The mobility and tactical efficiency of heavy antiaircraft units are, at
least to some extent, limited by their elaborate fire-control equipment. The
Germans have designed an auxiliary director (reported to be
the Kommandohilfsgerät 35) as an alternative to the standard
director (Kommandogerät 36) for occasions when the latter is
out of action or otherwise not available. The auxiliary director is also
reported to be used for fire control against ground
targets (see Tactical and Technical Trends, No. 6, p. 8).
The auxiliary director weighs about 400 pounds and does not need any
electrical equipment. Heights or ranges are obtained from a separate 13-foot
stereoscopic height- and rangefinder, and passed orally to the director. In the
standard director, the rangefinder is incorporated. This simplification has, of
course, only been introduced at the expense of accuracy in the data provided.
The director works on simple angular rates ignoring the meaning factor. By
following the target continuously in line and elevation, and by setting in
range (or height) continuously, deflections in terms of rate of change are
multiplied by present time of flight. It is claimed that these approximations
counterbalance each other, since with an approaching target, rates of change
of bearing and angle of sight will be too small, while time of flight
will be too great, thus giving a close approximation. At the crossing
point, when the error is greatest, it is considered that errors so caused
will be within the 50 percent zone of fire.
The fuze setting is obtained from the rate of change and the present
range. The data are corrected for abnormal ballistic conditions, dead
time, and drift and transmitted by telephone to the guns. The dead
time allowed is 3 seconds. No allowance is made for wind and displacement.
The setting-in of range is interesting, in that a target not flying at a
constant height can be engaged. Height, not range, is set in when the
target is flying at a constant height.
A crew of four are employed on the rangefinder, and distribution of duties
on the director is as follows:
No. 5 Layer for azimuth
No. 6 Layer for elevation
No. 7 Range setter
No. 8 Lateral rate-setter
No. 9 Vertical rate-setter
No. 10 Range rate-setter
No. 11 Reader of azimuth to guns
No. 12 Reader of elevation to guns
No. 13 Reader of fuze setting to guns