here to go to our main page on electronic warfare
here to go to our page on the Society of Old Crows
|New for November 2011!
Electronic decoys are used to protect combat aircraft. They
are basically stove-pipe networks, receiving signals, adding
some secret sauce and rebroadcasting, to tell incoming missiles
"hey, I'm over here, ignore that other radar return, stupid!"
Hey there big fella,
buy me a drink?
RT-1489 GEN-X has been around
a long time, used in the original Gulf War, and stand for "generic
expendable". When an aircraft gets in trouble, a dispenser
starts throwing GEN-X overboard. GEN-X is just a few inches long,
but contains sophisticated electronics, and a lithium thermal battery
GEN-X was one of the demonstrators
on Darpa's MIMIC program.
Such miniature systems would not have been possible until MMIC circuit
technology came of age.
According to the Navy's on-line
The GEN-X Decoy
is a small, one shot, expendable terminal, RF threat countermeasure
that receives an RF signal from a recognized threat, such as airborne
or land-based semi-active radar guided missiles, then transmits
RF power to counter that threat. The GEN-X Decoy can be launched
from the AN/ALE-39 or AN/ALE-47 Countermeasure Dispensers using
a CCU-63/B or CCU-136/A Impulse Cartridge. GEN-X has been designed
and cleared for flight on all Navy tactical aircraft.
RT-1489 GEN-X measured 5.80"
long by 1.35" diameter and weighs 1.10 lbs.
There are two fielded towed decoys.
ALE-50, the Raytheon system, which dates back to 1996, or about
five years too late for the first Gulf War. It was originally called
AAED (A-squared E-D) for advanced airborne expendable decoy. ALE-55
was developed by BAE Systems. The primary difference between the
two is that the 55 uses a fiber-optic link between aircraft and
decoy. The second and more noticeable difference is in the shape
A towed decoy needs to have some
aerodynamic drag to keep the tether taut and stable. You can recognize
the two decoys because they use two different means of drag. The
ALE-50 has the coffee-cup nose, which legend has it was designed
by a consultant for a very hefty chunk of change after original
spearheaded decoys failed to fly. Don't have a costume for that
Old Crow's Halloween party?
Bite down on khaki-colored Styrofoam cup so it covers your nose,
and everyone will recognize you are the ALE-50 decoy! You can have
your date lead you around with a tether for the full effect. The
ALE-55 has pop-up drag fins. Ask either manufacturer which is better,
and they will tell you many reasons why their idea is the best.
There are three parts to a decoy:
power supply, solid-state module and mini-TWT, and each one has
its own particular manufacturing pain points in this system that
must perform over extreme altitude and temperature ranges. Prime
power comes down the tether at thousands of volts and is converted
to whatever is needed; high voltage is used in order to keep the
current-carrying requirement very low. You would not want to drag
a fourteen-gage wire.
Future versions of towed decoys
will be needed to cover new frequency bands where threats are emerging.
There will come a time when multiple decoys are needed to cover
sub-bands, but ultimately a DC-to-light decoy is what everyone is
Decoys are presently only used
once. A tiny pair of scissors cuts off the tether before the aircraft
lands, presumably over friendly territory so enemies don't get a
chance to admire it up close. Discarding the decoy is necessary
to prevent the potential mishap during reel-in of wrapping the tether
around the aircraft's stabilizer fin which might cause a serious
distraction to the pilot. There have been attempts over the years
to create a reel-out/reel-in system so that decoys could be recovered
and used again. But if your business was in selling decoys, you
wouldn't want to rush in to such a development without a few decades
of research, right?
The price of a decoy is reported
as $22,000. The fuel tanks on F/A-18 hold 4,800 gallons (and can
be refilled in-flight). So one way to look at it is that the loss
of a decoy is probably less than the cost of the fuel for a mission.