Reference

Glossary

Every term the book defines, and the chapter that introduces it. Free and complete — useful on its own when a forum post or a product listing loses you.

180-degree shutter rule

A video exposure guideline where shutter speed is set to roughly double the framerate, such as 1/120 second at 60 frames per second or 1/240 second at 120 frames per second.Chapter 13 · Capture and Share — Filming What You Watched

4-in-1 ESC

An electronic speed controller board containing four motor ESCs in one board, commonly mounted in a 5-inch stack.Chapter 6 · Picking Your First Quad — The Whoop Build Sheet

5-inch freestyle quad

A powerful FPV quad using approximately 5-inch props, commonly used for acrobatics, proximity flying, and the type of freestyle edits that attract many new pilots.Chapter 1 · What FPV Actually Is

5-inch race quad

A 5-inch FPV quad optimized for speed, gate precision, and racing rather than durability, smooth capture, or beginner repairability.Chapter 1 · What FPV Actually Is

65 mm class

A common tinywhoop frame size suited to tight indoor spaces. It is lighter and more agile indoors than a 75 mm frame but has less room and lift for HD video hardware.Chapter 1 · What FPV Actually Is

7-inch long-range quad

A larger FPV quad intended for efficient cruising and longer-distance flying, with greater regulatory, safety, and recovery responsibilities.Chapter 1 · What FPV Actually Is

75 mm class

A larger tinywhoop frame size with more prop area and payload capacity. It is often the easier choice for HD digital whoops because it handles the extra VTX and camera weight better.Chapter 1 · What FPV Actually Is

A30

A small connector used on some 1S and 2S micro packs and builds. The exact connector must match the AIO pigtail and charger leads.Chapter 6 · Picking Your First Quad — The Whoop Build Sheet

accelerometer

The inertial sensor that senses acceleration, including gravity’s direction when the quad is not accelerating aggressively; it is used for self-leveling modes more than for acro freestyle feel.Chapter 2 · The Physics in Plain English

Acro mode

A flight mode where stick input commands rotational rate and the quad does not self-level when the sticks are centered. It is the standard mode for freestyle and racing.Chapter 2 · The Physics in Plain English

action camera

A self-contained recording camera carried by a quad as payload for high-quality footage. Common classes include full-size GoPro Hero (HERO12 Black ~154 g, HERO13 Black ~159 g), Naked GoPro Lite/Bare modules (~30–40 g), Insta360 GO and DJI Action 2-class lightweights (~30–40 g), and the recording capability built into the air unit itself on DJI O3/O4. On a sub-250 g build, action camera mass is the main pressure on the AUW ceiling.Chapter 1 · What FPV Actually Is

AETR / TAER

Channel order conventions describing which radio channel carries aileron, elevator, throttle, and rudder; the radio and Betaflight must agree.Chapter 11 · Betaflight Deep-Dive

air unit

An HD digital video module that combines the camera, video transmitter (VTX), and (in some systems) on-board recording into one unit on the quad. DJI O3/O4 and Walksnail Avatar ship as air units; HDZero packages camera and VTX in a similar combined form. Analog systems do not — the camera and VTX are separate.Chapter 1 · What FPV Actually Is

air-unit recording

Recording captured directly by a digital video system such as DJI O3/O4, Walksnail, or HDZero where supported, without carrying a separate action camera.Chapter 13 · Capture and Share — Filming What You Watched

all-in-one board (AIO)

A compact board that combines the flight controller and electronic speed controllers, and sometimes the receiver or video transmitter, into one board. At whoop size, AIOs save weight, wiring, and stack height.Chapter 6 · Picking Your First Quad — The Whoop Build Sheet

all-up weight (AUW) cost

The total weight penalty added to the aircraft by a camera, mount, screws, filters, and accessories, considered against the build's thrust, handling, battery life, and legal weight category. First used in Chapter 9 to choose between toothpick variants; expanded into a full capture-side framing in Chapter 13.Chapter 9 · Picking Build Two — 5-inch Freestyle or Sub-250 g Toothpick

AM32

An open-source ESC firmware family for compatible STM32-based ESCs. Exposes motor-direction configuration the same way Bluejay does and is interchangeable with Bluejay for the beginner motor-reversal workflow on AIOs that ship with it.Chapter 1 · What FPV Actually Is

analog 5.8 GHz video

The classic FPV video system that sends a standard-definition analog camera signal over 5.8 GHz channels, usually with low cost and graceful static as signal degrades.Chapter 3 · The Radio Link, the Video Link, and the Goggles

analog AIO

A compact analog camera/VTX solution, sometimes integrated with the FC on small builds. It is cheaper and lighter than HD digital but has lower image quality.Chapter 6 · Picking Your First Quad — The Whoop Build Sheet

Angle mode

A self-leveling mode where stick input commands a limited tilt angle and the quad returns toward level when the sticks are centered.Chapter 2 · The Physics in Plain English

ARM channel

The radio auxiliary channel assigned to arming, which tells the FC when it is allowed to spin motors.Chapter 11 · Betaflight Deep-Dive

arming

The state where the flight controller accepts throttle and motor commands; disarmed means the flight controller refuses motor commands.Chapter 8 · First Flights — Indoor to Park

AUW (all-up weight)

The total flying weight of the aircraft with everything installed, including battery and any camera payload.Chapter 1 · What FPV Actually Is

balance charging

Charging through both the main lead and balance lead so the charger can keep every cell in a multi-cell pack at the same voltage.Chapter 3 · The Radio Link, the Video Link, and the Goggles

battery buzzer

A small plug-in alarm with a JST-XH socket that connects to the pack's balance lead, reads each cell, and sounds when any cell drops below a configured threshold; also keeps beeping after a crash to help locate the quad. Distinct from the FC-driven buzzer wired to the flight controller's beeper output, which Betaflight uses for arming tones, low-voltage warnings, and lost-model beeping.Chapter 4 · Power — LiPos, Chargers, and Not Burning Your House Down

BEC (battery eliminator circuit)BEC

A small voltage regulator on the flight controller (and sometimes on the ESC) that steps the flight-pack voltage down to 5 V or 9 V for low-voltage peripherals like receivers, video transmitters, and LEDs. The reader meets BEC output ratings as a buying-checklist item; build chapters cover wiring.Chapter 3 · The Radio Link, the Video Link, and the Goggles

Betaflight

The flight-controller firmware this book uses on every build. It runs the gyro/PID loop, motor mix, OSD, blackbox logging, and configuration interface. Configured through the Betaflight Configurator desktop application. Other firmwares exist (INAV, EmuFlight, KISS) but Betaflight is the default.Chapter 1 · What FPV Actually Is

