fpv lexicon

FPV Lexicon

Below is a list of terms, abbreviations, expressions and acronyms that are often used in an RC hobby and especially FPV and quadcopter community.

Current state: in development. New entries might be added every few days

Last update: 2020-04-14

A

AC

Alternating Current

Accelerometer

A device that measures acceleration and gravity. Allows Flight Controller to know where the ground is. Required for Flight Modes with self-leveling

AGL

Altitude Above The Ground

Aileron

One of the control surfaces, responsible for roll control

Altitude Hold

Flight mode that keeps the altitude of a UAV on a predefined level. Uses IMU, Barometer, and GPS to compute current altitude and adjust it when needed

Angle Of Attack

The angle between airflow and wing chord

Angular Velocity

Rotation speed measured in degrees-per-second

ArduPilot

Flight Controller firmware oriented on an autonomous flight

ARF

Almost Ready to Fly – RC model that has most of the components preinstalled

ASL

Altitude Above Sea Level

B

Band Attenuation Filter

A filter that filters out – attenuates – frequencies from a given frequency range. Frequencies below and above the range (band) will not be attenuated

Band Pass Filter

A filter that attenuates frequencies below and above the range (band). Frequencies inside band will not be attenuated

Baro

Barometer – a device that allows measuring barometric pressure and relative altitude. Used for Altitude Hold

Baseflight

An attempt for port MultiWii to SMT32 platform. Deprecated and currently not developed

Battery

Rechargeable source of electricity

Betaflight

Flight Controller firmware oriented on a quadcopter acrobatic FPV flight – freestyle and racing. Forked from Cleanflight by BorisB. Currently maintained by Betaflight Team

Binding

Process of connecting radio control receiver with a transmitter

BlHeli

A family of ESC firmware. Very popular in Multirotor UAVs

BNF

Bind And Fly – RC model with a preinstalled receiver. All one has to do it to bind with own transmitter

BLDC

Blushless Direct Current Motor – a brushless motor that uses a special driver to convert Direct Current to Alternating Current using closed-loop control and Back-EMF detection. See ESC

Brushed Motor

An Electric motor with rotating electromagnets that uses brushes to transmit electricity to the rotor and switch active coils

Brushless Motor

An electric motor with stationary electromagnets and rotating magnets. To work requires either AC (Alternating Current) or a driver. See ESC

BVLOS

Behind Visual Line Of Sight

C

Cleanflight

Flight Controller firmware oriented on a quadcopter acrobatic FPV flight – freestyle and racing. Forked from Baseflight by Hydra

COG

  • See Center Of Mass
  • Course Over Ground – Direction in which the craft is to be steered. See Heading

Center Of Mass

It is a place where weighted relative mass distribution equals zero. A body supported in its CoM will be stable, will not rotate.

Compass

See Magnetometer

CPU

Central Processing Unit – processor of a computer system

C-rating

One of the ratings of Batteries. A battery of a capacity of 1500mAh is charged/discharged at 1C when current is equal to 1500mA.

CRSF

A serial protocol that connects Radio Receivers and Flight Controllers. Transmits RC channels and Telemetry. Used by Team BlackSheep Crossfire

D

dRonin

Flight Controller firmware, currently not actively developed

Drone

Remotely controller vehicle (aerial or not) capable of autonomous flight

DSHOT

Digital ESC protocol. It does not require calibration and is more precise than OneShot125 and Multishot. Comes in various speeds: DSHOT150, DSHOT300, DSHOT600, DSHOT1200

DC

Direct Current

E

EEPROM

Electrical Erasable Programmable Read-Only Memory – see Flash Memory

Elevator

One of the control surfaces on the airplane, responsible for pitch control

EMF

Electro-Magnetic Field

ESC

Electronic Speed Control – Electronic devices used to regulate the rotation speed of the electric motor. In the case of BLDC motors used in RC hobby, it’s also responsible for phase switching and conversion of DC to AC

F

Failsafe

State when RC receiver lost signal from the transmitter. A pilot is no longer able to control the behavior or the UAV. What UAV will do depends on the configured Failsafe scenario configured in the Receiver or Flight Controller

Fat Shark

A company most known for being a manufacturer of FPV goggles

Firmware

Software that controls the behavior of a hardware device like Flight Controller, Receiver, ESC

Flight controller

A computer (hardware + software) that controls the UAV. It takes input from sensors (gyroscope, accelerometer, barometer, GPS and other) and well as the pilot’s input from the Receiver or preprogrammed flight plan and converts it to motor and servo output.

