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F/A-18E/F Service Live Modification (SLM)

In an effort to extend the service life of its aging fleet of F/A-18E-F Super Hornets into the 2040s, the U.S. Navy is preparing to begin a comprehensive modification program that will enable the fighter jets to fly more than 50-percent longer than originally intended. The Navys answer to the challenge of extending the life of a platform that is aging faster than expectedis a Service Live Modification (SLM), which will authorize the Super Hornet to fly past 9,000 flight hours while also delivering major modifications and capability upgrades. Under SLM, the Super Hornet will receive capability upgrades meant to counter future threats that they may not have gotten in a SLEP, along with life-extending modification kits. If it was just extending the life of the aircraft, it would be called SLEP, Dailey said.

When it debuted in theater in 2002, the F/A-18E-Fs lifespan of 6,000 flight hours was expected to last about 20 years. But delays to the F-35 Lightning II program and unplanned squadron transitions from the F/A-18A-D Hornet to the F/A-18E-F mean the Navy needs the Super Hornet to last longer than initially planned. The platform having never known peacetime and racking up flight hours more quickly than anticipated over 15 years of constant combat operations in the Middle East exacerbates the problem. The first Super Hornet to reach 6,000 flight hours did so in April 2017, just ahead of its 15th birthday in June.

Service Life Assessment Program (SLAP)

The Service Life Assessment Program (SLAP) was developed in 2002 by the F/A-18 and EA-18G Program Office (PMA 265) in Patuxent, MD. The goal of SLAP was to determine the feasibility of the airframe to surpass its service life; specifically analyzing the stress that catapult and landing cycles had on the airframe. A test to determine airframe stress was created using actuators that were attached to an aircraft which underwent a 300-hour block of loads that included arrestments, catapults, and various 7-G maneuvers. The aircraft was tested to two life times. Results identified areas of the airframe where symptoms of stress fatigue were more prevalent; subsequently, inspections targeting those points were established. The Super Hornet began its required 10-year Service Life Assessment Program (SLAP) in 2008, midway through its expected 20-year service life. At the time, the plan was for the platform to transition straight into a SLEP, but in an effort to expedite the process, the program office decided in 2016 to give the F/A-18E-F a more-comprehensive SLM, with Boeingthe aircrafts manufacturerresponsible for the entire process. By having the aircraft, engineering resources, replacement parts and technology modifications all in the same location, the program office is expecting a significant uptick in aircraft throughput.

Throughout the SLAP, Boeing engineers predicted which modifications and upgrades each Super Hornet will need and placed the jets into bins based on fatigue lifehow stressed the airframe has been by its mission setand the amount of maintenance its expected to require. Thus, each Super Hornet will receive a tailored SLEP kit.

But because the aircraft were aging faster than expected, the process of extending their lifespan was also beginning sooner than planned. Ideally, you want the first SLEP kits ready at 6,000 hours, but that was not possible due to the Super Hornets high use, Dailey said. We have accelerated the program to accommodate as much as possible.

The Boeing Co., St. Louis, Missouri, was awarded April 25, 2017 a $49,760,000 indefinite-delivery/indefinite-quantity contract for the Service Life Assessment Program and Service Life Extension Program, Phase C, to extend the service life of the F/A-18E/F beyond the original design of the 6,000 flight hour service life. Work will be performed in St. Louis, Missouri (50 percent); and El Segundo, California (50 percent), and is expected to be completed in April 2021. No funds will be obligated at time of award. Funds will be obligated on individual task orders as they are issued. The Naval Air Systems Command, Patuxent River, Maryland, is the contracting activity.

High Flight Hour (HFH)

A second phase of SLAP was created in 2005 to include flight-hour issues and dual seat landings of the B and D Hornet models. The results were the basis for stand-alone (B and D specific) and basic High Flight Hour (HFH) inspections designed to ensure operational safety of the aircraft beyond the intended service life, to 8,000 flight hours. The basic HFH program began the following year and included disassembly of the aircraft to identify corrosion, cracks and fatigue-related issues.

Aircraft scheduled for the basic HFH program typically undergo the procedures in conjunction with routine Planned Maintenance Interval-One cycle (PMI-1). Examiners and evaluators (E&E) perform the PMI-1 cycle, and determine the scope of repairs or replacement to the aircrafts major components and other crucial parts. They also perform the HFH inspections, which are separate from the PMI-1inspections. Results of SLAP phase two indicated that if the service life of the legacy Hornets were to be extended further --- to 10,000 flight-hours --- then significant improvements were required. To that end, the Service Life Extension Program (SLEP) was created in 2008.

