Republished by F-111.net
with the express permission of Carlo Kopp. More articles here.
"New Defensive Avionics
for the F-111"
(Australian Aviation, December 1995.)
Carlo
Kopp, PEng
Carlo.Kopp@aus.net
© 2001, 1995, Carlo Kopp
Last
Updated 29 May 2001
The RAAF is at this
time in the early phases of a major project to replacethe now aging defensive avionic
suite in the F/RF-111C/G aircraft. Theexisting defensive avionic suite dates by design to
the seventies, and wasoptimised for defeating the Soviet IADS of the day. This equipment
ishowever becoming dated technologically and this will, by the turn ofthe century, result
in substantial maintainability and supportabilityproblems.
The existing defensive avionic suite is built
around the Dalmo Victor (General Instrument) AN/ALR-62(V) radar warning receiver, the
Sanders (Lockheed) AN/ALQ-94 and 137 defensive electronic countermeasures (ECM), an
AN/ALE-28 chaff/flare dispenser and the Cincinnati AN/AAR-34 Infrared Tail Warning system.
When penetrating hostile airspace, the ALR-62 is used to detect and identify threat
emitters. Where these cannot be avoided, the ALQ-94 or 137 in the G-model are then used to
jam the threat, which is typically the acquisition or fire control radar for a Surface to
Air Missile (SAM) or Anti Aircraft Artillery (AAA) system. Approaching missiles in the
tail quadrant are detected by the AAR-34 and decoyed with flares or chaff dispensed by the
ALE-28 equipment. This suite is conventional by modern standards, but in its time was the
most comprehensive of its kind to be deployed in a tactical aircraft. The fact that no
USAF F-111E/F aircraft were lost to hostile fire during the Gulf War reflects very
favourably, but we should not lose sight of the fact the Iraqis used largely seventies
generation Soviet AAA, SAM and acquisition radar systems, which the F-111 EW suite was
specifically built to defeat.
The RAAF's AIR5391 project is aimed at replacing
the existing defensive avionics, with a target Initial Operational Capability (IOC) around
the end of the decade. AIR5391 will be split into several components, the eventual tender
calling for the supply of a new Radar Warning Receiver (RWR), Defensive ECM (DECM),
Countermeasures Dispenser (CMDS) and Missile Approach Warning System (MAWS). The system is
expected to be highly integrated, with all components tied to a dedicated Mil-Std-1553B
databus, or if appropriate, a faster bus.
Three components of the upgrade will be open to
all bidders, these being the DECM, CMDS and MAWS. The RWR will most likely be the RAAF
sponsored DSTO/AWADI ALR-2002 equipment. Understandably the RAAF are cautious about
detailing the intended capabilities of the new defensive suite, but some aspects of the
upgrade have been revealed to Australian Aviation.
The new DECM will provide fore and aft coverage
against pulse mode and continuous wave (CW) SAM, AAA and airborne threats, from C band
through to J band. The CMDS is expected to be an intelligent reprogrammable system, with
the capability to flexibly accommodate a wide ranges of expendables. The RAAF have not
discussed their preferred expendables types, but it is reasonable to assume that these
will include chaff, flares and expendable jammers.
The MAWS will be either radar or optical, the RAAF
have no preference in this respect. Indications are that potential bidders will be
provided with a performance requirement for the equipment, and the bidders will be free to
offer their preferred technical solution. It is worth noting that while radar based MAWS
offer better detection and tracking performance, they are an active emitting device unlike
optical MAWS which passively detect the heat and ultraviolet emissions of missile rocket
motors. More complex dual mode MAWS will use passive optical techniques to detect an
inbound missile threat, and then employ Doppler radar techniques to track it in bearing,
elevation and range to provide optimal parameters for flare and chaff release.
The core of the AIR5391 upgrade will more than
likely be the DSTO developed ALR-2002, which is currently in Full Scale Engineering
Development by AWA Defence Industries (AWADI). AWADI are in the process of re-engineering
the DSTO technology demonstrator (prototype) ALR-2002 design into a production Milspec
item. Should the production design pass the RAAF's stringent Acceptance Test &
Evaluation (AT&E) process, it will be used, if not an alternative will have to be
considered.