Flash Memory

Non-volatile computer memory that can be electrically erased and reprogrammed. Used to store Firmware

Flaps

One of the control surfaces on an airplane. Increases lift and increases drag.

F.Port

A bidirectional protocol designed to connect radio receivers and flight controllers. Transfers up to 18 channels and Telemetry. Used by FrSky

FPV

First Person View – the vehicle is equipped with a camera and video feed that is received and presented to the Pilot

G

Galileo

European satellite-based positioning system

Gimbal

A device used to stabilize a camera or control stick on an RC radio transmitter

GLONASS

Russian satellite-based positioning system

GPS

Global Positioning System – USA owned system of a satellite-based positioning system. Synonym of all satellite positioning systems.

Gyroscope

Gyro. A sensor that measures angular velocity – rotation speed

H

High Pass Filter

A filter that attenuates frequencies below the threshold (cutoff frequency). Frequencies above cutoff frequency will not be attenuated

H-frame

Quadcopter frame that’s shaped like a letter H.

HD

High Definition video

Heading

The direction in which the vehicle nose or bow is pointed. See Course Over Ground

Heading Hold

Flight mode in which UAV will keep predefined heading using a compass/magnetometer sensor or course-over-ground from a GPS sensor

Headless Mode

Flight mode in which the pilot controls the UAV in his frame of reference, not the UAV frame of reference. For example, moving the transmitter stick forward means “fly away from me” not “pitch forward”

Headfree Mode

See Headless Mode

Hexacopter

Hexa – a multirotor with 6 motors and propellers

I

I2C

Inter-Integrated Circuit – bus allows connecting multiple slave devices to a master device

IMU

Inertial Measurement Unit – allows to merge accelerometer, gyroscope, barometer, compass, GPS and other sensor data and compute a 3D position and orientation

INAV

Flight Controller firmware oriented on navigation and FPV acrobatics capabilities. Forked from Cleanflight by DigitalEntity

INS

Inertial Navigation System – allows performing positioning and navigation based on accelerometer and gyroscope data only

J

K

KISS

Flight Controller software oriented on a quadcopter acrobatic FPV flights and simplicity of use

KV

One of the electric motor constants. Used to describe the relationship between the input voltage and rotation speed

Kwad

See Quadcopter

L

Li-Po

Lithium-Polymer battery type

Li-Ion

Lithium-Ion battery type

Low Pass Filter

A filter that attenuates frequencies above the threshold (cutoff frequency). Frequencies below cutoff frequency will not be attenuated

LRS

Long-range Radio System – RC radio link designed for long-range applications

LoRa

Long Range – low power, long-range radio transmission technology. Based on spread spectrum modulation techniques offers a high range and low power consumption. As a tradeoff, it has a relatively low transmission speed

LoRaWAN

Wide Area Network based on LoRa technology

LOS

Line Of Sight – flight condition in which UAV stays in the sight range from pilot and pilot relays only on his sight to control the UAV

M

Magnetometer

The sensor used to measure the direction of the magnetic field. Can be used to locate the magnetic north and thus provide information about absolute heading

Matek

Matek, Mateksys. Chinese based manufacturer of RC hobby electronics. Especially famous for their Flight Controllers running Betaflight, INAV, and ArduPilot

MCU

MicroController Unit – a small computer on a single chip

MTO

Mid-Throttle Oscillations. Characteristical oscillations that affect some multirotor drones when Throttle is in the middle position. MTO usually caused by too low frame resonant frequency. It overlaps with vibrations generated by motors when Throttle is in the middle position. Properly designed frames have resonant frequency shifted high enough to be not noticeable and/or simpler to filter out from the Gyro data. Usual ways of fighting with MTO are more aggressive filtering, Flight Controller soft mount, forcing 48kHZ PWM rate on ESCs, etc.

Multicopter

See Multirotor

Multirotor

Heavier than air airship that uses multiple (at least 3) rotors to achieve flight

Multishot

One of ESC protocols. Faster than OneShot125. Internally it is a PWM based protocol with higher frequency and shorter pulse times.

