Gliding instruments speak in abbreviations. A screen can tell you the netto, the required efficiency, the AIRAC date and the ENL trace without ever explaining what any of them mean, and the manual that would explain it is in the hangar. This is the plain-English version: the words you meet on an LX navigation screen, in its setup menus and in the paperwork after a flight.
Terms are grouped by where they come up rather than in one long alphabet, and sorted alphabetically inside each group. Each entry is deliberately short. Where a term has real theory behind it, the entry ends with a link to the LX Academy article that does the explaining properly.
Flying and performance
Ballast
Water carried in the wings, and sometimes in a tail tank, to raise the wing loading on a strong day. It shifts the polar to higher speeds — the same glide angle, flown faster — at the cost of a worse climb in weak lift. See ballast and when to carry it.
Bugs
A percentage degradation you enter to tell the computer that the wings are dirty, wet, or otherwise not the ones the polar was measured on. It flattens the assumed performance, so final glides come out more conservative rather than optimistic. See polar degradation.
Current and required glide ratio
Current glide, sometimes labelled efficiency, is your ground speed divided by your sink rate right now. Required glide is what you would need to reach the selected point, reserve altitude included. When current is comfortably better than required, the glide is coming in. See the final glide.
Final glide and dynamic final glide
Final glide is the last leg flown as a computed glide to the finish or the airfield. When the destination is a task finish line, LX computers calculate it dynamically: they expect you to cross the line at 27 m/s (97.2 km/h) and to convert any speed above that into height with a pull-up. Fly straight through fast without pulling up and you will arrive below the computed glide. See dynamic final glide.
Flap schedule
The table of flap positions against airspeed for your glider, held in the instrument so it can prompt the right setting as the speed changes. With a flap sensor fitted, the instrument also knows which position you are actually in. See flaps and the polar.
MacCready
The climb rate you expect in the next thermal, set by you. It is the one number that drives both speed to fly and final glide: set it high and the computer tells you to press on, set it to zero and it tells you to fly for maximum distance. See the polar and MacCready.
Polar
Your glider's sink rate as a function of airspeed — the performance model underneath every gliding calculation the instrument makes, from netto to final glide. It is measured for a clean glider at a stated mass, which is why ballast and bugs each get their own correction. See the polar and MacCready.
Reserve altitude
The height added on top of the arrival altitude in every final-glide calculation, so that "on glide" means "on glide, plus a cushion". It influences the result more strongly than pilot, copilot or ballast mass, so set it to a number you are happy with before take-off rather than in the circuit.
Speed to fly (STF)
The optimal cruise speed for the current MacCready setting, mass and air mass: faster through sink, slower through lift. The instrument shows it as a target speed, or as a command to push or pull. See the polar and MacCready.
Turnpoint, task and AAT
A turnpoint is a point you must reach, or a sector you must enter. A task is the ordered list of them. An Assigned Area Task replaces the points with large areas, so how deep you fly into each one, and the time you take, become the things you manage. See flying the task.
Weight and balance (W&B)
Masses, lever arms, and the centre of gravity that results — the check that says whether the aircraft as loaded today sits inside its envelope. The computer keeps the arms and warns you when the loading falls outside them. See weight and balance.
Wing loading
All-up mass divided by wing area, usually in kg/m². It is the number ballast changes and the number a polar is quoted at: higher loading buys speed for the same glide angle and pays for it in the climb. See ballast and when to carry it.
Air data and altitude
AGL
Height above ground level: your altitude minus the elevation of the terrain beneath you, taken from the instrument's terrain data. It is a computed number, not a measured one, and it is only as good as that data. See the altitudes you fly.
AHRS
Attitude and Heading Reference System — the gyro, accelerometer and magnetometer set that produces an artificial horizon. It is the sensor package behind the PFD page, and on smaller instruments it arrives as an accessory module on the CAN bus. See how an AHRS works and compass and magnetometer.
