A NOTE ON THE RULES

Regulatory entries describe United States requirements and were last reviewed in July 2026. Drone rules change frequently - always confirm current requirements with the FAA before you fly, and treat these defintions as a starting point rather than legal advice.

50 terms

4-in-1 ESC

A 4-in-1 ESC combines four speed controllers on a single board, mounted directly beneath the flight controller.

400 ft Rule

The 400 ft rule is the standard maximum altitude for drone flights in the United States, measured above the ground rather than above sea level.

Acro Mode

Acro mode turns off self-levelling entirely, so the drone holds whatever angle you leave it at until you correct it.

Additive Manufacturing

Additive manufacturing, commonly called 3D printing, builds a part by adding material layer by layer rather than cutting it away from a solid block.

Analog FPV

Analog FPV transmits a standard-definition video signal that degrades gradually into static as the signal weakens.

Angle Mode

Angle mode makes a drone level itself automatically whenever you release the sticks.

Antenna Polarization

Antenna polarization describes the orientation of the radio waves an antenna sends and receives, most commonly right-hand or left-hand circular in FPV.

ArduPilot

ArduPilot is open-source autopilot software used for autonomous drone flight in commercial, industrial and research applications.

Base Station

A base station is a fixed GNSS receiver at a known location that provides the correction data RTK and PPK positioning depend on.

Battery Puffing

Battery puffing is the visible swelling of a lithium battery, indicating internal damage and gas build-up.

Betaflight

Betaflight is the open-source flight controller firmware used by most FPV drones, designed around responsive manual flying.

Binding

Binding is the pairing process that links a specific transmitter to a specific receiver so they communicate only with each other.

Blue UAS

Blue UAS is a United States Department of Defense programme that approves specific drones for federal government use after independent cybersecurity and supply chain verification.

BNF

BNF means bind-and-fly: the drone is fully built and includes a radio receiver, but no controller — you pair it with a transmitter you already own.

Brushless Motor

A brushless motor drives a drone's propellers using electronically switched magnets rather than physical contact brushes, making it more efficient and much longer-lasting.

C Rating

The C rating tells you how much current a battery can safely deliver continuously, calculated as the C number multiplied by the capacity in amp hours.

Cell Count

Cell count, written as a number followed by S, is how many battery cells are wired in series, which sets the pack's voltage.

Compass Calibration

Compass calibration is a short pre-flight procedure that helps a drone establish its heading correctly relative to magnetic north.

Crossfire

Crossfire is a long-range radio control system made by Team BlackSheep, widely used for distance flying.

Digital FPV

Digital FPV transmits a high-definition video signal, giving a far sharper image than analog systems.

Diversity Receiver

A diversity receiver uses two or more antennas at once and automatically switches to whichever is receiving the best signal.

ESC

An ESC, or electronic speed controller, converts signals from the flight controller into the precise power each motor needs.

ExpressLRS

ExpressLRS, usually shortened to ELRS, is an open-source radio control system offering long range and very low latency at low cost.

Flight Controller

The flight controller is the drone's onboard computer, reading its sensors and translating pilot input into precise motor commands hundreds of times a second.

FPV

FPV, or first person view, means flying a drone by watching a live video feed from an onboard camera rather than watching the aircraft from the ground.

GNSS

GNSS is the collective term for satellite positioning systems, including GPS, GLONASS, Galileo and BeiDou.

Goggles

FPV goggles are the head-worn display that shows a drone's live camera feed, giving the pilot the sensation of sitting in the aircraft.

GPS Hold

GPS hold uses satellite positioning to keep a drone in a fixed spot in the air, correcting automatically for wind.

LiPo Battery

A LiPo battery is a lithium polymer rechargeable battery, valued in drones for delivering very high current at low weight.

Motor KV

Motor KV is how many revolutions per minute a motor turns for each volt applied, with no propeller fitted.

NDAA-Compliant

NDAA-compliant describes a drone that the manufacturer states meets National Defense Authorization Act restrictions on foreign-made drones and components.

Operations Over People

Operations over people are drone flights conducted above people who are not part of the operation, permitted only under specific FAA categories based on the aircraft's weight and injury risk.

OSD

An OSD, or on-screen display, overlays flight information such as battery voltage, timer and signal strength onto the pilot's video feed.

Part 107

Part 107 is the set of FAA rules covering commercial drone operations in the United States, requiring the pilot to hold a Remote Pilot Certificate.

PET-CF

PET-CF is a 3D printing filament made from PET plastic reinforced with chopped carbon fibre, producing parts with high stiffness and good heat resistance.

Pit Mode

Pit mode reduces an FPV video transmitter to very low power so a pilot can power up on the ground without interfering with others already flying.

Propeller Diameter

Propeller diameter is the width of the circle a propeller sweeps, and it is the first number in a propeller's size code.

Propeller Pitch

Propeller pitch is the distance a propeller would theoretically travel forward in one full rotation, and it is the second number in a propeller's size code.

Receiver

The receiver is the small radio on board the drone that picks up commands from the transmitter.

Remote ID

Remote ID is the FAA requirement for a drone to broadcast its identity and location while flying, effectively acting as a digital license plate.

Remote Pilot Certificate

A Remote Pilot Certificate is the FAA credential required to fly a drone commercially under Part 107, earned by passing an aeronautical knowledge exam at an approved testing centre.

Return to Home

Return to home is an automatic function that flies the drone back to its recorded launch point and lands it.

RSSI

RSSI measures how strong the radio signal reaching the drone is.

sUAS

sUAS means a small uncrewed aircraft system weighing less than 55 pounds (25 kg) at takeoff, including everything it carries.

TFR

A TFR, or temporary flight restriction, is a short-notice airspace closure covering events such as stadium games, wildfires and VIP movements.

Thermal Camera

A thermal camera creates an image from infrared heat rather than visible light, revealing temperature differences invisible to the eye.

Transmitter

The transmitter is the handheld controller a pilot uses to fly the drone.

TRUST

TRUST is the free online safety test that recreational drone flyers in the United States must complete before flying.

VTX

A VTX, or video transmitter, is the onboard radio that sends the live camera feed from an FPV drone to the pilot's goggles.

Waypoint Mission

A waypoint mission is a flight route planned in advance, which the drone then flies autonomously.