

AS3X® — The Foundation of Stability

Spektrum AS3X® technology is a part of the groundbreaking 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 HobbyZone®, 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.

Spektrum Stabilization Systems Flight Assistance Comparison
Roll and Pitch Limiting  
Panic Mode      
GPS Fence      
Return and Land      
Spektrum Stabilization Systems Feature Comparison
Rate Gyro
Heading Hold Gyro
Level Calibration on Startup  
Flight Modes 3 2 3 3
Programmable Gain & Priority Yes limited    
Wing/Aircraft Type Selection Yes limited    
Receiver Orientation      
Surface Setup    
Port Assignment & Failsafe    
Radio Adjustable AS3X Gain    

What is AS3X technology and what does it do?

The 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 Propeller Effect
AS3X Counters Wind
AS3X Holds Heading

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.

Beginner Mode

  • Pitch and Roll angles are limited to help you keep the aircraft airbourne
  • When controls are returned to neutral, SAFE returns aircraft to level flight
  • Stability assisted takeoff and landing
  • Throttle based climb and descent

Intermediate Mode

  • Pitch and Roll angle allowances are expanded to offer a larger flight envelope that protects the pilot from entering extreme flight conditions
  • The pilot experiences natural AS3X® technology assisted flight for smooth handling and outstanding prescision

Experienced Mode

  • The pilot experiences natural AS3X technology assisted flight for smooth handling and outstanding precision with a virtually unlimited flight envelope

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.

  • SAFE Select
  • SAFE
  • AS3X

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.

Upgrading Your Fleet with AS3X Technology

Adding the magic of AS3X technology to everything from small foamies to giant-scale warbirds is easy with these Spektrum™ AS3X receivers. All are compatible with DSM2® or DSMX® transmitters and are programmed using an intuitive interface that is available for PCs and popular mobile devices.

Installation and setup of these receivers is simple:

  1. Choose the AS3X receiver that's right for your model
  2. Install the receiver as directed
  3. Download the free programming app or software
  4. Setup the receiver for the aircraft using the new interface
  5. Fly!

The intuitive Spektrum AS3X receiver interface lets you:

  • Select the ideal AS3X mode setup
  • Activate different wing and tail mixes
  • Balance servos, adjust their travel, set absolute limits and more
  • Map output and gain settings for each channel
  • And more...

frequently asked questions

Q- My SAFE airplane does not seem to bind.

A- All SAFE equipped models, be it a SAFE, SAFE Plus or SAFE Select must be oriented on their landing gear (as if about to takeoff) and completely motionless for the system to calibrate and bind. The indicator lights in the receiver will stay off until the plane is put into the correct orientation.

Q- My airplane does not have much control throw and has nearly no down elevator.

A- This is due to an error in radio setup. Essentially the model is in Panic mode, which is controlled by channel 6 (Aux 1). Make sure you have this setup properly according to the manual. Most of the time it is because reversing Aux 1 was neglected.

Q- When I do a control correction test, I am not seeing any movement on the surfaces.

A- This could be one of two things. First, if this is an AS3X only plane or SAFE is not turned on, then the corrective movement on the controls can be subtle and is only proportionate to the disturbance that the model endures. Move the model quickly and watch the surface as the model is moving. Secondly, correction does not start until the throttle has passed 25% at least once. After that point, throttle can be brought back to the off position and the control correction test can be conducted. Try Beginner mode, which has self-leveling, where correction direction is most obvious.

Q- Can I take the receiver out of my SAFE equipped model and put it in something different?

A- It is not recommended. SAFE equipped receivers are specially tuned for the aircraft it came with. Putting it in a different aircraft can produce unexpected results, resulting in incorrect or over correction of the control surfaces and potential aircraft damage.

Q- I am having trouble with the AS3X App; it keeps crashing on start up.

A- Make sure you have granted the App the permissions that it requires from your device. This can be found in the App settings menu of your device. It is important that the volume of your headphones be at the full position. It is also important to delete all previous versions of the software, the AS3X named folders and AS3X App cache in your smart device.

Q- Can I enable SAFE technology in an open stock AS3X receiver?

A- Open stock AS3X receivers do not have SAFE flight assistance capabilities. Receivers with SAFE technology are intended as replacements for specific aircraft and should only be used with that aircraft.

Q- Neither the program or App will recognize my AS3X receiver.

A- Your AS3X receiver must be powered by a sufficient power source in order for the software to identify, read and write to it. Sometimes, turning the receiver power off and on will help the recognition process. It is also important to register your receiver so you can download and be notified of firmware updates.

Q- Is it better to adjust rates, expo, direction and mixing in the receiver or in my transmitter?

A- It depends on the AS3X receiver you have. With some AR636 receivers, due to hardware constraints, AS3X works better when the aircraft parameters are set in the receiver through the setup software or App . Newer AR7350, AR9350 and PowerSafe® receivers with AS3X offer more versatile adjustment options. Always refer to your user manual.

Q- Do I have to choose an unused transmitter switch in order to activate SAFE Select?

A- Any switch can be assigned the SAFE Select on/off feature, even if it’s already used for another channel or feature such as flaps, retracts, expo or dual rate. However, transmitters above 6-channels may require activation of the switch in the system menu.

Q- What is the difference between absolute and relative gain?

A- In the gain adjustment menu, absolute and relative is selectable; absolute is the default. Absolute means that the gain value can only be changed in the app or PC program. Relative means that mixing and changes to the channel from the transmitter will vary the gain value set through the app or PC program.

Q- Where do I start the gain levels?

A- The rule of thumb is to start with relatively low gain values. You can use the flight mode option to experiment with different levels on the fly. Another option is to find a BNF® airplane with AS3X technology that’s relatively similar. All registered receivers can accept AS3X presets available from the Spektrum.com website. Upload the preset and then use the flight mode option to fine-tune to your liking.

Q- Why would I want to use the flight mode option?

A- The flight mode option allows you to assign gain values and set gain levels for different flight conditions (pattern vs. 3D flight) or turn AS3X off completely from a switch on your transmitter.

Mobile Device and PC Programming Options

AS3X Receiver Quick Start Guide and Instructional Videos

PC Firmware Updates


We've put together a collection of materials and videos to help you learn more about Spektrum AS3X receivers and how to use them.