Betaflight Configurator

The desktop or web application used to inspect, configure, flash, and troubleshoot a Betaflight flight controller. Distributed as a native installer for Windows, macOS, Linux, and Android, and as a web app at app.betaflight.com; this book uses "Betaflight Configurator" as the single house term for either form.Chapter 6 · Picking Your First Quad — The Whoop Build Sheet

Betaflight passthrough

A USB flashing route where Betaflight Configurator passes serial traffic through the flight controller to a connected peripheral, used to flash ESC firmware (Bluejay/AM32) and ELRS receiver firmware without removing the chip from the board. The most common flashing route once a builder has done it once.Chapter 6 · Picking Your First Quad — The Whoop Build Sheet

bidirectional DShot

A DShot mode where ESCs send motor RPM telemetry back to the flight controller, enabling RPM filtering.Chapter 11 · Betaflight Deep-Dive

bill of materials (BOM)

The complete shopping and inventory list for a build, including part name, vendor, part number, quantity, weight, price, link, and compatibility notes.Chapter 1 · What FPV Actually Is

bind phrase

An ELRS feature where the radio and receiver pair automatically when they share the same short text phrase. Replaces the older "press the button three times" manual bind. Set it once on the radio, set the same phrase on every receiver you flash, and write it down so future flashes pair without fuss. The ExpressLRS Configurator field is literally labeled "Bind Phrase".Chapter 3 · The Radio Link, the Video Link, and the Goggles

bind-and-fly (BNF)BNF

A retail quad that ships pre-built and pre-configured for a specific radio protocol — the buyer binds it to their own radio and flies it without any soldering. The opposite of the from-parts BOM build path this book teaches.Chapter 1 · What FPV Actually Is

Blackbox

Betaflight’s flight data logging system, stored to flash memory or microSD, used for troubleshooting and tuning.Chapter 2 · The Physics in Plain English

BLHeli_32

Former closed-source 32-bit ESC firmware line that became end-of-life in 2023; still found on many ESCs but no longer the forward-looking default.Chapter 9 · Picking Build Two — 5-inch Freestyle or Sub-250 g Toothpick

BLHeli_S

Older ESC firmware family for 8-bit ESCs; often updated with Bluejay for current Betaflight features.Chapter 9 · Picking Build Two — 5-inch Freestyle or Sub-250 g Toothpick

Bluejay

An open-source ESC firmware family for BLHeli_S-class hardware. Exposes motor-direction configuration through a configurator tool and is the recommended motor-reversal path on this build's beginner workflow. Chapter 7 covers usage.Chapter 1 · What FPV Actually Is

bolt-together frame

A frame with separate arms bolted to center plates, usually heavier than an equivalent unibody but easier and cheaper to repair after crashes.Chapter 9 · Picking Build Two — 5-inch Freestyle or Sub-250 g Toothpick

bounce-back

A rebound after a sharp stick input or snap move, where the quad overshoots or springs back instead of stopping cleanly.Chapter 12 · Tuning — From Stock to Smooth

brushed motor

An older motor type that uses physical brushes to switch current. Brushed whoops are treated as legacy context in this chapter, not as a recommended Build One path.Chapter 6 · Picking Your First Quad — The Whoop Build Sheet

brushless motor

A motor driven electronically by an ESC rather than by brushes rubbing on a commutator. Brushless motors are the default for modern FPV whoops because they are more efficient, more durable, and better supported than brushed motors.Chapter 6 · Picking Your First Quad — The Whoop Build Sheet

BT2.0

A low-resistance connector commonly used on modern 1S whoop packs. It is preferred over older PH2.0 connectors when the build and charger support it.Chapter 3 · The Radio Link, the Video Link, and the Goggles

Build Two

The reader's second quad in the book: either the 5-inch freestyle quad used as the spine build or the alternate sub-250 g toothpick path.Chapter 1 · What FPV Actually Is

C-rating

A manufacturer-printed multiplier that claims how much current a pack can deliver relative to capacity. It is useful for rough comparisons but often overstated.Chapter 4 · Power — LiPos, Chargers, and Not Burning Your House Down

capacity

The amount of charge a pack can deliver, labeled in milliamp-hours (mAh). A 1500 mAh pack is 1.5 amp-hours.Chapter 4 · Power — LiPos, Chargers, and Not Burning Your House Down

CE mode

A radio firmware or device mode aligned with European-style limits and requirements, including LBT behavior where required.Chapter 3 · The Radio Link, the Video Link, and the Goggles

cell

One lithium battery unit inside a pack. FPV voltage rules are stated per cell because 1S, 4S, and 6S packs have different total voltages.Chapter 4 · Power — LiPos, Chargers, and Not Burning Your House Down

center of gravity

The balance point of the complete flying quad. Moving a heavy camera forward shifts this point and changes how the quad rotates and holds attitude.Chapter 2 · The Physics in Plain English

channel order

The mapping between radio stick/switch outputs and Betaflight inputs, commonly AETR or TAER; incorrect channel order makes the quad respond to the wrong control.Chapter 8 · First Flights — Indoor to Park

charger

The bench device used to charge flight packs. It is shared gear bought once and reused across builds when compatible with the packs.Chapter 1 · What FPV Actually Is

cinelifter

A large FPV platform built to carry heavier cinema cameras. It is expensive, dangerous when mishandled, and outside the beginner build path.Chapter 1 · What FPV Actually Is

cinematic prop

A prop selected for smoother footage and lower vibration behavior rather than maximum punch or efficiency; examples in this chapter include HQ Cinematic, T-Mount triblade, and HQ ProBuzz style choices.Chapter 13 · Capture and Share — Filming What You Watched

cinewhoop

A ducted FPV quad designed for close-proximity cinematic flying, usually carrying an action camera or high-quality onboard camera.Chapter 1 · What FPV Actually Is

CLI

command-line interface (Betaflight's text console). Command-line interface inside Betaflight Configurator where configuration can be read and changed as text commands.Chapter 8 · First Flights — Indoor to Park

CLI diff

A Betaflight command output that records settings different from defaults. A labelled diff is the chapter's rollback file for each tuning round.Chapter 11 · Betaflight Deep-Dive

clockwise (CW) prop

A prop intended to spin clockwise when viewed from above the quad.Chapter 2 · The Physics in Plain English

cold joint

A weak solder joint formed when the pad, wire, or solder did not reach proper temperature or was moved while cooling; it often looks dull, lumpy, cracked, or peaked.Chapter 7 · Building the Whoop

community contribution

A concrete act that gives value back to the hobby, such as mentoring, volunteering, repairing, documenting, contributing to open source, or sharing useful lessons from mistakes.Chapter 15 · Your First Year as an FPV Pilot

conformal coating

A thin protective coating applied to electronics to reduce damage from moisture, dust, grass clippings, and conductive debris.Chapter 3 · The Radio Link, the Video Link, and the Goggles

continuity check

A multimeter test that reports whether two points are electrically connected; in this chapter it is used to detect shorts before power is applied.Chapter 7 · Building the Whoop

control link

The radio connection carrying stick, switch, and arming commands from the handheld radio transmitter to the receiver on the quad.Chapter 1 · What FPV Actually Is

counterclockwise (CCW) prop

A prop intended to spin counterclockwise when viewed from above the quad.Chapter 2 · The Physics in Plain English

