I heard these terms thrown around in fighter jet communities alot, and I have a basic understanding of what the differences are (I.E turn fighters are able to turn tighter while energy fighters preserve kinetic energy while turning). But I’m still not sure what characteristics inherent in the plane turns a plane into a turn fighter vs an energy fighter. For example, the F/A-18 and F-14 and Su-27 are all considered turn fighters, while the F-16 and F-15 are energy fighters, but they’re all so different in size and design.
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Perhaps confusingly, these terms are used to describe both a set of *tactics*, as well as the type of aircraft that *lend themselves* to such tactics. Ultimately, all aircraft and all tactics involve a combination of, and a trade-off between, ‘energy fighting’ and ‘turn fighting’. Individual examples of how an aircraft is employed is not going to be as simple as calling an aircraft one or the other: every operator is going to employ their aircraft in a way that they believe gives them the best chance of success, and that will depend not only on the physical characteristics of their aircraft, but that of their enemy, the weather and climate, the physical geography of the region, overall forces doctrine, and other factors like how far these aircraft are going to have to fly before engaging the enemy. But of course, it doesn’t seem like you’re asking about what these terms are, but what physical characteristics of aircraft lend themselves to be described as one or the other? Importantly, some of these characteristics are design *choices*, while others are design *limitations*.
If we go back to the dawn of aerial warfare, biplanes are kinda the ultimate turn-fighter. That wasn’t a design choice (we didn’t really know much about aerial combat at the time), but just a consequence of the design and construction of the era, and engine limitations. Aircraft didn’t go fast enough for huge g-loading, for instance, and the low wing-loading of the era lent itself to really good low-speed turning performance. That is likely one of the first points of note: wing loading.
Wing loading is the amount of lifting surface an aircraft has available relative to the mass it has to move around. More wing area means more surface with which to generate lift, and so a low wing-loading *generally* means that the aircraft can turn quite well (though there are obviously other factors). The trade-off here is that to produce a low wing-loading, generally you need a big wingspan – you can’t get all of that wing in close to the aircraft. This inherently means larger bending moments at the wing root, which limits your high-speed turning performance (as maximum g-loading occurs at high-speeds, and structural g-limits are all about the wing root moment). So that’s a classical trade-off: stubby wings permit higher g-loading (due to structural limitations), but come with a higher wing loading.
The basic wing configuration is another decision-point. Certain wing geometries are more stable than others, and certain wing geometries permit greater surface area to be allocated to control surfaces than others. In a stable aircraft, if you make an adjustment to your aircraft attitude, the resulting aerodynamic moment counter-act that change. That means if you take your hands off the controls, the aircraft will fly straight and true. But it also means you will be less maneuverable. Unstable aircraft will bleed energy with their constant adjustments to control surfaces, which leans towards ‘turning’. But stability, like wing loading, isn’t an on-off switch – there’s a range of options. Likewise, additional wing elements may be added that improve low-speed turning performance, such as leading-edge root extensions on the F-18, or the dogteeth on the Eurofighter, which are meant to keep more of the flow attached at extreme angles of attack (ie, to delay stall or to maintain control post-stall). This wing configuration choices aren’t just about ‘turning’ versus ‘energy’ in dogfighting (although that has to come into play), but a huge number of other factors.
Wing configuration can affect payload, maximum speed and altitude, internal fuel capacity, radar return, and a huge number of other factors of general aircraft behavior and performance. Especially if you have a multi-role aircraft that has to manage air-to-ground work, or carry unique munitions, this might push the design to ‘turning’ or ‘energy’ based on external design choices or needs distinct from this particular aspect of fighter usage. For example, in European NATO states, most air-delivered nuclear weapons are tactical free-fall bombs, B-61s, supplied by the United States and carried by Belgian, Dutch, Italian, German, and Turkish aircraft, mostly the F-16. These bombs are small, smaller than the Mk 84 general purpose bomb, so they don’t have many special requirements. Meanwhile, not having a true bomber anymore, France needs a fighter that can carry its enormous ‘sub-strategic’ nuclear cruise missiles as part of its nuclear deterrent, which means that this nuclear-strike requirement – completely unrelated to dogfighting – is going to come in and affect the dogfighting characteristics of the Dassault Rafale versus the F-16.
Then there is engine configurations. More power to weight lends itself to energy-fighting. This is often more of a design limitation than a design choice. Engine designs from North America and Europe tend to have much greater performance than those from Russia or China (although China appears to be closing that gap). Because of this fact, many Russian and Chinese designs emphasize turning performance: the theory being, if you try to counter American designs based on the strengths of American designs, you’re just going to have a worse version of an American aircraft. If you want to compete, therefore, they have to do something different. This leads to other design choices that reinforce this reality, like thrust vectoring and so forth, which are almost common in Russian designs but only appear on the F-22 among Western ones (despite the fact that American and European designers actually produce much more impressive thrust vectoring designs, frankly).
Likewise, it’s important to remember that none of these are absolute. The F-16 is unstable, but it’s usually considered an ‘energy’ fighter. The F-22 has thrust vectoring and its energy performance is likewise considered phenomenal. You have to consider that, since these terms relate to tactics as much as hardware, that this distinction also has to be made in the context of the planned doctrine of their operators. The F-18 is broadly considered a ‘turn fighter’, for example. But that’s in the context of its primary operator, the US Navy. In the air-to-air role, Canada primarily uses its CF-18s as air defense interceptors, by contrast, and so the practical realization of ‘turning’ versus ‘energy’ is quite different even if it’s the exact same aircraft.
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