The Death Throes of the F-35
by David Archibald
4 May 2022
Originally the US Department of Defense (DOD) contracted the development of two separate engines for the F-35. These were the F135 from Pratt & Whitney and the F-136 from General Electric. While the F135 was chosen and the first flight of the F-35 was in 2006, development of the F-136 wasn’t stopped until 2011.
The F135 engine pushed technology to its limits. The turbine inlet temperature of the F119 engine that powers the F-22 fighter is 1,649°C. In the F135 engine it is 1,982°C. The turbine blades downstream from the combustors in the engine are made from a nickel-based alloy that starts softening and melting at 1,427°C. The blades are kept from melting by air forced through a network of holes.
Ten years have passed since the development of a second engine for the F-35 was dropped, and 15 years since the first flight. Then from April 2021 there were a slew of articles in the military press saying that a new engine for the F-35 would be a good thing — here, here, here, here and here for example.
The cause of the sudden agitation for a new engine became apparent with the release last month of a report by the US Government Accountability Office entitled “F-35 Sustainment: DOD faces several uncertainties and has not met key objectives”. In that report is this graphic:
That graph shows that the number of F-35s without an operating engine rose from two at the beginning of 2020 to 36 in February 2022. Normally less than 1% of USAF aircraft are grounded due to lack of an operating engine. For the F-35 this rate has increased to near 10% and is on trend to reach 43% by 2030.
What is causing the engine wear is dust melting in the F-35’s combustors and sticking to the turbine blades. This produces a layer of material similar to house bricks. Normal jet engines don’t suffer from this so much because they run much cooler.
The DOD “has set a goal for the F-35 program that no more than 6 percent of available aircraft should be grounded at any time due to engine status.” One solution is to buy more spare engines from Pratt & Whitney and spend money on preventative maintenance.
This explains the sudden interest in an alternative engine from early 2022. Without a new engine, the F-35 will be too expensive to maintain. A new engine wouldn’t come before 2027 at the earliest, and in the interim all the F-35 coming off the production line would be deficient.
But the proponents of a new engine don’t understand that the F-35’s engine problem is baked in the cake. That is why Pratt & Whitney developed such a hot engine — to produce the most thrust relative to engine weight in order to get the vertical takeoff version to work.
For its 2023 budget the USAF cut its planned F-35 buy from 48 units to 33 units. It is also reducing the number of F-15s planned. These production cuts are likely to be for freeing up funds for the production of the Next Generation Air Dominance (NGAD) fighter which has been flying as a black program for at least a couple of years.
The NGAD is said to be going to cost a multiple of the cost of the F-35 per plane. A congressional inquiry into the costs of restarting F-22 production found that the cost would be US$205 million per aircraft. Added to that will be the cost of a lot more electronics for the plane’s electronic countermeasures (ECM) package. The USAF is said to be abandoning stealth achieved through the application of radar absorbent material and are adopting the approach of the French Rafale and the Swedish Gripen-E, which is the use of ECM to mislead enemy radars.
The cost of the NGAD is likely to be of the order of US$250 million per unit. The Rafale costs US$200 million per unit. Saab in Sweden has priced the Gripen-E, just as capable as the Rafale, at half the Rafale’s cost so US$100 million-odd.
The F-35’s engine problem means that the RAAF will be needing a new fighter aircraft much sooner than they are expecting.
David Archibald is the author of The Anticancer Garden in Australia.