Crossfire

A long-range control-link family from Team BlackSheep (TBS) that uses a 900 MHz radio link; once the dominant long-range option, now largely superseded by ExpressLRS but still in active use. Often referred to as TBS Crossfire.Chapter 1 · What FPV Actually Is

crosshair antenna

A directional antenna style used on goggles or ground stations to focus reception in one direction rather than equally around the pilot.Chapter 3 · The Radio Link, the Video Link, and the Goggles

CRSF (Crossfire serial protocol)CRSF

The serial framing format the receiver uses to send stick positions (and return telemetry) to the flight controller over a UART. Originally created by TBS for Crossfire and now reused by ELRS, Ghost, and others. The reader does not need to study the protocol; they only need to choose CRSF in Betaflight's receiver tab and pick the correct UART, both covered in build chapters.Chapter 3 · The Radio Link, the Video Link, and the Goggles

D term

The derivative term. In practical tuning language, D is damping: it resists fast changes and helps stop bounce-back, overshoot, and propwash oscillation, but it can heat motors when pushed too far.Chapter 12 · Tuning — From Stock to Smooth

deadband

A small range around stick center where small inputs are ignored, so a not-perfectly-centered gimbal does not produce unintended motion. Set in the radio per channel and in Betaflight on the Receiver tab; too much deadband makes the quad feel mushy near center, too little produces twitch on every neutral release.Chapter 5 · Sim Before Sky

deadcat frame

A frame geometry that moves the front props outward and rearward enough to keep props out of the FPV camera or action-camera view, usually at the cost of some symmetry compared with true X.Chapter 9 · Picking Build Two — 5-inch Freestyle or Sub-250 g Toothpick

DFU mode

Device Firmware Update mode, a bootloader state that lets a flight controller accept firmware flashing even when normal USB connection or firmware startup is broken.Chapter 14 · Maintenance, Troubleshooting, and Crash Repair

diagnostic flowchart

A branching repair process that starts with a symptom, eliminates likely causes in a safe order, and ends with a verified fix or a replace decision.Chapter 12 · Tuning — From Stock to Smooth

diff

A shorter CLI export showing settings that differ from the firmware defaults. The house command is `diff all`; the resulting text file is the practical rollback artifact used across Chapters 8, 11, and 12.Chapter 8 · First Flights — Indoor to Park

dipole antenna

An antenna with two radiating elements whose orientation affects signal strength and link reliability; placement and polarization matter for video performance.Chapter 10 · Building the Quad

DJI O3/O4

DJI digital FPV air unit generations that combine high image quality, onboard recording options, and an ecosystem tied to compatible DJI goggles.Chapter 1 · What FPV Actually Is

double-elimination bracket

A race format where pilots remain in contention until they lose twice, creating a winners bracket and a lower bracket.Chapter 15 · Your First Year as an FPV Pilot

DShot

The digital ESC protocol Betaflight builds use today, replacing older analog OneShot/Multishot protocols. Variants are written DShot300, DShot600, and DShot1200; numbers reflect bitrate.Chapter 6 · Picking Your First Quad — The Whoop Build Sheet

ducted whoop frame

A frame with circular guards around the props. The ducts make indoor practice safer and protect props and furniture, but add weight and drag compared with open-prop frames.Chapter 6 · Picking Your First Quad — The Whoop Build Sheet

dump

A full text export of the flight controller’s current Betaflight configuration.Chapter 11 · Betaflight Deep-Dive

DVR

Digital video recorder — the goggle's onboard recording feature. Captures what the pilot sees during a flight to a microSD card or internal storage. Useful for crash review and learning playback.Chapter 3 · The Radio Link, the Video Link, and the Goggles

dynamic notch filter

A moving notch filter that searches for resonant peaks in the gyro signal and suppresses them without cutting the entire frequency range.Chapter 12 · Tuning — From Stock to Smooth

EdgeTX

The open-source operating system this book assumes on the radio. Provides model setup, telemetry screens, mixers, and USB joystick output for sim training. Most current hobby radios (RadioMaster Boxer, Pocket, TX16S Mark II, etc.) run EdgeTX. Avoid radios that do not support it.Chapter 1 · What FPV Actually Is

error

The difference between what the quad is doing and what the FC wants it to do.Chapter 2 · The Physics in Plain English

ESC (electronic speed controller)ESC

The board that drives a brushless motor by switching its three phases in the right sequence. Modern FPV builds usually run a 4-in-1 ESC stacked under the flight controller, or an all-in-one (AIO) board that combines the FC and ESCs on one PCB. Build chapters cover wiring, sizing, and firmware.Chapter 1 · What FPV Actually Is

ESC current rating

The current an ESC is designed to handle. For whoop AIOs, the rating must fit the motor, prop, and battery cell count so hard throttle does not burn the ESC.Chapter 6 · Picking Your First Quad — The Whoop Build Sheet

ESC desync

A loss of synchronization between an electronic speed controller and motor where commanded motor timing no longer matches motor position, often seen as sudden twitches, motor squeal, hot motors, or abrupt drops under throttle. Previewed as a crash-mode symptom in Chapter 2; full diagnostic flow in Chapter 14.Chapter 14 · Maintenance, Troubleshooting, and Crash Repair

EU Open A1

An EASA Open Category operating subcategory relevant to light aircraft, including sub-250 g paths; exact requirements must be verified locally as of the year of flight.Chapter 1 · What FPV Actually Is

expo

A curve that softens stick response near center while preserving stronger response near the stick ends.Chapter 5 · Sim Before Sky

ExpressLRS (ELRS)ELRS

The open-source 2.4 GHz / 900 MHz long-range radio control link this book defaults to. Chosen for low latency, long range, and a vendor-agnostic ecosystem of radios and receivers. Older links (Crossfire, Ghost, FrSky) work but are not the recommended path. Chapter 3 covers the radio link in full.Chapter 1 · What FPV Actually Is

F411

An older STM32 microcontroller family still found on small AIOs. It can work on lightweight whoop builds, but has less processing headroom and fewer resources than newer options.Chapter 6 · Picking Your First Quad — The Whoop Build Sheet

