RadioLink F121 Pro User manual

F121 Pro
Mini Racing Drone with Manual Mode
Altitude Hold by Inertial Navigation
User Manual
* Please be kindly noted that this manual will be updated regularly and please visit RadioLink official website to download the
latest version：www.radiolink.com
V 1.1

RadioLink Electronic Limited
www.radiolink.com
Thank you for purchasing RadioLink mini racing drone F121 Pro.
To fully enjoy the benefits of this product and ensure safety, please read the manual carefully and set up the
device as instructed steps.
If any problems found during the operation process, either way listed below can be used as online technical
support.
1. Send mails to [e-mail] and we will answer your question at the earliest.
2. If purchased from an approved dealer or distributor, you can contact them directly for support.
All manuals are available on RadioLink official website www.radiolink.com and more tutorials are uploaded.
Never operate models during adverse weather conditions. Poor visibility can cause disorientation and loss of
control of pilot’s model.
Never use this product in a crowd or illegal areas.
Always ensure the trim levers of the transmitter at 0 and battery properly charged before connecting the
receiver.
Stay at a certain distance from the aircraft during flight to avoid getting hurt by the components of high-speed
rotation (e.g., Propellers, brushed motors)
After landing off, make sure the aircraft is disarmed and propellers have stopped moving before getting
close to touch the aircraft.
Always be sure about turning off the receiver/powering off the aircraft before the transmitter.
Follow the instructions of propellers installation in case of dropping during flight.
To ensure the best radio communication, please enjoy the flight at the space without interference such as
high voltage cable, communication base station or launching tower.
This product is not a toy and is NOT suitable for children under the age of 14. Adults should keep the product
out of the reach of children and exercise caution when operating this product in the presence of children. Water or
moisture may enter the mini drone and the transmitter through gaps of electronics and cause model instability,
even out of control. If flying in the wet weather (such as game) is inevitable, always use plastic bags or waterproof
cloth to cover the transmitter.
This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions:
This device may not cause harmful interference, and prevents external wireless interference, including
interference that may cause undesired operation.
Any Changes or modifications not expressly approved by the party responsible for compliance could void the
user's authority to operate the equipment.
WARNING
SAFETY PRECAUTIONS

1
CONTENT
Chapter 1 Features of F121 Pro......................................................................................................................................... 2
Chapter 2 Before Flight...................................................................................................................................................... 2
2.1 Power Supply.................................................................................................................................................... 2
2.2 Transmitter......................................................................................................................................................... 2
2.3 F121 Pro............................................................................................................................................................ 3
Chapter 3 Get Ready to Flight............................................................................................................................................6
3.1 Motor Installation.............................................................................................................................................. 6
3.2 Propellers and Propeller Protectors Installation..........................................................................................7
3.3 Power on F121 Pro.......................................................................................................................................... 8
3.4 Flight Note..........................................................................................................................................................8
3.5 Setup Compatible Transmitters......................................................................................................................8
3.6 Binding................................................................................................................................................................9
Chapter 4 Flight at Different Flight Modes...................................................................................................................... 10
4.1 Arm and Disarm F121 Pro............................................................................................................................ 10
4.1.1 How to Arm.............................................................................................................................................10
4.1.2 How to Disarm........................................................................................................................................ 11
4.2 Altitude Hold Mode......................................................................................................................................... 11
4.2.1 Rise/Descend.......................................................................................................................................... 11
4.2.2 Hover.......................................................................................................................................................11
4.2.3 Forward/Backward/Right/Left................................................................................................................12
4.2.4 Clockwise/Anticlockwise Rotation..........................................................................................................12
4.3 Stabilize Mode.................................................................................................................................................12
4.4 Manual Mode...................................................................................................................................................12
4.5 Switch for 360 Angle Flips Mode................................................................................................................. 12
4.6 Low Battery Alarm.......................................................................................................................................... 13
4.7 Calibration........................................................................................................................................................13
Chapter 5 Image Transmission of F121 Pro..................................................................................................................... 14
Chapter 6 FPV Goggles of F121 Pro................................................................................................................................. 15
6.1 Buttons and Connector..................................................................................................................................15
6.2 FPV Goggles’ Battery.................................................................................................................................... 16
6.3 DVR Mode....................................................................................................................................................... 16
6.4 Assembly and Disassembly of Goggles..................................................................................................... 16
Chapter 7 Specification.................................................................................................................................................... 16
7.1 Aircraft.............................................................................................................................................................. 16
7.2 Remote Controller.......................................................................................................................................... 17
7.3 Charger............................................................................................................................................................ 17
7.4 Camera & Video Transmission.....................................................................................................................17
7.5 FPV Goggles................................................................................................................................................... 17

