[REFERENCE] Aviation Glossary / Guide (after having fallen down the rabbit hole :-) )

Start reading up on one abbreviation leads to the next abbreviation, leads to the next wiki, leads to …

Seriously unhealthy amount of abbreviations in aviation.

Anyhows, to start off well with MSFS 2020 I read through a lot and made notes for myself on points that for me, as newb, were relevant to avoid continuous question marks above my head.

Thought to share, can be handy for other new simmers as well.

Some entries may not seem relevant at first as you won’t encounter them in the cockpit but they help with context.

EDIT : updated per Sep 11th, quite some tweaking, may add or change more depending on what I encounter during sim flight and which wiki’s that triggers me to dive into.

1. Instruments

2. Altitude

3. Speed

4. Direction

5. Landing

6. Communication

7. Leaning

8. Other



Navigation instrument showing direction relative to the geographic cardinal directions (N, E, S, W).

Has variation error in that true north (used by maps etc) is (slightly) different then magnetic north (used by compass), so conversion needed depending on what is used.

Maps usually reference true poles (north and south pole along rotational axis earth), magnetic compass lines up with magnetic poles, a slightly different axis.

Deviation error is caused by interference from other magnetic and electric sources in airplane and can be minimized by calibrating counter magnets in compass via knob. Any residual error is noted on a compass correction card in the cockpit.

Turbulence, turning and accelerating can also disturb readings.

Compass is backup tool, HI is primary tool.

(or other way round, compass is primary instrument with accuracy flaws which the HI overcomes, not being bound by pole deviation as it’s gyro based instead of magnetic).

Magnetic compass turns in opposite direction as HI because HI display is actually the back of the instrument.


Gyroscopic instrument (older name, Directional Gyro, DG), designed to facilitate use of the magnetic compass.

Not radio related, uses a gyro to keep a straight course, provides alternative to MC and is generally used when MC reading may be inaccurate (non straight and level flight).

Needs manual calibration to magnetic compass in cockpit before take off with engine running (above idling to provide sufficient vacuum suction to drive gyro) via card turning knob and checked every 15 minutes in flight (can veer off due to friction or precession).


Instrument indicating lateral position in relation to a course. When used with VOR also called Omni Bearing Indicator (OBI).

If aircraft is to the left of course, needle deflects to right, and vice versa.

Uses VOR and/or ILS signals (not NDB signals like ADF uses).

The OBS (Omni Bearing Selector) knob allows selection (via the outer ring) of the radial (straight line between station and aircraft) to track to or from a VOR station, by turning the card to align its relative heading to the HI heading.

When tracking a radial only left/right deviation is indicated with a single needle.

For instrument landing you also need to track approach glide slope (GS) and thus vertical deviation may also be displayed on a CDI when using ILS.


HI and CDI into one, providing left-right deviation along with glide slope and heading indication in turns.


Similar to CDI, can be used for ADF or VOR navigation. Consists of fluxgate compass eliminating the need to re-calibrate regularly like is needed for the HI (which is used in conjunction with CDI).

With two needles fixed on two different VOR’s position can be determined, allowing for flight paths in between stations instead of only to or from.


Instrument to display ADF’s direction to or from an NDB. Fixed compass card with a needle superimposed, with 0 degree corresponding to plane’s centerline. Needle at 0 degree position tracks towards NDB (without wind).

- ADF vs VOR

Automatic Direction Finder (ADF) and Very High Frequency (VHF) Omni Directional Range (VOR) are both radio navigation methods but ADF is based on Non-Directional Beacons (NDB’s) or commercial radio stations which signals do not contain directional information (needs to be calculated by ADF equipment on board) while VOR stations send signals with directional information, radio beams called radials, one per degree, 360 degrees around it.

Both obsolete due to GPS but are backup.

If plane has Distance Measuring Equipment (DME), most VOR’s (and some NDB’s) can send a DME signal indicating distance.

After tuning in to NDB or VOR frequency an aural Morse identifier code is transmitted, to verify the correct station and active signal. Continuous repeat can be annoying so can be turned off but unlike VOR, ADF does not visually indicate a lost NDB signal so it is advised to regularly check that the Morse transmission is still active. Some ADF unit’s have a knob labelled BFO for this (from Bead Frequency Oscillation, the method that makes Morse code radio signals audible).

‘ANT’ (Antenna) mode in ADF improves signal reception but switches of the direction finding capability. Used to test the unit as needle should swing to 90°. Could also help tuning into frequency with bad reception.


Instrument displaying the rate of heading change and indicating the slip or skid of a turn.