F722

A more capable STM32 microcontroller family used on many modern AIOs. It gives more firmware headroom and is preferred when budget and availability allow.Chapter 6 · Picking Your First Quad — The Whoop Build Sheet

failsafe

What the flight controller does when it stops hearing the radio receiver. The default behaviour is to cut motor power so the quad falls to the ground rather than flying away. Long-range builds may configure smarter behaviour (GPS Rescue, drop). Configured primarily in Betaflight's Failsafe tab, with receiver protocol and link-loss behaviour set through the Receiver and Ports tabs, plus a bench test with the radio's RF module disabled before any field flight.Chapter 1 · What FPV Actually Is

failsafe stage 1

The short initial reaction after receiver signal is lost, usually holding or applying configured channel behavior briefly while Betaflight confirms link loss.Chapter 11 · Betaflight Deep-Dive

failsafe stage 2

The final link-loss action after stage 1 expires, commonly dropping/disarming or activating GPS rescue when correctly configured.Chapter 11 · Betaflight Deep-Dive

FCC mode

A radio firmware or device mode aligned with US-style rules and channel behavior; power and channel legality still depend on the specific device and jurisdiction.Chapter 3 · The Radio Link, the Video Link, and the Goggles

feedforward

A Betaflight stick-response term that reacts directly to the pilot's stick movement before the PID loop waits for gyro error. In Betaflight 4.5 and later, FF is treated as a peer tuning lever alongside P, I, and D.Chapter 12 · Tuning — From Stock to Smooth

field of view (FOV)

The apparent angular size of the goggle image. Larger FOV feels more immersive but can be harder for some pilots to scan.Chapter 3 · The Radio Link, the Video Link, and the Goggles

filter

A signal-processing step that removes selected gyro noise before the PID loop acts on it. Filtering makes data cleaner but adds delay.Chapter 12 · Tuning — From Stock to Smooth

flight controller (FC)

The onboard computer that reads the radio command and sensors, computes the control response, and sends commands to the electronic speed controllers.Chapter 2 · The Physics in Plain English

flight log

A simple record of packs, minutes, crashes, conditions, problems, and fixes used to make early practice visible and repeatable.Chapter 8 · First Flights — Indoor to Park

flux

A chemical cleaner that helps molten solder flow by removing surface oxidation from metal.Chapter 7 · Building the Whoop

FPV (first-person view)

A way of flying where the pilot sees a live video feed from the aircraft, usually through goggles, and controls the quad as if seated inside it.Chapter 1 · What FPV Actually Is

framerate

The number of video frames recorded per second, commonly 30, 60, or 120 fps for FPV capture.Chapter 13 · Capture and Share — Filming What You Watched

full-charge voltage

The normal maximum charge voltage for a standard LiPo cell: 4.2 V per cell unless the manufacturer specifies a different chemistry or high-voltage mode.Chapter 4 · Power — LiPos, Chargers, and Not Burning Your House Down

fume extractor

A small bench fan with an activated-carbon filter that pulls solder smoke and flux fumes away from the builder's face during soldering work. Required workstation safety equipment; venting alone is not a substitute.Chapter 7 · Building the Whoop

Gemini

An ELRS diversity mode that can transmit or receive across multiple RF paths to improve link robustness on supported hardware.Chapter 3 · The Radio Link, the Video Link, and the Goggles

Ghost

A control-link family from ImmersionRC that targets low-latency racing at 2.4 GHz. A smaller installed base than ELRS or Crossfire; mentioned in this book only as an alternative pilots may encounter.Chapter 3 · The Radio Link, the Video Link, and the Goggles

GNB27

A small whoop pack connector used on some Gaoneng (GNB) 1S packs. Less common than BT2.0; the BOM must match the connector to both the AIO pigtail and the charger lead.Chapter 3 · The Radio Link, the Video Link, and the Goggles

goggle perspective

The first-person camera view from the simulated quad, matching the visual frame used in real FPV flight. Used as a noun ("from the goggle perspective"), and hyphenated when attributive ("a goggle-perspective replay").Chapter 5 · Sim Before Sky

goggles

The display worn by the pilot to view the live video feed from the quad. This book uses 'goggles,' not 'headset.'Chapter 1 · What FPV Actually Is

GPS Rescue

A Betaflight emergency mode (UI label capitalized as "GPS Rescue") that attempts to climb and fly the quad back toward the recorded home point; it is not full autonomous return-to-home. The book matches Betaflight's capitalization.Chapter 8 · First Flights — Indoor to Park

graduation criteria

The practical minimum skills the reader must demonstrate in the sim before moving to real whoop flight or later to Build Two.Chapter 5 · Sim Before Sky

gravity

The downward force caused by the quad’s mass. Gravity is what the motors must overcome to hover and climb.Chapter 2 · The Physics in Plain English

gyro

The inertial sensor that measures rotational rate around the roll, pitch, and yaw axes.Chapter 2 · The Physics in Plain English

gyro lowpass filter

A filter that reduces high-frequency gyro noise above a selected cutoff frequency. Modern Betaflight builds often use gyro lowpass 2 as the main lowpass filter, while gyro lowpass 1 is often disabled or minimized on clean builds.Chapter 13 · Capture and Share — Filming What You Watched

gyro stabilization

Post-processing that uses camera gyro data to smooth footage after the flight, commonly through Gyroflow or ReelSteady.Chapter 13 · Capture and Share — Filming What You Watched

gyro trace

The rotation rate the FC measured from the gyro. Comparing gyro to setpoint shows whether the quad followed the command cleanly or lagged, overshot, or oscillated.Chapter 12 · Tuning — From Stock to Smooth

Gyroflow

Free, open-source gyro-data-based video stabilization software used in post to align footage to the camera's recorded motion. Chapter 13 uses Gyroflow as the default stabilization tool for FPV footage.Chapter 13 · Capture and Share — Filming What You Watched

HD digital video

The umbrella category for modern non-analog FPV video systems that deliver high-resolution color video over a digital link. The three families this book covers are DJI O3/O4, Walksnail Avatar, and HDZero. Distinct from analog 5.8 GHz, which is the legacy alternative. Chapter 3 covers the choice between HD digital and analog in full.Chapter 3 · The Radio Link, the Video Link, and the Goggles

HD VTX

A high-definition video transmitter system such as DJI O4/O3, Walksnail Avatar, or HDZero that sends digital video to compatible goggles.Chapter 1 · What FPV Actually Is

HDZero

A digital FPV video ecosystem designed around low and consistent latency, commonly favored by racers and pilots who value predictable timing.Chapter 1 · What FPV Actually Is

HDZero whoop module

An HD digital FPV VTX option designed for lightweight whoop builds and low-latency digital video.Chapter 1 · What FPV Actually Is

heat

A scheduled race group where several pilots fly the course at the same time on coordinated video channels.Chapter 15 · Your First Year as an FPV Pilot

heat shrink

Plastic tubing that shrinks when heated and is used to insulate exposed solder joints or reinforce wires.Chapter 7 · Building the Whoop

