Above ground level (AGL). Height measured from the ground directly beneath the aircraft. Your 400-foot ceiling is an AGL number, which is why flying off the edge of a cliff doesn't buy you altitude.
Acute fatigue. The ordinary tiredness that follows exertion or a short night, and which a good sleep actually fixes.
Administrator. The FAA, in the language of the regulations. When a rule says the Administrator may do something, read it as the agency.
Advection fog. Fog formed when warm, moist air moves over a cooler surface. It needs wind to form and it can sit there all day.
Aeronautical decision-making (ADM). The systematic mental process pilots use to pick the best course of action from a set of circumstances. It's the skill that prevents most accidents, and it's teachable.
Aeronautical knowledge recency. The requirement to have passed a test or completed training within the previous 24 calendar months. Your certificate never expires, but this does.
Air Almanac. The publication that gives the real civil twilight times for a given place and date. Everywhere in the United States except Alaska uses a flat thirty minutes either side of the sun; Alaska uses this instead, because that far north the sun slides along the horizon rather than dropping through it.
Air Defense Identification Zone (ADIZ). Airspace where aircraft must be readily identifiable for national security reasons. The rules live in Part 99.
Air mass. A large body of air with fairly uniform temperature and moisture throughout.
Air traffic control (ATC). The service that separates and sequences aircraft. Its presence is what makes airspace "controlled".
Airman Certification Standards (ACS). The FAA document that lists exactly what the exam may test you on. The blueprint you keep hearing about lives here.
Airman Knowledge Test Report (AKTR). The printed result you walk out with, showing your score and any topic codes you missed. You need it for your application.
Airport beacon. The rotating light at an airport. White and green alternating means a civilian land airport, white and yellow means a water airport, green with yellow and white means a heliport, and two quick white flashes then green means military.
Airport data block. The cluster of text printed next to an airport symbol on a chart, giving the name, identifier, frequencies, field elevation in feet MSL, lighting, and the longest runway in hundreds of feet.
Airspeed. How fast the aircraft is moving through the air around it. Not the number the 87 knot limit cares about, which is groundspeed. On a windy day the two can be twenty or thirty knots apart.
Airworthiness certificate. An FAA certificate issued under Part 21 stating that a specific aircraft meets an approved design. It's the entire basis of Category 4.
Alert area. Charted airspace with a high volume of pilot training or unusual activity. You may fly there, and everyone in it shares responsibility for not hitting anyone.
Altimeter setting. The local barometric pressure, given in inches of mercury, that lets an altimeter read true altitude above sea level. In a METAR it's the number after the letter A.
Anti-authority. The hazardous attitude that says "don't tell me what to do". The antidote is to follow the rules, because they're usually right.
Anti-collision lighting. Lighting on your aircraft visible for at least 3 statute miles, with a flash rate sufficient to avoid a collision. Required at night and during civil twilight.
Antidote. The specific sentence you say back to yourself when you catch a hazardous attitude. The exam wants the exact words.
Approved third party provider. One of the flight-planning companies the FAA has authorized to plug into LAANC on your behalf. You don't send an airspace request to the FAA yourself; you send it through one of these, usually as an app on your phone.
ASOS (Automated Surface Observing System). An automated weather station broadcasting continuous observations on its own frequency. Not all of them sit at airports.
ATIS (Automatic Terminal Information Service). A looping recorded broadcast at busier airports carrying weather, the active runway, and notices. It's identified by a phonetic letter and updated hourly or when things change.
Attitude-only mode. What your aircraft falls back to when it loses GPS. It keeps itself level but no longer holds position, so it drifts with the wind and you fly it manually.
AWOS (Automated Weather Observing System). A close cousin of ASOS, providing the same kind of continuous automated weather report.
Base leg. The short leg of the traffic pattern flown at right angles to the runway, between downwind and final.
Broken (BKN). A sky cover code meaning 5 to 7 eighths of the sky is covered. A broken layer counts as a ceiling.
