Investigators knew soon after a TriCoastal Air plane crashed nearly 20 months ago in Tennessee that the pilot had discovered trouble with the balance of fuel in his craft's tanks - he told air traffic controllers so.
But they may never know why the problem, known as "fuel asymmetry," developed and couldn't be corrected before the Swearingen SA-226-TC nose-dived into a wooded area near Paris, Tenn., on the chilly afternoon of Feb. 8, 2006.
The National Transportation Safety Board's final report on the crash identifies as its probable cause "the pilot's in-flight loss of control following a reported fuel asymmetry condition for undetermined reasons."
While components from all areas of the aircraft's structure and flight controls were recovered from the wreckage, "impact and postcrash fire damage precluded the examination of the airplane's fuel system and components," the report noted.
Among components not found at the scene was a valve that would control the transfer of fuel between the plane's fuel tanks. Having significantly unequal amounts of fuel in its tanks can make an airplane unstable.
Pilot Abdulgader Zbedeh, 42, of Louisville died in the crash. He was the only person aboard the flight to transport about 300 pounds of automotive wiring from Dayton to Harlingen, Texas.
TriCoastal is owned by Grand Aire Inc., a charter cargo carrier headquartered at Toledo Express Airport.
Katrina Cheema, Grand Aire's president, did not return a call yesterday seeking comment on the NTSB report.
Butch Wilson, the NTSB's crash investigator based in Atlanta, also could not be reached for comment yesterday.
But in an interview after the crash, Mr. Wilson said the pilot's request to air traffic controllers before the crash - to fly circles - demonstrated an attempt to correct fuel asymmetry.
But after flying a circle in each direction, Mr. Zbedeh asked controllers for a vector to the nearest airport and permission to descend to 4,000 feet from his 16,000-foot cruising altitude - requests indicating he had not solved the fuel problem.
About a minute after receiving instructions directing him to an airport at Camden, Tenn., Mr. Zbedah announced "Mayday" six times over his radio before the plane disappeared from radar screens and communication was lost.
The fatal crash followed three between 2002 and 2004 involving planes belonging to Grand Aire, in which six other pilots died, including Tahir Cheema, the company's co-founder.
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