As the Australian Defence Force’s F-35A fleet approaches full operational capability, the US Congress and Pentagon mull upgrading the Block 4 propulsion systems with adaptive engine technology

With over 700 aircraft operational the F-35 is becoming the centrepiece of air forces and navies across the globe. Not only is the aircraft itself a stunning success with its range of unmatched stealth and strike capabilities, but it is a remarkable exercise in international interoperability. Any potential adversary must reckon with the force multiplication effect of taking on combined forces with seamless operational and logistic capability. Next month Australia will host the Avalon 2023 International Air Show at Geelong where the centre of attention will be the jewel in the crown of Australian combat air power, the F-35A. Australia is a major partner in the programme and has committed to purchasing 72 of the most advanced fighter aircraft.

Australia’s decision to use the F-35 as a major pillar of defence capability is shared with other nations and has resulted in the F-35 rapidly becoming the most ubiquitous tactical aircraft in the world, the fighter every ally wants and every adversary fears. By any reasonable standard, the F-35 is a remarkable success and is possibly one of the greatest military technological achievements of this generation. It is not simply the stealth, sensor and shoot performance of the aircraft which defeats potential adversaries at a ratio of 20:1, with its Multifunctional Advanced Data Links (MADL) it can rapidly direct data through the joint battle space connecting C2 and weapons systems across all domains. The F-35 is set to define the concept of air dominance beyond the mid-century and the Pentagon plans to operate its own F-35 fleet until 2070, with plans for technology upgrades to overmatch potential adversaries who already lag behind, even now well advanced.

Global F-35 sales are expected to exceed 3000 with over 300 operating in the Asia-Pacific region. Australia is significantly invested in the F-35 programme, both from its future defence capability but also its economic engagement. The country has stood up the first full-service depot for maintaining F-35 engines in the Indo-Pacific. Not only will Australian F-35s be maintained there but also those of Japan, South Korea, and U.S. services operating in the region. This facility represents an important first in the concept of global allied interoperability. In addition, Australia has over fifty aerospace and defence companies involved in component manufacture and management of global supply chains, meaning that not only will the F-35 form the backbone of Australia’s air combat operational capability for the next four decades. Its F-35 programme is expected to contribute over A$3 Billion to the Australian economy and will sustain up to 6,000 jobs.

The platform still has to mature. A common criticism is that the aircraft could do with more thrust from its propulsion system. The F-135 engine at the heart of the aircraft design is a remarkable unit and its designer and manufacturer, Pratt & Witney, delivered a propulsion system that combined unprecedented thrust, flexibility, and even stealth, that few thought could be delivered. But operational experience has demonstrated that a higher cooling requirement and an increase in electrical power for its complex systems is needed, as well as an extension to its combat range and better thermal management ability.

The success of the F-35 programme has been achieved in large measure by the lack of partisanship on the part of the United States. It has reached across national boundaries to forge design, technology and operational relationships with trusted partners that have used procurement processes not closed on the altar of national security. The F-35 programme provides a development, procurement and operational model that could secure western dominance against potential adversaries across the warfare domains for a generation or more.

Against this success there is some disquiet amongst allied operators about the current U.S. initiative to retro-fit the propulsion systems of the F-35 with Adaptive Engine Technology (AET), a system under development to drive sixth-generation Next Generation Air Dominance (NGAD) fighter capability. This initiative is currently working its way through Congress and would see the U.S. Air Force fleet of F-35A aircraft have their propulsion plants replaced with this unproven although remarkable technology. 

While few can disagree with the national ambition that its F-35 inventory is equipped with the best propulsion that technology can provide, the sixteen countries currently buying and operating the F35, are wondering where this initiative may leave them. Some commentators view the current AET debate as a partisan return to the U.S. looking after its own interests and aspirations first. 

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The retro-fit initiative carries an anticipated price tag in the region of US$6Billion and this cost will have to fall somewhere. The AET initiative is technically complex and carries large financial risk and at present there is no budgetary allocation for AET retrofit. A unilateral transition to AET could leave U.S. allies wondering about their own maintenance and future procurement costs. Suspicion is beginning to emerge that the change to AET will include having the inevitable costs (and delays) passed on to them in one form or another. As AET consumes effort and resources there is likely to be an impact on allied interoperability and sustainability.

Alongside these concerns is the view as to whether the initiative is necessary at this stage of the aircraft’s development. While also bringing forward an AET design of its own, Pratt and Witney have proposed the Enhanced Engine Package (EEP), which is a major upgrade initiative to the F-35’s current propulsion system. The EEP goes a long way to achieving the improvements thrust and range required and raises questions as to whether the cost and effort of changing the aircraft’s propulsion system is justified. It has taken two decades of careful international cooperation to bring the F-35 programme to its current level of maturity. Eyebrows may rise at the expectation of a rapid decision coming from Congress which will see a decision on AET reflected in the FY2024 Pentagon budget. Many have noted that the submissions taken by Congress contained little consideration of the retro-fit impact on the cost and capability impact on allied operators.

In the meantime, the close-knit community of F-35 operators are left to wonder whether the non-partisan approach to the aircraft’s development is at risk from the single largest operator of the aircraft. The U.S. ambition to equip its aircraft with bleeding-edge capabilities that will stretch further the aircraft’s air dominance is laudable but could result in compromises to the unique procurement and operating partnership model that has represented a step change in international defence cooperation.

The Author. James Maclaren is a freelance journalist and writer specialising in defence and security. He is a former UK military officer with command, staff, joint experience in a variety of roles and operational environments. He is based in London. You can connect with Maclaren by visiting his website.