Calendar month. A month counted to its last day rather than to an anniversary. Training completed on 3 March 2026 keeps you current through 31 March 2028, and that free stub at the end is yours.
Call sign. The identifier a pilot uses on the radio. A United States registration number starts with N, spoken as "November".
Careless or reckless operation. Operating in a way that endangers the life or property of another, prohibited by 107.23. It's the catch-all the FAA reaches for when nothing more specific fits, and it's not waivable.
Category 1. The over-people route based purely on weight: 0.55 pounds or less on takeoff including everything attached, with no exposed rotating parts. No paperwork at all.
Category 2. The over-people route based on an 11 foot-pound kinetic energy threshold, requiring a declaration of compliance and a label.
Category 3. The over-people route based on a 25 foot-pound threshold. More energy allowed, much tighter leash, and no open-air assemblies ever.
Category 4. The over-people route for aircraft holding an airworthiness certificate, flown inside the limitations of an approved Flight Manual.
Ceiling. The height of the lowest broken or overcast layer. Scattered and few layers don't count, no matter how gloomy they look.
Center of gravity (CG). The point where the aircraft's weight is effectively concentrated. On a multirotor it wants to sit at the geometric center of the rotors, and an offset one costs you endurance, stability, and control authority.
Certificate of Aircraft Registration. The document proving a specific airframe is registered. It costs $5, is issued per aircraft under Part 107, and expires 3 years after issue.
Certificate of waiver. The document the FAA issues when it lets you deviate from one of the ten waivable rules, on terms it sets.
Certificate of waiver or authorization (COA). The permission instrument issued to an agency rather than to an individual, used by public aircraft operations such as some fire and police flying. If an exam question mentions a public aircraft operation, this is the phrase it's fishing for.
Chart Supplement. The FAA publication, formerly the Airport/Facility Directory, holding the full detail on every airport: runway dimensions, all frequencies, tower hours, traffic pattern altitudes, and which runways use right traffic.
Chronic fatigue. Fatigue built up over weeks or months. One good night's sleep doesn't touch it, which is what makes it dangerous.
Civil twilight. The half hour before official sunrise and the half hour after official sunset, except in Alaska, where the Air Almanac defines it.
Class A. Controlled airspace from 18,000 feet MSL up to flight level 600, flown entirely under instrument flight rules. You can't legally get there, so it's always a wrong answer.
Class B. The busiest airspace, surrounding major airports, typically from the surface to about 10,000 feet MSL in widening shelves. Drawn with a solid blue line. Authorization required.
Class C. Airspace around moderately busy towered airports with radar service, usually an inner ring and an outer shelf. Drawn with a solid magenta line. Authorization required.
Class D. Airspace around a towered airport without radar, roughly circular and about 4 nautical miles across, existing only while the tower is open. Drawn with a dashed blue line. Authorization required.
Class E. All the controlled airspace that's not A, B, C, or D. It shows up as surface areas, as floors at 700 or 1,200 feet AGL, and from 14,500 feet MSL upward.
Class E surface area. The one shape of Class E that reaches the ground, designated for an airport with instrument approaches but no operating tower. Drawn with a dashed magenta line, and the only Class E that needs authorization.
Class G. Uncontrolled airspace, from the surface up to the base of the overlying Class E. Most of your flying happens here, and it needs no permission from anybody.
Closed or restricted access site. A site where access is controlled and everyone present has been told a drone may fly over them. It unlocks parts of Category 3 and the moving-vehicle rule.
Cloud clearance. The minimum distance you must keep from a cloud: 500 feet below it and 2,000 feet horizontally from it. There's no figure for flying above one.
Code of Federal Regulations (CFR). The shelf where all federal rules live, sorted by subject. Title 14 is the aviation shelf, and Part 107 is the drone book on it. The current text is free at eCFR.gov.
Cold front. The boundary where a cold air mass shoves under a warmer one. It moves fast, brings a narrow band of violent weather, and clears quickly.