RadioLink Electronic Limited
www.radiolink.com
2
Chapter 1 Features of F121 Pro
As the mini racing drone that can fly at high speed at Altitude Hold Mode, F121 Pro is very easy to master for
drone freshman. The inertial navigation system technology blending Kalman filtering, gyro, accelerometer, and
barometer makes F121 Pro possible to flight through narrow space with accuracy and hold altitude even it’s less
than ten centimeters height to the surface or at high speed.
F121 Pro have three flight modes that AltHold Mode, Stabilize Mode and Manual Mode. Even beginners can
flight stably at the first trial at AltHold Mode.
F121 Pro is monitored by RadioLink mini racing drone flight controller F121, which is different from other flight
controllers with PID needs to be set before use, will tune automatically. The software noise reduction technology
not only enables a more pleasant flight but also makes the motors more responsive and more efficient than
traditional 8520 brush-less motors. It can be thrown and start to fly at any angle even under high-speed and
remains stable even facing with sudden airflow fluctuations such as during takeoff, under braking, or after
extended flying. Without compass locking, F121 Pro always automatically modify angles during flight.
Chapter 2 Before Flight
2.1 Power Supply
Power for transmitter T8S: Make sure the transmitter is fully charged.
Power for F121: The voltage of 1S LiPo battery packed with F121 Pro by default is not fully charged so the
battery needs to be charged with the charger CM120 before flight.
The LiPo battery charger CM120, specially designed for 1S LiPo battery, sharing the professional development
and high precision of CB86PLUS, ensures safer charging and battery life span.
Charging current can be set as 1A or 2A by toggling the switch at the side of the charger.
The Red LED always on indicates the battery is under charging. The Green LED always on indicates the battery
is fully charged. The Red and Green LED Flashing alternately indicates fault prompt.
CM120 applies general USB connector, both computer and power bank for mobile phone can be used with
CM120.
Note Voltage output of power supply should be NO higher than 5V.
2.2 Transmitter
The two joysticks of T8S correspond to the four basic channels respectively. The below example takes RadioLink
radio T8S Mode 2 (Throttle on the left stick).
Left joystick
Make the F121 Pro rise or descend by toggling the left stick (THROTTLE) vertically upward or downward and
turn clockwise or anticlockwise by toggling the left stick (YAW) to the left or right.
Right joystick
Make the F121 Pro fly forward or backward by toggling the right stick (PITCH) vertically upward or downward and
to left or right by toggling the right stick (ROLL) to the left or right.

RadioLink Electronic Limited
www.radiolink.com
3
MODE 2
Note If it’s the transmitter from other brands used with RadioLink F121 Pro, make sure that the receiver should
be SBUS signal output supported. Once the receiver is installed on the mini drone, the phase of the throttle
should be reversed while the other three channels normal and the CH5 should be set with a 3-way switch to
change the flight mode and the CH7 set a switch (a 2-way switch or a 3-way switch is OK) for arm or disarm.
Servo phases of transmitters from other brands should be set according to the actual situation.
2.3 F121 Pro
Assembled as building block makes the RC students exercise their DIY ability and free from lengthy mobile
games. Learning knowledge of science and technology when assembling, setting parameters and flight.
2.4 Joysticks & Flight Movements
A. Throttle: Rise/ Descend/Hover
65mm prop(CW)
8520 motor(CCW)
Prop protector
Motor
Protector
65mm prop
(CCW)
8520 motor
(CW)
Prop
protector
Motor
protector
65mm prop(CW)
8520 motor(CCW)
Prop protector
Motor protector
65mm prop(CCW)
8520 motor(CW)
Prop protector
Motor protector
Camera
Camera protector
F121 flight controller
Fiber
Frame
Cable(receiver& flight controller)
Battery frame
R8SM receiver
PA1.7*8
Screws
F121 cover
* CW: Clockwise
* CCW: Counter Clockwise
*There are screws packed with F121 Pro to ensure the firm installation of the propeller’s protector
to the F121 Pro frame even with collision. Pilots can fix them on as necessary.

RadioLink Electronic Limited
www.radiolink.com
4
Toggle the throttle stick (on the left) vertically upward and F121 Pro will rise and toggle the throttle vertically
downward, then F121 Pro descends.
If at Alt-Hold Mode, toggle the throttle stick vertically upward till the F121 Pro rises to the preferred height, then
toggle back to center position and release, the F121 Pro will remain at this height.
1m
2m
Rise
Descend
Hover

RadioLink Electronic Limited
www.radiolink.com
5
B. Yaw: Clockwise/Anticlockwise
Toggle the yaw stick (on the left) to the left and F121 Pro will turn anticlockwise and toggle the yaw stick to the
right, then F121 Pro turns clockwise.
C. Pitch: Forward/Backward
Toggle the pitch stick (on the right) vertically upward and F121 Pro will fly forward and toggle the pitch stick
vertically downward, then F121 Pro flies backwards.
D. Roll: Right/Left
Toggle the roll stick (on the right) to the left and F121 Pro will fly to the left side and toggle the roll stick to the right,
then F121 Pro will fly to the right side.
Pitch stick upward, F121 Pro moves forward
Pitch stick downward, F121 Pro moves backward
Yaw stick to the left, F121 Pro turns anticlockwise
Yaw stick to the right, F121 Pro turns clockwise

