A shop floor cleanup. A truck driver's delay. A pair of labeling errors.
Together, they led to a cargo of oxygen canisters being placed on a May 11 ValuJet flight - canisters now suspected of contributing to the flight's fiery crash.The wreck of ValuJet Flight 592 was caused by a "tragic, thin line of human errors," said Steven D. Townes, president of SabreTech, a contracting firm that did maintenance for ValuJet.
The sequence of events was detailed to the House Transportation Committee last week by Lewis Jordan, head of the embattled airline, and Townes.
SabreTech brought the five boxes of oxygen generators to the airline in Miami on May 11, where they were placed aboard the plane to Atlanta.
The plane crashed into the Everglades minutes after takeoff, killing all 110 aboard. The crew reported smoke in the cabin, and investigators have indicated the generators were a possible factor.
Used in many airplanes, oxygen generators are relatively small metal cylinders containing a mixture of chemicals that produce oxygen for emergency breathing.
The chemical reaction can heat the generators to nearly 500 degrees Fahrenheit, so when in use they are stored in special, insulated compartments.
When shipped as cargo they are considered hazardous materials, which ValuJet is not authorized to carry. Even used, empty canisters are classified as a hazardous material because of chemical residue from their operations.
Townes told the committee that SabreTech removed about 150 outdated generators from three MD-80 aircraft it was servicing for ValuJet between February and May.
The generators were stored in several cardboard boxes in SabreTech's shop, he said. Two mechanics reported they had installed required safety caps, he said, although it turned out none of the caps was available and thus weren't used.
"Nothing can forgive those two people for making a misrepresentation," Townes said.
The two men were employed by two SabreTech subcontractors - STS Services Inc. of Nashville, Tenn., and PDS Technical Service Inc. of Dallas - Townes said.
Although the two men did not put on the required safety caps, they "made a good-faith attempt to provide an equivalent level of safety," Townes said. The generators are started by pulling a lanyard, and the mechanics either cut the lanyards or taped them around the generators.
In early May, a SabreTech employee, "apparently as part of an effort to straighten up the shop floor in advance of an inspection by a potential customer," prepared to ship some ValuJet property back to the airline, Townes said. That included the generators.
Another worker, a clerk, seeing a green "repairable" tag on the generators, "apparently believed this meant that the generators were empty and could be recharged," Townes said. It was not clear who put the green tag on the canisters.
"Although this clerk appeared to know what the generators were, he has told us he did not know whether or not they were hazardous," Townes said.
The clerk listed the five boxes on a shipping form as containing empty canisters and placed them for return to ValuJet.
"I won't minimize the obvious error of the word `empty' on that ticket," Townes said.