Color tinting. The bands of shading on a sectional chart that fill the space between contour lines, darker for higher ground. The legend gives the elevation band each tint stands for.
Condition for safe operation. The standard your aircraft must meet before and during every flight. Part 107 gives you no maintenance schedule and no logbook requirement, so this judgment is yours.
Cones. The receptors packed into the center of your eye that give you color and fine detail. They need good light, which is why the middle of your vision goes nearly blind at night.
Contour line. A line on a chart joining points of equal ground elevation, with color tinting showing which band of terrain you're looking at.
Control authority. How much control you've left over the aircraft. Load it badly or heavily and you've less of it, which is when a gust starts making the decisions.
Control link. The radio link between your control station and your aircraft. Checking it works properly is one of the six preflight duties.
Control station. The interface you use to fly, meaning the controller and whatever it's plugged into. A standard remote ID aircraft broadcasts its location.
Control tower. The facility issuing instructions and clearances at a towered airport. On a chart its frequency appears as CT followed by the number.
Controlled airspace. Airspace where air traffic control service is provided, meaning Classes A, B, C, D, and E. It doesn't mean closed, and it doesn't mean you need permission everywhere in it.
Controlled firing area (CFA). An area containing hazardous activity that's suspended the moment a spotter sees an aircraft coming. Because the activity stops rather than you being excluded, it's not charted.
Controlling agency. The air traffic facility that has authority over a piece of special use airspace when the using agency isn't using it.
Corrective lenses. Glasses or contact lenses. Nothing else counts as unaided vision under 107.31, which is what rules out binoculars, zoom lenses, and goggles.
Crew resource management (CRM). Using every resource available to you, human, mechanical, and informational, rather than trying to hold the whole operation in your own head.
CTAF (Common Traffic Advisory Frequency). The frequency pilots use to announce themselves at an airport with no operating tower. On a chart it's the frequency followed by a solid circle containing a white letter C.
Cumulus stage. The first stage of a thunderstorm, defined by a continuous updraft.
Currency. Your permission to actually use the certificate you hold, maintained by completing the free recurrent training within the previous 24 calendar months. The certificate never expires. This does, and nobody sends a reminder.
DECIDE model. A six-step decision loop: Detect, Estimate, Choose, Identify, Do, Evaluate. It gives you something to run when a situation changes and your instinct is to freeze.
Declaration of compliance. The FAA-accepted filing that certifies a particular aircraft model meets a category's requirements. It says that the aircraft complies, where a means of compliance says how.
Dehydration. Fluid loss that brings headache, dizziness, cramps, and impaired judgment. It creeps up on long outdoor jobs, and heatstroke is where it ends.
Density altitude. Pressure altitude corrected for nonstandard temperature. It's the altitude your aircraft thinks it's at, and high, hot, and humid all push it up.
Dew point. The temperature air must cool to before it becomes saturated. When it's within about 2 degrees Celsius of the actual temperature, expect fog or low cloud.
Direct participant. Someone genuinely involved in your operation, such as your visual observer or a crew member. You may fly over them, and you owe them a briefing.
Direct supervision. The condition under which an uncertificated person may fly your aircraft, and only alongside your ability to take control immediately. Both halves are required.
Displaced threshold. A marked portion of runway that may be used for taxi and takeoff but not for landing.
Dissipating stage. The final stage of a thunderstorm, defined by a predominant downdraft.
Downwind leg. The leg of the traffic pattern flown parallel to the runway in the opposite direction to landing.
Emergency status. An indication that something has gone wrong with the aircraft. A standard remote ID aircraft broadcasts it, a broadcast module doesn't, and that's one of the three differences.
Endurance. How long the aircraft can stay airborne on the power it has. Weight, wind, and temperature all eat into it.
Exposed rotating parts. Propellers or rotors that would lacerate human skin on impact. Categories 1, 2, and 3 all require that there are none.
External surface. The outside of your aircraft, where your registration number must be legibly displayed. Inside a battery compartment stopped being acceptable in 2019.
