The second production F-35 is flown during an airframe loads envelope expansion mission June 11. (Tom Reynolds / Lockheed Martin)
WASHINGTON — The F-35 Joint Strike Fighter test fleet will be able to fly six hours between engine inspections for weapon test and refueling missions, as restrictions on the fifth-generation fighter continue to ease.
Previously, the entire F-35 fleet was limited to three hours of flight time before an engine inspection was required as an investigation continues into a fire that heavily damaged an F-35A model on June 23.
The test fleet is made up of 20 F-35 fighters. The remaining 79 F-35s are still operating under the full restrictions.
During the inspection into the cause of the June 23 fire, the Pentagon grounded the entire fleet. On July 15, the planes were cleared to fly with heavy restrictions.
In late July, the Pentagon eased up on some restrictions for the test fleet. Speed restrictions were relaxed from Mach 0.9 to Mach 1.6, while maneuverability restrictions were eased slightly from 3 Gs to 3.2.
The Department of Defense is taking a “multipronged approach to expanding the envelope for our flight test engines,” said Joe DellaVedova, spokesman for the F-35 joint program office. Bumping the operating limit from three to six hours “allows our test fleet to conduct dedicated weapon test and refueling missions.”
DellaVedova also said the root cause analysis into the fire continues. While inspectors have determined the fire was caused by “excessive” rubbing of a fan blade inside the Pratt & Whitney designed F135 engine, it is unclear why the issue arose.
Top officials from the US Air Force, the largest customer for the F-35, have expressed confidence that the engine problem will be overcome.
Army Awarded Contract
The US Army has finally found a way to get a piece of the F-35 pie.
The service’s Aviation and Missile Research Development and Engineering Center (AMRDEC) was selected to provide an independent software analysis for the fighter, the Army announced Wednesday.
This represents the first Army action on the F-35 program, which covers the US Air Force, Marines and Navy as well as 11 other countries.
The service will provide safety crosschecking on a small portion of the plane’s 24 million lines of code, including pilot systems software, DellaVedova said.
“The Army was selected as part of a fair and open competition between industry and governmental sources to do a software safety evaluation,” DellaVedova said. “This is a very specific software safety evaluation they are doing.”
In essence, Army engineers will double-check work done by corporate partners Lockheed Martin, Northrop Grumman and BAE. Contracts for similar double-checks to software have been awarded to corporate partners in the past, but this is the first time the Army has taken part.
“We do tests on software to make sure it works and meets requirements and won’t be harmful,” DellaVedova added. “They are helping to ensure that some software within some of the subsystems will ensure safe operations.”
“The F-35 has over 24 million lines of code and is clearly the most complex weapons system ever designed by the DOD,” James Lackey, AMRDEC’s acting director, said in a statement posted to the Army’s website.
“The department’s decision to select the Software Engineering Directorate to provide the independent software safety evaluation speaks highly of our expertise, credibility and our past demonstrated successes.” ■