Providing affordable sustainment was a key goal for the Joint Strike Fighter (JSF) program before Lockheed Martin [LMT] beat out Boeing [BA] to win the JSF contract on Oct. 26, 2001.
On April 11, 2000, the Pentagon’s Joint Requirements Oversight Council (JROC) validated a Joint Operational Requirements Document (JORD) with six key performance parameters (KPPs) for the fighter. Among the KPPs was high mission reliability. The mission reliability KPP for the U.S. Marine Corps and U.S. Navy versions of JSF is 95 percent, while the KPP for the longer legged U.S. Air Force version is 93 percent.
The mission reliability requirements, run through extensive modeling, would dovetail with F-35 pilots enjoying nearly the same turn-the-key performance as commuters starting their cars in the morning.
That has not come close to happening. F-35s are now aiming for an availability rate of 65 percent. “Regardless of whether it’s an F-35 squadron or an F-16 squadron in the Guard or an F-16 squadron in the Reserve or an F-16 squadron on active duty, bar napkin math [says] if we run about a 65 percent aircraft availability rate, we’re giving the aviators the training they need, [and] we’re holding the readiness we need, and we have the deployability we need,” Air Force Gen. Mark Kelly, the head of Air Combat Command (ACC), said last month. “When you take a squadron and you count the jets you have down for depot or down for maintenance or supply, you come out with a 65 percent aircraft availability. You’re actually doing okay because we can surge up to deploy or into combat above 70 [percent], but I tend to look at 65 percent aircraft availability as pretty much a steady state line that I need to get for my readiness and my training proficiency.”
Air Force Lt. Gen. Eric Fick, the F-35 program executive officer, has said that over the years “decisions to defer spares and the stand-up of organic maintenance have had long reaching impacts on the program,” but he said that, while aircraft availability “is not where we need it to be,” availability rates are headed up, as the military services devote more funds to spare parts and organic depot maintenance.
In September, 46-48 of the Air Force’s 297 F-35As under ACC were grounded for work on their Pratt & Whitney [RTX] F135 engines, parts or fuel systems, but recent work by Air Force personnel at Oklahoma City Air Logistics Center and Pratt & Whitney has reduced the number of unavailable engines below 40, Kelly said.
Mission capability (MC) rates for the three F-35 variants have been below targets. For the last three months, the MC rates for the F-35A and the Marine Corps’ F-35B have been 59 percent—31 points below the objective for the F-35A and 26 points below the goal for the F-35B, and the MC rate for the Navy F-35C during that time has been 54 percent—31 points below target, the F-35 Joint Program Office (JPO) said.
In fiscal 2020, such rates were 71 percent for the F-35A, 68 percent for the F-35B, and 59 percent for the F-35C, per the Government Accountability Office (GAO). For fiscal 2020, the Air Force reported a higher 76 percent MC rate for the F-35A, which the service said had the highest MC rate for the service’s fighter models–above the second-ranked F-16C at nearly 74 percent.
For DoD, the MC rate is the percentage of unit-assigned aircraft capable of performing at least one defined mission, not including aircraft in depot status or undergoing major repairs. Full mission capable (FMC) planes are those capable of flying all unit-assigned missions.
In fiscal 2020, the FMC rate for the F-35A was 54 percent—18 points below the goal, per GAO, while the FMC rate for the F-35B was 15 percent—60 points below the goal, and the FMC rate for the F-35C was seven percent—68 points below the objective, GAO said.
While past F-35 sustainment contracts evaluated Lockheed Martin on MC rates, the three-year possibly $6.6 billion F-35 sustainment contract to Lockheed Martin in September is to award incentive payments to the company for meeting FMC rate, on-time availability of parts, and cost-per-flight hour goals, the F-35 JPO said.
The JPO said that it is moving “supply chain contracting to multiple-year, outcome-based contracts to stimulate industry investments in demand reduction and accelerated repair velocity.”
“The supply chain challenges on the program will not be resolved with more spare parts and added capacity only – rather we are working a holistic solution that encompasses demand reduction, best commercial practices, an acquisition approach, and the global use of the repair network,” the program said.