FAA DroneZone. The FAA's online portal for registering aircraft, filing safety event reports, and applying for waivers and the airspace authorizations LAANC cannot handle.
FAA Tracking Number (FTN). The personal identifier IACRA generates for you. You need it before you can book the test.
FAA-Recognized Identification Area (FRIA). A defined patch of ground where aircraft without remote ID may fly, provided both the aircraft and the pilot stay inside its boundaries.
Few (FEW). A sky cover code meaning 1 to 2 eighths covered. It never constitutes a ceiling.
Final approach. The last leg of the traffic pattern, lined up with the runway and descending to land.
Final authority. The remote pilot in command's position in law. Whatever anyone else on site thinks, the decision is yours and so is the consequence.
First person view (FPV). Flying from the aircraft's camera feed. It doesn't satisfy visual line of sight, so it's legal only where a visual observer keeps unaided eyes on the aircraft.
Flight Manual. The approved document that sets out how a Category 4 aircraft may be operated. If its limitations forbid flying over people, no amount of wishing changes that.
Flight review. The recurring check a Part 61 pilot completes under 61.56. Holding one current is what lets a manned pilot take the online training instead of this exam.
Flight visibility. How far you can see from your control station, measured as the average slant distance at which prominent objects can be seen and identified. Your minimum is 3 statute miles.
Fly-away. A loss of control where the aircraft ignores your inputs and doesn't run its programmed lost link procedure. Worse than a lost link, because nobody knows where it's going.
Foot-pound. The unit of kinetic energy behind the Category 2 and Category 3 thresholds. Think of it as a measure of how hard the aircraft would hit.
Form 8710-13. The application you complete in IACRA after you pass. Submitting it's what triggers the TSA background check.
Front. The boundary where two air masses meet. Weather happens at boundaries.
Geometric altitude. Altitude measured from a fixed reference such as the ellipsoid used by satellite navigation, rather than from air pressure. Remote ID broadcasts it.
Global Positioning System (GPS). The satellite network your aircraft uses to know where it is. Lose it and most drones drop into attitude-only mode, which holds the aircraft level but stops it fighting the wind, so it drifts.
Groundspeed. Your speed over the ground, which is airspeed plus or minus the wind. Your 87-knot limit is a groundspeed limit, so a strong tailwind can make a legal aircraft illegal.
Group obstruction. Two or more obstructions drawn joined together on a chart. The height printed belongs to the tallest one in the group.
Hazard. A condition or circumstance that could contribute to an unexpected event. The power line is the hazard.
Hazardous attitude. One of five recognized patterns of thinking that reliably lead pilots into trouble, each with its own antidote.
Hazardous material. Material defined as hazardous in 49 CFR 171.8. Your aircraft may not carry it, ever, and no waiver exists.
Heatstroke. The severe end of heat and fluid stress, and a genuine medical emergency. Stop the operation.
Heliport. A landing area for helicopters, with its own chart symbol.
Hyperventilation. Breathing too fast or too deeply, usually from stress, which blows off too much carbon dioxide. It produces dizziness and tingling that can be mistaken for hypoxia, and slowing your breathing fixes it.
Hypoxia. Insufficient oxygen reaching the body's tissues. Its early symptoms overlap with hyperventilation, which is why the two get confused.
IACRA. The Integrated Airman Certification and Rating Application system at iacra.faa.gov. It generates your FAA Tracking Number and hosts your certificate application.
Icing. Ice forming on the aircraft in cold conditions with visible moisture. On rotors it ruins the aerodynamic shape, adds weight, and throws the balance out.
IMSAFE. A six-item self-check before you fly: Illness, Medication, Stress, Alcohol, Fatigue, Emotion. It works only if you answer honestly.
Impulsivity. The hazardous attitude that says "do something quickly". The antidote isn't so fast, think first.