Upper tick mark is level flight, lower tick mark is standard rate turn, being 3°/sec or 180°/min, taking two minutes to complete a circle.

Inclinometer (little ball in fluid reacting to gravity and aircraft’s centrifugal (or centripetal ?) acceleration) indicates slip or skid. To correct unbalanced forces in slip or skid ‘step on the ball’, i.e. apply rudder in its direction.

(‘Turn Coordinator’ (TC) unit is successor to the ‘Turn and Slip Coordinator’ (T/S), former of which due to 30° gyro position displays a change more quickly as it will also react to change in roll before aircraft has begun to yaw. Both units having a turn indicator (main gauge) and slip/skid indicator, the little ball).


Instrument displaying plane’s orientation (roll and pitch) relative to horizon.


Instrument overlaid on attitude indicator showing attitude required to follow a planned trajectory.


Speedometer, usually in KIAS, Knots Indicated Airspeed.

White - flaps range

Green - Normal

Yellow - Only when smooth air

Red - Max


Instrument displaying rate of descent or climb. Also called Variometer.


Onboard identification device for Air Traffic Control (ATC) radar, using a 4 digit identifier, the ‘Squawk’ code.

‘On’ only transmits Squawk to ATC, must be set to ‘Alt’ to also send position and height.

‘Ident’ function is to highlight the plane’s blip on the radar as may be requested by ATC.

Uncontrolled airspace Squawk for US is 1200, Europe 7000.



Height above Mean Sea Level (MSL).


Height Above Ground Level (AGL).


As shown on altimeter.


Indicated altitude with altimeter set to 29.92 inHg (or 1013 hPa).

Is ISA Standard Pressure, being 29.92 inHg (inches of Mercury) at MSL.

For non-standard pressures, use conversion chart to calibrate altimeter.


Pressure altitude corrected for non-standard Outside Air Temperature (OAT).

PA + (120 x (OAT - ISA temp)).

DA chart gives altitude corrections for non-standard temps and pressures.

Pilot documentation contains performance charts accounting for DA (like take off speed, ground roll (distance to rotate), range etc).

ISA Standard Temperature is 15° at MSL and then about -2° per 1000 ft.

(-4.8° at 10k ft, -24.6° at 20k ft, -44.4° at 30k ft and -56.5° at 40k ft).

ISA is International Standard Atmosphere, with standard values for a.o. temp and pressure.


Pressure Altitude (PA) divided by 100 feet.


VFR (Visual Flight Rules) heights end in 500’s of feet, IFR (Instrument Flight Rules) in 1000’s.

Max VFR altitude differs, in US 18000 MSL.



Speed shown on the airspeed indicator. Accurate at ground level under standard conditions but when air density changes, for instance by climbing (pressure/temp/humidity changes), not anymore.

Calculated based on dynamic pressure, the difference between pressure at Pitot tube (RAM pressure, air flow) and Static Port (static pressure, no air flow).

Not consistent like ground speed, so unsuitable to calculate travel time or fuel load for instance, but it is accurate for pressure differences and hence relevant for stalls, take off and landing speeds which don’t care about ‘true’ speeds but about the pressure available for lift (difference between flowing and static air), which IAS indicates.


Calculated via airplane conversion table accounting for position error (slow speed and/or flap deflections), instrument and installation error (airspeed meter itself and its plumbing)


CAS corrected for compressibility (of air or something).


Equivalent airspeed corrected for temperature and pressure altitude.

Calculation still to check but for meantime can (probably) be shown on speed indicator by inputting temp and altitude. Pilots also have a tool for this (E6-B paper ‘computer’).


Head wind, TAS minus wind speed.

GS is lower than TAS because airplane is opposed by the wind and car can go slower to travel same distance in same time.

Tail wind, TAS plus wind speed.

GS is higher than TAS because airplane is helped by the wind (free speed) and car has to go faster to travel same distance in same time.

TAS is relative to the air mass so wind speed is not a factor (speed indication is compared to the surrounding air, so with head or tail wind the plane’s TAS is what it is relative to those flows), but wind does have impact on TAS compared to ground speed.

Air speed is measured by the amount of air hitting the plane, with head wind more air molecules hit the Pitot tube so it will read higher compared to without wind for same ground speed.

Tail wind vice versa, reads lower TAS (less molecules over Pitot tube) than without wind for same ground speed.



Direction in which longitudinal axis of aircraft is pointed, usually expressed in degrees from North (whichever is used, true, magnetic, compass or map grid North).


The horizontal direction to or from any point, usually measured clockwise from true or magnetic north or other reference point through 360 degrees.


