Glossary of Terms

Revised November 9th, 2018

A device that measures acceleration or “g-force". Single and multi-axis models of accelerometers are available to detect magnitude and direction of the acceleration.

AGL - Above Ground Level:
Altitude expressed in reference to height above the ground at that particular location.

Relating to or using signals or information represented by a continuously variable physical quantity such as spatial position or voltage.

Angle of Attack:
Specifies the angle between the chord line of the wing of a fixed-wing aircraft and the vector representing the relative motion between the aircraft and the atmosphere.  By properly managing the angle of attack, one can control the amount of lift generated by the aircraft.

ATC - Air Traffic Control:
A service provided by ground based controllers who direct the movement of manned aircraft in their area of responsibility.

Flight location such as a structure or building that is or was normally occupied by people and property but regarded as safe for FPV operations when abandoned.

A form of entertainment in which stunt pilots performed tricks, either individually or in groups called flying circuses. Devised to impress people with the skill of pilots and the sturdiness of planes.

BVLOS - Beyond Visual Line Of Sight:
Aircraft that is beyond the ability of the pilot/operator or VO to maintain visual line of sight of the sUAS unaided by any technology other than corrective lenses.

Center of Pressure:
The center of pressure is the point where the total sum of a pressure field acts on a body, causing a force to act through that point. The total force vector acting at the center of pressure is the value of the integrated vectorial pressure field.

CG - Center of Gravity:
A point from which the weight of a body or system may be considered to act. In uniform gravity it is the same as the center of mass.

Civil Infrastructure:
Infrastructure involving anything to do with water, earth or transport.

The fellowship with others, as a result of sharing common attitudes, interests, and goals.

Control Authority:
The amount of response afforded to the pilot’s commands, inherent in any aircraft.

Controlled Flight:
The act of retaining control of any aircraft.

Control Surface:
Aerodynamic devices allowing a pilot to adjust and control the aircraft's flight.

CRSF is a proprietary TBS communication protocol between the Crossfire transmitter and Crossfire receiver that operates in the 868 MHz and 915 MHz frequencies.

Data expressed as series of the digits 0 and 1, typically represented by values of a physical quantity such as voltage or magnetic polarization.

Also known as Exponential, or simply Expo. It reduces the sensitivity near the centre of the stick where fine controls are needed (for Roll, Pitch and Yaw), while retaining the maximum rotation speed at the ends of the stick.

FAA - Federal Aviation Authority:
Federal agency that is primarily responsible for the advancement, safety and regulation of civil aviation.

A system or plan to minimize or prevent damage and safely terminate a flight in the event of signal loss.

FARs -  Federal Air Regulations:
Federal Aviation Administration rules that govern all of aviation in the United States.

FC - Flight Controller:
A package of components including an IMU and a computer to provide automation to selected aspects of the operation such as RTH and flight stabilization.

FHSS - Frequency Hopping Spread Spectrum:
Ability of a radio system to frequency hop between frequencies in a pseudo-random pattern known to the transmitter and receiver to add reliability to the control link and free the signal from any potential interference.

Formation Flight:
The disciplined flight of two or more aircraft under the command of a flight leader usually with the aircraft in close proximity to one another.

First Person View Flight:
Use of an on-board live video camera system to assist in remotely controlling an aircraft by presenting the camera view in front of the aircraft. This allows visual determination of the unmanned aircraft’s flight path, location, orientation, and height.  The innovation of FPV flight was developed to give the operator the perspective of the aircraft within the airspace, despite flying behind and around objects that would otherwise inhibit safe flight of the model aircraft.

Fixed Wing Aircraft:
A heavier than air aircraft with a fixed wing that has wings and uses forward speed to generate lift.

A maneuver that put the aircraft above the critical angle of attack in order to reduce the amount of lift that the wings generate.  Most commonly used when landing an aircraft to reduce forward speed and vertical lift.

Flight Envelope:
The range of combinations of speed, altitude, angle of attack, etc., within which a flying object is aerodynamically stable.

Flight Line:
Pre-planned or agreed upon location of ground personnel involved in the flight operations. Used for parking and servicing of aircraft, often located near or adjacent to launch and landing areas.

Flight Control Modes:
Aircraft with fly-by-wire flight controls require computer-controlled flight control modes that are capable of determining the operational mode (computational law) of the aircraft.

  • Manual or Acro Mode:  The most unaided mode of multirotor flight controllers requiring the pilot’s inputs to remain aloft.

  • Horizon Mode:  A hybrid of self-leveling stabilization mode and manual mode, where the mode of the FC changes at a certain control stick deflection.

  • Stabilization Mode: Self leveling multirotor flight control mode.

Flight Pattern:
A planned route within a given area that allows the aircraft to follow that path repeatedly and consistently.  Allows the operator to become comfortable controlling the aircraft in a predetermined and predictable path. Term is also applicable to aircraft course racing, in which laps are used.

