Radar System Engineering

228 THE EMPLOYMENT OF RADAR DA 1’.4 [SEC. 75
from this point. The detailed control of fighter interceptors was carried
out from group and sector headquarters, where plots were maintained on
the basis of information repeated from Fighter Command Headquarters.
The operation of this system was much more difficult than might be
inferred from this brief description. If the CH stations had been perfect,
it would still have been difficult to interpret some hundreds of plots every
minute, all subject to variable delays and to the personal errors of the
observers. Quite trivial difficulties proved surprisingly hard to overcome.
It was hard to find room for all the plotters around the table.
They could not plot fast enough. They might disturb one set of plots
when they leaned over to plot another aircraft. Such rather simple
difficulties could be, and often were, the limiting factors on the use that
could be made of the radar plots, and an intensive study of all the stages
in plotting and filtering was made throughout the early years of the
war.
Despite the large number of people necessary to this system, and its
prodigal use of telephone land lines for the telling of plots, its operational
limitations were severe. Under conditions of moderate aircraft density,
a good filter officer with a good organization could filter plots with an
accuracy of perhaps 70 per cent. When plots were sparse, the accuracy
was excellent, and the on]y objection to the system was its unavoidable
time lag in reporting. Under conditions of high aircraft density, the
system broke down, and it was commonplace to cease reporting in certain
areas where the density was so high that filtering was impossible.
In spite of these handicaps, very considerable success attended the
use of this system in the Battle of Britain and thereafter. A tendency
grew to forget that the main reason for organizing the reporting and control
system in this centralized way was that a single radar could not be
relied on to give a sufficiently complete or accurate picture of events
in the air. The great technical improvements of 1943 and early 1944
resulted in long-range, high-definition microwave radar having good
coverage if proper] y sited. This improved equipment made it possible
to depend on a single radar installation for a substantially complete
picture of the air situation.
Delays and errors unavoidable in a complicated scheme of telling and
plotting are largely eliminated in a system that combines the operational
organization with the radar equipment. Controllers who give instructions
to aircraft are able to work directly from the radar display and
therefore have a far more accurate and up-to-date appreciation of the
situation than can be obtained from a plot, however well maintained it
may be. This was eventually appreciated, and such systems have been
put into very successful operation. Such a system is described in the
following section.