In-flight emergency. A situation requiring immediate action, during which 107.21 lets you deviate from any rule of Part 107 to the extent necessary. You may have to file a written report afterward, but only if asked.
Invulnerability. The hazardous attitude that says "it won't happen to me". The antidote is that it could happen to me.
Kinetic energy. The energy an object carries because it's moving. It's what Categories 2 and 3 measure, and it's why speed matters as much as mass.
Knot. One nautical mile per hour, and the unit aviation uses for almost everything that moves. Your groundspeed limit is 87 of them, which the regulation itself notes is the same as 100 miles per hour.
Knowledge test. The Unmanned Aircraft General, Small exam itself. Sixty scored questions, five unscored, 120 minutes, three answer options.
LAANC. The Low Altitude Authorization and Notification Capability, which grants airspace authorizations automatically through approved providers, usually in seconds.
Lapse rate. The rate at which temperature drops as you climb. An unstable lapse rate is one of the three ingredients a thunderstorm needs.
Latitude. Distance north or south of the equator, from 0 to 90 degrees, on lines that stay parallel. In the continental United States it's always north.
Left traffic. The standard direction of turns in an airport traffic pattern. Right traffic is the exception and is noted on the chart and in the Chart Supplement.
Lithium polymer (LiPo). The battery chemistry almost every drone flight pack uses. It stores a remarkable amount of energy in a soft pouch, which is why your aircraft flies for half an hour and also why a damaged pack deserves real caution.
Longitude. Distance east or west of the prime meridian, from 0 to 180 degrees, on lines that converge at the poles. In the continental United States it's always west, and it increases as you go west.
Lost link. Loss of the radio link between control station and aircraft. Most aircraft can be set to hover, return home, or land, and you should know which yours will do before you take off.
Macho. The hazardous attitude that says "I can do it", usually to an audience. The antidote is that taking chances is foolish.
Mature stage. The middle and most dangerous stage of a thunderstorm, beginning when rain starts falling from the cloud base, with updrafts and downdrafts running side by side.
Maximum elevation figure (MEF). The large bold number in the middle of each chart quadrangle, in thousands and hundreds of feet MSL, showing the highest known thing in that box. A large 5 above a smaller 3 means 5,300 feet MSL.
Maximum takeoff weight. The heaviest your aircraft may be when it leaves the ground, including everything on board or attached. The regulatory ceiling is less than 55 pounds; your manufacturer's figure will be far lower.
Mean sea level (MSL). Altitude measured from sea level rather than from the ground beneath you. Every boxed airspace figure on a chart is MSL, and mixing this up with AGL fails more candidates than anything else.
Means of compliance. The test, analysis, or inspection method that shows how an aircraft meets a category's requirements. It's the method; the declaration of compliance is the claim.
Message elements. The pieces of information a remote ID broadcast contains. Eight for a standard aircraft, seven for a broadcast module.
METAR. A routine surface weather observation, issued hourly, reporting what the weather is doing right now.
Microburst. A small, violent downdraft producing severe wind shear, with downdrafts over 6,000 feet per minute and winds over 45 knots. It typically lasts 5 to 15 minutes, which is plenty.
Military operations area (MOA). Charted airspace set aside for military training, named rather than numbered. You may enter it, but be extremely careful when it's active.
Military training route (MTR). A charted corridor for high-speed military flying, drawn as a thin gray line labeled IR or VR. Four digits means it includes segments at or below 1,500 feet AGL; three digits means it stays above.
National airspace system (NAS). The whole network of airspace, navigation aids, airports, rules, and people that keeps American aviation working. You're now part of it.
National Transportation Safety Board (NTSB). The independent federal agency that investigates transportation accidents. One of the four parties whose authorized representative may ask to see your certificate.
Nautical mile. A unit of distance equal to about 1.15 statute miles, used for airspace dimensions. Your visibility minimum, confusingly, is in statute miles.
Night adaptation. The roughly 30 minutes your eyes need to become fully sensitive in the dark, and which one glance at a bright white screen destroys.
