Two powerful lawmakers sent letters to the defense secretary and government auditors yesterday decrying the Pentagon’s decision to lift a probation on the development of a variant of the F-35 Joint Strike Fighter.

Senate Armed Services Committee Chairman Carl Levin (D-Mich.) and Ranking Member John McCain (R-Ariz.) tell Defense Secretary Leon Panetta they are “seriously concerned about the lack of notice and consultation” about his Jan. 20 move to lift the two-year probation on the Marine Corps’ short-takeoff vertical-landing (STOVL) F-35B. Former Defense Secretary Robert Gates put the program on a two-year hold in January 2011 so the Pentagon could address technical issues unique to that version, which could impact its cost and weight, and officials could determine whether to keep or cancel it.

“When Secretary Gates originally decided to put the F-35B on probation, he intended his decision to invoke specific courses of action by Lockheed Martin and the program management office to help ensure that the F-35B program established technical maturity and design stability in several key areas,” Levin and McCain say in the Jan. 6 letter to Panetta. “Have these actions been taken? If not, your decision may have foregone a valuable opportunity to continue driving desired improvements through the still-nascent, enormously challenging program to develop the F-35B.”

The two senators, who have closely monitored cost overruns and technical challenges with Lockheed Martin’s [LMT] F-35 program, also asked the Government Accountability Office (GAO) yesterday to assess the STVOL aircraft’s status and the appropriateness of lifting of the two-year probationary period after one year.

They pose 14 detailed questions on the F-35B to Panetta, asking him to answer them “as soon as possible” as they assess the “appropriateness” of his probation-ending decision. They ask, for example, which senior Pentagon officials were part of the decision to remove the STOVL off probation.

“We believe that every opportunity to focus Lockheed Martin's attention and disrupt ‘business as usual’ in this multibillion-dollar effort, as Secretary Gates' probation decision had done, should be maximized,” they say.

They cite concerns with the overall F-35 effort, including that in recent days the Pentagon’s chief operational tester reported that the Joint Strike Fighter Operational Test Team assessed the program as not on track to meet operational effectiveness or stability requirements.

On the Marine Corps’ STOVL variant, Levin and McCain note that even though engineering solutions to problems with the structure and propulsion have been identified, more issues of the same sort, “potentially as serious as those that were originally identified a year ago,” have been found.

Noting that the F-35B has completed only 20 percent of its developmental test plan, the senators tell Panetta his decision “appears at least premature.”

Panetta traveled to Naval Air Station Patuxent River, Md., on Jan. 20 to declare he was removing the F-35B from probation.

He said the Patuxent River workers made more progress than planned in addressing known problems, saying the F-35 STOVL “is demonstrating the kind of performance and maturity that is in line with” the Air Force and Navy F-35 variants (Defense Daily, Jan. 23).

Steve O’Bryan, Lockheed Martin’s F-35 vice president for program integration and business development, at the time attributed the lifting of probation to the plane’s increase in flights last year and its meeting of or exceeding testing points.