GNSS
Global Navigation Satellite System: the family name covering GPS, Galileo, GLONASS and BeiDou together. It supplies position, ground speed, track and a GPS altitude that owes nothing to pressure or to your altimeter setting. See GNSS.
IAS, CAS and TAS
Indicated airspeed is what the pitot-static system reads, calibrated airspeed is that corrected for installation error, and true airspeed is what you are actually doing through the air — the gap widening with altitude. The wing cares about IAS; the navigation computer cares about TAS. See indicated, calibrated and true.
QNH, QNE and QFE
Three pressure references for the same altimeter. QNH is set so it reads altitude above mean sea level, QFE so it reads zero on your airfield, and QNE is what the altimeter reads with the standard 1013.25 hPa set — the figure flight levels are built on above the transition altitude. See the altitudes you fly.
VA, VNO and VNE
Manoeuvring speed, maximum normal operating speed and never-exceed speed, all read as indicated airspeed — but check the flight manual: for most gliders VNE is a true-airspeed limit, so the indicated speed you may not exceed falls with altitude. Above VNO you fly only in smooth air, and above VA full control deflections are no longer safe. See gust loads.
The variometer
Averager and integration time
The averager shows the mean climb over the last few seconds; the integration time is the length of that window. A short window tells you about this part of the thermal, a long one about the thermal as a whole. See netto, relative and the averager.
Dead band
The range around zero in which an indication asks nothing of you. On the speed command it is the window where neither push nor pull is commanded; the silence settings below are its audible equivalent.
Filter
How hard the vario damps changes in pressure. A small value is quick and shows every twitch of the air; a large value is smooth and slow to react, levelling out the small vertical movements. There is no correct setting, only the one that suits how you read a needle. See filters and vario lag.
Max circling speed
The airspeed above which the vario stays silent in speed-command mode, so that a fast cruise does not fill the cockpit with noise you cannot act on.
Netto
The vertical speed of the surrounding air mass: the vertical speed the vario measures, plus the sink rate your glider has at that airspeed, taken from the polar. It answers "is this air going up", not "am I going up". See netto, relative and the averager.
Relative netto
Netto minus the sink rate you would have while circling — what you would climb if you stopped here and turned. On LX instruments it is netto minus 0.7 m/s, and it is sometimes called super netto. See netto, relative and the averager.
SC (speed command)
The vario mode in which the needle stops reporting climb and starts telling you to fly faster or slower for the MacCready you have set. Switching between vario and SC can be manual on a stick button, automatic above a set speed, or automatic on detected circling — and circling is declared after a heading change of at least 5° per second sustained for eight seconds — at a normal thirty-second turn, about a third of a circle.
TE and TE level
Total energy compensation removes the climb and sink you create yourself with pull-ups and push-overs, so the vario reports the air rather than the stick. It comes either from a TE probe in the fin, or, via the TE level setting, from an electronic calculation that needs no probe at all. See total energy.
Thermal assistant
The page or overlay that plots the lift found around your last circle as a ring, so you can see which side of the turn was strongest and shift the circle towards it. See centring a thermal and where lift comes from.
Vario silence and SC silence
Two bands in which the instrument deliberately says nothing: vario silence mutes readings close to zero while thermalling, SC silence does the same for small speed commands while cruising. Both exist so the audio only speaks when it has something worth saying. See the audio vario.
Traffic, recording and claims
AIRAC
The 28-day cycle on which aeronautical data — airspace, airfields, frequencies — is reissued worldwide. Every database carries an AIRAC date, and if yours predates the current cycle then the airspace on your screen is history rather than law. See database hygiene.
Airspace
The three-dimensional volumes drawn around and above you, carried as a database and warned about in flight. What the warning means depends on the altitude reference in use and on the database being current. See airspace.
ENL
Engine Noise Level, recorded with every fix by recorders that carry the sensor. It makes an engine run plainly visible to anyone reading the file afterwards, which is exactly the point for badge and record claims. See reading IGC logs.
