Air Force Grounds ‘Combat Ready’ F-35 Over Coolant Line Flaw

Updated on
  • ‘Crumbling’ insulation found during routine maintenance
  • Air Force sees quality glitches, not design flaw, in aircraft

Seven weeks after the Air Force declared its first F-35 jets combat ready, 10 of the aircraft aren’t flying after service mechanics discovered “peeling and crumbling” insulation wrapped around lines that carry liquid to cool combat systems and computers.

The poor insulation is suspected on 57 aircraft, including 42 on Lockheed Martin Corp.’s production line. The issue is not a design flaw with the aircraft but instead caused by manufacturing quality glitches with one of two subcontractors which make the 18 lines through which the coolant flows, according to an Air Force statement and an interview with a service official, who asked not to be identified.

If not fixed, the crumbling insulation could become lodged in the lines connecting the aircraft’s wing and fuselage fuel tanks causing potential overpressure or underpressure that “may cause structural damage to the fuel tanks,” according to a statement sent Friday to House and Senate defense committees.

“The issue was discovered during depot modification” of an Air Force jet and has resulted this month in a “temporary pause in flight operations,” according to a separate statement from the service. Ten of the 15 aircraft not flying are located at Hill Air Force Base, Utah, home of the service’s first combat-ready squadron. The other five aircraft don’t have the flawed insulation and continue to fly regular sorties, the office said. Two aircraft delivered for Norway are also not flying, said the official. Another three F-35s have been grounded at other bases, for 15 total.

‘Corrective Actions’

Twenty of the aircraft that need to be fixed on the production line belong to foreign countries, according to Air Force data: Eight to Israel, six to Japan, and three each to Italy and Norway.

Lockheed Martin spokesman Michael Rein said in a statement that “safety is always our first consideration and Lockheed Martin is committed to resolving this issue as quickly as possible to return jets to flying status.” The issue “is confined to one supplier source and one batch of parts,” he said. Rein declined to identify the subcontractor involved.

‘Proven Track Record’

F-35 spokesman Joe DellaVedova said in an e-mail that the Pentagon program office and Lockheed Martin “have a proven track record of solving issues and we’re confident we’ll continue to do so. The government and industry team is now developing repair procedures to remedy the problem and return the affected aircraft back to safe flying operations.”

The Marines Corps and Navy versions are not affected by the problem, which has been traced to the “use of nonconforming material for the tubing insulation and improper manufacturing processes during fabrication of the cooling lines,” DellaVedova said. “The nonconforming material that was used is not compatible with fuel, causing degradation of the insulation and resulting in it falling off the tubing.”

A spokesman for the Pentagon’s director of combat testing said the office was made aware this week of the problem. The issue does not appear at this time to be affecting test aircraft the service has designated for the intense combat evaluation the program is planned to undergo in 2018, he said.

As to the 42 aircraft on Lockheed Martin’s production line, “the extent and nature of the repairs needed are not known at this point,” spokesman Army Major Roger Cabiness said in an e-mail statement. “However, it is not unreasonable to assume the repairs will require
opening the fuselage and/or wings to access the fuel tanks to replace components or make repairs, which would be very intrusive and could require extensive downtime.”

The Air Force has taken delivery of 104 F-35A models but the Pentagon’s Defense Contract Management Agency has suspended delivery of additional aircraft “until corrective actions” are in place, according to the Air Force statement.

“Lockheed Martin has begun developing the repair process for these aircraft,” the Air Force statement said.

The unnamed service official, who follows the F-35 program closely, said the Air Force, Lockheed Martin and the Pentagon program office know precisely which planes have the suspect insulation, so the overall program impact is not widespread.

Still, it’s unknown at this point how long the aircraft will be grounded and when the 42 aircraft currently on Lockheed Martin’s production line will be modified with new insulation, the official said. Air Force and Lockheed engineers should finalize a formal recovery plan by next week, the official said.

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