Friday June 2 2:47 AM ET 

 FAA Said Considering New Rules on Jet Fuel Tanks

WASHINGTON (Reuters) - The Federal Aviation Administration is considering requiring all commercial airlines to pump inert  gas into aircraft fuel tanks before takeoff to prevent explosions like the one that brought down TWA Flight 800 in 1996, The Washington Post reported Friday.

Elizabeth Erickson, the FAA's director of aircraft certification service, told the paper in an interview on Thursday that new cost estimates showed that the requirement would not be prohibitively expensive.

The FAA has examined the issue in the past but has rejected the idea as expensive and probably impractical. But now, rapidly advancing technology had made the process, called nitrogen ''ground inerting,'' practical, and cut its previously estimated costs in half, the paper quoted Erickson as saying.

Erickson estimated the cost of providing every commercial airport in the country with equipment to make inert all aircraft tanks  -- including wing tanks -- at about $1.6 billion, the Post said.

Making only the more vulnerable center tanks inert alone would cost less, she told the paper.

``The bottom line is, it's a lot cheaper than the advisory committee that first looked at this thought,'' she said.

As a result of the July 17, 1996, explosion and crash of TWA Flight 800 that killed 230 people,
the National Transportation and Safety Board in December 1996 issued an ``urgent''  recommendation that center fuel tanks be modified in some way to prevent the buildup of explosive vapors.

In the case of TWA 800, the NTSB has determined that fumes in the Boeing 747's nearly empty center fuel tank exploded, although no ignition source has yet been found. The plane exploded over the Atlantic Ocean about 12 minutes after it took off from New York's John F. Kennedy International Airport on a flight to Paris.

Pumping an inert gas such as nitrogen into aircraft tanks before takeoff would render them safe during the initial climb to higher altitudes where fuel vapors would cool to the point that they would not be in danger of explosion. At higher altitudes there is insufficient oxygen to support combustion.

Erickson told the Post that for large airports, the best way to introduce inert gases would probably be a truck-mounted system using ``permeable membranes.''

Air pumped through the membranes would scrub most of the oxygen from the air, leaving mainly nitrogen flowing into the tank. It is not pure nitrogen, but what scientists call ''nitrogen-enriched air.''

Smaller airports could use stationary platforms to pump nitrogen into smaller portable units that could be taken to nearby planes, Erickson said, according to the Post report.

She said a more detailed final advisory committee report will be released later this month or in July. 

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