The ALR-2002 is of particular significance because
it is indigenously developed equipment, the design of which was wholly carried out in
Australia. As the RWR is the most critical component of any EW suite, the use of locally
built equipment is the safest strategy for safeguarding the effectiveness of the equipment
in any strategic circumstances.
The ALR-2002 is intended to be a state of the art
Radar Warning Receiver, built with some of the latest semiconductor technology, much of
which has been developed locally. This equipment will provide coverage from the C band
through to the J band, against pulse mode and CW threats. The equipment can detect,
discriminate and display more than fifteen threat emitters, and is capable of cueing
external DECM equipment and controlling a countermeasures dispenser where required.
Currently in Full Scale Engineering Development
(FSED), the ALR-2002 installation on the F-111 will use a modern microprocessor
controller, and will employ non-volatile memory which allows flightline loading of
firmware updates. The F-111 installation will employ a new cockpit display, designed and
built by AWADI, and the intention is to use the existing ALR-62 antenna suite, should it
provide adequate performance. Grown options under consideration could include a laser
warning receiver. The ALR-2002 FSED program is expected to be completed by December, 1997,
and airborne performance testing is expected in early 1998.
The importance of the ALR-2002 to Australia's
domestic industries cannot be understated. It is the first time in many decades that the
Australian government has done what most Western nations always have done, and sponsored a
domestic high technology program. The ALR-2002 will provide Australian industry with the
international credibility which is necessary for the export of high technology, high value
added military equipment, as well as providing our industry with an opportunity to
demonstrate what can be achieved by our engineers and scientists. It is most unfortunate
that many government departments preferentially source foreign built equipment, and the
RAAF's commitment to the ALR-2002 project demonstrates that it has the long term strategic
vision and courage to defy the self destructive "buy foreign" cargo cult mindset
which has so catastrophically gripped this nation in the last decade.
There are many other practical benefits which will
stem from the ALR-2002 program. From a military perspective, control of vital defensive
technologies is the best guarantee that political pressure from overseas cannot be brought
to bear so as to compromise Australia's position in any major dispute or military
confrontation. Withdrawing access to core EW technologies is a most effective means of
crippling a modern air force. A no less critical issue is cost and timeliness of software
upgrades in EW equipment, as changes to internal libraries must be carried out quickly and
efficiently to maintain pace with any opponent. Finally, the project will create more work
for Australian scientists and engineers, hard hit by the collapse of much of the
manufacturing base in the last half decade.
The ALR-2002 is hopefully the first step in the
process of restoring Australia's credibility as a developer and manufacturer of cutting
edge high technology military equipment. We can hope that the RAAF will be given the
support it properly deserves in this matter, and the public recognition due for its
contribution to enhancing Australia's long term position in this vital area of military
technology.
Pic.1, 2 (AN/ALR-62)
The Dalmo-Victor AN/ALR-62 Radar Homing And
Warning System (RHAWS) is the core of the existing F/RF-111C/G defensive avionic suite.
This capable receiver is now verging on obsolescence and will be replaced during the F-111
EW Upgrade later in the decade. The leading candidate for this role is the DSTO developed
ALR-2002 which is currently in Full Scale Engineering Development by AWADI. The nose
mounted antenna suite includes the pyramidal and circular warning antennas, and the pair
of unused wedge shaped homing antennas. The trailing edge of the stabilators mount the aft
facing warning antennas (author).
Pic.3 (AN/AAR-34)
The bullet on the top of the vertical stabiliser
houses the Cincinnati AN/AAR-34 infra-red tail warning system, which was the first ever
Missile Approach Warning System (MAWS) fitted to a tactical fighter. The EW upgrade will
see this obsolescent system replaced with a modern radar or optical MAWS (author).
Pic.4 (ALQ-94/137)
The dielectric fairing on the leading edge of the
glove conceals the forward facing antennas of the AN/ALQ-94/137 defensive jammer, which
provides E/F, G/H and I/J band coverage against fire control as well as acquisition
radars. This system provides both continuous wave noise jamming, as well as a range of
trackbreaking and deception jamming techniques. Subtypes with aft facing jammer coverage
employ the antenna cluster in the two bullet fairings outboard of the engine nozzles. The
ALQ-94/137 will be replaced with a state of the art defensive jamming system in the
upcoming upgrade (author).
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