Radar System Engineering

SEC. 7.6] THE U.S. TACTICAL AIR COMMANDS 231
and issue radiotelephone instructions to friendly fighters in an effort to
bring them into favorable positions to counter air attacks. For defensive
operations, thk sort of control is usually adequate; enemy air attacks will
ordinarily be directed at one of a few vital areas where substantial damage
can be done. Even with his five-minute-old information, the controller
can make a shrewd guess as to the target of such an attack, and can
marshal defensive fighters accordingly. For many types of mission
however, direct control from the FDP’s is required.
RepoTting Capabilities of FDP’s.—Between Oct. 21 and Nov. 16, 1944,
a study was made by the Operations Analysis Section of Ninth Air Force
of the reporting work done by the three FDP’s of IX TAC. Because of
the difference in the amount and character of air activity by day and by
night, daily and nightly averages were separately computed for the
follo\ving data: the average number of separate plots per track reported,
the average track duration in minutes, and the average number of plots
per height reported. The results are shown in Table 7“1.
TAELE 71.-REPORTING BY FDP’s OFIX TAC, 21 OCTOBERTO 16 NOVEMBER1944
Station
Total
tracks
Avg. track
duration
Avg. number
)lots per track
.4vg. number
,lotsper height
Day averages
FDP “C” (Microwave)
FDP” A”
FDP’’ II”..
Night averages
FDP “C” (Microwave)
FDP “A”
FDP’’B”..
1561
2416
828
1249
1805
774
11.1 min.
10.0
8.4
15,1 min.
10.5
8.2
5.4
5.6
5.9
7,8
6.3
6.6
8,7
8.7
5.0
10.4
9,0
5.4
The FDP “C” was equipped with one of the preproduction 10-cm
radar sets designed for long-range air warning and control (see Chap.
15). The other two FDP’s had British long-wave equipment. The
longer range of the microwave radar shows in the longer track duration
for the FDP equipped with that set.
Differences in the total number of tracks reported arwe from a differing
density of air traffic in different areas, and from the fact that the fraction
of time spent off the air for maintenance and other reasons differed
from one FDP to another.
All the plots observed at the FDP are not passed to the FCC. Since
control executed by the FDP makes sector control by the FCC outdated
for many operations, it is unimportant to report all plots. A study made
at one of the FDP’s of .X1X TAC from Sept. 22 to Oct. 21, 1944, a period
d]lring which air activity was limited by bad flying weather, showed that