YUMA, Ariz. — The most recent grounding of the F-35 Lightning II by a cracked engine blade has been lifted and flight operations for the futuristic jet fighter restored.

According to a statement released late Wednesday evening by the F-35 Joint Program Office, the decision to restore the F-35's flight status concludes a cautionary flight suspension that began on Feb. 21 after a 0.6-inch crack was found on a third-stage turbine blade of a test aircraft at the Edwards Air Force Base F-35 Integrated Test Facility during a routine inspection.

“Following engineering analysis of the turbine blade which developed a crack, F-35 flight operations have been cleared to resume,” wrote Kyra P. Hawn, deputy director of the Public Affairs F-35 Joint Program Office.

Wednesday's announcement comes six days after flight status was restored from a previous suspension that lasted about a month. Unlike the past suspension, which was only for the B jump jet variant designed for the Marine Corps, this suspension was for all versions of the F-35 fleet, including the F-35A Air Force conventional takeoff version and the F35-C carrier variant for the Navy — a total of 51 planes.

Hawn wrote that comprehensive tests on the damaged blade were conducted at the Pratt & Whitney facility in Middletown, Conn. The engine in question is part of the F-35 test aircraft fleet, she wrote, and had been operated at extreme parameters in its mission to expand the F-35 flight envelope.

Prolonged exposure to high levels of heat and other operational stressors on this specific engine were determined to be the cause of the crack.

According to Hawn, no additional cracks or signs of similar engine stress were found during inspections of the remaining F-35 inventory. “No engine redesign is required as a result of this event.”

Within the current Department of Defense inventory, 17 F-35s are employed in test and development at Patuxent River Naval Air Station and Edwards Air Force Base. The remaining aircraft are assigned to Marine Corps Air Station Yuma and Eglin Air Force Base, Fla., and comprise the initial F-35 operational fleet.

Both F-35 suspensions, now, are due to problems with the engines. The F-35B variant was initially grounded after a Jan. 16 test flight at Eglin Air Force Base was aborted due to a problem later identified as a fueldraulic system failure.

That failure was caused by an improperly crimped fueldraulic line. After an investigation by the Joint Strike Fighter Program Office and engine manufacturer Pratt & Whitney, six non-compliant lines were discovered.

A day before the most recent suspension, which happened on Feb. 22, an F-35B variant from VMFA-121 took of from MCAS Yuma, becoming the first time a flight was conducted by the Marine Corps or any service branch primarily responsible for the maintenance of the aircraft.

MCAS Yuma is home to VMFA-121, the world's first operation F-35 squadron. The squadron, once fully staffed, will consist of approximately 300 Marines. While the squadron currently has three Lightning IIs, it is expected to receive additional F-35s throughout the next eight to 12 months, with a total of 16 aircraft scheduled to arrive by late 2013.

jgilbert@yumasun.com
 

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