Non-towered airport. An airport with no operating control tower, where pilots coordinate among themselves on a common frequency.
NOTAM. A Notice to Air Missions, carrying temporary information such as flight restrictions, closed runways, and laser activity. Temporary flight restrictions live here, not on your chart.
Obstruction. A charted tall structure, marked with its height above sea level on top and its own height in parentheses below. Anything 1,000 feet AGL or taller gets a bigger symbol.
Off-center viewing. Looking about 5 to 10 degrees to the side of what you're trying to see at night, so the light lands on the rods rather than the near-blind center of your vision.
On notice. The condition where everyone at a site has been told that a drone may fly over them. It's what turns a location into a closed or restricted access site.
Open-air assembly. A gathering of people out in the open, with no covered structure over them. Category 3 may never fly over one, and the other categories may only with remote ID.
Overcast (OVC). A sky cover code meaning all 8 eighths of the sky are covered. It counts as a ceiling.
Part 107. The rulebook for flying a small drone in American airspace for any reason other than pure fun. It covers registration, airman certification, operation, and eligibility to fly over people.
Part 48. The registration rule for small unmanned aircraft. It sets the five dollar fee, the three year term, and the requirement that the identifier be displayed on an external surface.
Pattern altitude. The height at which aircraft fly the traffic pattern, commonly 1,000 feet above airport elevation for light aircraft.
Payload. Anything you carry or attach: cameras, gimbals, mounts, sensors. It counts toward your takeoff weight and it must be secure.
Person manipulating the flight controls. Whoever is physically flying at that moment. They may or may not be the remote pilot in command, and the responsibility doesn't move with the controller.
Phonetic alphabet. Alfa through Zulu, used so that letters survive a bad radio. Numbers are spoken individually, with nine as "niner", three as "tree", and five as "fife".
Preflight familiarization. The set of checks and assessments 107.49 requires before every flight, covering the environment, the briefing, the links, the power, the payload, and category eligibility.
Pressure altitude. Altitude read with the altimeter set to 29.92 inches of mercury. It's the starting point for working out density altitude.
Preventive maintenance. Simple, routine upkeep such as replacing propellers or cleaning contacts. Part 107 doesn't schedule it for you, but Category 4 does.
Prior authorization. Permission from air traffic control to operate in Class B, C, or D airspace, or in a Class E surface area. The word "prior" means before you take off, not while climbing.
Prohibited area. Charted airspace where flight is prohibited outright, protecting a site of national significance. Designated with a P and a number, and there's no way in for you.
PSI Services LLC. The company that administers FAA knowledge tests at affiliated test centers. You book through them, you sit the exam in their room, and they hand you the score report on the way out.
Radiation fog. Fog that forms on clear, calm nights as the ground cools the air above it. It settles into low ground and usually burns off after sunrise.
Recurrent training. The free online course that resets your 24 calendar month currency. It's training, not a test, and you don't reapply for anything.
Remote identification. The requirement that your aircraft broadcast who and where it is throughout the flight. Think of it as a license plate that shouts.
Remote identification broadcast module. A bolt-on device that adds remote ID to an aircraft that lacks it, broadcasting seven message elements and requiring you to keep the aircraft in sight yourself.
Remote pilot certificate. The credential this exam earns you, formally a remote pilot certificate with a small UAS rating. It doesn't expire.
Remote pilot in command (remote PIC). The person designated before or during a flight who is directly responsible for it and is its final authority. Every operation has exactly one.
Resignation. The hazardous attitude that says "what's the use?". The antidote is that I am not helpless, I can make a difference.
Restricted area. Charted airspace containing hazards you can't see, such as artillery or missile activity. You may enter only with permission from the using or controlling agency, which isn't an FAA waiver.
Right of way. Who gives way to whom. Your aircraft yields to everything, always, and may never pass over, under, or ahead of another aircraft unless well clear.
Risk. The assessment of how bad a hazard could actually be, taking likelihood and consequence together.
