Four of the US Air Force’s of E-8C JSTARS are back in operation following a radar mishap that grounded part of the fleet last week.

The USAF assembled an independent investigation of four aircraft recently delivered from depot maintenance at Northrop Grumman's facility in Lake Charles, Louisiana. One aircraft experienced water damage to the Northrop APY-7 radar after the glassfibre canoe did not properly drain water.

"The inspections did reveal some concerns that warranted noting and/or correction before returning to flight," a USAF spokesman said in an email to FlightGlobal. "The concerns were able to be immediately remedied on-site at Robins Air Force Base by the 116th Air Control Wing."

The damage to the equipment could exceed the class A mishap threshold, at least $2 million, the USAF says. But the decision to inspect the other three aircraft was not based on that incident alone, but rather a recent trend of workmanship issues, a USAF spokesman told FlightGlobal. Although the radar damage alone does not constitute a flight safety issue, Air Force Materiel Command is concerned that the trend in quality issues at the Lake Charles facility could lead to safety issue.

"The recent significant mishap was declared based on the cost estimate of the damage to equipment rather than an in-flight incident," the USAF says.

While the current JSTARS fleet gets back on its feet, the next-generation of surveillance is aircraft is still lagging behind. Congressional language in the annual defense policy bill forcing a fixed-price contract would delay the recapitalisation programme’s request for proposals by at least three months and could push back initial operational capability by a year, USAF acquisition leaders said last week.