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                       HIGH SPEED INTERCEPTIONS.

Introduction.

1.   In World War II and for some time afterwards, targets for fighter
interception comprised slow flying aircraft in large formations operating
at medium altitude. Against such a threat large errors in fighter positioning
during an interception did not always matter. With a considerable speed
advantage and a selection of targets, all within visual range, a "kill" could
usually	be obtained.

2.   Today we have to intercept bombers which fly closer to our fighters'
maximum speed and ceiling then ever before. The margin for error is much
smaller and therefore fighter positioning has to be much more precise.

The Problems Evolved.

3.   The difficulties of intercepting high speed high altitude bombers are
caused by:-

     (a)  rapid change of position of fighter and target "blips " on the
     P.P.I. tube.

     (b)  large radius of turn

     (c)  reduced sighting ranges.

     (d)  low overtake speed.

The displaced parallel head-on interception.

4.   The quickest form of interception against a head-on target is one which
takes the fighter to a particular point from which a 180° turn will place it
in a firing position on its target. because of the high closing speeds involved
this form of interception is too difficult to judge (NOTE: a target at .85
and fighter at .9 m will close 4 n.m. in between "paints" on a Type 80 tube).
It has therefore been replaced by the displaced parallel head-on interception.
This type of interception splits the turn-in into two turns of approx. 90° each
with a one minute straight leg in the middle. The object of this one minute
to is two fold:-

     (a)  to give the fighter pilot a steady/searching platform.

     (b)  to allow the controller to compensate for errors in fighter
     positioning.

5.   The beam displacement of the fighter from the target's projected line of
flight is always kept to a minimum to prevent an impossible tailchase should
the target aircraft alter its heading away from the fighter during the initial
setting up period.

6.   Using this form of interception and knowing the radii of turns for fighter
aircraft at various speeds and at various altitudes the controller is able to
measure up the interception on his tube. For example, a Hunter intercepting, a
.85 m target at 45,000 feet will have to be turned in when it reaches a direct
distance of 23 n.m. from the target, and from a position displaced 17 n.m. from
the target's line of flight, in order to achieve a one minute straight leg
before the final turn in.

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