Radar System Engineering

232 THE EMPLOYMENT OF RA DAR DATA [SEC.7.6
50 per cent of the total plots obtained were passed on. However, 84 per
cent of the tracks were reported, the difference being due to single-plot
tracks which were not reported. The average number of plots per track
was 6.2 and the average track duration 9.5 min. Hence, on the average,
a plot was obtabed on each track once every 1.8 rnin, which is considered
to be fairly continuous tracking.
Close Control by the FDP.—At the turn of the year 194041, the
Luftwaffe abandoned its daytime attacks on England and turned to night
bombing, the attacking aircraft operating individually. This led to ~he
development by the British of an elaborate system of nightfighter defense
which has been described elsewhere. 1 One of the features of this system
was exact control of the nightfighter, prior to his interception of the hostile
bomber, by a ground controller at a GCI (for Ground-controlled Interception)
radar station. The aim of this control was to put the nightfighter
behind, a little below, and on the same course as the hostile
aircraft, in which position he was well situated to complete the interception
~vith the help of airborne radar equipment he himself carried.
By 1943, both this GCI technique, involving precise control of single
aircraft by a controller located at a radar station, and the daytime sectorcontrol
technique described in Sec. 7.5, involving the control of formations
of fighter interceptors from a central station at which radar data were
assembled and assessed, were firmly established procedures. In that
year two things happened which gave rise to the technique of close control
as it was practiced by the FDp’s of the -herican TAC’S in the
continental phase of the Iluropean war. A young .Imerican officer, lyho
was \vorking with the R.\F as a member of the Electronics Training
Group sent to the united I1ingdom soon after the ~nited States went to
war, conceived the idea of controlling formations of day fighters directly
from the information available at his radar station alone. lleanf~-bile
bat tle experience in ilfrica shom-ed that an independent radar set could
pass to airborne fighters useful information on the disposition of enemy
aircraft.
The American officer’s novel idea did not gain immediate
acceptance
since control of several squadrons of fighters in daylight requires techniques
quite different from those of the GCI control of a single nightfighter.
Finally, the officer ~f-as giiren permission by the late .Iir C7hief
IIarshal Sir Trafford Leigh-lIallory to control wings of fighters directly
from his radar station, entirely independently of the sector-control
system.
l~hile the ne\v technique \\-asbeing worked out and the confidence of
pilots and controllers was being developed, 1,5 R,lF planes were lost for
1See, for example, “ Radar (.i Report on Science at \Yar),]’ Superintendent of
Documents, U.S. Go\.ernment Printing Office, H-ashington, D,(i) .iug, 15, 194.5.