The use of commercial technologies for upgrades to Pratt & Whitney‘s [RTX] F117 engine for the U.S. Air Force C-17 airlifter by Boeing obviates the need for a re-engining of the 222 C-17s in the service’s fleet, according to the U.S. Air Force.
Boeing delivered the aircraft between 1993 and 2013.
In an email response to questions on Feb. 12, Air Force Life Cycle Management Center (AFLCMC) at Wright-Patterson AFB, Ohio, told sister publication Defense Daily that the center “has affirmed the continued viability of the Pratt & Whitney F117 engine for the C-17 fleet.”
“The F117 engine, in its present configuration, continues to exceed reliability and performance benchmarks, ensuring the C-17 fleet remains a robust asset for global mobility missions,” according to AFLCMC. “AFLCMC implements continuous improvement for the F117 through ongoing sustainment efforts. This approach leverages existing commercial technologies and an existing industrial base, allowing for the rapid incorporation of performance enhancements. This method circumvents the need for a complete re-engining program and is considered the best value for the operational requirements of the C-17.”
Last November, the Air Force said that it plans to award a 10-year firm fixed price contract at the end of fiscal 2027 to Pratt & Whitney for the restoration of the F117.
F117 overhaul and repair under the Engine Performance Restoration contract “will require depot overhaul and field repair services for the F117 propulsion system to ensure a serviceable, ready-to-install engine to meet the required war readiness engines and serviceable propulsion system levels,” the Air Force said at the time. “Modules will be broken out and planned and programmed each year based upon engine build requirements. LLPs [life-limited parts] will be separately priced and ordered based upon need. Engine Build Unit, which is comprised of Quick Engine Change kits and modules in the power section, will be the line of tear down inspect, disposition build and test of the F117 engine. The F117 Speedline will be set up for quick repair of stub time engines that require off wing maintenance for return to service.”
Stub time engines have LLPs nearing the end of their service lives.
A key part of the coming F117 Engine Performance Restoration contract “is comprehensive sustaining engineering, covering both recurring and nonrecurring work across multiple disciplines,” according to AFLCMC’s propulsion directorate at Tinker AFB, Okla. “This includes design and maintenance engineering, systems analysis, flight safety assessments, accident investigations, material evaluations, field diagnostics, and 24/7 emergency response— ensuring the engine’s safety, reliability, and readiness.”
In 2017, Pratt & Whitney received a more than $2.7 billion contract for F117 sustainment.
More than a decade ago, the Air Force said that its C-17s would last until 2040, but now the service projects that some will keep flying until 2075.
“Uninterrupted inter-theater airlift capacity is paramount for global operations during fleet recapitalization,” according to a letter last November from Air Force Brig. Gen. David Fazenbaker, Air Mobility Command’s director of strategy, plans, requirements, and programs. “Current recapitalization projections require C-5M viability until 2045 and C-17A viability through 2075.”
Lockheed Martin built the Air Force’s 52 C-5M Galaxy transports which are an average of 37-years-old. The Defense Department’s joint airlift relies on the Air Force C-17s, C-5Ms, and 277 Lockheed Martin C-130s. The fleet of 551 Air Force transports has an average age of 23-years-old.
As the Air Force develops systems to operate from austere locations and counter adversary attempts to disrupt U.S. military supply chains, the service has sought industry insights on the future Next Generation Airlift (NGAL) platform to replace the service’s C-17s and C-5s.
“With an accelerated NGAL Analysis of Alternatives in FY27 and an uninterrupted acquisition process with consistent funding, the first NGAL aircraft could be produced as early as FY38,” according to Fazenbaker’s letter. “It is estimated the NGAL program will reach Initial Operational Capability in FY41. One NGAL aircraft will replace one C-5M aircraft until the entire C-5M fleet is retired. Then, the C-17A fleet will be replaced by NGAL at a one-for-one swap.”
The Air Force has said that it takes several dozen C-17s to support a fighter wing from an established base and hundreds of C-17s to set up an expeditionary base in an austere area, while the deployment of a Patriot missile defense battery by RTX’s Raytheon requires seven C-17 sorties, and a Patriot battalion needs 73 to 128 C-17 sorties.
An “extreme example” noted by the Air Force includes the 1999 deployment of the ill-fated Task Force Hawk to support Operation Allied Force against Serbia when it took 500 C-17 sorties to deploy two battalions of U.S. Army AH-64 Apache helicopters into Albania, as the Army, “from an airlift perspective, has no ‘light’ units, only heavy and incredibly heavy ones,” according to the Air Force.
In addition to the Air Force’s cargo planes, the joint force can rely on the Civil Reserve Air Fleet of 450 airliners, but military access to the commercial fleet has decreased from 15 percent in the 1960s to 7 percent today, according to the Air Force.
The service has been below a goal to have at least 25 percent of its airlifters with secure, beyond-line-of-sight data links and communications, which the Air Force has said will be important over long distances in the Pacific theater.
A version of this story originally appeared in affiliate publication Defense Daily.