Horizon mode

A hybrid self-leveling mode that allows flips and rolls at high stick deflection while behaving more like angle mode near center stick.Chapter 2 · The Physics in Plain English

I term

The integral term. In practical tuning language, I is resistance to slow drift and long-duration error, such as wind push, battery sag, or a quad that will not hold attitude through a move.Chapter 12 · Tuning — From Stock to Smooth

inrush current

The brief surge of current that flows when a battery is plugged into electronics and input capacitors charge.Chapter 10 · Building the Quad

internal resistance

Electrical resistance inside the pack, usually shown in milliohms by better chargers. Rising or uneven internal resistance is a sign of aging, damage, or mismatch between cells.Chapter 4 · Power — LiPos, Chargers, and Not Burning Your House Down

interpupillary distance (IPD)

The distance between the centers of the pilot's pupils. Goggles need enough IPD adjustment for the image to line up comfortably.Chapter 3 · The Radio Link, the Video Link, and the Goggles

jello

Rolling, wavy distortion visible in FPV video or recorded footage caused by vibration reaching the camera or image sensor faster than the rolling-shutter readout. Indicates a mechanical problem (loose mount, unbalanced prop, hard-mounted camera on a flexing frame) — fix the source rather than tune around it.Chapter 7 · Building the Whoop

JST-XH

The standard balance-lead connector on multi-cell LiPo packs (2S and above). Used by every common balance charger to read individual cell voltages.Chapter 4 · Power — LiPos, Chargers, and Not Burning Your House Down

Kapton tape

Heat-resistant insulating tape used to protect parts of a board or secure small wires without melting during soldering.Chapter 7 · Building the Whoop

KV

motor velocity constant, in RPM per volt unloaded. A motor rating that approximates revolutions per minute per volt with no load. On whoops, KV must be matched to cell count, prop size, and frame class so the motor has enough punch without overheating or draining packs too fast.Chapter 1 · What FPV Actually Is

latency budget

The total delay between pilot input or camera exposure and the result the pilot sees or the quad produces, measured by adding each stage of the control and video path.Chapter 3 · The Radio Link, the Video Link, and the Goggles

LBT

Listen Before Talk, a regulatory behavior used in some CE regions where equipment checks whether a channel is clear before transmitting.Chapter 3 · The Radio Link, the Video Link, and the Goggles

LHCP

Left-hand circular polarization, the opposite circular polarization from RHCP; using LHCP around RHCP pilots can help reject their video signal when channels and setup allow.Chapter 3 · The Radio Link, the Video Link, and the Goggles

liability insurance

Insurance intended to cover damage or injury claims from flight operations; many clients require proof of coverage before paid drone work.Chapter 15 · Your First Year as an FPV Pilot

lift

The upward aerodynamic force created when the props accelerate air downward. In this chapter, lift is treated as the useful upward part of thrust.Chapter 2 · The Physics in Plain English

lifted pad

A copper solder pad that has separated from the circuit board substrate because of heat, force, crash damage, or repeated rework.Chapter 7 · Building the Whoop

LiHV (high-voltage LiPo)LiHV

A LiPo variant whose cells charge to 4.35 V per cell instead of the standard 4.20 V, giving a small capacity bonus at the cost of reduced cycle life. Only safe to charge as LiHV when both the pack and the charger are explicitly LiHV-rated. Treated as an exception in this book; the default is standard LiPo at 4.20 V per cell.Chapter 4 · Power — LiPos, Chargers, and Not Burning Your House Down

link quality (LQ)LQ

An ELRS-reported metric, the percentage of control packets the receiver successfully decoded. Distinct from RSSI (which measures raw signal strength). LQ tells you how much of the conversation actually got through; it appears in the OSD and on the radio screen.Chapter 3 · The Radio Link, the Video Link, and the Goggles

LiPo batteryLiPo

A lithium-polymer flight pack. FPV LiPos are optimised for high power delivery rather than energy density, which is why hard flights last only a few minutes. Cell counts are written nS (1S, 2S, 4S, 6S) where each cell is roughly 3.7 V nominal. Capacity is given in mAh. LiPos are flammable when damaged or over-discharged; safe handling and storage are non-skippable. Chapter 4 is the full safety treatment.Chapter 1 · What FPV Actually Is

lollipop antenna

A small omni-directional circularly polarized antenna style with a protective rounded cover, common on quads and goggles.Chapter 3 · The Radio Link, the Video Link, and the Goggles

long-range build

A quad designed for efficient, stable flight farther from the pilot than a typical freestyle setup, commonly using larger props, larger packs, GPS, conservative tuning, and more planning.Chapter 1 · What FPV Actually Is

loop frequency

How often the FC runs the PID calculation, commonly 2 kHz, 4 kHz, or 8 kHz depending on board processor, gyro, firmware settings, and DShot mode.Chapter 12 · Tuning — From Stock to Smooth

lost-quad finder

A buzzer or battery-backed finder that helps locate the whoop after a crash. For outdoor whoop flying, the chapter treats this as mandatory, not optional decoration.Chapter 6 · Picking Your First Quad — The Whoop Build Sheet

Low-ESR capacitor

A capacitor with low equivalent series resistance, used across the battery input to absorb voltage spikes and reduce electrical noise on the power rail.Chapter 10 · Building the Quad

low-side filtering

Noise reduction strategy focused on the ground side and return paths of circuits, preventing high-current return noise from contaminating sensitive video, receiver, or camera signals.Chapter 10 · Building the Quad

LUT

A look-up table used in editing software to transform color and contrast, often from a flat or log camera profile into Rec. 709.Chapter 13 · Capture and Share — Filming What You Watched

Matty flip

A freestyle trick named after pilot Matt Sciuto involving a rapid yaw rotation performed while inverted at the apex of a loop, then exiting the maneuver upright. Cited in this book as a long-term motivational marker, not a Build One requirement.Chapter 5 · Sim Before Sky

minimum safe voltage

The lower voltage landmark beginners memorize as 3.0 V per cell under load or as a hard danger floor; packs repeatedly pushed this low age quickly and may become unsafe.Chapter 4 · Power — LiPos, Chargers, and Not Burning Your House Down

model match

An ELRS feature that prevents the radio from controlling the wrong model by requiring the model ID in the transmitter and receiver to match.Chapter 3 · The Radio Link, the Video Link, and the Goggles

modes

Betaflight switch-controlled functions such as arm, angle mode, acro mode selection, beeper, and turtle mode.Chapter 8 · First Flights — Indoor to Park

moment of inertia

Resistance to rotational acceleration. A quad with mass farther from its center takes more motor authority to start and stop rotations.Chapter 2 · The Physics in Plain English

motion blur

The natural streaking of moving objects during each video frame; controlled blur helps FPV footage feel fast and smooth instead of brittle and jittery.Chapter 13 · Capture and Share — Filming What You Watched

motor direction

The clockwise or counterclockwise spin direction of each motor as expected by Betaflight and matched by prop orientation.Chapter 1 · What FPV Actually Is

motor mix

The flight controller’s calculation that turns desired roll, pitch, yaw, and throttle into four separate motor outputs.Chapter 2 · The Physics in Plain English

