A portion of the Air National Guard's F-15 Eagle fleet at Kingsley Field, Oregon, has been grounded over significant maintenance issues affecting the aircraft's structure, Military.com has learned.
Col. Jeff Smith, commander of the 173rd Fighter Wing, last week grounded the fleet of 30 aircraft over pilot safety concerns.
"Due to a possible maintenance issue, out of an abundance of caution and concern for air crew safety, we have decided to stand down our flying while we take a closer look and determine the path forward," said Maj. Nikki Jackson, spokeswoman for the 173rd.
Jackson said the concerns were over "structural issues that we want to take a closer look at before we clear our aircraft to fly."
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"The safety of our air crew is our number one priority," she said in an email Wednesday.
The 173rd anticipates F-15 flight operations to resume tomorrow, Jackson said.
It remains unclear if the issue pertains only to F-15s at Kingsley thus far, or if it will lead to a service-wide inspection of all of the 1980s-era aircraft.
The temporary grounding is not expected to affect training or deployment schedules for the 173rd, Jackson said.
"A team from the F-15 Aircraft Structural Integrity Program is on site and looking into the issue, to determine the path forward," she said.
Kingsley Field in Klamath Falls is home to the only F-15C training schoolhouse in the Air Force, a robust training program for both active-duty and Guard pilots. The 173rd also houses a few D aircraft models.
The single-seat F-15C and two-seat F-15D models entered the Air Force inventory in 1979 and have been in almost every theater across the globe.
In 2007, the Air Force grounded its entire F-15 fleet after a fighter from the Missouri Air National Guard broke apart mid-air and crashed. The pilot ejected.
The service conducted a nearly three-month inspection of the fleet, in which investigators found the cause of the crash to be a faulty beam in the frame of the aircraft, known as the longeron.
Engineers concluded that the longeron -- part of the multi-fastened support beams that work as building blocks within the aircraft's fuselage -- had cracks in it, and that there had been no proper maintenance procedures to detect the deficiency.
"No inspection requirements existed for detecting a crack in the longeron," according to the 2008 Accident Investigation Board report, as reported by CBS News. Similar issues were detected in more than 150 F-15s, the report said.
The Air Force in recent months has dedicated funding just to keep up with maintenance for its longerons.
According to the service's fiscal 2018 budget request, it asked for roughly $7 million just for service life extension, or SLEP, on the support beams.
The funding was recently approved through the $1.3 trillion omnibus bill signed last week by President Donald Trump, with fixes beginning later this year.
"Air superiority is a demanding mission set, and the newest F-15C was built in 1986," the budget documents said. "Consequently, the F-15C/D fleet will need a Service Life Extension Program on its fuselage longerons to reach its planned service life within acceptable risk margins.
"The longeron SLEP entails replacing 14 primary tension members in the structure of the forward fuselage and is critical to the safety of flight of these aircraft. There are other structural issues with the F-15Cs besides the longerons, and full-scale fatigue testing is ongoing to assess these matters," the budget request said.
The service plans to forgo other upgrades to the legacy F-15 in order to focus on SLEP.
The F-15C is unlikely to receive its Eagle Passive/Active Warning Survivability System upgrade, known as EPAWSS, that would heighten its threat assessment and survivability with advanced electronic warfare technology, according to a recent report from Aviation Week.
The latest F-15 woes come at a time when the service has mulled retiring the C/D models, which mainly reside in the Air National Guard.
Last March, officials told lawmakers they were looking at possible plans to retire the two models as early as the mid-2020s.
Air National Guard Director Lt. Gen. L. Scott Rice at the time said the Air Force as a total force was in "deep discussions" regarding the retirement, with plans to further assess the F-15 inventory in 2018.
Rice and other Air Force officials said the F-16 Fighting Falcon would take over in the multi-mission role.
The service has 212 F-15C and 24 F-15D models, according to the Air Force Association's 2017 aircraft inventory almanac.
-- Oriana Pawlyk can be reached at oriana.pawlyk@military.com. Follow her on Twitter at @Oriana0214.
