FAA Orders New Safety Devices To Prevent Fuel-Tank Explosions

The FAA announced Tuesday that it will require airlines to install safety devices in order to to prevent fuel-tank explosions. However, the cost of these fuel tank flame reduction systems -- or inerting systems as they are often called -- is not cheap. The devices, which flush oxygen from the fuel tanks, will cost airlines millions of dollars to install.

The FAA's move appears to meet one of the key recommendations (Safety Recommendation A-96-174) that was issued by the National Transportation Safety Board after the crash in 1996 of TWA Flight 800, a Boeing 747 that exploded shortly after takeoff from New York City. All 230 people aboard died.

In the last 14 years alone, 346 persons have lost their lives due to explosions of flammable fuel/air mixtures in airliner fuel tanks. Here is a short list of some of those tragic accidents:

March 3, 2001
A Thai Airways International Boeing 737 bursts into flames on the ground in Bangkok. Investigators find no evidence of a bomb and trace the explosion to the center fuel tank. No passengers are aboard, but an airline employee is killed.

July 17, 1996
A TWA Boeing 747 explodes after leaving New York City, killing all 230 aboard. The explosion is traced to the center tank. Investigators with the National Transportation Safety Board say they suspect that a short circuit created a spark that triggered the explosion.

May 11, 1990
A Philippine Air Lines 737 explodes on the ground in Manila. The blast ruptures fuel tanks on the wings, and the jet bursts into flames. Eight passengers are killed. Faulty wiring is suspected.

Nov. 27, 1989
An Avianca Boeing 727 explodes on a flight from Bogota to Cali, Colombia. Investigators say a bomb detonated in the cabin and ignited the center fuel tank, which caused a larger explosion that destroyed the jet. All 107 people aboard are killed. 

The safety board concluded that a measure such as injecting non-flammable nitrogen gas into fuel tanks was needed to ensure the tanks could not explode. Since that time, the FAA has followed several recommendations regarding the prevention of sparks or electrical arcing in or fuel tanks. However, the latest mandate is the first to address the specific issue of flushing oxygen from the fuel system. 

The FAA plans to give airlines seven years to install the devices on existing fleets and additionally plans to order changes in the design of fuel tanks on new jets to further reduce the risk of explosion. The new devices work by slowly pumping non-flammable nitrogen gas into fuel tanks. The theory behind the device assumes that if the nitrogen reduces the normal amount of oxygen in the air by half, fuel won't burn and the tank can't explode.

Officials say much of the credit for the new requirement goes to FAA scientist Ivor Thomas. Thomas, a Scottish immigrant, has spent years studying fuel tanks with Boeing and more recently the government. He oversaw research at the FAA's William J. Hughes Technical Center near Atlantic City into devices that extract nitrogen from the air and pump it into fuel tanks. The non-flammable nitrogen pushes out the air through vents. The oxygen in air is needed to cause an explosion.

In a key finding late in 2002, Thomas demonstrated that less nitrogen was needed than previously thought to prevent an explosion. The FAA tests showed that a fuel tank would not explode if oxygen levels were at 12 percent. That small difference allowed engineers to design much smaller nitrogen gas systems, substantially lowering the cost and weight of the devices. Some military jets already contain equipment that pumps nitrogen into fuel tanks to reduce the oxygen level to 10 percent or less.

While new for the civilian world, these devices are not uncommon in military aircraft, which tend to operate in unforgiving environments. Nevertheless, the struggling airline industry must now work with this expensive remedy for safety's sake.

The proposed changes would affect some Boeing and Airbus jets in which the center fuel tank is heated by adjacent equipment. That condition exists about 35 percent of the time the aircraft is in operation. The devices would be installed on about 3,500 jets owned by domestic airlines. That would bring the costs to roughly $350 million. Spokesmen for Boeing and Airbus said they had not seen the FAA's proposal and could not comment. Airbus has insisted that its jets are not at risk for fuel-tank explosions. Boeing says it has already designed a device to protect fuel tanks on its jets.

FMI: www.faa.gov