SALT LAKE CITY (AP) -- Inspectors say Hill Air Force Base strips and repaints some F-16 fighter jets so often that "the structural integrity of the aircraft may have been compromised."
The Pentagon made the same complaint back in 1999, and recently found a problem remained despite improvements.
In a written response to the Deseret Morning News, Hill officials said recent studies have shown the stripping process, which uses a high-powered stream of small, soft plastic beads, is safer than inspectors assume.
Hill said it has found "no evidence of aircraft structural stress or fatigue failures" caused by it, the News reported in a copyright story Monday.
The concerns were in a report by the Air Force Audit Agency a high-powered stream of small, soft plastic beads. It was obtained by the News through a Freedom of Information Act request.
Although the report contended too much stripping still was being done, the inspectors did say that Hill had begun to use a softer plastic bead in the stripping process. They said studies should be conducted on whether they cause as much damage as harder beads used previously -- and whether time restrictions on stripping should be lifted or modified.
In 1999, the agency said maintenance depots, including Hill's Ogden Air Logistics Center, stripped and repainted aircraft every time they came in for scheduled maintenance because customer wings "wanted aircraft to look new when they returned."
Inspectors said then that had wasted $157 million in six years.
The agency in 1999 said stripping too often would cause structural fatigue and shorten aircraft life-span. It said planes should not be stripped more often than once every six years, and no more than three times in their life-span. It found that 96 percent of aircraft had been stripped more often than that.
The new report said Hill had "significantly improved oversight of F-16 bead blasting and painting frequency," but "some F-16 aircraft were still bead blasted too often."
Inspectors looked at records for a sample of the 500 or so F-16s that are repainted at Hill each year.
They found that five of 43 F-16s they reviewed had still been stripped and repainted more than once every six years.
Inspectors also said that "structural engineers were not inspecting the structural integrity of those aircraft that were bead blasted more than three times" in their life-span -- which they said is required before additional stripping occurs.
Inspectors said the problems continued because base personnel did not always review maintenance records to see how often planes had been bead blasted, and because maintenance forms were not always accurate or complete.
Hill's response to the News said that several studies have been conducted on the use of the softer beads, and, "Study results consistently show that plastic media stripping causes negligible structural damage when established procedures are followed.
In all instances, fatigue crack growth rate and fatigue life cycles remain within established parameters," the response said.
Hill said the policy is still not to strip aircraft more often than once every six years, however, and personnel try to ensure that.
It said periodic inspections are scheduled throughout an aircraft's life cycle to look for any material failure.
(Copyright 2005 by The Associated Press. All Rights Reserved.)