Velocity Vector and Lift Vector

We need to introduce some terminology used to explain basic fighter maneuvers.

The first is the velocity vector. In physics, a vector is a quantity that also has a direction. So the velocity vector is the direction of our velocity or speed in three dimensions. Essentially, it is where our nose is pointed. This is not exactly correct, as there is a difference between nose position and velocity vector (angle of attack) but for the purposes of air combat we will use where the nose is pointed as a rough approximation of velocity vector. From the pilot seat, we have a very convenient aid in determining velocity vector, the gun sight. Where the sight points is our velocity vector. Modern aircraft actually display the velocity vector on the Heads Up Display (HUD). Normally this is termed the Flight Path marker or something similar.

Velocity Vector

The second term we need is the lift vector. The lift vector is the direction of lift. For our purposes it is considered to be perpendicular to the velocity vector. Imagine an arrow from your cockpit seat extending upwards out the top of the canopy. This is the lift vector. When you look straight up when seated in the cockpit, you are looking at the direction of the lift vector.

Lift Vector

Now let us talk about the 3-9 line. Imagine your aircraft on a clock face. The nose points to 12 o’clock. The tail points to 6 o’clock. The left wing at 9 o’clock and the right wing at 3 o’clock.

Clock positions

The 3-9 line extends through your wingtips into space. If you imagine an arc connecting the 3-9 line with the lift vector, you will create a visual representation of the complete lift vector and have an easy visual reference for the offensive and defensive hemispheres.

Imagine your aircraft in the center of a sphere as large as the distance from your aircraft to the bandit. Where the bandit is on the sphere determines your “status”.

Your 3-9/lift vector arc bifurcates that sphere into two hemispheres. The hemisphere behind your 3-9 line is the defensive, the one in front in the offensive. A bandit on the lift vector arc is “neutral”.

When asked for your “status” by your wingman, you answer according to bandit position according to the above. The four possible answers are “defensive”, meaning the bandit is in my rear hemisphere, “neutral”, meaning the bandit is on my lift vector arc, “offensive”, meaning the bandit is in my forward hemisphere and “clear”, meaning I am not engaged with a bandit.

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