US Air Force, LANGLEY AIR FORCE BASE: Gen. John D.W. Corley, Air Combat Command commander, returned 149 grounded F-15s to flight Feb. 15 contingent upon the completion of customized inspections on each of the aircraft's longerons.
This “stand-down release” order brings the total number of cleared A, B, C and D-model F-15 aircraft to 429. Nine aircraft, however, will remain grounded due to cracked longerons, the critical support structures that run along the length and side of the aircraft.
The ACC release directly applies to ACC F-15 A-D aircraft. ACC also recommends the release and return to flying status of F-15 A-D aircraft assigned to the Air National Guard, Pacific Air Forces, United States Air Forces in Europe, Air Education and Training Command and Air Force Materiel Command.
The F-15s are cleared after the completion of any necessary and previously ordered inspections, follow-on engineering technical reviews on each aircraft longeron and any associated repair actions.
The recommendation to return these aircraft to flying status is based on assessments performed by the engineering staff at Warner Robins Air Logistics Center with technical assistance provided by industry partners and the Air Force Research Laboratories.
Warner Robins ALC F-15 systems program manager created the time compliance technical order inspections that each F-15 A-D aircraft have to complete before returning to flight. In addition to the TCTOs, additional inspections are required via an engineering technical assistance request process.
The purpose of the ETAR inspections is to validate unique discrepancies at specific locations on any given aircraft longeron among those aircraft recommended for release.
These are tailored inspections, which are tail-number unique, and are directed via the ETAR process. Once the ETAR inspections are complete, and TCTOs have been completed, the aircraft may return to flying status.
On Feb. 12, General Bruce Carlson, AFMC commander, approved the report of an Independent Review Team, which endorsed WR-ALC plans for releasing aircraft after an extensive analytical investigation. Subsequently, Maj. Gen. Thomas J. Owen, WR-ALC commander, recommended that F-15s with longerons not meeting specifications but, which have passed all previous published TCTOs and do not have cracks, be returned to flight. The Warner Robins ALC F-15 SPM has developed additional fleet-wide recurring inspection requirements for the F-15 A-D model longerons, which will account for individual aircraft usage severity, part thickness variations and other factors as required.
“The priority in returning these F-15s to flight is to provide combat power for the defense of our nation and, particularly, as an essential component to our nation's alert force,” said General Corley. “After careful review of engineering data and upon the recommendation from both military and industry experts, I believe we can release and return our F-15s to their important air superiority mission.”
The F-15s were first grounded after a Nov. 2 mishap when an F-15 C assigned to the Missouri Air National Guard broke in half due to the failure of the upper right longeron. Based on data recovered by the accident investigation board investigating that mishap, and from engineers at the WR-ALC, aircraft were found to have cracks in their longerons, which resulted in the grounding of the entire fleet until appropriate inspections and evaluations could be accomplished.
On Jan. 9, ACC cleared approximately 60 percent of its F-15 A-D model aircraft for flight and recommended a limited return to flight for Air Force units worldwide. This decision followed engineering risk assessments and data received from multiple fleet-wide inspections. At that time, it was determined that 40 percent of the F-15 A-D model fleet's longerons did not meet manufacturing specifications.
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