Risk management. The process of spotting hazards, judging the risk each one carries, and deciding what to do about them.
Rods. The receptors outside the center of your eye. They see no color, but they're far more sensitive in low light, which is why night vision lives in your peripheral view.
Safety defect. A known problem with an aircraft that undermines its category eligibility. Categories 2 and 3 require that there are none.
Safety event reporting. The duty under 107.9 to report certain events to the FAA within 10 calendar days. It was renamed from accident reporting in December 2022, and it's not waivable.
Scattered (SCT). A sky cover code meaning 3 to 4 eighths covered. It doesn't constitute a ceiling.
Seaplane base. A water landing area, with its own chart symbol.
Sectional chart. The detailed aeronautical map covering a region of the country, showing airspace, terrain, obstructions, and airports. Learning to read one is the highest-value skill you can build.
Security Identification Display Area (SIDA). A controlled part of an airport where security badges are required. Your remote pilot certificate gives you no right of access to one.
Segmented circle. The ground marking at an airport that shows runway alignment and which way the traffic pattern turns.
Self-test. The check a standard remote ID aircraft runs on its own broadcast equipment before takeoff. If it fails, the aircraft isn't supposed to be able to take off.
Session ID. A rotating, privacy-preserving alternative to broadcasting your aircraft's serial number. Only standard remote ID aircraft can use one.
Shelf. A step in the layered structure of Class B or Class C airspace. Standing under a shelf isn't the same as being inside it, and the boxed figures tell you where the floor is.
Situational awareness. An accurate picture of everything affecting your operation right now: weather, battery, people, traffic, and how much daylight is left.
Sky cover. How much of the sky is covered by cloud, reported in eighths as SKC or CLR, FEW, SCT, BKN, or OVC.
Small UAS rating. The rating attached to your remote pilot certificate, saying what kind of aircraft you may fly.
Small unmanned aircraft. An unmanned aircraft weighing less than 55 pounds on takeoff, including everything on board or otherwise attached. That last phrase turns up again and again.
Small unmanned aircraft system (small UAS). The aircraft plus everything needed to fly it safely: the control station, the communication links, and the control components.
Sparsely populated area. An area with few people in it, judged against the situation rather than by a number. It's one of the two conditions for flying from a moving vehicle.
SPECI. A special weather observation issued between the routine hourly ones because something changed materially.
Special use airspace. Airspace set aside for activity that has to be kept apart from ordinary flying: prohibited, restricted, warning, alert, military operations, and controlled firing areas.
Spot elevation. A dot on a chart with a number beside it, giving the elevation of that exact point in feet MSL.
Stable air. Air that resists vertical motion. It gives you stratus cloud, smooth flying, steady drizzle, and poor visibility.
Standard atmosphere. The reference conditions used for performance figures: 15 degrees Celsius and 29.92 inches of mercury at sea level, with temperature falling about 2 degrees Celsius per 1,000 feet.
Standard remote identification unmanned aircraft. An aircraft with remote ID built in from the factory, broadcasting all eight message elements from takeoff to shutdown.
Statute mile. The ordinary mile, 5,280 feet. Your visibility minimum and your anti-collision lighting requirement are both in statute miles.
Steam fog. Fog that forms when cold air moves over warmer water, rising off the surface like a kettle.
Structure exception. The rule that lets you exceed 400 feet AGL by climbing up to 400 feet above a structure, but only while you stay within a 400-foot radius of it. Both conditions have to hold.
Sustained flight. Staying over something rather than passing across it. It's the word that separates crossing a road from loitering above it.
TAF. A Terminal Aerodrome Forecast, covering roughly a 5 statute mile radius around an airport for the next 24 to 30 hours. It forecasts; a METAR reports.
Take-off location. Where the aircraft left the ground. A broadcast module reports this instead of your control station location, because it has no way of knowing where you are.
Takeoff weight. What the aircraft weighs the moment it leaves the ground, batteries, payload, mounts, and all.
