Although the explosion that brought down TWA Flight 800 started in the plane’s center fuel tank, the tanks in only 52 of the world’s nearly 1,000 other 747s have been inspected, officials said Tuesday.
But the most famous 747 - Air Force One - had its center fuel tank inspected after Boeing Co., the plane’s manufacturer, made the recommendation in July.
“I’m sure most citizens would want it accomplished on the 747s they’re traveling on as well” as on the president’s plane, said Jim Hall, the chairman of the National Transportation Safety Board.
During the second day of public hearings into the crash of TWA Flight 800, Hall and others grilled representatives from Boeing and the Federal Aviation Administration about what they have done to make sure other 747s are safe.
Also, during a lunch break at the hearings, FBI Assistant Director James Kallstrom met with families of the crash victims and told them the agency would cooperate with French authorities conducting a criminal negligence inquiry against Boeing and TWA. He said U.S. authorities would not pursue such charges.
In another important development, both Boeing and FAA officials reversed course and said they now realize they need to reduce the flammability of jet fuel vapors in tanks. In the past, they have said they simply need to change plane design to eliminate any potential source of a spark in the tank.
The NTSB has pushed for eliminating potential sources of sparks and reducing the flammability of fuel vapors. Last week, the FAA made something of a concession and set up a committee to reduce the possibility of fuel tank explosions.
Boeing and an industry trade group, the Air Transport Association, have opposed most of the safety-board recommendations and argued that adding jet fuel to lower the explosiveness of the fuel tank would not significantly reduce the flammability and could have steep costs.
More fuel would add weight to an aircraft and could throw out of whack a series of economic calculations from the range of jets to the price of airline tickets.
Joseph Shepherd, an aeronautics associate professor at California Institute of Technology, which conducted tests on the fuel vapors, testified that the hotter it gets inside the tank, the more likely the vapors are to ignite with just a tiny spark.
Three air-conditioning packs were operating for about two hours on the ground before TWA Flight 800 departed from New York’s John F. Kennedy International Airport for Paris on July 17, 1996. The plane exploded shortly after takeoff, killing all 230 people on board.
Shepherd’s testimony was important because the NTSB has been advocating a number of measures to cool fuel tank temperatures, including adding nitrogen to the tanks. That technique has been used for more than 25 years in military airplanes.
Ivor Thomas, a chief engineer at Boeing, said his company’s planes are “remarkably safe. … Our concern is that we not rush into something unnecessary … especially if six months later we find out it was the wrong thing to do. We appear to be slow. We would prefer to be slow and careful and correct.”
Hall quickly replied that safety officials don’t want Boeing to do something wrong, but “we do want you to rush into looking at the problem.”
Safety officials know the explosion occurred in the center fuel tank. They do not know the source of the spark that caused it, although they have ruled out sabotage and terrorism. The board’s $30 million investigation over the past 17 months has focused on finding that spark and reducing the explosiveness of the fuel.
“Had the vapors in TWA Flight 800’s fuel tank not been explosive, this accident would not have occurred, no matter what the ignition source,” Hall said.
Jerry Hulm, a Boeing manager of electrical systems, said his company in July recommended airlines inspect their center fuel tanks at their planes’ next major maintenance check. Boeing added the inspection should come within the next 2-1/2 years.
Officials said since then, 52 of the 970 747s in operation have been inspected. Of the 970 planes, 750 of them are considered “classic 747s,” the version used for TWA Flight 800. During those 52 inspections, no ignition source has been found, officials said.
Daniel Cheney, a manager in the FAA’s Seattle office, said the FAA is considering making the inspections mandatory. But the agency hasn’t done so, he said, because there are still several issues to resolve.
Hall and his colleagues on the safety board have complained about the FAA’s lack of speed in addressing the matter.
“It has been 16 months since this accident occurred, and this is just a recommendation,” Hall said. “To me, that is frustrating. I get criticized for being frustrated, but to me, this is frustrating.”
Boeing manager Hulm, however, said his company has done extensive work. “We haven’t been idle,” he said.