WASHINGTON Nov 20 (Reuters) - The U.S. Air Force fleet of F-22 Raptors, designed to be the world's top fighter jet, needs more than $8 billion dollars of upgrades to be made "capable and affordable to operate," the Pentagon's top arms buyer said on Thursday.
The comments by John Young, the undersecretary of defense for acquisition, highlighted Pentagon opposition to buying more than the 183 F-22s on order from Lockheed Martin Corp (LMT.N), the prime contractor.
The Air Force long has argued it needs 381 F-22s to be able to dominate the skies at the start of any major war and clear the way for other U.S. and allied warplanes.
Young said the Air Force already had budgeted about $8.3 billion for software upgrades and unspecified modifications to about 100 of the F-22s that would otherwise "kind of be lesser models."
Those outlays should be taken into account before talking about buying more jets, he told reporters at a breakfast.
"I don't think the debate is informed by all those facts," he added.
In addition, the F-22's "mission capable rate," a measure of its readiness, fell in the 62 percent range in the 2008 fiscal year, Young said.
"I think that's troubling," he went on, adding the fighter, which features advanced technology to reduce detection by radar, "is proving very expensive to operate."
Christopher Bolkcom, an expert on warplanes at the Congressional Research Service, said the mission capable rate was an incomplete gauge of an aircraft's availability.
"As a rule of thumb, however, 62 percent is unsatisfactory," he said.
Young said there were also struggles with low-observability and other issues that he did not name.
"Clearly, (there's) work to be done there to make that airplane both capable and affordable to operate," he said.
The F-22 had failed to meet most of its "key performance parameters" in operational tests last year and the trend was negative. Maintenance manpower hours per flying hour had gone up since previous tests, with the last one a "substantial" increase, he said.
Lockheed Martin, which has delivered 131 F-22s to the Air Force, declined to comment on Young's remarks, referring calls to the Air Force, which did not immediately respond.
The Pentagon last week released $50 million in bridge funds to preserve a decision on future F-22 production for the incoming administration of President-elect Barack Obama.
The production line must start shutting down early next year unless Obama opts to buy another batch.
Lockheed produces the F-22 aircraft in partnership with Boeing Co (BA.N) and United Technologies Corp's (UTX.N) Pratt & Whitney, which builds its dual F-119 engines.
In June, Gates ousted the Air Force's top military and civilian leaders amid a tug-of-war over funds for the F-22, which he considers ill-suited for post-Cold War conflicts such as Iraq and Afghanistan. (Reporting by Jim Wolf; Editing by Andre Grenon)