FeiYu Tech FY-21AP User Manual

FeiYu Tech Accessories communication

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GuiLin FeiYu Electronic Technology Co., Ltd http://www.feiyudz.cn E-mail:

[email protected]

GuiLin FeiYu Electronic Technology Co., Ltd http://www.feiyudz.cn E-mail:

[email protected] page


FY-21AP Flight Stabilization System

Installation & Operation Manual

Dear Pilot,

Thank you for purchasing the FY-21AP Version II stabilizer from FeiYu Tech.
In order to achieve full potential and safe operation of this product, please carefully read this

manual prior to installation


The installation and use of this device require some skill and knowledge in flying remote
controlled fixed wing aircraft.

If you are a complete beginner and have never flown one before, we do not recommend you
install this device on your own.

Please find assistance from an experience flier who may provide you with the basic knowledge
required to use this device successfully.

If you are already an experienced flyer, you will find the installation to be easy and logical. Just
follow the instructions as stated in this manual and you won‟t go wrong.

You may e-mail us directly for assistance;

[email protected]

How It Works

Attitude Flight Stabilization System (AFSS)

FY-21AP Version II is an advance Attitude Flight Stabilization System (AFSS) and Autopilot

for RC aircraft.

The FY-21AP utilizes a 3-axis gyroscope and tri-axial accelerometer to form an accurate drift

free attitude stabilization system. The unit also utilizes Global Positioning System (GPS) and a
barometric altitude sensing for accurate 3-dimensional positioning of the aircraft. By combining
attitude control and positioning, a comprehensive inertial navigation system and autopilot is
provided to you in a small compact light-weight package.

The AFSS achieves its attitude control via FeiYu Tech‟s proprietary algorithm, the unit

calculates the aircraft attitude in 3-dimension and detects any changes to the model‟s horizontal
position. If attitude change occurs, controlling signals will be sent out to the plane‟s ailerons,
elevator and rudder to counter the change. By continuously doing this, the plane is kept in a state of
stabilized equilibrium, resulting in a smooth level flight.

When activated, you only need to release the flight control sticks so that they return to the

transmitter neutral (middle) position. The model will immediately revert to level flight. The unit can
be activated or de-activated via a spare channel from your receiver.

GPS, Barometric Sensing and Autopilot

Upon initial boot up, the FY-21AP will search for GPS positioning signals. When a minimum

of 5 satellites have been detected, a fixed position is established. The FY-21AP will record that
position as the return to launch (RTL) point.

The on-board barometric sensor and GPS altitude readings will be combined to establish an

accurate relative-altitude of the aircraft.

When the Autopilot Mode is activated via a spare channel, the aircraft will automatically turn

and fly back to the take off point (RTL). The aircraft altitude will be constantly maintained. After
reaching the home position, the plane will automatically circle with a radius of 120 meters. By using
the same autopilot algorithm, you can also activate an auto circling flying pattern at a fixed altitude
anywhere you wish.


FY-21AP Attitude Flight Stabilization System

Constant stabilized flight in any condition – the FY-21AP will automatically level the flight
attitude of your aircraft in any weather condition. If you are just learning to fly, this will help
you gain experience, log more flying time and increase your confidence. The FY-21AP can be
activated throughout the flight duration, from take off to landing.

Emergency Recovery – in case you lose orientation or you feel the aircraft is out of control,
activate the FY-21AP and let go of the control sticks. The FY-21AP will immediately bring the
plane back to stabilized level flight.

Precision Flying: For the experienced pilot, FY-21AP can help you achieve more leveled and
precise flight paths, especially when flying and landing in strong wind.

First Person View (FPV): For long distance flying or FPV, the FY-21AP will take over the job
of leveling and stabilizing the plane for you. Just point the plane where you want to go and
enjoy the view!

FY-21AP GPS and Barometric Sensor

Fixed altitude flight - When this function is activated, the unit will maintain your aircraft
altitude. You only need to input the right throttle level and point the plane in the direction you
want to go.

Return to Launch (RTL) – You can flip the designated RTL switch on your radio and the
aircraft will return to the take-off point. RTL can also be programmed into your Receiver
failsafe so that the aircraft returns home if RC link is lost.

Fixed Position circling

– by activating this function, the aircraft will automatically circle the

selected area at a fixed altitude. Very useful for aerial photography.

Optional Upgrade with FYOSD and 606 Data Radio

The FY-21AP provides an optional upgrade combining the FYOSD with the FY-606 Data

Radio. With this add-on, you will receive:

Real time telemetry – real time by-directional telemetry is monitored directly by your ground station
computer. Changes to aircraft altitude, circle radius and flight path can be controlled from your ground
station computer.

Record and monitor your flight - you can monitor and download your flight path into your ground
station computer.