In contrast to the MC rate, the availability rate includes aircraft capable of performing at least one mission divided by all aircraft assigned, including aircraft in depot status or undergoing major repairs. Officials say availability for older fighters has traditionally been below 80 percent, as more than 20 percent of those planes are normally in planned depot maintenance or undergoing unscheduled repairs.
“In October 2020, USAF F-35As completed 18 months of continuous Middle East combat, flying roughly 4,000 combat sorties and employing just shy of 400 weapons while maintaining a 74 percent fully mission capable rate,” the F-35 JPO said. “The F-35 production line is stable, and aircraft rolling off the line are performing well. Many earlier lot aircraft require modifications and we are working through retrofits. We anticipate fleet availability will continue to climb as F-35 maintenance systems and best practices mature.”
Analysts who monitor the F-35 program have said that Lockheed Martin data rights to the entire F-35 supply chain have been an obstacle to on-time repair.
Regarding aircraft that sometimes wait months for spare parts and whether there should be an overarching agreement to require Lockheed Martin to release design data for the 1,100 identified reparable parts in order to increase the supply of new parts, the JPO said that it “continues to work to ensure that we have the appropriate intellectual property and technical data required to execute the mission of the F-35 enterprise, including the standup of component repair depots, each of which comes with the appropriate technical data.”
“We have established an intellectual property strategy that we are actively executing with a number of underlying guiding principles that lead us to conduct cost-benefit analysis of whether we should consider purchasing or securing the use of the intellectual property based upon our desired and required end state,” per the JPO. “It’s not necessarily about purchasing all of the data, but rather targeting the data that’s required to allow us to do the things that we need to do. Since 2014, we have assessed 447 different maintenance data changes; approved 207 of them, and completed 105 of them, with a resulting anticipated net savings of about $1.9 billion over the cost of the F-35 lifecycle. Additionally, the government’s ability to increase the supply of ‘new parts’ does not require release of Lockheed Martin design data. We have an active Tech Data Working Group identifying provisioning & cataloguing data needs that would allow procurement of spares by the government, if the business case supports it.”
The reasons why DoD has not held the F-35 accountable for reliability shortfalls are difficult to nail down, although comments offered by program experts for this story include that DoD has put all its tactical aircraft eggs in the F-35 basket without alternatives and that DoD has not emphasized and incentivized logistics and sustainment. The F-35 JORD in April, 2000 gives the JROC the ability to cancel the F-35 or halt F-35 production and put conditions on the program for production resumption, if the F-35 does not meet the KPPs.
“I influence the F-35 more through the F-35 [Executive] Steering Group, which A&S [the acting undersecretary of defense for acquisition and sustainment] chairs,” said Vice Chairman of the Joint Chiefs of Staff Air Force Gen. John Hyten, the chair of the JROC. “What the JROC is doing is trying to get out of the system requirements business because that’s really service or agency business. What we’re trying to do is look at the mission. So the mission for the F-35 is TACAIR. We’re trying to look across, at the JROC level, what force mix we need across everything—4th gen, 5th gen, next gen—how are we going to look at tactical air as we go forward to make sure we’re buying the right thing as we move forward.”
“The key with the F-35 is getting Block 4,” Hyten said, referring to the software upgrades that are to give the aircraft a number of enhancements to counter aerial threats posed by China and Russia.
The Technology Refresh 3 (TR3) software effort—an improved aircraft memory system, panoramic cockpit display and integrated core processor by L3Harris [LHX]—is to enable the 69 capabilities in Block 4, which is to begin on Lot 17 jets. TR3 is to enter with Lot 15 in 2023, and the program is discussing how many older F-35s it will upgrade to TR3 and how many older jets will remain with earlier software versions for training and test squadrons.
Top Pentagon officials have said that the F-35 is key to future U.S. warfighting prowess, as the aircraft will be able to use its stealth to penetrate enemy air defenses and shoot down adversary aircraft before the latter are able to detect the F-35.
The officials have also said that the F-35 has been dominant in air-to-air mock battles against potential adversaries. While F-35 officials have often pointed out the next generation performance quality of the fighter, analysts wonder how the fighter could play any significant role in future conflicts, if the F-35 is unreliable.
Indeed, F-35 planners originally wanted the F-35 to feature not only next-generation performance but next-generation reliability.
