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Groundspeed Corrections.                               

41.  Errors in E.T.A. may be unacceptable in cases of, for example,

     (a)  Rendezvous

     (b)  Predetermined attack time

A rough rule of thumb for gaining or losing time to arrive at a particular
E.T.A. is as follows: -

NOTE:  the time in minutes to be lost or gained and the total time remaining;
then increase or decrease the indicated airspeed by the fraction of
the former over the latter applied to the groundspeed.

Example.  ½ minute late -5 minutes to go, increase speed by 1/10th.
Therefore 360 kts. becomes 396 kts.

42.  Any errors should be corrected for as early as possible where the correction
will be small.

Unforeseen Diversion.

43.  It may be necessary to avoid the high ground or bad weather. This need
not cause the flight plan to be abandoned if a predetermined dog leg is used.

44.  If an aircraft alters course by 60 degrees in either direction for a
certain time and then alters course 120 degrees in the opposite direction for the
same time, track will be regained and E.T.A. will be increased by ½ the time
spent on the dog log.

45.  If a 30 degree dog lag is employed the E.T.A. will be increased by 7th
time of the dog leg.

Feature Tracking.

46.  By flying along clearly defined topographical features the pilot is
provided with a continuous and accurate fix. In hilly or mountainous terrain
this method may not only be easier but also of advantage tactically.

Conclusions. 

47.  It is well known that the presence of mind of the average pilot is
reduced by at least 50% once the cockpit canopy is closed. Planning must
therefore be accurate and simple to follow. The pilot must fly accurately
and have a clear picture in his mind of what he expects to see and when he
is likely to see it.

48.  Operationally navigation is one of the many problems thrust upon the fighter
leader, but at least he can meet this problem more than half way.

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