chicago-based carrier's plane never lost power.

"We are replacing the generator and running additional checks so as to return the aircraft to service," David said. She couldn't say when the plane might resume flying. Boeing also is involved in the troubleshooting, Gunter said.

Flight 1146 from Houston to New Jersey's Newark Liberty International Airport was diverted to New Orleans at about 9.30am local time yesterday. The jet made an emergency landing and its 174 passengers and 10 crew members were put on another plane to Newark. No one was injured.

One pilot told New Orleans airport emergency responders that the plane needed "a visual inspection to make sure they don't see any discoloration or dripping plastic" on the aircraft or "anything abnormal on either side," based on an air traffic control recording posted on LiveATC.net.

Reuters/Bloomberg