Forenote:- This guide assumes a basic understanding of flight and a very basic understanding of physics. The application of what follows to jet aircraft is limited due to the relatively high speeds and engine powers of those aircraft. I am not covering anything relating to specific energy fighting techniques intended to be used with any plane. If you already know how a plane?s energy state operates, feel free to do whatever the blooming heck you want with that knowledge and feel superior in not reading this post. Or not. Your call really.
Energy, as the word is used in relation to aeronautics in Warthunder, is essentially the sum of your kinetic energy (forward motion) and potential energy (altitude). While both types of energy are closely interlinked and must be taken as such to truly apply them to a combat situation, it is far easier to separate each energy type for purposes of conceptualization and understanding. However in dog-fighting (including in game) pilots are constantly exchanging one energy state for another in an attempt to either render the other plane incapable of further flight at their combat speed or to obtain an advantageous position to fire upon them ? or to attain both goals ? and as such must be capable of accounting for both forms of energy at all times to be truly in command of their plane.
As stated, this refers to the forward motion of your aircraft. Any sort of maneuver will ?use up? your kinetic energy ? deflecting flaps increases drag for instance ? while your engine?s thrust will constantly replenish it. The limiting factor on this value is the drag, engine power, and structural integrity of your airframe. In game, this is indicated as the speed of your aircraft, which may be referred to as ?SPD?, or, as some may have seen when hurtling toward the ground at terminal velocity, as ?IAS?. ?SPD? ? speed ? refers to the ground speed of your aircraft, as such it is a decent indicator of your actual kinetic energy state; this, unfortunately, is an inaccurate indication of your plane?s maneuverability. To remedy ?IAS?, indicated airspeed, shows the speed of your aircraft accounting for the relative density of the surrounding air. The interface may be switched between the two settings within the control options -> interface menu, allowing you to decide whether knowing the maneuvering capability or exact kinetic energy of your aircraft is more important. In general, maintaining a high speed ? and thus, kinetic energy ? is advised when in combat, as it permits you a wider range of maneuvers you can opt for prior to running out of energy. Of course, different planes ?bleed? kinetic energy and ?recharge? it at different rates in different maneuvers, which is something one must learn. So, overall, your goal is to be energy ?efficient? by limiting yourself to maneuvers which have little impact on your kinetic energy while still being able to effectively dogfight with your opposition.
Potential energy is essentially a measure of the speed or kinetic energy your plane could gain at any time by reducing its current altitude. This, obviously, is gained by climbing, and is actually more efficient a gain of energy than pure forward acceleration ? for instance, in 5 seconds on a standard Spitfire one can accelerate ~75km/h toward your top speed or climb 100 meters. The ?energy? (technically speed) gain this can actually be derived for general use from a basic SUVAT equation. On the vertical axis your plane?s initial speed is 0, while the acceleration of gravity is 9.81m/s2, with an interval (distance traveled) of 100m, with v as final velocity, u as initial velocity, a as acceleration, and s as total displacement, using the equationv2 = u2 + 2as would provide us with a final velocity of 44.29m/s ? converted that?s a velocity gain of 160km/h or 100MPH. Essentially, discounting your airframe?s drag, if you dive at exactly 0G then every 100 meters would provide 160km/h extra speed ? and that?s ignoring the thrust from your engine! And, generally, as heavier airframes typically p have proportionately higher drag due to their relative increase in forward surface area, you can assume that the difference in the drag coefficient between most aircraft will be negligible so long as they are of a similar general shape. However, this energy ?store? is slower to build than it is to ?use?, and as such should not be squandered. So, as you can see, for a pilot, altitude is the largest energy store, something which permits the higher pilot to conduct the terms of an entire duel assuming they are a competent pilot, because, as you now know, the kinetic energy of your aircraft dictates the maneuvers you have practically available to you; and the quickest energy store to ?charge?.
Speed is important, but you can get more speed by climbing in a far more efficient manner ? and if you don?t climb, your overall energy store will be meager at least in comparison to your opposition?s. As such, while maintaining a decent airspeed is important, gaining and maintaining an altitude advantage over your opponents is far more important. Of course, this can be hard to do and harder to remember ? something everyone is guilty of ? but the advantage it gives you far exceeds the heartache in reaching altitude. Unless you want Silver Lions, you filthy lawnmower.