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Throughout these pages, we have talked about the Receiver all RC Planes need to control and fly your plane. There is a wide range of Receivers and they differ in if or what assistance they will provide while your plane is in flight. The Receiver can be thought of as the "Brain" of your plane. It controls every moveable part, including Servos and connection to the Electronic Speed Control (ESC) which in turn controls the amount of movement and speed. A basic receiver doesn't add any aids to these movements and are usually used by the Experienced Pilot. If the pilot moves the stick on the Radio to the left for a left bank, they have to move the stick to the right, then centre to maintain level flight.

Spektrum has developed a range of Receivers that provide different levels of aids to flying, that can be of benefit to all levels of pilots, but especially new pilots. They range from AS3X which while not providing any control of the plane, will "Smooth" out the flight. The next level up from that is the group of "Safe". Safe is available in three versions which are displayed in the following information and charts. Basically, Safe does provide certain control of your plane while in flight. It will assist in keeping your plane level and in the case of Safe Plus, even keep your plane withing a certain distance of you and even land the plane on its own, just about in the same place it took off from. Whereas the experienced pilot with a basic receiver had to do all direction corrections, with Safe, after making a turn, you simply move the Radio stick back to centre and Safe will automatically bring the plane back to level and straight flight. This feature is a huge benefit to the new pilot and takes a lot of the stress out of your training program. As you advance, you can change the level of assistance Safe provides and eventually turn it off, all from your radio. A good example would be, you use Safe during takeoff and landings, but turn it off once you are at a comfortable height.




Spektrum AS3X technology is a part of the SAFE assisted flight envelope protection system found in many Ready-to- Fly and Bind-n- Fly airplanes and helicopters offered from Horizon Hobby brands such as Hobby Zone, E-flite and Blade. Every SAFE system has AS3X technology at its heart. AS3X technology has proven so versatile, that different versions of SAFE technology, such as SAFE Select and SAFE Plus, are now available so a better flying experience can be enjoyed for a wider range of RC pilots.


The charts below identify what each system is capable of and how they assist in flight.




What is AS3X technology and what does it do?


AS3X PlanesThe purpose of AS3X technology is to enhance the flight stability of all model types. AS3X technology works behind the scenes to help stabilize the aircraft in whatever attitude you command. It does so using a sophisticated combination of sensors and exclusive flight control software. Every BNF® airplane or helicopter with an AS3X system is custom tuned by RC product development experts to deliver the best flying experience possible. An AS3X system counters outside forces such as wind, turbulence, torque, tip-stall, control sensitivity issues due to CG position or aircraft design to make your flight smoother. As a result, a model custom tuned with AS3X technology is easier to fly and performs with greater precision. AS3X does not fly the aircraft for the pilot. It’s not autonomous, nor does it interfere with pilot commands. The beauty of AS3X technology is that it takes advantage of onboard sensing to react perceptively faster. Behind the scenes, AS3X is following along with you, calculating an infinite number of possible corrections. All you see is an aircraft that flies smoothly and goes exactly where you point it with greater accuracy. Ultimately, pilot workload is reduced, making it easier for the pilot to focus on aircraft position and maneuver symmetry for a better flight experience through a wider range of conditions. A model equipped with a well-tuned AS3X system actually gives a pilot more control.


AS3X gives you more control


For a 3D aerobatic model, an AS3X system can make slow speed and knife-edge maneuvers feel much more stable and precise even when the pitch and roll rates are set extremely high. In a scale park flyer or ultra-micro, it will counter the effects of turbulence on windy days so the plane will track smoother and give the pilot a “locked in” feeling. Maybe you’re a scratch builder who finds that scaling and CG limitations make it tough to create an agile or realistic looking model that isn‘t a handful to fly. AS3X technology can help by battling the conditions that interfere with having a smooth flight. The AS3X system never limits your control or interferes with your commands. You always have control. The AS3X system simply gives a higher-level of stability which makes a more enjoyable flight possible.


When you buy an “Open Stock”* receiver with AS3X technology such as the Spektrum AR636, AR7350, AR9350 units, it operates very similar to a standard DSMX® receiver out of the box—the AS3X system is inactive. Setup of the AS3X system is accomplished though the AS3X App and/or PC Program interface. Each requires a cable or Bluetooth module to establish a link with your device and the AS3X system. The interface makes it possible to easily setup many of the features found in computer radios such as travel adjust, sub-trim, mixing, wing type and more. You don’t have to have a computer radio to enjoy AS3X technology. Gain adjustments for each axis allow you to fine tune the appropriate amount of AS3X assistance desired, just like the way Horizon Hobby product developers do. One of the coolest features is the flight mode capability that allows you to program different AS3X settings on a transmitter switch position. That way you can experiment with different AS3X settings in flight. Always follow the specific recommendations for the AS3X receiver model you choose. A number of tutorials on using these features with success are available online.


Open Stock indicates that it was purchased separately, not as a replacement part or previously installed in an RTF or BNF® model.


SAFE® technology: Turning beginner’s luck into the beginner’s advantage


SAFE technology is an advanced flight assistance system that gives pilots the ability to fly without the worry of crashing due to common mistakes such as orientation loss or over-control. Built upon the successful Spektrum AS3X system, models with SAFE technology, such as the E-flite® Apprentice™ S 15e, have multiple flight modes with progressive flight envelope limitations as well as self-leveling and flight stabilization. By simply changing the position of a switch on the transmitter, a pilot can choose any flight mode for results that promote confidence and flight proficiency at a comfortable and often faster rate.


Safe Chart


Self-leveling, heading-hold and bank-limit flight mode capabilities of SAFE technology reduce the chance of crashing and allow a pilot get comfortable with an airplane. No other electronic system compares in options or ease of use. When a pilot becomes proficient enough to turn the SAFE flight modes off, turning it back on again is always a simple solution. An important difference between SAFE and AS3X technology equipped receivers is that an AS3X only receiver can be tuned by the user and suitable in nearly any model. A SAFE receiver is a complex system custom made for the aircraft. A SAFE receiver is not intended to be taken from one model and put in another.


The Next Advancements: SAFE® Select and SAFE+ (Plus)


If we think of AS3X technology as part of the “Pyramid of Stability”, Safe Select and Safe Plus are currently at the peak.



Building again on top of SAFE and A3SX, SAFE Plus adds breakthrough automated flight features that employ GPS sensing. With SAFE Plus technology new pilots no longer need worry about flying beyond line of sight. But that’s not all. SAFE Plus even takes the worry out of landing by providing assistance features that virtually allow the model to land itself. A SAFE Plus receiver is not intended to be taken from one model and placed into another and it’s AS3X gain settings are not adjustable. SAFE Select technology is the newest addition to the SAFE product line and is available in a wide range of BNF models from ultra-micro to giant-scale. SAFE Select is the answer for the experienced pilot who wants to relax with an aircraft that can shoulder the burden of keeping the wings level at the flip of a switch. SAFE Select also allows pilots use the AS3X PC and Mobile app to fine tune some settings such as rate gain, channel assignments and flight mode switch position. Pilots get more freedom and more control to explore the advantages SAFE and AS3X technologies offer. Once again, a SAFE Select receiver is not intended to be taken from one model and placed into another.

Go to the next chapter RC Plane Propulsion (power) Types