MultiWii

Legacy Flight Controller software, not actively developed

N

NMEA

The serial protocol used for communication with GPS modules

Notch Filter

See Band Attenuation Filter

O

OneShot125

One of ESC protocols. Faster than standard PWM protocol, slower than Multishot

OSD

On-Screen Display – a function that overlies flight parameters on top of FPV video feed

Octocopter

Multirotor with 8 motors

P

PDB

Power Distribution Board – an element that distributes electrical power from Battery to motors, servos, and other elements

PID

Proportional Integral Derivative – a control loop mechanism for a system with a feedback loop. Used on Multirotors and RC airplanes for stabilization

Pilot

A person that controls the behavior of a UAV

Pitch

The horizontal axis around which nose of a UAV moves up or down

Pixhawk

Open-hardware project for a Flight Controller hardware compatible with ArduPilot

PPM

Pulse Position Modulation – also known as CPPM – improved radio receiver protocol that allows connecting the Receiver to the Flight Controller. Allow to send up to 12 RC channels. Currently deprecated

Propeller

Propulsion devise that converts torque into thrust

PWM

Pulse Width Modulation. One of the protocols that are used to send value using On/Off keying. The value is encoded as a between rising and falling edge of an electrical signal. Standard PWM works at 50Hz and encodes values between 1000 and 2000 (range vary)

Q

Quadcopter

Multirotor that uses 4 motors

R

Radio

See Radio Transmitter

Radio Transmitter

A wireless device used to control a remote vehicle (UAV)

Receiver

Part of radio link that receives commands from the Transmitter

Rangefinder

A sensor used to measure the distance to objects. Can use different methods of measurement: Laser, Sound, IR. See TOF & Sonar

RC

Remote Control

Roll

The horizontal axis around which side of a UAV moves up or down

RSSI

Receiver Signal Strength Indication – a measure of the power present in the received radio signal. Can be used as a measure of received signal quality

RTF

Ready To Fly – a model kit that has everything required for operation

RTL

Return To Land – see RTH

RPM

Revolutions Per Minute

RPM Filter

One of the Betaflight gyro filters – a series of band attenuation filters – Notch Filters – are set based on motors RPM speed

RTH

Return To Home – flight mode that autonomously returns UAV to the place when it took-off and optionally lands it

Rudder

One of the control surfaces on an airplane, responsible for yaw control

S

Servo

A device used to control the position of an element with an internal feedback loop. RC hobby servos control angle of a servo arm

S.BUS

A serial protocol that connects radio receivers to flight controllers and some other devices. Allows sending 18 channels. Used by Futaba, FrSky and multiple other manufacturers. Does not transfer Telemetry data

SkyZone

A company most known for being a manufacturer of FPV goggles

SmartAudio

A serial protocol used to control (change band, channel, and power) a VTX

Sonar

A Rangefinder device that uses sound to measure the distance. See Rangefinder & TOF

SPI

Serial Peripheral Interface – a very fast interface between electronic devices

Stall

A state, caused by an Angle Of Attack higher that Critical Angle, when a wing or propeller, loses lift and increases drag

STM32

A family of 32-bit microcontrollers

T

Telemetry

Data sent from Flight Controller and other Sensors to the Radio Transmitter.

Tricopter

Multirotor that uses 3 motors and a servo

Triflight

A Flight Controller software created to improve Tricopter performance. Forked from Cleanflight

Throttle

Control element that contains information about thrust

TOF

Time Of Flight – a method of measuring distance – sensor measures time it takes the signal (light, IR, laser, sound) to reach the object, reflect and go back to the sensor. See Sonar & Rangefinder

Tramp Protocol

A serial protocol used to control (change band, channel, and power) a VTX

Transmitter

Part of a radio link that sends commands to the Receiver

TX

See Transmitter

U

UAS

Unmanned Aerial System

UAV

Unmanned Aerial Vehicle

UBLOX

Serial protocol communication with GPS modules

U-blox

A company that produces GPS chipsets

UHD

Ultra High Definition video

V

VRX

Video Receiver

VTX

Video Transmitter

U

UART

Universal Asynchronous Receiver/Transmitter – serial port – one of the digital interfaces between electronic devices

USART

Universal Synchronous/Asynchronous Receiver/Transmitter

W

Waypoint

Preprogrammed destination in an autonomous flight

X

X-class

One of the classes of quadcopters used for racing and freestyle. Characterized by big dimensions: 800 to 1200mm motor-to-motor

X-frame

Quadcopter frame that resembles in shape a letter X

Y

Yaw

The vertical axis of a UAV. Yawing means moving the nose side-to-side

Z

Z-84

Very popular foam airplane model Zeta Z-84 Wing Wing