MSP DisplayPort

The serial protocol Betaflight uses to push the OSD (on-screen display) overlay onto an HD digital video system. On HD whoop and HD 5-inch builds the OSD does not ride on the camera signal; it is sent over a UART using MSP DisplayPort and rendered by the goggles or air unit.Chapter 7 · Building the Whoop

MultiGP

A large organized drone racing community with local chapters, race classes, events, rankings, and standardized practices for FPV race days.Chapter 1 · What FPV Actually Is

Naked GoPro

A GoPro modified by removing the factory housing, battery, screens, and other parts to reduce weight; it saves grams but loses durability, weather protection, and much of the original passive cooling.Chapter 9 · Picking Build Two — 5-inch Freestyle or Sub-250 g Toothpick

ND filter

A neutral density filter: a darkened filter that reduces light entering the camera so the shutter speed can stay near the desired cinematic value in bright conditions.Chapter 13 · Capture and Share — Filming What You Watched

nominal voltage

The middle-of-use label voltage, commonly 3.7 V per LiPo cell, used for pack naming rather than a precise charge target.Chapter 4 · Power — LiPos, Chargers, and Not Burning Your House Down

open class

A racing class with broader equipment freedom, where pilot skill, tuning, build choices, and hardware performance all influence results.Chapter 15 · Your First Year as an FPV Pilot

oscillation

Unwanted repeated movement caused by the control loop or vibration system feeding energy back into itself. In flight it can look like shaking, buzzing, or rapid wobble.Chapter 12 · Tuning — From Stock to Smooth

OSD (on-screen display)OSD

A live overlay of telemetry — battery voltage, link quality, flight timer, warnings — drawn over the FPV video feed so the pilot can read it without looking away from the goggles. Driven by the flight controller and configured in Betaflight; the build chapters cover layout. Used throughout the book.Chapter 3 · The Radio Link, the Video Link, and the Goggles

P notation

Parallel cell grouping inside a pack. FPV flight packs are usually described mainly by S count; P count matters when cells are paralleled to increase capacity or current capability.Chapter 4 · Power — LiPos, Chargers, and Not Burning Your House Down

P term

The proportional term. In practical tuning language, P is stiffness: how strongly the quad pushes back against an attitude-rate error right now.Chapter 12 · Tuning — From Stock to Smooth

pack

A flight battery. FPV packs are usually optimized for high power delivery, which is why hard flights often last only 2-4 minutes.Chapter 1 · What FPV Actually Is

pad

An exposed copper area on a circuit board designed for soldering a wire or component lead.Chapter 7 · Building the Whoop

pagoda antenna

A compact circularly polarized antenna style common in FPV, often used on goggles or quads where size and durability matter.Chapter 3 · The Radio Link, the Video Link, and the Goggles

parallel charging

Charging multiple packs of the same cell count together on a parallel board after verifying that their voltages are close enough; it saves field-session prep time but adds setup risk.Chapter 4 · Power — LiPos, Chargers, and Not Burning Your House Down

Part 107

The U.S. Federal Aviation Administration rule framework for certificated commercial small unmanned aircraft operations; this chapter treats it as orientation only, not legal training.Chapter 3 · The Radio Link, the Video Link, and the Goggles

PH2.0

An older 1S/2S whoop pack connector. Functional but supplanted by BT2.0 on most current whoop builds because BT2.0 has lower internal resistance.Chapter 3 · The Radio Link, the Video Link, and the Goggles

PID

proportional-integral-derivative (the flight controller's control loop). A control rule that decides how hard the FC should push back against error. This chapter gives the concept; Chapter 12 handles tuning depth.Chapter 1 · What FPV Actually Is

PID loop

The flight controller feedback loop that compares what the pilot asked for with what the gyro says the quad is doing, then changes motor output to reduce the error.Chapter 2 · The Physics in Plain English

pit mode

A reduced-power mode on most modern VTXs (a few milliwatts) intended for safe powering at the field — strong enough to confirm video on your own goggles, weak enough not to step on another pilot's feed. Triggered via SmartAudio/Tramp from the OSD or the radio. Use it before switching to flight power, and ask the field before going live.Chapter 3 · The Radio Link, the Video Link, and the Goggles

plug-and-play (PNP)PNP

A retail quad that ships pre-built but without a receiver, so the buyer installs and binds their own receiver before flying. Less common than BNF and RTF (ready-to-fly) but still a recognized retail tier.Chapter 1 · What FPV Actually Is

power loop

A vertical loop maneuver — full forward speed, pitch back hard, fly over the top inverted, and exit going forward at the original altitude. Builds vertical-energy management. Used as a sim drill in Chapter 5 and as a freestyle move on the 5-inch in Part III.Chapter 2 · The Physics in Plain English

pre-flight check

A short repeatable inspection and arming-confidence routine performed before a pack is flown, covering mechanical condition, antennas, battery voltage, configuration readiness, and field safety.Chapter 14 · Maintenance, Troubleshooting, and Crash Repair

prearm

A safety mode that requires a second switch or button before arming is allowed, reducing accidental arming risk.Chapter 11 · Betaflight Deep-Dive

Presets

Betaflight Configurator tab containing curated setting bundles and tune recipes that can apply many related CLI settings at once.Chapter 8 · First Flights — Indoor to Park

prop direction

The orientation of clockwise and counterclockwise props so each motor pushes air downward instead of upward or sideways.Chapter 7 · Building the Whoop

prop pitch

A prop geometry measurement that describes how aggressively the prop bites into air. Higher pitch usually feels faster and heavier on current draw; lower pitch usually feels smoother and more efficient.Chapter 2 · The Physics in Plain English

propeller (prop)prop

The plastic blade(s) that move air down so the quad goes up. This book uses "prop" as the house term after first mention. Specs are written as diameter × pitch × blade-count (e.g., a 5×4.3×3 is a 5-inch tri-blade with 4.3 inches of pitch). Chapter 2 covers prop pitch; build chapters cover prop choice.Chapter 1 · What FPV Actually Is

propwash

Disturbed air that a prop has already pushed downward, which can hit the quad again during hard descents, dives, or sharp direction changes and make the quad shake or bounce.Chapter 2 · The Physics in Plain English

quad

A multirotor aircraft with four motors. In this book, 'quad' refers to the FPV aircraft the reader builds or flies.Chapter 1 · What FPV Actually Is

radio

The handheld transmitter used to send stick commands from the pilot to the quad.Chapter 1 · What FPV Actually Is

radio transmitter (TX)