Flight Plan:
A plan consisting of the area or route of flight as well as the estimated duration of the flight.  Includes both distance and altitude

Flight Stabilization:
A mode or feature provided by flight controllers and simple gyros to aid the pilot in control of the aircraft by minimizing the impact of external forces such as wind and changing air currents.

Flight Time:
The maximum time of one flight, allowed by the aircraft’s specifications, typically the limits of its energy source.

Flow State:
In positive psychology, flow, also known colloquially as being in the zone, is the mental state of operation in which a person performing an activity is fully immersed in a feeling of energized focus, full involvement, and enjoyment in the process of the activity.

A system that replaces the conventional manual flight controls of an aircraft with an electronic interface. The movements of flight controls are converted to electronic signals transmitted by wires.

FPV Distance Classifications:

  • Long Range FPV - FPV operations which include flight beyond the visual line of sight of the pilot and the visual observer. Other FPV distances are defined below:

  • Medium Range FPV - FPV operations which reach the limit of BVLOS

  • Short Range FPV - FPV operations contained within 1 square mile (2.58km2)

FPV -  First Person View:  
Use of an on-board live video camera system to assist in remotely controlling an aircraft.

Fresnel Zone:
A cylindrical ellipse drawn between transmitter and receiver. The size of the ellipse is determined by the frequency of operation and the distance between the transmitter and receiver.

Frequency Management:
The process used by FPV pilots to coordinate RF frequencies when flying in groups of 2 or more to avoid interference in signals in both control and video feeds.

A small area through which an aircraft can pass in close proximity.  Often takes a higher degree of skill to pass through a gap cleanly.

GNSS - Global Navigation Satellite System:
A general term describing any satellite constellation that provides positioning, navigation, and timing services.

GPS - Global Positioning System:
A USA owned, satellite-based radio-navigation system.

Ground Effect:
The effect of added aerodynamic buoyancy produced by a cushion of air below a vehicle moving close to the ground.

Ground Station:
The ground based components of the FPV system which provide FPV vision to the pilot.

An activity done regularly in one's leisure time for pleasure.

IBUS is a serial communication protocol used by FlySky.  It uses two way communication to send and receive data.

IMD - Intermodulation Distortion:
The amplitude modulation of signals containing two or more different frequencies, caused by non-linearities or time variance in a system.

IMU - Inertial Measurement Unit:
An electronic device that measures and reports a craft's velocity, orientation, and gravitational forces.

KM - Kilometer:
A unit of measurement equal to 1,000 meters, approximately 0.62 SM, 0.54 NM,

Lighter than Air Aircraft:  
Aircraft such as blimps, balloons, and dirigibles that contain within their structure a lighter-than-air gas that displaces the surrounding air and floats the aircraft.

Mistakes High:
A level of sufficient altitude to allow for recovery of the aircraft in case anything supporting controlled flight fails momentarily. Will generally be stated as a number of mistakes high as in “three mistakes high”.

Multirotor Aircraft:
An aircraft with more than two rotors. Due their relative ease of construction and control, they are frequently used in RC aircraft and UAV projects.

NM - Nautical Mile:
Historically used as mile of measurement at sea and used a Minute of Latitude on a chart. A NM equals approximately 6,000 ft or 1.15 statute miles, SM,

NOTAM - Notice To Airmen:
A notice filed with an aviation authority to alert aircraft pilots of potential hazards along a flight route or at a location that could affect the safety of the flight.

NPRM - Notice of Proposed Rule making:
A notice of proposed rule making (NPRM) is a public notice issued by law when one of the independent agencies of the United States government wishes to add, remove, or change a rule or regulation as part of the rule making process.

OSD - On-Screen Display:
Overlays flight information onto your video feed. It allows you to monitor your telemetry from the UAV status while flying FPV.  Examples would be battery voltage, GPS heading, or altitude.

PCM - Pulse Code Modulation:
PCM is a method used to digitally represent sampled analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications.

The scope or freedom of a control mechanism, its movement without input.

PPM - Pulse Position Modulation:
A PPM signal is used by most transmitters and receivers to transfer information from the transmitter to the receiver. The signal itself is a series of pulses of fixed length.

Pre-Flight Checklist:
A list of aircraft checks that should be performed by pilots and aircrew prior to takeoff.

Prop Wash:
Disrupted and accelerated air existing a prop contributing to any wake

The act of flying any aircraft close to objects, other aircraft or the ground itself. The  term was invented by BASE jumpers and borrowed for FPV including the flight style and culture to go with it.

Setting which defines much much servo throw will be allowed, measured in %.

RC - Radio Control:

  • Radio Controlled: with electronic guidance.

  • Radio Controller: a radio transmitter that sends control commands.

A activity done for enjoyment when one is not working.

Purpose of a component, not strictly necessary to functioning, but included in case of failure in another component.