For more information, please refer to the FY-OSD Version 2.0 and FY-606 manual.


In each set of FY-21AP, you will receive the following:
• 1 x FY-21AP Version II unit
• 6 x RC receiver connecting wires;
• 1 x GPS Receiver;
• 1 x Current Sensor;
• 1 x OSD circuit board;
• 2 x Velcro double sided tape
• 1 x instruction manual;
• 1 x vibration absorbing mount;
• GPS wire with ferrite filter
• Some related wirings

Technical Specification and working requirements:

Working voltage

: 4.0~6.0 Volt

Current draw

: 52mA (at 5V)


: 55 x 33 x 20 mm(2.17 x 1.3 x .79 in)

Weight (exclude wire)

: 20g (0.71oz)

Working Temperature

: -25°C~ +70°C (-13°F~+150°F)

Maximum rate of rotating

: ≤ 1200 °/s

Aircraft Suitability

The FY-21AP has been proven to operate in the following aircrafts:


Normal / Traditional fixed-wing planes


Delta-winged plane with rudder


Delta-winged plane without rudder,


Plane without aileron,


V –tail plane with aileron


V –tail plane without aileron


Any other configuration, please e-mail us for enquiry:

[email protected]

Remote Control system requirement:

The FY-21AP has been tested to work with the following RC systems:

Robbe-Futaba PPM / PCM 1024 / PCM G3 mode, 2.4 GHz systems;

Graupner/JR PPM 8, PPM 12, SPCM mode;

MPX PPM8, PPM 12 with UNI mode

Any remote control system using the standard of 1.5 ms neutral position.

FY-21AP Flight Modes


The FY-21AP has three flight modes. You may activate any of the flight modes via a free Receiver
channel and a 3-position switch on your computer radio:

MODE 1: Deactivated Mode. In this mode, all control of the aircraft is by the pilot. The FY-
21AP does not participate in flight control.

MODE 2: Stabilized mode. In this mode and your transmitter control sticks at center, the FY-
21AP will continuously send out controlling signal (aileron, elevator, rudder) to ensure the
aircraft maintains a stabilized, horizontal flight and constant flight direction. In this mode FY-
21AP will not allow acrobatic flights.


The Auto Balance Mode will provide a smoother leveled landing for your aircraft.

However, note that the turning radius is much larger when AFSS is activated. Please ensure
your landing area has adequate clearance for this larger flight radius.

MODE 3: Fixed–Altitude Flight Mode. In this mode the aircraft Stabilized Mode is activated
combined with fixed altitude flight. Upon activation, the aircraft is immediately stabilized while
altitude is maintained autonomously. You only need to control the direction of the plane.


The FY-21 AP has no control over your throttle channel. When flying in

MODE 3, please ensure you have enough forward movement to prevent your aircraft from
stalling. If your forward movement cannot compensate for the autopilot‟s active altitude hold
action, your aircraft will stall.


FY-21AP Autonomous Flight Modes

Two autopilot modes are incorporated into the FY-21AP algorithm:

AUTOPILOT MODE 1: Deactivated. The autopilot function is not activated.

AUTOPILOT MODE 2: Auto Return to Launch (RTL). When activated in this mode, the FY-
21AP will automatically fly the plane to the take-off point, while maintaining altitude. Upon
reaching the launch area, the unit will automatically fly the plane in a circle at a default circling
radius of 120 meters.

Note: Should you change the Autopilot Mode during lost of RC signal, the RTL Mode will
immediately change to this latest mode upon RC signal re-establisment.

AUTOPILOT MODE 3: Auto circling mode (ACM). When activated in this mode, the plane
will immediately fly in a circle. The centre of the circle is the point of activation. The default
circle radius is 120 meters. The aircraft altitude will be automatically maintained throughout the



The FY-21AP has no control over the throttle channel. Therefore when flying in Autopilot Mode,
please ensure you have enough forward movement to prevent stalling.


If your forward movement cannot compensate for the autopilot‟s active altitude hold, your aircraft
will stall.


This is especially important if RTL is part of your RC failsafe. In the event of RC Link lost, you can
set RTL into your Receiver failsafe. However, please do not forget to also set your throttle failsafe to
between 25 % to 50% to prevent stalling.


Never set your throttle failsafe to zero. If you do so, your aircraft will RTL in a continuous stalled
flight which will result in a crash.

Gyroscope initialization (re-setting):

Out of the box, the FY-21AP has been fully initialized. However, if the following conditions occur,
initialization is recommended:


The device has not been used for a long time.


There is a change in environmental temperature of
over 30 degrees since last flight.


When in Mode 2: Stabilized Mode, and the
installed device in the horizontal position, the plane
control surfaces begin to move and deflect by itself,
without input from the pilot.