Data is being sought to find out the operational service life limit for the DC-4 tankers owned by ARDCO Inc. of Tucson, which drop retardant on wildfires, according to U.S. Forest Service and Bureau of Land Management officials.
An engineering study on the structural life of the aircraft that ARDCO provided is identical to a report used by two Canadian companies that fly Douglas-built DC-4 aircraft, said Meegan Garrett, who co-owns ARDCO with her husband.
At least one of those companies still flies the aircraft to fight wildfires for the Forest Service, Garrett said.
A Forest Service official called Monday and ``just told us there wasn't enough information,'' she said.
The ARDCO planes were among 33 large tankers cut off from operating on behalf of the federal government May 10, just as the wildfire season took hold.
Dale Bosworth, chief of the U.S. Forest Service, and the Interior Department ended the contracts with private companies for use of the planes after the National Transportation Safety Board determined their airworthiness couldn't be assured.
Three large tankers crashed between 1994 and 2002, killing seven crew members, and Bosworth said then that continued use of the tankers posed ``an unacceptable risk'' to aviators, ground firefighters and communities near the fires.
The move drew heavy criticism, but in June officials said they had contracted with private operators for up to 38 smaller air tankers and 71 large and medium-sized helicopters to fill the gap.
The next month, five of the 33 tankers -- all P-3 Orions -- were allowed back in the air after their private operator showed they were safe to fly.
In all, 10 of the 33 planes, but none of eight DC-4s, have been allowed to return to firefighting on behalf of the government, said Rose Davis, a spokeswoman for the National Interagency Fire Center in Boise, Idaho.
``The OSL (operational service life) information wasn't provided to us from ARDCO,'' Davis said. The information is needed by Dyncorp Technologies, the contractor hired by the government to evaluate the planes' airworthiness, she said.
Dyncorp plans to examine the history of the planes, which date to the mid-1940s to early 1950s.
Davis said they plan to talk to the original equipment manufacturer, Douglas Aircraft Co., which is now part of the Boeing Co., to find out if they are too old to continue operating.
They need to know what the manufacturers expected when they built the planes. Then an engineering study has to incorporate the types of missions they have flown, Davis said.
Garrett said her company's aircraft haven't been grounded by the Federal Aviation Administration, but that Gov. Janet Napolitano ran into obstacles from the Forest Service when she tried to hire ARDCO for use in fighting major fires in the state this summer.
Garrett said the Forest Service told Napolitano that the planes could not fly over any fires on Forest Service land nor use any of four Forest Service air tanker bases, and that the state might lose funding for fighting fires if ARDCO planes were used.