The handheld radio used by the pilot to send control commands. In this book, radio means the transmitter, not the video transmitter.Chapter 3 · The Radio Link, the Video Link, and the Goggles

rates

Settings that translate stick movement into rotational speed. Higher rates make the quad rotate faster for the same stick movement.Chapter 5 · Sim Before Sky

ready-to-fly (RTF)

A drone or quad sold as a complete package intended to fly with minimal assembly. In this chapter, RTF includes fixed-configuration consumer drones such as DJI Mavic-style aircraft and some FPV packages.Chapter 1 · What FPV Actually Is

Rec. 709

The standard color space used for most web video delivery; many log or flat camera profiles need a Rec. 709 transform or LUT before they look normal on YouTube, Instagram, or a phone.Chapter 13 · Capture and Share — Filming What You Watched

receiver (RX)RX

The small board on the quad that receives stick commands from the radio and hands them to the flight controller. Receiver protocol must match the radio's protocol family (ELRS, Crossfire, Ghost). Chapter 3 covers the radio link in full.Chapter 1 · What FPV Actually Is

ReelSteady

Commercial gyro-data-based video stabilization software (now bundled with GoPro Player) covering the same workflow as Gyroflow for GoPro-recorded footage with HyperSmooth metadata.Chapter 13 · Capture and Share — Filming What You Watched

Remote ID

A regulatory identification broadcast requirement for many drones in the United States under FAA Part 89; applicability depends on aircraft, use, and current rules.Chapter 1 · What FPV Actually Is

repair journal

A running log of crashes, symptoms, diagnosis, fix, parts used, time spent, and outcome that becomes the pilot's build-specific troubleshooting reference.Chapter 14 · Maintenance, Troubleshooting, and Crash Repair

replace-vs-repair decision

A practical judgment about whether a damaged part is safe and economical to fix, or whether replacement is faster, safer, and more reliable.Chapter 14 · Maintenance, Troubleshooting, and Crash Repair

resource map

Betaflight's assignment table connecting processor pins, timers, motor outputs, UARTs, LEDs, and other functions to firmware resources. Referenced in Chapter 11 for motor-output remapping; the full diagnostic and FC-swap context is in Chapter 14.Chapter 14 · Maintenance, Troubleshooting, and Crash Repair

RHCP

Right-hand circular polarization, the de-facto common FPV antenna polarization where the radio wave rotates in a right-handed direction.Chapter 3 · The Radio Link, the Video Link, and the Goggles

RPM filter

A dynamic filter that uses live motor RPM telemetry to reduce motor-noise harmonics; it is configured and tuned in Chapter 12 after RPM telemetry is verified here.Chapter 11 · Betaflight Deep-Dive

RSSI

Received Signal Strength Indicator, a measure of how loud the radio signal is at the receiver, expressed in dBm. Distinct from Link Quality (LQ), which measures decoded-packet percentage. A drop in LQ before RSSI hits the floor is a warning that interference is climbing.Chapter 3 · The Radio Link, the Video Link, and the Goggles

S notation

Series cell count. A 1S pack has one cell, a 4S pack has four cells in series, and a 6S pack has six cells in series, raising total pack voltage.Chapter 4 · Power — LiPos, Chargers, and Not Burning Your House Down

setpoint

The target rotation rate or attitude the FC is trying to achieve based on pilot stick input and flight mode.Chapter 2 · The Physics in Plain English

simulator

Desktop software used to practice FPV flying with the radio before risking a real quad.Chapter 1 · What FPV Actually Is

SmartAudio

A serial protocol used between a flight controller and a VTX to set channel, band, and power from the OSD or transmitter switches without unplugging the goggles or rebooting. The dominant analog/HDZero VTX-control protocol.Chapter 3 · The Radio Link, the Video Link, and the Goggles

smoke stopper

A current-limiting device placed between the battery and quad during first power-up to reduce damage if a short or reversed polarity is present.Chapter 10 · Building the Quad

smoke test

The first controlled power-up of a new build with props removed, while watching for shorts, heat, smoke, abnormal current draw, or missing startup tones.Chapter 7 · Building the Whoop

solder wick

Braided copper used to absorb excess solder from a pad or bridge.Chapter 7 · Building the Whoop

spec class

A racing class that restricts parts, weight, or performance so pilots compete on a more equal equipment baseline.Chapter 15 · Your First Year as an FPV Pilot

Split-S

A freestyle maneuver consisting of a half-roll to inverted followed by a pitch-back dive that exits at a lower altitude in the opposite direction. Used to start freestyle lines and to recover from inverted situations.Chapter 2 · The Physics in Plain English

squashed X frame

A frame geometry between true X and deadcat, with a wider or shorter stance that trades camera view, balance, and arm leverage differently depending on design.Chapter 9 · Picking Build Two — 5-inch Freestyle or Sub-250 g Toothpick

stator size

The diameter and height of the motor stator, commonly written as numbers such as 0802 or 1002. It gives a rough sense of motor torque, weight, and prop compatibility.Chapter 6 · Picking Your First Quad — The Whoop Build Sheet

storage voltage

The safe long-term resting target for LiPo packs, treated in this book as 3.85 V per cell; 3.80 V per cell appears in some sources as a practical equivalent.Chapter 4 · Power — LiPos, Chargers, and Not Burning Your House Down

strain relief

A mechanical support method that prevents a wire, connector, or ribbon cable from taking crash or handling force directly at the solder joint or fragile plug.Chapter 3 · The Radio Link, the Video Link, and the Goggles

sub-250 g toothpick

A lightweight open-prop FPV quad in the 3-inch to 4-inch prop class, sized to keep AUW below 250 g for small-field flying and EU Open A1-friendly planning when local rules allow. The Build Two alternate path. Two common variants — a light 1S/2S build on 1404-class motors, and a heavier 4S build on 1507-class motors.Chapter 1 · What FPV Actually Is

target hex

The compiled Betaflight firmware file for a specific flight controller target; flashing the wrong target can leave hardware features unmapped or unusable.Chapter 14 · Maintenance, Troubleshooting, and Crash Repair

telemetry

Data sent back from the quad to the radio, such as receiver link quality, battery voltage when configured, and signal warnings.Chapter 3 · The Radio Link, the Video Link, and the Goggles

threadlocker

A liquid thread-adhesive applied to fastener threads to keep screws from backing out under vibration. The book defaults to medium-strength (blue) threadlocker on motor screws, stack screws into metal standoffs, and action-camera mount screws; never on plastic, bearings, motor windings, or near electronics. Use the generic term in prose; the brand "Loctite" is one common manufacturer.Chapter 10 · Building the Quad