RF - Radio Frequency:
Electronic signal used for aircraft control link and video image transmission.  Aspects of radio frequency are generally described with the following terms:

  • Channel:  A 'channel' is an agreed-upon set of specific frequencies

  • Band:  A range of frequencies with a specific least frequency and greatest frequency.

  • Frequency:  The vibration of waves, measured per second, at which a radio transmitter or receiver operates.

RFI - Radio Frequency Interference:
A disturbance generated by an external source that affects signal quality.

Risk Mitigation:
A systematic reduction in the extent of exposure to a risk and/or the likelihood of its occurrence. Also called risk reduction.

Proven level of measurement for any system relied upon for controlled flight

RTH - Return to Home:
Return to home will attempt to bring any aircraft currently in flight back to launch location. Launch location is defined as a point where flight controller was armed.

Rx -  Receiver:
A device that converts an electronic signal transmitted through the air into usable information.

Safe FPV Flight Location:
Location that is deemed safe for flight based on risk mitigation.  Generally, there should be no risk of damaging people or property, should be relatively free from RF interference, and be located within airspace that is free from TFR’s.

Safe Operating Distance:
Operation of the aircraft a sufficient distance away from people and property so that any failure of control does not result in damage.

SBUS is a type of serial communication protocols, used by Futaba and FrSky. It supports up to 18 channels using only one signal cable. SBUS is an inverted UART communication signal.

A postulated sequence or development of events.

Feature of robust systems allowing repair and changes

Servo Throw:
The measurement of how far a servo will move when activated by moving the stick on the transmitter.

Situational Awareness:
Is the perception of the surrounding environment and the comprehension how it affects or may affect your operation.

SM - Statute Mile:
A linear measurement equal to 5,280 feet.

(See VO) - Model aviation’s traditional term for the new definition of Visual Observer.

STOL - Short Take Off and Landing:
Aircraft that have short runway requirements.

sUAS - Small Unmanned Aerial System:
An unmanned aerial vehicle weighing less the 55 lbs including the weight of anything attached to or carried by the aircraft and its control systems.

The process of recording and transmitting the readings of an instrument.

TFR - Temporary Flight Restriction:
A type of Notices to Airmen (NOTAM). A TFR defines an area restricted to air travel due to a hazardous condition, a special event, or a general warning for the entire FAA airspace.

A small constant offset applied to a control surface in order to make an aircraft fly correctly.

UAS -  Unmanned Aerial System:
An unmanned aircraft and associated elements (including communication links and the components that control the unmanned aircraft) that are required for the operator to operate safely and efficiently in a national airspace system.

UAV - Unmanned Aerial Vehicle:
An aircraft that is operated without any possibility of direct human intervention from within or on the vehicle.

Under the Hood:
Term used when transitioning from line of sight control to FPV control, either by putting on goggles, or when utilizing a screen.

VLOS - Visual Line Of Sight:
The ability of the operator, or a visual observer co-located and in direct contact with the pilot/operator, to see and maintain visual line of sight of the sUAS unaided by any technology other than glasses or contact lenses.

Visual Line Of Sight Aircraft Operation (LOS Flight):
With vision that is unaided by any device other than corrective lenses, the pilot/operator or the visual observer (if one is used), must be able to see the unmanned aircraft throughout the entire flight in order to:

  • Know the unmanned aircraft location;

  • Determine the unmanned aircraft's attitude, relative altitude, and direction of flight;

  • Observe the airspace for other air traffic or hazards; and

  • Determine that the unmanned aircraft does not endanger the life or property of another.

Throughout the entire flight of the small unmanned aircraft, the ability described above must be exercised by either:

  • The person manipulating the flight controls of the small unmanned aircraft system; or

  • A visual observer.

VO - Visual Observer:
Person who assists the sUAS operator avoid conflicts with manned aircraft and other changes adversely affecting the aircraft’s operating area such as non-participating personnel entering the area, changing flight conditions, etc.

Visual Observer duties:

If a visual observer is used during the aircraft operation, all of the following requirements must be met:

  • The pilot/operator manipulating the flight controls of the small unmanned aircraft system, and the visual observer must maintain effective communication with each other at all times.

  • The pilot/operator must ensure that the visual observer is able to see the unmanned aircraft in the manner specified in (insert VLOS aircraft operating guideline reference # here).

  • The pilot/observer and the visual observer must coordinate to do the following:

    • Scan the airspace where the small unmanned aircraft is operating for any potential collision hazard; and

    • Maintain awareness of the position of the small unmanned aircraft through direct visual observation.

    • Assist in awareness of potential changes adversely affecting the operating area.

VTOL - Vertical Take Off and Land:
The ability to hover, take off, and land vertically.

VTx - Video Transmitter:
A device that transmits video and audio signals from one location to another.

VRx - Video Receiver:
A device that receives and converts airborne video and audio signals into a useable form.

Turbulent air trailing behind an aircraft that can upset the flight of other aircraft entering the disturbed air.

The distance between successive crests of a wave, especially points in a sound wave or electromagnetic wave.