After the F-135 engine, the F-35 will also change radar with the AN/APG-85

In a synthetic way, it is common to say that a combat aircraft is none other than the association of a cell, an engine and a radar. And the devices that marked their time, such as the F4 Phantom II, the Mirage III, the Mig-21, the F-15, the F-16 or the Su-27, all respected this definition, relying on the perfect complementarity of these 3 key components. For fifteen years, Lockheed-Martin's F-35 has also been presented as the most striking aircraft of its generation, and as such has been adorned with all the virtues. However, under the leadership of the US Air Force, it seems that two of these 3 key components will be replaced in the years to come on the flagship of Lockheed-Martin.

The replacement of the F-135 turbojet which propels the 3 models of F-35, the A version intended for conventional air forces, the B version with vertical or short take-off and landing capabilities to operate from aircraft carriers, and the C version operating from aircraft carriers equipped with catapults, has been considered for several years by the US Air Force, which in 2016 awarded development credits to engine manufacturers General Dynamics and Pratt & Whitney a 1 billion dollar contract to develop a new triple-flow turbojet to equip his aircraft. Indeed, the F-135 is proving to be poorly sized today for the operational needs of the F-35, with insufficient thrust limiting aircraft performance, excessive consumption handicapping his autonomy, or even particularly heavy maintenance reducing the availability of the aircraft. In addition, the engine is complex to build, and particularly expensive.

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the single-engine configuration of the F-35 was imposed by version B take-off and short or vertical landing of the aircraft, forcing the engine manufacturer Pratt & Whitney to develop a very powerful turbojet engine to support the 30 tons max of the F-35 at take-off.

To meet these needs, the two American engine manufacturers have undertaken to develop a new generation of turbojet engine, referred to as the Adaptive Engine Transition Program, or AETP. Unlike the F-135, which uses turbofan technology, the AETPs are based on the triple-flow turbojet model, allowing for lower fuel consumption and increased engine thrust, while reducing, in the hypothesis, constraints on mechanical parts, and therefore simplifying maintenance. However, the development of such an engine, despite the advances made by US engine manufacturers on their prototypes, would still require very heavy investments of several billion dollars, while the replacement of engines on existing cells would generate an investment estimated at over $40 billion. This is the reason why Pratt&Whitney has concomitantly developed an "improved" version of its F-135, offering certainly less performance than the AETP, but superior to that of the current F-135, for lower overhead. The final arbitration on the subject must soon be rendered by the US Air Force which, with a targeted fleet of more than 1700 aircraft, acts as the sole decision-maker in this area.

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