JAL Checking 12 More Planes After Engine Fire

Japan Airlines has been conducting emergency inspections of 12 aircraft equipped with the same model of engine as the one that caught fire on a passenger jet earlier this week.

Fire broke out on the left engine of the Boeing 777 shortly after it took off from Tokyo's Haneda Airport on a flight to New York on Tuesday. The plane made an emergency landing at Haneda. No one was injured.

More than 200 metal turbine blades of the engine were determined to be broken or missing.

Japan Airlines began the emergency inspections on Wednesday. Its officials say the focus is on areas near engine turbines.

They add they expect to finish the work by Sunday and that flight operations will not be affected.

About the engine that caught fire

The engine was a GE90-115B manufactured by General Electric.

It's 7.3 meters long with a diameter of 3.4 meters. It's one of the most powerful jet engines in the world.

GE's Japan office says it was first used by Japan Airlines in 2004. It says that more than 2,000 of the engines are in use around the world and have a total of more than 48 million flight hours. The company says there have been no reports of turbine-related problems.

Past cases of damaged blades

Turbines on jet engines spin at high speeds to produce thrust and move the aircraft. They are driven by gas generated through burning fuel.

Turbines are divided into several stages. Each stage contains metal blades -- in some cases more than 100.

The blades have been damaged during flights on several occasions.

In May of last year, the engine of a Korean Air jet caught fire during takeoff at Haneda Airport. The passengers were forced to evacuate.

Investigations by the Japan Transport Safety Board found that the engine's blades were damaged.

Last year, All Nippon Airways reported 3 cases of engine problems on its Boeing 787s. Investigations revealed that the blades could corrode and break faster than initially estimated.

ANA says it has addressed the issue by replacing engines at shorter intervals.

Reports from past incidents show that the blades' continuous exposure to high-temperature, high-pressure gas makes them susceptible to damage from metal fatigue and corrosion. The reports show that turbines on the front-side nearest the gas are especially vulnerable.

Expert suspects metal fatigue caused the damaged blade

NHK asked Professor Toshiyuki Kusuhara of the Daiichi Institute of Technology, a former member of the Transport Safety Board, what he thinks caused the damage to the turbine on the JAL flight.

Kusuhara says engine parts can suffer from metal fatigue because they are exposed to high-temperature, high-pressure air moving at high speeds. He says a turbine blade or nearby part may have been damaged and come off due to metal fatigue. He says it could have then struck the blades behind it.

As for why the engine caught fire, Kusuhara says it was probably because the broken turbine blades obstructed airflow toward the rear. This would have changed the ratio of air to fuel inside the engine, leading to incomplete combustion and fire.