Originally posted by Agent360
Some planes have the ability to sustain corner velocity at their min turn radius. Some do not. The "why" is a very complicated aerodynamic mathmatical answer.
There is a difference between "corner velocity" and "turn rate". Optimum turn rate is not always at corner velocity.
If we have two circles. One being twice as big as the other. The small circle is placed inside the bigger one on center.
#1 plane flies the arc of the small circle
#2 plane flies the arc of the bigger circle
#1 plane flying at corner speed in the small circle and #2 plane flying at a faster speed but following the bigger circle will both have equal turn rates but different corner velocities.
#2 plane may have a higher corner velocity but can travel faster around the arc than #1 plane.
Take a A6m vs a 109k4 for example. In this example the 109 can keep up in turn with the A6m but must take a larger turn radius to do so. The A6m will be flying slower and the 109 faster. The question becomes who burns E faster at this turn radius.
Another good use of corner velocity is in the initial merge of a dual. If you can turn your plane around...meaning you can get your nose pointed at the other guy firstl...this is an advantage. Here we are not sustaining corner velocity. We are using it to make a 180 turn "in less TIME".
TIME is the factor. It doesnt really matter what the turn radius is but how fast in TIME you can make the 180 turn. This can be done using either min radius or inversly a faster air speed at a larger turn radius.
The bottom line is the best "turning" plane does not always win the fight.
Corner velocity simply means the shortest turn radius at the maximum speed possible. So the absolute smallest turn radius possible in any givin plane can be changed depending on speed.
Let's clairify this. Corner velocity (i.e., corner speed, or maneuvering speed) is the minimum speed an aircraft must have in order to pull to its structural G-limit. In other words, flying at corner velocity gives you the ability to obtain your maximum load factor (G) at the lowest speed. Corner velocity varies according to altitude and aircraft weight.
Both the minimum turn radius and maximum turn rate that the airplane is capable of producing are
always at corner velocity. Slower than corner you can't pull maximum G's (the airplane will stall first) and G's are what turn an airplane (i.e., G generates turn rate). Faster than corner and you can still pull up to your G limit but you can't pull more because you're limited by blackout (and structural divergence). Your excess speed works against you and significantly increases your turn radius.
WWII airplanes (except the Me-163) cannot sustain a level turn at corner velocity, they just don't have the power to overcome the induced drag. This brings us to your real question, what good is corner velocity if you can't sustain it?
As Spatula mentioned, with WWII fighters you have to use gravity to offset drag and make your turns nose-low if you want to sustain your maximum performance turn for more than an instant. Obviously, there are tactical and physical limits (the ground) to a constant nose-low turn. Also as TC mentioned, the best use of corner with a WWII fighter is to reverse. If you're faster than corner velocity do a nose-high oblique or vertical turn (depending on how much above corner you are) to convert your excess e to altitude and decelerate to corner to complete the turn. If you're below or at corner do a nose low sliceing turn or even split-s and trade altitude to gain or sustain energy in the turn.
