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16.  Since the broadcast is accurately timed it is only necessary for
fighters to remain on the broadcast frequency for two periods within each
minute.

     (a)  to obtain their target's latest position.

     (b)  to listen to the additional information period.
     
Recommended Procedure.

17.  Interceptions are best carried out using the Pilot Plotter Interception
Mk. 1. This is designed to be used on the right leg. If this is found to be
awkward	it may be used on the loft leg by reversing the base plate and map
plates. Provision is made on the base plate to hold a watch, but a stop watch
clipped to some convenient position in the aircraft is preferable.

18.  Proceed as follows:-

     (a)  Leader selects suitable natter channel end sets up his No. 2 on it.

     (b)  Leader goes to broadcast channel; listens to target information.

     (c)  Leader plots target position, notes timing of broadcast cycle in
     relation to sweep of stop watch second hand. He then marks stop watch
     at points where he must return to Broadcast frequency.

     (d)  Leader goes to natter frequency, briefs No. 2 on DME selection
     (depending on position); obtains HAYRAKE from No. 2 and plots fighter
     position from his own and No. 2 DME distances

         ((i)   use pencil for accurate marking
          (ii)  differentiate between target and own positions by marking
          differently).

     (e)  Leader decides on interception speed and calculates vector to
     make an interception.

     (f)  Leader turns onto vector and informs No. 2 of target's relative
     position.

     (g)  Leader returns to broadcast frequency for next target information
     period.

Selection of Fixing Aids.

19.  Fixes can bey obtained either by DME/DME: DME/CRDF or CRDF/CRDF.

20.  Accuracy. The accuracy of DME and CRDF are as follows:-

     (a)  DME ± 2% or ± ¼ n.m. whichever is the greater

     (b)  CRDF - Class A bearing ± 2 degrees.

Taking a nominal distance of 100 n.m. from a beacon this means that position
errors can be as great as:-

     (a)  DME - 2 n.m.

     (b)  CRDF - 3½ n.m.
     
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