throttle management

The habit of using small, timed throttle changes to control altitude and momentum instead of stabbing the throttle after the quad is already falling.Chapter 5 · Sim Before Sky

thrust

The force a motor-and-prop combination produces by pushing air. On a quad, total upward thrust must exceed all-up weight before the quad can climb.Chapter 2 · The Physics in Plain English

thrust-to-weight ratio

Total available thrust divided by all-up weight. It estimates how much extra authority the quad has beyond hover; freestyle builds commonly aim for ratios above about 4:1.Chapter 2 · The Physics in Plain English

timer conflict

A hardware-resource conflict where two functions need incompatible timer assignments, often breaking bidirectional DShot or motor outputs after an FC swap.Chapter 14 · Maintenance, Troubleshooting, and Crash Repair

tinning

Coating a wire end, soldering iron tip, or pad with a small amount of solder before making the final joint.Chapter 7 · Building the Whoop

tinywhoopwhoop

A small ducted FPV quad designed for durable indoor practice and calm outdoor flying. The book's default Build One whoops sit in the 65 mm/75 mm class and land roughly ~30-40 g all-up for an analog 65 mm and ~50-75 g for the HD digital 75 mm class on a 1S pack, with the heavier end of that range reserved for 75 mm/85 mm builds carrying a DJI O4 air unit — these are still classed as whoops and are the path readers take when they bought DJI goggles in chapter 3. After first introduction, "whoop" is acceptable as informal shorthand.Chapter 1 · What FPV Actually Is

torque

A twisting force. Each spinning prop tries to twist the air one way and the quad the opposite way; paired clockwise and counterclockwise props keep that twisting balanced during hover.Chapter 2 · The Physics in Plain English

TPU

thermoplastic polyurethane (flexible 3D-printing filament). Thermoplastic polyurethane, a flexible 3D-printing material often used for antenna mounts, camera wedges, ducts, and small protective parts.Chapter 6 · Picking Your First Quad — The Whoop Build Sheet

training log

A simple record of date, duration, drills attempted, drills landed, and rate/expo settings used so progress is visible instead of guessed.Chapter 5 · Sim Before Sky

Tramp

An alternative VTX-control serial protocol comparable to SmartAudio, common on certain VTX families. Either works once the FC is configured for the matching protocol.Chapter 3 · The Radio Link, the Video Link, and the Goggles

transponder

A small timing device or built-in timing system identifier used to record laps during races.Chapter 15 · Your First Year as an FPV Pilot

true X frame

A frame geometry with motors arranged symmetrically around the center, favored for balanced handling and predictable response.Chapter 9 · Picking Build Two — 5-inch Freestyle or Sub-250 g Toothpick

Turtle mode

A Betaflight feature that briefly reverses motor direction on user command to flip an inverted quad upright after a crash. Configured via Betaflight modes and a switch on the radio. Taught in the Build One bring-up chapters.Chapter 5 · Sim Before Sky

TVS diode

A transient voltage suppression diode that clamps voltage spikes on a power rail, often used as extra protection against hot-plug and motor-induced transients.Chapter 9 · Picking Build Two — 5-inch Freestyle or Sub-250 g Toothpick

twisted pair

Two related wires twisted together so electrical noise picked up or emitted by the pair is reduced; useful for battery leads, motor signal pairs, and some video or serial runs depending on the system.Chapter 10 · Building the Quad

UART

universal asynchronous receiver/transmitter (a serial port). A simple serial-data bus on the flight controller. Receivers, GPS modules, video transmitters with telemetry, and similar peripherals each connect to a UART. Build chapters cover wiring; for shopping, the reader only needs to confirm the FC has enough free UARTs for the planned peripherals.Chapter 3 · The Radio Link, the Video Link, and the Goggles

unibody frame

A frame where the arms and bottom plate are one carbon piece, usually light and stiff but more expensive to replace after arm damage.Chapter 9 · Picking Build Two — 5-inch Freestyle or Sub-250 g Toothpick

venting

The failure mode where a damaged or abused LiPo releases hot gas and flammable electrolyte vapor; it may precede fire and requires immediate distance and containment.Chapter 4 · Power — LiPos, Chargers, and Not Burning Your House Down

visual line of sight (VLOS)VLOS

The regulatory and operational requirement that the pilot (or a designated visual observer) keep direct unaided sight of the aircraft during flight. Most recreational rules in the US and EU Open category require VLOS at all times; HD goggles do not satisfy VLOS by themselves. Verify locally as of 2026.Chapter 1 · What FPV Actually Is

VRX (video receiver)VRX

The receiving radio in an FPV video system, mounted in the goggles or as a separate module that feeds the goggles' display. In analog systems the VRX is a 5.8 GHz tuner; in HD digital systems it is a tightly-paired digital receiver matched to the video transmitter family (DJI O3/O4, Walksnail, HDZero).Chapter 3 · The Radio Link, the Video Link, and the Goggles

VTX (video transmitter)VTX

The on-board radio that beams video from the quad's camera to the pilot's goggles. Modern HD systems (DJI O3/O4, Walksnail Avatar, HDZero) integrate the camera and VTX into one unit; analog systems have a separate camera and VTX. Chapter 3 covers video systems in full.Chapter 1 · What FPV Actually Is

Walksnail Avatar

A digital FPV video ecosystem from Caddx/Walksnail that offers HD video, multiple air unit sizes, and goggles/VRX options outside the DJI ecosystem.Chapter 1 · What FPV Actually Is

Walksnail Avatar Mini

A lightweight HD digital FPV VTX/camera option commonly used in small builds where digital image quality matters more than the lowest possible cost.Chapter 1 · What FPV Actually Is

wallet-card

A printed, field-bag checklist small enough to laminate or sleeve, used as a fast reminder when conditions, nerves, or friends at the field make memory unreliable.Chapter 14 · Maintenance, Troubleshooting, and Crash Repair

wetting

The way molten solder flows onto and bonds with the metal surfaces of the pad and wire instead of sitting on top as a blob.Chapter 7 · Building the Whoop

X-class

A very large high-power racing or demonstration quad category, far outside the beginner build path.Chapter 1 · What FPV Actually Is

XT30

A smaller current-rated cousin of XT60 used on toothpick and lower-current builds. Same physical family, lower amperage rating.Chapter 3 · The Radio Link, the Video Link, and the Goggles

XT60

A high-current battery connector standard on 4S and 6S FPV packs, 5-inch builds, and bench charge leads. The single most common pack connector at 5-inch scale.Chapter 3 · The Radio Link, the Video Link, and the Goggles

No term matches that. The glossary covers what the book defines, so a miss usually means the term belongs to a part of FPV the book does not cover — ArduPilot, racing strategy, or fixed-wing.