S155 Smart Charger

Flying RC models has always been fun. Learning to fly them, on the other hand, has not. Exclusive SAFE® (Sensor Assisted Flight Envelope) technology from Spektrum™ changes everything by making RC flight just as fun for the beginner as it is for the expert. How? Using a combination of sensors and flight control software, Spektrum SAFE technology can make an RC aircraft aware of its attitude relative to the ground. This ‘attitude awareness’ makes it possible to program aircraft with different levels of assistance pilots can choose from based on their level of experience and needs during the flight.

Custom-tuned for fixed or rotary-wing aircraft, this evolutionary combination of multi-axis sensors and software makes the aircraft intelligent enough to understand its flight attitude. This groundbreaking spatial awareness means that roll and pitch can be limited while flight stability is enhanced and freedom of control is preserved. Its multiple flight mode selection allows the pilot to instantly choose a level of envelope protection that suits the moment. The result is that beginners have a far more relaxing learning experience, and experts get outstanding control with protection benefits accessible at the flip of a switch.

SAFE technology allows an RC model to be aware of its attitude relative to the horizon. This attitude awareness is key to SAFE technology’s three core benefits: Flight Envelope Protection, Multiple Flight Modes, and Smoother Flight Capability.


This is the most significant benefit SAFE technology delivers. SAFE uses attitude awareness to create an electronic flight envelope for a model that prevents extreme or unusual attitudes. For example, SAFE technology in a typical trainer aircraft creates a beginner flight envelope, preventing extreme bank and pitch angles with assists with takeoffs and landings. All SAFE-equipped models will roll, pitch, or yaw as fast or as slow as designed but remain within the limits of the flight envelope, or mode, selected.


From the transmitter, the pilot can select the level of flight envelope protection desired at any time. Each mode offers a progressive performance so pilots can naturally develop their flying skills safely.


In addition to its levels of flight envelope protection, multi-axis AS3X stability keeps the aircraft flying rock solid even in windy conditions. The workload reduction improves confidence and significantly helps the aircraft handle cross-wing conditions so the pilot can focus better on aircraft guidance.

Spektrum SAFE technology began with the success of the Horizon Hobby AS3X® System. Designed to work behind the scenes, an AS3X System delivers instantaneous attitude corrections when turbulence, torque, and tip stalls haphazardly interrupt the way you want to fly. The specially tuned benefit makes the aircraft fly incredibly smooth while providing the pilot with control that feels natural and utterly accurate.

You can find this popular feature in a wide range of E-flite® airplanes, HobbyZone® airplanes, and Blade® helicopters.


One of the most important aspects of SAFE Technology is Panic Recovery. If a pilot loses control of an airplane, they can simply press the Panic Recovery button or switch to Beginner Mode and release the control sticks. SAFE automatically returns the airplane to level flight.

While SAFE is usually placed on a two or three-position switch, Panic Recovery is usually placed on a momentary contact switch. SAFE is designed to be active over time, while Panic Recovery is designed to activate only temporarily.

The primary point of Panic Recovery is to allow new pilots to get used to flying free form without limits but be able to recover an error such as a spin, dive, or inverted flight momentarily in order to catch a breath and regain orientation and composure. The effect is temporary so that the pilot can then go back to free form flying or experimenting again.


SAFE Select technology is the latest addition to the SAFE product line and is available in a wide range of Bind-N-Fly 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 to use the AS3X PC and Mobile app to fine-tune settings such as rate gain, channel assignments, and flight mode switch position. Pilots get more freedom and 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.