Home' Asia Pacific Defence Reporter : APDR May 2015 Contents Asia Pacific Defence Reporter MAY 2015 13
intercept sonar to detect, classify and localise the
presence of active sonobuoys or dipping sonars.
Sonobuoys don’t betray an aircraft’s location, rather cue
a submarine commander to the fact that one is about.
A dipping sonar is different; from its pulse a submarine
can establish an accurate bearing, sometimes a range
and make an assumption about the hover height.
ESM is another passive sensor for developing
a helicopter or MPA fire control solution. This can
be done by analysis and measurements on the
aircraft’s periscope detection radar pulses or any
other electromagnetic emission. ESM can give good
classification information and relatively accurate bearing
information. It does require a mast be exposed.
Periscopes and optronic masts are very important
anti-aircraft sensors working in both the visual and
infrared parts of the spectrum. It requires a mast to
be raised and appropriately trained at the aircraft
such that it falls within the sensor’s field-of-view,
after which accurate classification, bearing, range
and height information can be obtained. Performance
of the optronics system may fall away in certain
atmospheric conditions (e.g. rain and fog), as will the
IR seeker heads on the missiles that will be used as the
foundation of the anti-air capability (see below).
Finally, radar can be employed to detect and localise
an aircraft. It must be appreciated that submarines do
not carry air search radars; rather navigation radars
characterised by limited range, varying beam heights,
no height finding capabilities and probably lacking
the right data input rates and algorithms to track agile
aircraft. Apart from the need to raise a mast above the
water line, radar is an active sensor that will likely limit
its employment by submarine’s command; the cost of
using radar more often exceeds the benefits.
The sensors used will depend on the circumstances
the submarine command finds itself in.
A ‘surprise’ depth charging or torpedo attack by an
aircraft is considered an unlikely occurrence and will
not be considered here. A more likely scenario of
escalating danger is discussed.
Submariners will always try to avoid counter detection
by an airborne nemesis. They will use their sensors to
detect the threat and avoid counter detection by the
aircraft; counter detection can bring about a quick
change of fortune for the aircrew and hard times for
The crew will use a combination of sensors; acoustics
when deep and a likely combination of acoustics, ESM
and E/O when at periscope depth (PD). The air picture
will be compiled by cherry picking the best information
from each of the detecting sensors. As they detect the
presence of an aircraft they will work to establish what
the aircrew are trying to achieve and whether there is
any danger of aircraft counter detecting the submarine.
The submarine command will not likely seek to
engage an aircraft at the first instance. In all but the
most exceptional of circumstances the submarine
command will put ‘remaining un-detected’ before
‘achieving the mission’. Of course, firing a sub-surface
to air missile under the pressure of evasion, perhaps
at depth with little in the way of sensor information
(against a fast agile target) may prove nugatory,
perhaps even counterproductive. The right answer on
when to shoot will be an ‘experience call’ from a CO,
XO or Warfare Officer, based on all the circumstance
of the situation.
As to those circumstances... Is the threat a lone MPA
that has just established ‘POSSUB’? Is it a helicopter/
ship combination working on a ‘PROBSUB’? Is it a
helicopter pair working effectively against a ‘CERTSUB’
using their dippers? How far away are back-up sea
and airborne assets? Does the aircraft have missile
23/04/2015 2:43 pm
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23/4/15 10:57 PM
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