The US Air Force has ordered the grounding of 13 F-35A models, as well as a pair of Norwegian F-35As, following the discovery of “peeling and crumbling” coolant tube insulation.

The issue appears to have been with a supplier of coolant lines, which are installed in the wings of the jet. During a routine maintenance check, it was discovered that the insulation on the lines were in some cases decomposing, which left residue in the fuel itself, according to a release from the Norwegian government on the grounding.

The issue has been traced back to the insulated coolant tubes manufactured by one particular provider that have only been installed in the wing fuel tanks of the 15 aircraft — 10 from Hill Air Force Base, Utah, two US and two Norwegian F-35As at Luke AFB, Ariz., and one plane at Nellis AFB, Nev.

The problem was first discovered this summer during depot maintenance of an F-35A being prepared for initial operational capability, Lockheed Martin spokesman Mike Rein said.

After maintainers found three aircraft with crumbling coolant tubes, Lockheed conducted subsequent tests that “indicated it was possible for this crumbling insulation to become lodged in the siphon lines connecting wing and fuselage fuel tanks,” said US Air Force spokeswoman Ann Stefanek. “This could result in excessive negative pressures in the fuel tanks during flying operations or excessive positive pressures during air or ground refueling. In either case, the under- or over-pressure could cause structural damage to the fuel tanks.”

Read More: Defense News

The F-35 . . . So far –


• The U.S. DOD announced an agreement known as Blueprint for Affordability in July 2014, aimed at reducing the price of an F-35 to the equivalent of today’s 4th generation fighters by the end of the decade.