INTERCEPT PROCEDURES TEXTBOOK
A cutoff vector is one that will place the interceptor in a position between the bogey and the
defended force (Figure 1). A collision course is a vector that will allow the fighter to close on
the bogey in the fastest possible manner.
A collision course is a straight line course where the angle at which the fighter sees the bogey
(angle off) and the angle at which the bogey sees the fighter (target aspect or aspect angle)
remains constant with decreasing range. In a co-speed situation, the two angles will be equal,
but in opposite directions. This is also known as constant bearing, decreasing range (CBDR).
When a speed differential exists, the angles will not be equal. However, if the fighter is on a
collision course, the angle off (AO) and the target aspect (TA) / aspect angle (AA) will remain
constant. There exists only one collision course for a given speed ratio.
If a collision course is pursued to zero range, with both aircraft at the same altitude, a midair
collision will occur, as shown in Figure 2.
Types of Intercepts
There are three types of pursuit intercepts flown during the intercept: Pure Pursuit, Lead
Pursuit, and Lag Pursuit.
Pure pursuit is the primary means for achieving position in the rear quarter of the bogey.
Essentially, pure pursuit occurs when the fighter constantly turns to keep the nose of his aircraft
pointed directly at the bogey. Depending on the geometry initially generated, increasingly
harder turns may be required to achieve a position at the bogey's six o'clock.
Pure pursuit is a form of collision when the fighter has a speed advantage or if both the
fighter and bogey are in a pure pursuit scenario (fighter dead ahead of bogey).