F-35 mission reliability in the year 2000 JORD—now termed the Capabilities Production Document—is the ability for an F-35 to meet sortie generation rate requirements for a given mission profile and execute the mission in that profile. For the Air Force F-35A that is a “low, high, high” mission in which the aircraft launches, refuels, climbs, engages an adversary fighter high, releases ordnance and flies back to base.
The F-35 variants are required to meet the mission reliability KPPs when they reach 200,000 flight hours. To meet the mission reliability KPP, military personnel in the F-35 JPO have run models and simulations for the three variants and used field data, the JPO said, to meet such KPPs. It appears that the F-35A is not meeting the KPP, however.
“As of July 31, 2021, the U.S. F-35A has about 202,170 flight hours, and a mission reliability rate of 88 percent,” the F-35 JPO said. “The F-35 Joint Program Office and Lockheed Martin are implementing a robust Reliability & Maintainability Improvement Program (RMIP) that is designed to improve all R&M metrics, including mission reliability. Mission reliability performance for the F-35B and F-35C variants currently exceed their key performance parameter values and are expected to remain above at design maturity. The mission reliability rate is calculated monthly and measures the probability that the system will perform mission essential functions for a period of time under the conditions stated in the mission profiles. Mission reliability can also be stated as the probability a system can complete its required operational mission without an operational mission failure.”
The F-35 JPO said that it “uses actual data to perform all reliability and maintainability metric calculations including mission reliability (MR).”
“The JPO reports this [MR] data monthly by variant,” the program said. “The JPO does not use adversary aircraft or drones to track MR of this [F-35] platform.”
The original intent of F-35 planners was not for mission reliability to be a models and simulations exercise but for mission reliability to use real-world data, including availability, to ensure the F-35 was meeting the KPP.
As initially conceived, the F135 engine was supposed to last 1,500 hours, but the duration—“time on wing”–before unscheduled maintenance has been significantly below that. Pratt & Whitney did not disclose the requirement it has to meet for F135 mean flight hours between removals (MFHBR), but the company said in a list of bullet points that the F135 has exceeded the MFHBR specification and that the F135 has outperformed all other Pratt & Whitney engines.
“With its advanced damage tolerant design and fully integrated prognostic health monitoring, the F135 continues to deliver unsurpassed reliability for the warfighter,” Pratt & Whitney said. “There have been over 70 foreign object ingestions in flight with the F135, including very large birds, instrumentation and other debris, and each time the engine continued to operate so the pilot could safely land. The 5th Gen F135 has demonstrated a 93 percent reduction in unscheduled engine removals over 4th generation fighter engines. The global F135 engine fleet is averaging a mission capability rate above 90 percent.”
Yet, at times, the F135 has lasted just 300-400 hours before change out or module insertion. The lift fan for the F-35B was to last 3,000 hours, yet the fan has had transmission failures and has at times only lasted between 400 and 500 hours.
Pratt & Whitney said that future advanced weapons for the F-35 will require more engine air diversion for cooling and that the engine is already operating outside of its designed specification, as each capability increment requires more kilowatts. Diverting more bleed air for cooling weapons means that the engine has decreased thrust, burns more fuel, runs hotter and degrades more quickly, thus resulting in more frequent maintenance.
For the F-35B, the company said it has mitigated thrust cutbacks since 2019 through “software, operating guidance, and water wash.”
Pratt & Whitney said that it has been investing internal funds in an F135 Enhanced Engine Package (EEP) that could save some $40 billion in engine life cycle costs and provide the cooling needed for advanced weapons on the fighter by 2027-28. The EEP engine is to increase F-35 range and thrust by more than 10 percent each, boost thermal management capacity by more than 50 percent, and increase powered lift for the Marine Corps F-35B by five percent.
Begun in 2018, Continuous Capability Development and Delivery (C2D2) for the F-35 envisions software updates for the fighter every six months and has included the development of Block 4, TR-3 updates, and making F-35s capable of carrying conventional and nuclear ordnance. Cost estimates for C2D2, which the F-35 program is to pursue through fiscal 2025, have varied from $7 billion to more than $10 billion.
Pratt & Whitney has argued that C2D2 has focused on the air vehicle and that DoD should add a propulsion requirement for C2D2 because of the increased cooling requirements for weapons in each new F-35 capability increment.
