March 10, 2023: Since mid-December 2022, when a new F-35B developed a vibration problem in its engine that caused the aircraft to be seriously damaged, production and deliveries of new F-35s engines were halted and some F-35s were grounded. It took over two months to find the problem and develop a fix. It will take three months to apply this fix to all F-35s.

While the F-35 stealth fighter is very popular with pilots, both American and foreign, the aircraft continues to have readiness problems because of unexpected problems with the F135 engine that powers each aircraft. These problems were predictable before the air force decided to save money by only having one source for the engine. Early on the air force was urged to heed similar bad past experiences and spend the extra money to have two engines available. The second engine, the F136, was developed by General Electric and Britain’s Rolls-Royce. Britain was a major export customer for the F-35 and contributed over $2 billion to F-35 development partly because of the Rolls-Royce involvement with the F136. The air force was facing larger problems with escalating F-35 development costs and in 2007 decided to drop the F136 to help deal with those.

The air force made two other mistakes; introducing the new ALIS (Autonomic Logistics Information System), a spare parts management system that did not work as expected, and underestimating the difficulty of updating the complex F-35 software in a timely manner. These three bad decisions are now combining to keep F-35 readiness (mission capable) rates low while those for older aircraft, including the F-22 stealth fighter, increase.

The F135 engine’s current problem is that its turbine rotor blades wear out faster than expected. Nearly seven percent of the 665 F-35s delivered as of mid-2021 were out of service because of engine shortages caused by so many engines needing repairs. The rotor blade fix is a special coating for the rotor blades applied to engines which routinely come through the maintenance depots for checkups and fixes to any other problems found, as well as dealing with rotor blade failure. The engine shortage and some other problems with an inadequate supply of spare parts were a key reason the F-35 readiness fell from 74 percent in 2019 to 52 percent in 2022. The other reasons had to do with continuing problems with ALIS and managing the software update.

There is no simple solution for problems arising from defects in the only engine model available for the F-35. With two suppliers of engines, problems like the current one are usually spotted by one of the engine suppliers early and the other engine supplier alerted. The Department of Defense, acting on U.S. Air Force advice, believed that such problems were not going to arise because engine technology had advanced to the point that this was no longer an issue. The air force was wrong.

Additional costs of fixing the readiness problems produced a cost per flight hour of over $35,000, which is substantially more than for the older F-16s and F-15. The F-35 manufacturer earlier said it was possible to reduce F-35 cost per flight hour to about $25,000 by the end of the decade. That is not very convincing because it will cost a lot to achieve that goal, which was supposed to be available early on at much less development cost.

The Department of Defense acceptance of the air force cancellation of the F136 alternative engine program turned out to be a perfect example of "penny wise and pound foolish". By trying to save money needed to develop and field the F136 it could cost our country billions down the road because of the lack of competition, and shrinking the knowledge and manufacturing base required to design and build military jet engines. By 2021 that proved to be correct.

There was another factor at work here; heavy wartime use of all American jet fighters, except the new F-35, between 2001 and 2018. This was revealed because of a 2018 order from the Defense Department requiring the air force and navy to raise the readiness rate to 80 percent for several key combat aircraft and get it done during fiscal 2019 (which ended September 30, 2019). The aircraft involved were the air force F-16, F-22 and F-35 as well as the late model navy F-18s (F-18E/F and EA-18G). Only the navy made it, hitting 80 percent in September 2019. The navy had the hardest job because, when this order was issued, its F-18s had a readiness rate of only 50 percent. Even though they came up short, some of the air force aircraft made remarkable progress, The F-16 went from 70 to 75 percent while the F-22 went from 52 percent to 68 percent and the F-35 went from 50 percent to 74 percent.

Overall, the “80 percent challenge” had a positive effect because aircraft readiness rates had been falling for over a decade. There were reasons for that. Since 2001 air force and navy aircraft have been largely operating under wartime conditions. American military aircraft readiness rates have traditionally been high compared to all other major air forces, but age and two decades of heavy use took their toll. The workload for maintenance personnel is higher, while budgets for maintenance were not keeping up. This reduced readiness rates noticeably by 2018, but compared to ten years earlier the air force was doing rather well. Readiness rates or the percentage of your aircraft that are “mission-capable” varies by aircraft type and technology an aircraft is based on. Age is important but has less to do with it than you might think.

The F-22 rate was higher in 2010, partly because it had overcome the problems of being a new aircraft but problems of failure to pay higher maintenance costs from overuse plus lack of durability led to a slide from a high of 65 percent readiness in 2014 to 52 percent in 2018.

The many stealth features of the F-22 required special, time consuming and expensive attention, and provided more items that could break. The F-35 did not start entering service until 2015 so this new stealth fighter is where the F-22 was back then. The F-35 was designed to overcome the readiness problems of the F-22 but failed, mainly because of more engine problems plus the introduction of a new parts supply management system and inexperience managing aircraft software as extensive as found in the F-35.