First Norwegian, Third U.S. F-35 Fly After Insulation Fix

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The first Norwegian F-35 took to the skies today at Luke Air Force Base, Ariz., after wrapping up repairs on its coolant lines, Aviation Week has learned.  

Meanwhile, a third repaired U.S. Air Force F-35A returned to flight at Hill Air Force Base, Utah, Air Force spokesman Micah Garbarino tells Aviation Week. Work on two more will likely wrap up by the end of the day, and the aircraft are expected to fly sometime next week, he says. The first two U.S. aircraft flew for the first time Oct. 24. 

The Norwegian F-35 at Luke and U.S. jet at Hill are the latest to return to flight after the discovery of faulty insulation inside the fuel tanks grounded 15 operational F-35As in September. Work continues on the remaining 11 aircraft, including one additional Norwegian and 10 U.S. Air Force models. 

The above pictures of Norway's AM-4, provided to Aviation Week by the Norwegian ministry of defense, are the first in-flight images of the repaired F-35s to emerge since the affected aircraft began flying again.

Repairs on the impacted aircraft at Luke and Hill are progressing faster than expected, and all 15 operational F-35s affected by the cooling lines problem are expected to fly by the end of the year. 

Hill Air Force Base provided Aviation Week the below photo of one of its repaired aircraft on the ground. 

In total, 57 operational and in-production F-35s were affected by the problem, which comes down to faulty cooling lines that were installed in the wing fuel tanks. Due to a supplier mistake, the tubing insulation on the Polyalphaolefin (PAO) coolant tubes was not compatible with the fuel, which caused the insulation to crumble and peel off the tubing. This left residue in the fuel that could potentially obstruct fuel flow in and out of the various tanks.

The repair work has not been as extensive as many initially anticipated. Despite early concerns that technicians were going to have to completely tear apart the wings to access and remove the loose insulation, engineers designed small access holes to allow maintainers to get into the aircraft without massive cutting. Once inside the aircraft, maintainers strip the faulty coating from the coolant lines and install screens to prevent any foreign object from flogging the fuel siphon-tubes.

The news that four operational F-35s are now flying again bodes well for the affected in-production jets, which include Japanese and Italian aircraft, as well as the two Israeli planes that are supposed to be delivered to the Israeli air force in December.

The JPO hopes to have the last of the production jets repaired by the end of April 2017.

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