I've always read about corner speeds and so forth , but does anyone actually use that information in a typical engagement ?
I'm usually thinking of speed and turn etc in relative terms to the other guy. At what point does anyone actually look at a gauge ? Am i missing something completely in regard to the importance of these technical things.
Since it's impossible to sustain corner for long it really serves as either a reference or target speed. Everyone is familiar with the common terms "fast" and "slow" but how fast is "fast" and how slow is "slow"? Knowing your corner velocity helps you put some numbers to those terms that actually relate to the performance capabilities of your aircraft.
As for "looking at a gauge" is concerned your ability and need to time share your attention varies according to where you're at in an engagement and the type of engagement you're in. Just cruising around in Indian country you want to stay above corner so you have the best defensive options available should you get jumped. If you're climbing out you can climb at corner velocity. This reduces your climb rate but you're less likely to be picked off because you're too slow to maneuver effectively. In a close knife fight you have little time to reference your instruments and little need to do so since the precise position and relative movement between aircraft is more important. You may glance occasionally at speed but in a knife fight you're probably more interested in how close you are to flap and stall speeds than corner. In an energy fight though, there's more opportunity and need to check your speed frequently.
You can use corner as a "reference" speed to determine the best maneuver to employ. For instance just before a merge you have plenty of time to check your speed and it's one of the most important pieces of information you can have. If you're significantly above corner you know that you will be G limited so you want to use a nose-high high-G turn and, as you convert E to altitude and decelerate you will slow to corner your turn rate and radius will improve. How much you are above your corner reference speed gives you an idea of how "vertical" your turn can be. The closer you are to corner the more oblique your turn while if you're significantly above corner you can use a more vertical turn. (For a pure vertical turn I use another reference speed (typically around 300)). If you're below your corner reference then you know you're lift limited so you will probably be better off choosing a nose-low slice. The slice lets you sustain the turn rate you have and may even improve it if it's tactically suitable to go very nose low (even to a split S). What you're looking for is a reference speed that will give you an idea of which maneuver is best.
Also, using corner as a reference can help you decide on the tactic to employ. If you're at or above corner, you may chose an energy fight while if you're below corner, you may choose to go straight to an angles fight using your nose position to intimidate your opponent. Of course, I'm simplifying again as there is a lot more to consider than just your speed relative to corner. The tactical situation, the relative position/number of bandits, individual bandit E states, etc., are all extremely important. Your speed relative to corner gives you your first indication of what options you may have.
In an energy fight there is plenty of time and reason to look at your airspeed and corner becomes your "target" airspeed. It's the speed at which you want to conduct the fight. You can't sustain it in a constant turn but you can stay in the vicinity of corner using high and low maneuvers. Simplistically speaking, your maneuver sequence is "straight-line, turn, straight-line, turn..." You gain E in the straight-line and convert E to angles in the turn followed by another straight-line to regain E.
For instance, in an extension/pitchback fight, you should target corner velocity in preparation for the reversal (pitchback). Since corner will give you the best turn rate/radius it's where you want to be for the pitchback. If you start your extension below corner then use WEP and unload the aircraft a bit for best acceleration (straight-line) to just above corner then pitchback (turn). At the completion of the pitchback, you unload and accelerate again (straight-line) for another merge. If, when you start your extension you're already above corner, use the excess speed to gain separation (if needed) then go a bit nose high to convert your excess E into altitude. Once you're near corner then reverse. How nose-high or nose-low you go during the extension depends on how far above or below corner you are. (Also, just to be clear there are other tactical reasons why you would reverse before reaching corner including your opponent's speed and nose position.)