FLARM
The collision-avoidance system gliders use: each aircraft broadcasts its position and predicted path, and each receiver warns about the ones that actually threaten. LX instruments merge it with other traffic sources, ADS-B among them. See how FLARM works and transponders and ADS-B.
IGC file
The flight log in FAI/IGC format, digitally signed by the recorder so a scorer can confirm it has not been edited. It carries the fixes, the pressure altitude, the ENL trace and the declaration. See reading IGC logs.
MOP
Means Of Propulsion: a recorded sensor that does the job of ENL for gliders whose propulsion the acoustic sensor cannot detect reliably — electric and jet. See reading IGC logs.
OGN
The Open Glider Network — a community network of ground receivers that picks up FLARM and similar transmissions and republishes them over the internet. NAVIA can use it as an additional traffic and tracking source, subject to the aircraft being in range of a receiver.
PEV
Pilot EVent: a mark you place in the flight log by pressing a button. Competitions use it for start procedures, and it is also the honest way to flag a moment you want to find again in the trace.
PIC
Pilot In Command — the pilot recorded in the flight log as responsible for the flight. Set it before take-off: a claim filed under the previous pilot's name is not a claim.
The panel and its wiring
CAN bus
The two-wire data bus LX instruments use to reach their accessories: vario indicators, AHRS modules, flap sensors, the LX Joy remote. One cable carries both data and power, and a device joins the bus rather than being wired point to point. See the CAN bus.
EMU
Engine Monitoring Unit — the NAVIA sensor box that reads temperatures, pressures, fuel and RPM from a powerplant and puts them on the system's displays. See engine monitoring.
NMEA
The elderly serial sentence format that flight computers, transponders, traffic receivers and tablets still use to talk to one another: plain text, fixed baud rates, one sentence per line. A surprising share of panel interoperability questions turn out to be NMEA questions. See the NMEA protocol.
Pitot, static and TE ports
The pneumatic connections on the back of the instrument: pitot for total pressure, static for ambient pressure, TE for a total-energy probe if you fly one. Leaks and swapped tubes explain most reports of a vario that reads oddly. See the pitot-static system and pre-flight instrument checks.
Power budget
The sum of what everything in the panel draws, measured against the battery you actually carry. Displays and anything heated dominate it, and the internal backup battery is a reserve for getting home, not a plan. See power systems and planning a panel.
NAVIA, accounts and the cloud
Core
The computing unit of a NAVIA system. It runs the navigation, the calculations and the voice assistant, and has no display of its own — displays attach to it over the PoE network, and sensors such as Sense and Traffic wire to its serial ports.
Display
A NAVIA screen, from 4″ to 11.6″, reaching the system on a single CAT 6 cable that carries data and power together. A system can carry several, each showing what that seat needs to see.
Firmware and database updates
Instrument software and the data it navigates on are separate things that expire on separate schedules: firmware when a version is published, databases every AIRAC cycle. On NAVIA both arrive over WiFi. On the Era, LX 10K and Colibri X both come in on the microSD card — their WiFi only sends flights out. See database hygiene.
Hub
The centre of a NAVIA installation, distributing gigabit Ethernet and power over one cable per device. Growing the system means adding a box and a cable rather than rewiring the panel.
LX account
Your login on lxnavigation.com, tying together orders, downloads, registered devices and support requests. Dealers use the same login, with the dealer portal behind it.
Sense
The NAVIA air-data and attitude unit: pressures, airspeed, altitude and attitude for the whole system. Gliding or airplane is a hardware choice made at order time; within a family the Pro and Pro+ steps add angle of attack (Airplane Pro), high-speed sensing (Pro HS) or the inertial wind engine (Gliding Pro+).
Where to go next
- Which instruments and accessories combine into one system: which LX devices work together
- Choosing between the product lines: Era, LX 10K or NAVIA
- The theory behind the numbers on the screen: the LX Academy
- Everything else we have written down: the knowledge base