The first F-35s are to enter scheduled maintenance late next year or early 2023 after 2,000 flight hours. Such scheduled maintenance is to occur every 2,000 flight hours up to an F-35’s scheduled life of 8,000 flight hours. Pratt & Whitney has said that the F135 downtime for unscheduled maintenance is not an engine reliability problem. The company has attributed such downtime to a lack of depot capacity and said that an increased pool of spare engines and power modules is decreasing the number of jets down for engine maintenance.
While the engines spares pool for older fighter jets is between 25 and 30 percent of total engines, the F135 has a spares pool of just 11 percent, and the F135 is to have just a six to 10 percent non-mission capable rate—a rate that policy makers should revisit in favor of designing the F135 around a war readiness reserve for spares or target stock levels for spares, Pratt & Whitney said.
The company cited the Air Force’s submittal of a fiscal 2022 unfunded requirements list that included 20 F135 power modules for the F-35A.
For the F-35A, newer aircraft, such as those at Hill AFB, Utah, have proven significantly more reliable in their core hydraulics and electrical systems, officials said, than older F-35s used for training. Spare parts availability has been a problem for the older jets.
Audrey Brady, vice president for F-35 global sustainment at Lockheed Martin, told a Mitchell Institute for Aerospace Studies podcast last month that Lockheed Martin is using “fifth generation sustainment capabilities,” predictive health maintenance and condition-based maintenance to boost the mission capable rates for the aircraft—a rate that she said stands at 65.5 percent. Brady said that the mean time between failure for parts on the aircraft is “twice that of fourth generation weapons systems,” that 50 percent of the parts on the aircraft have never failed, and that 92 percent of aircraft components have met engineering reliability. Lockheed Martin has been working on reliability improvements for aircraft coming off the line, including preventing panel fastener corrosion by limiting the amount of time required to work on the panels and eliminating the amount of time required for electrical bonding cure time, which was 24 hours. In addition, Lockheed Martin has reduced its portion of the F-35 cost-per-flight-hour by 45 percent in the last five years and has significantly improved the Autonomic Logistics Information System (ALIS) for tracking parts in the last two years, Brady said.
A GAO analyst, however, said that such efforts may be too little, too late.
“DoD focused on sustainment far too late in the program,” Diana Maurer, GAO’s director of defense capabilities and management, wrote in an email. “The current leadership at OSD, JPO, and the services are now digging into sustainment. But they are grappling with significant challenges–ALIS, depot stand up, tech data, global supply chain, engines, etc.–stemming from decisions that were baked into the program many years ago. Unwinding all of that is not easy and in some instances may not even be possible.”
Decisions made two decades ago may have imperiled the F-35 program’s original aim to build a start-and-go fighter.
For example, while the Pentagon judged Lockheed Martin to have a significantly better overall proposal in the JSF competition, DoD evaluated Boeing’s sustainment approach, using its decades of experience with commercial airliners, as superior. Despite industry and government discussions about the advisability of a teaming arrangement between Lockheed Martin and Boeing on sustainment after the contract award to take advantage of Boeing’s maintenance expertise, Lockheed Martin opposed such an arrangement, and the arrangement did not happen. An idea to use F-35 simulators, rather than aircraft, to train pilots and thus increase the number of F-35s in operations squadrons also did not see fruition. Parts woes and low mission capability and aircraft availability rates have saddled the F-35’s training squadrons, as the training squadrons have served as parts suppliers for the F-35s’ operations squadrons.
Maurer said that “a myriad of challenges have contributed to less than desirable [F-35] aircraft readiness.”
“The primary challenges include, but are not necessarily limited to: not meeting reliability and maintainability (R&M) requirements, underestimating the difficulties of establishing a global spares pool & related supply chain, delays in depot stand up, problems with propulsion sustainment, maintenance challenges, and a deeply flawed ALIS,” per Maurer.
“We have seen DOD gradually shift its attention toward sustainment over the last five to six years, which is really encouraging,” she wrote. “But because the F-35 program came late to the game on serious sustainment planning, current program leadership has to dig itself out of a big sustainment hole from decisions made by others, in some cases many years ago. These are complex challenges that cannot be solved overnight, even once problems have been identified.”