ChopperAddict's Hints & Tips


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   INFORMATION - All the facts about the Alien Command Auto pilot system

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 ADVANCED version.

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 balls.

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 really....)

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 channel.

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.


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 provided.  

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 movements).

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 ?

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