The soaring glossary

56 terms you will hear in your first season, in plain English. Where American and British usage differ — and they differ more than you would expect — both are given, because that is one of the genuinely confusing things about reading soaring material online.

A B C D F G H I L M N O P R S T V W

A

Aerotow: Being towed into the air behind a powered aircraft on a rope, typically to 2,000 or 3,000 feet, then releasing. The most common launch method in the United States. In the UK the towplane is usually called a tug.
Airbrakes: Panels that extend from the wing to increase drag and steepen the descent, used to control the approach and landing. Called spoilers in much US usage. They do not slow the glider down so much as let it come down more steeply at the same speed.

B

Ballast: Weight carried deliberately. Two quite different things share the name. Cockpit ballast is fixed weight added so a light pilot meets the minimum cockpit load. Water ballast is water carried in the wings by cross-country pilots to fly faster between thermals, and it is dumped before landing.
BFR (Biennial Flight Review): A review flight and ground session with an instructor that a US pilot must complete every 24 calendar months to keep exercising the privileges of their certificate. Not a test you pass or fail; a review you complete.
Boundary layer: The lowest part of the atmosphere, stirred by heating from the ground. Its top is roughly where thermals stop climbing, so its depth sets the working height of the day. Forecast products usually plot it directly.

C

Cable break: A winch launch failure where the cable parts, or the launch is otherwise stopped early. Practised deliberately in training. The aerotow equivalent is a rope break.
CFI-G: Certificated Flight Instructor, Glider. The US rating held by someone qualified to teach in gliders. The UK equivalent is a BGA instructor rating, of which there are several levels.
Circuit: The rectangular pattern flown around the airfield before landing: downwind, base, final. Called the pattern in most US usage. Judging it without an engine is much of what pre-solo training is about.
Convergence: A line where two airmasses meet and air is forced upward, often marked by a line of cloud. Can produce lift that runs for tens of miles, which makes it disproportionately valuable for cross-country flying.
Cross-country (XC): Flying away from the home airfield, using lift to get somewhere and back. The point of the sport for many pilots, and the thing badges measure. It brings with it the possibility of landing out.

D

Density altitude: The altitude the air feels like it is at, once temperature and pressure are accounted for. On a hot day a 3,000 ft field can perform like 6,000 ft, degrading both the towplane's climb and the glider's takeoff.
Dolly: A small wheeled cradle that supports a glider's wing or fuselage on the ground. Also, the launch trolley some single-wheel gliders sit on before takeoff.
Downwind: The leg of the circuit flown parallel to the landing direction, with the wind behind. Also used loosely to mean anywhere the wind is taking you away from the airfield, which is a different and more serious matter.

F

Field landing: See landing out. Also called an outlanding, or in UK usage a field landing or land-out. A normal part of cross-country flying, not an emergency, though it is trained for carefully.
Final glide: The last leg home, flown without expecting to climb again. Calculating whether you can reach the airfield with a safe margin is one of the defining skills of cross-country flying, and one of the classic ways to get it wrong.
Flight recorder: A GPS logger that records a flight in a tamper-evident file, used to substantiate badge and record claims. For FAI badges it must be an approved unit, and the approval level required depends on the claim.
Flutter: A destructive vibration that can occur above a certain speed. It is why VNE exists, and why VNE is reduced with altitude on many modern gliders — the limit is really about true airspeed, not indicated.

G

Glide ratio: How far a glider travels forward for each unit of height lost, in still air. A 40:1 glider covers 40 km for each kilometre of descent. Quoted through the air, so wind changes what you actually achieve over the ground.
Ground crew: The people running the launch point — hooking on cables or ropes, holding wingtips, driving the retrieve. Almost always members rather than staff, and where most of a club's volunteer hours go.

H

Hangar rash: Minor damage caused on the ground rather than in the air: a scraped wingtip, a dented fuselage from a trailer. Statistically far more common than damage from flying.

I

IGC file: The standard file format a flight recorder produces, named after the FAI's International Gliding Commission. Contains the GPS trace plus a security record (the G-record) that lets an official observer confirm it has not been altered.

L

L/D: Lift-to-drag ratio, numerically the same as glide ratio. A glider quoted at "L/D 40" travels 40 units forward per unit down, at one particular speed and weight.
Landing out: Landing somewhere other than an airfield, usually a field, because the lift ran out. Routine in cross-country flying and specifically trained for. Followed by a retrieve.
Lift: Any air going up faster than the glider is sinking through it. Comes in three main kinds: thermal, ridge and wave. Not to be confused with the aerodynamic force of the same name.

M

MacCready setting: A number, set on the instrument, representing the rate of climb you expect in the next thermal. It tells you how fast to fly between thermals: expect a strong climb and it pays to push on; expect a weak one and it pays to slow down. Named after Paul MacCready.
Minimum cockpit load: The lightest a pilot (sometimes including parachute) may be in a given glider, placarded per aircraft. Below it the centre of gravity moves aft and spin recovery is degraded. Light pilots fly with approved ballast to meet it, which is entirely routine.

N

Netto: A variometer reading corrected to show what the air is doing, rather than what the glider is doing in it. Useful for deciding whether a patch of air is worth stopping in while flying straight through it.

