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- All the facts about the Alien Command Auto pilot
Many people Seem to be confused about these types of
Auto Pilot systems, and there seem to be several myths around, one of
the most common being that they do not work below 30 feet. - RUBBISH
The Alien Command system can be used for take off and
landings with no problem at all.
There are several different types of stabilizer
systems around today, some are
clones of each other, and they vary in price quite a bit.
The one I am going to discuss here in this Tip & Trick
is the Alien Command, which comes in two different versions, the Alien
Command STANDARD, and the Alien Command ADVANCED. Prices for the
units are around £60 for the STANDARD version, and £120 for the
There are two separate versions for a very good
reason. The STANDARD version will ONLY work on helicopters that
have what is known as a 90 degree, single servo mixing system, which is
also commonly known as a mechanical mixing system. The Interceptor 400
is a good example of such an arrangement
On the left above is a typical 120 degree swash plate,
as you can see by the angle between each of the connecting balls on the
outer edge of the Swash Plate. On the right is the Interceptor 400 swash
plate, which you can see only has 90 degrees between those connector
The ADVANCED version was introduced because a great
many training style helicopters use the more common 120 degree, 3 servo
mixing system, more commonly known as CCPM, or electronic mixing, which
is always performed by the Transmitter (TX). To allow Alien Command to
handle this, an additional electronics module called the CSI is required
that handles the CCPM mixing rather than the TX doing so. A good example
of this is the Esky Belt CP, and many T-Rex helicopters.
In the simplest possible terms, AC (Alien Command) has
a sensor unit that will typically be mounted on the horizontal
stabilizer of a Pod & Boom (P&B) helicopter. This has four small
lenses each one at 90 degrees to the other, and these must be positioned so
that they can ALL see the horizon.
As you can see in the above picture the
lens are on the FLAT sides, and do NOT point directly forward backward,
left and right, but rather at about 45 degrees from them. That is
handled by the AC module, which understand this orientation, and
corrects for it, so that when it is control of the cyclic, and you put
the nose DOWN, the AC module will not only apply backward elevator, but
it will also provide the relevant amount of corrective aileron. (Clever
The picture above shows a Futaba FASST 6
channel Rx mounted upside down behind the AC electronics
module. The wiring here is normal, (in other words the AC unit is
not yet wired into the system.
In the above picture, we have moved the red, brown and
orange Aileron and Elevator connections from the RX to the AC module,
and connected the two black, red & white coiled AC cables to the RX
in their place. The small red and black cable goes to the control switch
mounted on the skid arm, while the large flat cable is routed to the
sensor on the boom. The unused wire from the AC module is tucked away on
top of the RX as it is not in use on this helicopter as there is no
spare channel on the Futaba 6Ex radio to use for the control
To set the AC unit up, you have to go into SETUP MODE, which means you need to hold that
small red switch push in AS WELL AS CONNECTING the lipo cell to the
Helicopter. The servos cycle 3 times to indicate that you are in setup
mode. The electronics is then taught to get the swash plate
level, and which way to move it to counter cyclic movements, by you
simply blocking each lens, one at a time and ensuring the swash moves in
the correct direction. Thereafter it is constantly monitoring the horizon during flight, using
the difference in the heat signatures between them to identify a
straight and level position. As soon as you stop introducing
cyclic commands, such as in a hover, AC (Alien Command) takes over
automatically and provides all the cyclic inputs needed to maintain a
level, stationary hover for you.
As soon as you touch the cyclic stick, AC (Alien
Command) relinquishes command and you are totally in charge again.
So if you get it all wrong, you just let go the cyclic
stick, and let AC (Alien Command) recover the helicopter to a hover, and
then you can take command again and land it safely.
Equally, on takeoff, AC will happily take care of
keeping the helicopter level, so all you really need to to do is
increase power and let the helicopter rise into the air under Alien
Command's cyclic control
With the STANDARD version, all you have is the sensor on the
Horizontal stabiliser, and a single small box of electronics that
handles all of the the mixing.
You MUST SET YOUR
TRANSMITTER UP so that it DOES NOT PROVIDE ANY FORM OF MIXING AT ALL
On the Spektrum DX6i and DX7 this is
handled easily on the swash menu, where you select the one servo, 90
degree swash plate option. On a Futaba 6EX, it is a little more
complex, but you still find the SWASH menu and select the 1 S option
The CTRL lead that is provided on the AC
module can be connected to a spare channel on your RX if you have one to
provide switching on the TX, but you DO NOT NEED to use
this. If you have a spare proportional channel, you can use it to
control the gain of the AC system in flight.
Finally, you connect the long flat
connector between the sensor and the module.
The AC module has small DIP switches that
allow you to reverse the
direction the AC mixing occurs so that the swash plate moves in the correct
direction when controlled by AC (This does not effect your stick control
Finally you follow the instructions out
on the field to ensure that AC is working correctly, and off you go.
AC has a GAIN control (called THROW for
some reason) that effects the
sensitivity of the system, zero sensitivity means the helicopter will be
getting NO INPUT AT ALL from the AC system, so you are in normal flight
totally. FULL GAIN means AC will provide maximum effort to control it for
you if you let go of the cyclic stick or keep it still.
This gives you the best of both worlds,
as you can use it to try out new manoeuvres, like flying nose in, and
then disable it to go off doing aerobatics or 3D flight.
Overall, AC is an excellent aid in
learning to fly a helicopter, and will save a great many crashes and the
resultant costs thereof. You can have it on when taking off, and
AC will control the helicopter to keep it level while you apply power.
How much easier can a take off into a stable hover get really ?