RadioLink Electronic Limited
www.radiolink.com
6
Chapter 3 Get Ready to Flight
3.1 Motor Installation
To make the aircraft fly, motors usually rotate clockwise (CW)/counterclockwise (CCW) with the propellers. The
rotation direction of F121 Pro motors can be identified by the cable colors. That is, motor with red and blue wire
means motor of clockwise (CW) while with black and white wire means that of counterclockwise (CCW). It is very
important to make sure about the rotation direction as below when installing motors. Otherwise, the drone would
fail to take off.
* Motors installation can be skipped as the whole F121 Pro is already assembled by factory default. If any of the
motors is worn out and needs to be replaced, it’s essential to identify the correct motor rotation.
Roll stick to left, F121 Pro fly to the left side
Roll stick to right, F121 Pro fly to the right
side

RadioLink Electronic Limited
www.radiolink.com
7
3.2 Propellers and Propeller Protectors Installation
F121 Pro is installed propellers protector by factory default, you can follow the steps below if you need
change them. To ensure a safety flight, it’s strongly advised to check if the protectors are well installed.
①Find the two notches respectively on the motor protector
and propeller protector as image on the right.
②Put on the propeller protector from the bottom and adjust
the position of the notches correspondingly.
③Stabilize the frame with left hand and buckle the notch
of one side with right hand. Then buckle the notch of the other
side with left hand. A “DA” sound will be heard if the installation is done with success.
④Extra 4 screws are in the package and pilot can installed on the propeller protector as prefer.
Note After the installation of the four propeller protectors, double confirm if they are leaning or slightly shake
F121 Pro to see if they drop. If they are crooked or drop, repeat the above steps to ensure the well installation.
Propeller installation can be skipped as the whole F121 Pro is already assembled by factory default. If the
default propellers get worn and needs to be replaced after a period of flight, it is important to well identify the
rotation direction of propellers. If installed incorrectly, F121 Pro can’t take off even the throttle is pushed to max.
In order to identify the propellers rotation, take a propeller and observe there’s a radian at both sides of the
small cylinder in the middle. The higher part (also called windward side) of the right propeller is at the front and
the rotating motor will make propeller rotate counterclockwise (CCW). On the contrary, that is clockwise (CW)
rotation. For the 65mm GEMFAN propellers used on F121 Pro, there are two marked with a letter R, meaning
they should be installed on the motors of clockwise.
When the installation is done, make sure the four motors are vertical to the aircraft frame. If necessary, adjust
them to vertical positions, otherwise F121 Pro may not flight successfully.
Screw Installation

RadioLink Electronic Limited
www.radiolink.com
8
3.3 Power on F121 Pro
Before powering on F121 Pro, make sure T8S is fully charged. Put the throttle stick at the lowest position and
long press power key to power on T8S. Then power on F121 Pro. Fully charge the 1S LiPo battery first. Plug the
PH2.0 end of the battery into the F121 Pro, then insert the battery into the battery frame under at the bottom of
F121 Pro.
(1) Orange propellers indicates the head of F121 Pro by default. make sure they point to the same direction as
the pilot when powering on and be ready to fly, to ensure safety.
(2) The green LED of F121 Pro will begin flashing when powered on. When it’s off, it means F121 Pro finishes
calibration.
Note Head direction is determinate. If F121 Pro is calibrated with the direction different from the default, it will
turn back to the default direction automatically when starts flying, that’s what we called Head Front Forward Point
Without Compass.
3.4 Flight Note
If it’s the first time of flying drone, flight mode of Altitude Mode is strongly advised to set. At the Altitude Mode,
when toggle the throttle upward till the drone reaches a certain height and release, F121 Pro will remain at this
height. It’s simpler because pilots only need to toggle the other joystick to make the F121 Pro move
forward/backward or turn left/right. If it’s the Stabilize Mode especially Manual Mode chosen, try to toggle the
joysticks slightly to correct the flight and avoid the drone having sudden moves.
If F121 Pro drops by hitting something, toggle the throttle joystick to the bottom position immediately to stop
motor rotation.
Make sure the signal output of receiver is SBUS to ensure normal operation of F121 Pro. For RadioLink
receivers(R8SM/R6DSM) installed on F121 Pro, the LED indicator is blue/purple when it’s SBUS working mode.
3.5 Setup Compatible Transmitters
By factory default, RTF version of F121 Pro is packed with the transmitter T8S and receiver R8SM combo.
Receiver R8SM is also compatible with RadioLink T8FB.
If you ready to change the transmitter to AT10/AT10II/AT9/AT9S/AT9S Pro to control the F121 Pro, compatible
receiver should be R6DSM.
If it’s transmitters of other brands used, compatible receiver chosen should capable of supporting SBUS output.
T8FB/T8S
RadioLink 8-channel transmitter are well set by factory default with the flight modes. To control F121 Pro, binding
is the only thing needs to be done.
There are three flight modes for F121 Pro including Altitude Mode, Stabilize Mode and Manual Mode. It can be
changed by pressing the three-way switch on the right of T8FB- SWB or of T8S- CH5 as below