O

Official Observer (OO): A person appointed by a national association to verify FAI badge and record claims. In the US they must be an SSA member holding at least a B badge with a working knowledge of the Sporting Code. Getting one lined up before the flight is part of a successful claim.
OLC: The Online Contest, where pilots upload flight traces and are scored against others. Popular and motivating, and importantly **not** the same thing as an FAI badge claim, which goes to your national association through an Official Observer.

P

PIC: Pilot in command. The person responsible for the flight, which in a two-seater is not always the person doing the flying.
Polar: The curve describing how fast a glider sinks at each airspeed. Everything about performance comes from it: best glide speed, minimum sink speed, and how fast to fly between thermals. Published polars are measured at a stated wing loading, and yours is probably different.

R

Release: Letting go of the tow rope or winch cable, by pulling the release knob — almost universally a yellow handle. Also the height at which you did so.
Retrieve: Recovering a glider that landed away from the airfield: driving out with the trailer, derigging, and bringing it home. Frequently takes longer than the flight, and is a social obligation as much as a practical one.
Ridge lift: Lift produced when wind is deflected upward by a hill or ridge. Reliable while the wind holds and blows across the ridge, and it works when thermals do not — which makes it valuable early and late in the season.
Rigging: Assembling a glider from its trailer: joining the wings to the fuselage, fitting the tailplane, connecting controls. Derigging is the reverse. Always followed by a positive control check.
Rope break: A launch failure on aerotow, where the rope parts or the tow is otherwise stopped early. Practised at safe height in training so the decision — land ahead, or turn back — is already made before it happens for real.

S

Sailplane: A glider designed for soaring rather than merely gliding. In practice the words are used interchangeably, with "sailplane" more common in US writing and "glider" more common everywhere else.
Sink: Air going down. Also the glider's own rate of descent through still air. Strong sink between thermals is the thing that ruins final glides, and it is far harder to forecast than lift.
Soaring: Staying up, or gaining height, using rising air. A glider without lift simply glides down; soaring is the act of finding and using lift to stay airborne, which is the whole sport.
Solo: Flying alone for the first time, typically after around 60 launches with an instructor, though the real range is 30 to 100. In the US you may fly solo in a glider from age 14. Everyone remembers the date.
Speed to fly: How fast to fly between thermals to make the best average cross-country speed. Faster in sink and headwind, slower in lift and tailwind. The MacCready setting is the input to it.
Spin: An autorotating stall, where one wing is more stalled than the other and the aircraft descends rotating. Recovery is trained and standard, but it depends on the centre of gravity being within limits — which is why minimum cockpit load matters.
Spoilers: See airbrakes. Strictly, spoilers and airbrakes are different devices, but in gliding usage the terms are used for the same thing, with "spoilers" more common in the US.
Stall: What happens when the wing is asked for more lift than its angle of attack can supply, and the airflow separates. It happens at an angle, not a speed — which is why a glider can stall at any airspeed if loaded hard enough in a turn.

T

Thermal: A column or bubble of rising warm air, produced when the sun heats the ground unevenly. The main source of lift in most of the world, and the reason gliding is a summer-afternoon sport in most places.
Total energy (TE): A variometer compensation that removes the false climb you get from simply pulling up and trading speed for height. Without it, the instrument reports a thermal every time you raise the nose.
Tow pilot: The pilot flying the towplane. At most clubs a volunteer member with a power licence and a tow endorsement, and one of the two roles whose absence cancels a flying day.
Towplane: The powered aircraft used for aerotow launching. Called a tug in the UK. Commonly a Piper Pawnee, a Cessna 182 or similar — an aircraft chosen for climb performance rather than speed.
Trial flight: An introductory flight for a non-member, usually with an instructor. Called a discovery flight or intro flight in much US usage. The main way most people first get into a glider.
Turnpoint: A defined geographic point that a cross-country task routes around. Reaching it correctly, and having declared it in advance where the rules require, is what makes a flight count for a badge.

V

Variometer: The instrument showing rate of climb or descent — the single most-watched instrument in a glider. Comes in mechanical and electronic forms, usually with an audio tone so you can listen rather than look.
VNE: Never-exceed speed. On many modern gliders it is reduced with altitude, because the underlying limit is flutter, which depends on true airspeed rather than indicated. The flight manual carries the table.

W

Wave: Standing atmospheric waves formed downwind of a mountain range in strong, stable wind. Produces the smoothest and highest lift in the sport, with altitude records set in it. The rotor beneath it is the opposite of smooth and is treated with great respect.
Winch launch: Being pulled into the air by a cable wound in by a powerful ground-based winch. Much cheaper per launch than aerotow, and much lower — typically 1,000 to 1,500 feet. Common in the UK and Europe, less so in the US.
Wing loading: All-up weight divided by wing area. Higher wing loading means flying faster for the same glide angle, which is why cross-country pilots carry water ballast on strong days and dump it on weak ones.
Wing runner: The person who holds a wingtip level at the start of the launch and runs with it until the ailerons bite. Usually the first job a new member is given, and a good one — it puts you at the launch point talking to people.

Missing a term?

If you heard something at the launch point and could not find it here, tell us what it was. That is exactly how this list should grow — from things newcomers actually got stuck on rather than from a textbook index.

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New to all this?

Our honest guide to a first year covers the questions the glossary does not: age and medical rules, weight limits both ways, how long it takes, what it costs and how safe it is.

Read: learning to fly gliders →