Service Life Extension Authorization (SLEA)

Full SLEP kits will not be available until fiscal 2023; in the meantime, the Super Hornets that reach 6,000 flight hours will require a Service Life Extension Authorization (SLEA), which permits the aircraft to fly up to 7,500 hours before requiring a full SLEP kit. Super Hornets inducted before fiscal 2023 will get a partial SLEP kit, followed by a full modification post-2023. The program office also hoped to avoid the waves of inspections and retrofits that could sometimes bog down the legacy Hornets SLEP. If the program office noticed a glut of Super Hornets approaching 6,000 flight hours, it would shift some of them into SLM ahead of schedule in order to maintain a steady flow of aircraft through Boeings hangars.

When complete, Fleet Readiness Center Southwest (FRCSW) sends a Service Life Extension Authorization (SLEA) message to the respective squadron. The message relays the interim flight extension hours granted; usually 1,000 flight hours, and the next maintenance interval for the aircraft. An HFH program was developed for the F/A-18 Super Hornet E and F models. As part of the Service Life Modification (SLM) program, there will be a Super Hornet HFH inspection. The first aircraft is scheduled to be inducted in mid-2018. The inspection locations are based on results of E and F SLAP hot spot analysis. The inspection procedures were still being developed as of 2017, but would be based on the SLAP results and not necessary be the same as A-D.

Service Live Modification (SLM)

In preparation for the SLM, Boeing engineers despliced or split in half two retired, high-use Super Hornets to examine their interior structures for anomalies and signs of fatigue such as cracks that validate SLAP predictions. They also inspect and analyze material condition of the aircraft, checking for things like corrosion, frayed wiring and damage to hydraulic and fuel tubing. One of the despliced jets retired with the most carrier takeoffs, landings and flight hours in the fleet, while the other accumulated the most total landings.

Boeing is examining the forward fuselage and wings, while Northrup Grumman is looking at the center aft fuselage. As of September 2017, a total of 190 areas on the two aircraft had been accessed with no major negative findings, though minor corrosion was found on one of their dorsal decks. SLM is a new approach to extending the life of a platform and its initial success is receiving positive feedback from the acquisition community, and now similar initiatives are following suit, Dailey said.

The SLM process began in 2018 with the arrival of four Super Hornets at a Boeing facility in St. Louis. By 2023, Boeing expected to induct about 50 Super Hornets into the program each year10 in St. Louis, and 40 in San Antonio at a former C-17 hangar currently being retrofitted for the SLM. At first, the aircraft would take about 18 months to move through the first six Super Hornets were projected for delivery in fiscal 2020but as Boeing nails down the process it anticipates cutting down that timeline to 12 months.

The SLM program is the result of lessons learned from the Hornets own Service Life Extension Program (SLEP), which pushed the legacy fleets lifespan from 6,000 flight hours beyond 8,000 and, in some cases, up to 10,000 flight hours. Under SLEP, the Hornet aircraft have received high-flight-hour (HFH) inspections and necessary repairs at Navy and commercial maintenance depots. But those repairs have oftentimes had to wait for engineering solutions and for parts to be ordered from and delivered by a commercial manufacturer.

Under the legacy SLEP, we had to go through multiple partieswhen the Navy depot found a failed part, it had to order a replacement from industry and wait for the part to be shipped, and most of those parts have not been produced for decades, said Scott Dailey, the F/A-18 & EA-18G Program Office deputy program manager for air vehicle systems.

The Naval Air Systems Command (NAVAIR), Patuxent River, MD announced 27 March 2018 plans [Solicitation Number: N00019-18-D-0001-TBD] to negotiate and award a sole source Indefinite-Delivery Indefinite-Quantity (IDIQ) contract-modification with The Boeing Company (Boeing) for the performance of F/A-18E/F SLM for FY19/20. It is anticipated that a contract will be issued to cover the induction of up to fifteen (15) FY19 SLM aircraft and up to thirty (30) FY20 SLM aircraft. The contract will include the following in support of comprehensive service life modifications to the Super Hornets to maximize aircraft in-reporting status, and return aircraft to the fleet with increased service life and capability: aircraft inspections and physical verification of fleet usage; warranty and non-warranty modifications; repairs incident to modification; recurring and non-recurring engineering efforts; logistics; project management; parts, kits, associated materials; and data.

The Government does not have license rights in a technical data package that would allow another contractor to produce the F/A-18E/F aircraft. Therefore, Boeing is the only known source available with the requisite technical knowledge, experience and tooling to perform the efforts in order to satisfy the Government's requirement.



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