American Airlines is checking the fuel systems in its entire fleet of Boeing MD-80 aircraft, after a mysterious spate of incidents in which cockpit gauges showed the wrong amount of fuel on board.
The source of the problem remains a puzzle, airline officials say. It appears to stem from an increase in microbes growing in fuel tanks. Those particles can affect the probes that tell pilots how much fuel is on board.
"Everybody has their theory about why this is coming up right now," said Don Dillman, an American pilot who is also managing director of flight operations. "We still don't know for sure."
American officials say that their airplanes remain safe, pointing out that all flights carry a fuel reserve far in excess of the reported discrepancies. Still, the problem has been a major headache for the airline's maintenance department, which, according to one internal report, has been working "around the clock" on the issue.
It also demonstrates the increasing challenges American faces in maintaining its fleet of airplanes as it ages. The airline has deferred or canceled many aircraft purchases in recent years to save money, and plans to buy only two new airplanes before 2013.
"There's always a trade-off," said Alan Sbarra, an aviation consultant with Roach and Sbarra Airline Consulting in San Francisco. "You save money when you don't buy new aircraft, but then you spend a lot more time and money on maintenance as they get older."
According to Dillman, the problem has also surfaced at other airlines operating MD-80s. "This is an industry issue," he said.
American officials declined to say how much the fuel-gauge issue has cost the airline. Last year, American spent $228 million on maintenance, materials and repairs.
Unlike most carriers, American still services its aircraft in-house, rather than outsourcing the job. The carrier has maintenance bases in Fort Worth, Tulsa, Okla., and Kansas City, Mo.
That's an advantage when it comes to issues like the fuel problem, Dillman said.
"We've maintained the MD-80 for years in-house," he said. "At this point, I think we know more about this aircraft than Boeing does."
American operates the world's largest fleet of MD-80s, with 337 in service. The aircraft is used heavily at Dallas/Fort Worth Airport.
When it comes to the mysterious microbes in the fuel tanks, one theory is that the growth of the tiny pests was spurred by excess seawater that was blown into the jet fuel supply during Hurricane Katrina, Dillman said.
Others say the MD-80 is particularly susceptible to the problem because it doesn't burn off water in the fuel tanks as well as other aircraft. And one airline report says a polyurethane coating on the fuel tank probes in some older airplanes may have lost its effectiveness.
Regardless, American officials have moved aggressively in recent weeks to investigate the problem and ensure that no flight ends up short on fuel. This month, mechanics manually inspected every fuel tank on each of American's MD-80s to ensure that they were not giving critically inaccurate readings. They have also beefed up maintenance procedures to focus more intently on the fuel systems.
Mechanics at American's maintenance base in Tulsa "have been working around the clock to find a solution to this dilemma," stated a recent message to pilots from David Johnson, the airline's MD-80 fleet captain.
The work includes:
A one-time, manual check of the fuel level in the tanks of every MD-80 in the fleet.
More frequent draining of water from the airplanes' fuel tanks.
Adding a chemical that slows the growth of the microbes.
Increased inspection of the fuel systems during regular maintenance checks.
Paper fuel reports are given to pilots before every flight so they can double-check the gauges.
American has also sent a team of workers to inspect fuel stations on the East Coast that are supplied by Gulf Coast refineries, to test the hurricane theory, Dillman said.
Airline officials stress that even with the inaccurate readings, no airplanes have been in danger of running out of fuel while flying. Airplanes typically take off with several thousand pounds of extra fuel.
"There is an extremely large cushion of safety out there," said John Hotard, a spokesman. He added that American's maintenance department spotted the trend early and has worked to solve the problem before it could become a larger issue.
Still, inaccurate fuel-gauge readings are a serious matter for an industry where safety is crucial. Last summer, an incorrect fuel reading caused an engine on an MD-80 to flame out as it approached Chicago.
The plane landed safely with the remaining engine. Mechanics later determined that the problem in that case was because of a mechanical breakdown in the fuel system rather than microbe growth in the tank, Dillman said.
According to one internal report obtained by the Star-Telegram, American found 50 instances last year when fuel gauges gave inaccurate readings.
Of those 50, the report stated, 10 were off by 500 or more pounds of fuel.
"We must have complete assurance that our fuel quantity gauges are accurate," the report stated. "Reasonable assurance is never good enough in the flying business."
Dillman said that although any fuel-gauge error is considered serious, it should be taken in context with the total number of flights operated with MD-80s.
"Certainly it's significant, but keep in mind we flew 460,000 flights last year," he said.
The airline has also been communicating regularly with pilots and has advised them that the airplane is safe to fly. But officials have also warned that pilots need to remain vigilant and aware of potential problems.
"You are a proud bunch of aviators flying a proud bird," wrote Johnson in his message to pilots. "I'm glad we are keeping it pointed in the right direction together."
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