Tamper resistance. The requirement that standard remote ID aircraft be built so the broadcast function is hard to disable.
Task management. Deciding what to do first, and what can wait, so you're not trying to do everything at the worst possible moment.
Temporary flight restriction (TFR). A restriction that appears at short notice for disasters, airshows, sporting events, presidential movement, or space operations. It's published by NOTAM and never printed on a chart.
Testing supplement. The book of charts, figures, and legends the test center gives you. Chart images are moving into the questions themselves, so treat the supplement as a convenience rather than a plan.
Tetrahedron. A wedge-shaped wind indicator at an airport that points into the wind.
Thermal runaway. A lithium battery failure where one cell overheats and drives its neighbors to fail in turn. It makes its own oxygen, so smothering doesn't work and it can reignite after it appears to be out.
Time mark. The UTC timestamp in a remote ID broadcast, saying exactly when the reported position was true.
Towered airport. An airport with an operating air traffic control tower issuing instructions and clearances. Drawn in blue on a sectional chart. The opposite is a non-towered airport, drawn in magenta.
Traffic pattern. The standard rectangular circuit manned aircraft fly around a runway, with five legs: departure, crosswind, downwind, base, and final.
Transportation Security Administration (TSA). The agency that runs the security vetting on your certificate application. The check happens when you apply in IACRA, not when you book the test and not at the test center.
TRUST. The Recreational UAS Safety Test, which recreational flyers take. It's not a certificate, it never becomes one, and it permits no commercial work.
UAS Facility Map. The FAA's published grid showing the maximum altitude at which LAANC can approve a flight in each square of controlled airspace.
Uncontrolled airspace. Airspace where no air traffic control service is provided, which means Class G.
UNICOM. A non-government radio station at an airport, usually run by the fixed base operator, giving advisory information such as wind and the active runway. It's a service; CTAF is a frequency designation.
Unique identifier. The registration number assigned to your aircraft, which must be legibly displayed on an external surface and stay attached for the whole flight.
Unmanned aircraft. An aircraft operated with no possibility of anyone intervening from on board.
Unmanned Aircraft General, Small (UAG). The full name of the knowledge test you're studying for. Worth knowing exactly, because you have to pick it out of a long list of similarly named FAA tests on the booking site.
Unstable air. Air that rises readily. It gives you cumulus cloud, turbulence, showers, and excellent visibility.
Upslope fog. Fog formed when moist air is pushed up rising terrain and cools as it climbs.
Using agency. The organization that actually conducts the activity inside a piece of special use airspace, and the one whose permission a restricted area may require.
Validation question. One of the five unscored questions mixed into your 65 while the FAA tries them out for future exams. Nothing on screen marks them, they eat your clock, and they're thrown away afterward. An unfamiliar question is not proof your preparation failed.
Visual line of sight. The requirement to keep your aircraft visible throughout the flight with unaided vision. It's the rule that quietly explains most of the other rules.
Visual observer. A person you designate to help see and avoid other traffic and obstacles. They extend who is watching, not how far the aircraft may go.
Warm front. The boundary where warm air slides slowly over cooler air. It brings widespread stratus, long periods of steady rain, poor visibility, and often fog.
Warning area. Charted airspace starting 3 nautical miles off the coast, containing activity hazardous to aircraft. It's a warning rather than a restriction because it sits over international waters.
Well clear. Far enough from another aircraft that there's no risk of collision. Part 107 gives no number for it, which is deliberate.
Wind shear. A sudden change in wind speed or direction over a short distance. A microburst is the extreme version.
Wind sock. The fabric cone at an airport that fills with the wind and points downwind. How fully it extends tells you the strength.
Wind tee. A ground indicator shaped like a small aircraft that points into the wind.
Zulu time. Coordinated Universal Time, on a 24-hour clock, used for METARs, TAFs, NOTAMs, and sunset tables. Convert it carefully, because getting it wrong is a tidy way to end up flying at night without meaning to.