Magnetic bearing extending from a VOR station (or military TACAN or combi of the two, VORTAC).


Projection on earth’s surface of airplane’s path, direction of which at any point is usually expressed in degrees from North (true, magnetic, compass or map grid).


Ball park method of correcting for crosswind drift on a track is to turn into the wind by half the number of the wind strength, so 10kt wind from left is steering 5° to the left to stay on track.

Too much or little correction will move course instrument (CDI, HSI, RMI and/or RBI) needle off to the right or left gradually.

When using ADF :

  1. Turn the plane to where RBI needle is at 0°, indicating a bearing straight to the station.
  2. Note the heading on the HI and remember by head or move the ‘bug’, the little sliding arrow thingy on the outside, to mark it.
  3. Watch RBI needle move left or right from wind drift. When needle goes right the station is to the right and plane is drifting left away from it by a right crosswind. Steer a bit to the right to counter this right crosswind and observe needle movement. If still creeping to the right more counter steer is needed, if moving to the left less. Observe needle and fine tune counter steer until needle is stable.
  4. Note how much degrees the HI heading changed compared to step 2.
  5. Turn the plane back to original heading of step 1, being 0° on the RBI.
  6. Add the amount of counter steer angle found in step 4 to the HI heading and mark that direction with the ‘bug’ or if not available remembering it.
  7. Follow that heading.

This should be the heading that gets you straight to the station, compensating for crosswind.

Basically it’s tweaking the counter steer until finding the steering angle that will stop the drift. Then pointing the plane back to the station and adding that angle.


- General

Ideal glide slope is 3 degrees (in Cessna 152 some 400 ft/min VSI).

Adjust vertical speed via throttle, airspeed via pitch.

- Instrument Landing System (ILS)

System for horizontal and vertical guidance when landing. Localizer is (sub-)system for the horizontal component.

- Non-precision approach

Instrument approach and landing with lateral guidance only, no vertical guidance (no electronic glide slope).

- Go Around (GA)

Aborted landing on final approach.

- Pattern

Also called ‘circuit’, standard path for taking off or landing while maintaining visual contact with runway, consisting off Crosswind section (perpendicular to runway end), 90° left into Downwind (parallel to runway), 90° left into Base, 90° left into Final approach (towards runway).

Right or left Downwind is determined from the perspective of the Base (looking in the direction of runway).

At airports used as standard (holding) path for coordinating traffic. Mostly used for General Aviation (GA) airfields, not the bigger commercial fields.

- Runway

Runway (RWY) number indicates its direction in degrees from North, minus the last digit, so 360° is indicated as 36 and 93° as 9 (or 09 in some countries).

Runways can usually be used in both directions so have two numbers specifying the direction, for instance RWY 27 (in direction of 270°) and the opposite RWY 90 (at 90°). Runway numbers on the same strip are always opposite on a 360° scale as one take off / landing direction is 180° opposite the other.

If there are multiple runways in the same direction then an L, R or C for Left, Right or Center is designated, like RWY 18L and RWY 18R (being the same runway strips as 9R and 9L but from the other direction).


Two similar lighting systems as visual aid beside runway to indicate optimal glide slope; evenly white and red is correct path, more white is too high, more red is too low.

- OMI lights

Indicators in cockpit linked to Beacon Markers at varying distance from runway to aid landing by lighting up when passing over them; O for Outer (at 4-7 nm, Final Approach Fix point), M for Middle (at 0.5-0.8 nm, Category I Missed Approach point, usually 200 ft AGL) and Inner (at runway thresshold, where Decision Height (for missed approach) is <200 ft).


Common radio contacts :

Center : IFR flights exiting class B airspace (VFR may request Center for ‘flight following’)

Ground : taxiing, fuel, tug etc.

Tower : take off / landing

Approach / Departure : prep before landing / take off

Many airfields do not have ‘Approach / Departure’ so then comms go straight to ‘Tower’, either after hand over by ‘Center’ or by pilot directly.

Some airfields do not have anything in which case UNICOM (Universal Communications, non-ATC private advisory companies) or CTAF (Common Traffic Advisory Frequency, comms between pilots) can be used to obtain or exchange relevant information.

ATIS (Automatic Terminal Information Service) : info on weather, runways and NOTAM’s (Notification to Airmen).

AWOS (Automated Weather Observing System, run by US Federal Aviation Authority, FAA)


ASOS (Automated Surface Observing System, run by US National Weather Service, NWS ) : automated weather info.

VHF (Very High Frequency) radio is between frequencies 118.00 - 132.00.


Optimizing fuel to air mixture ratio as less dense air is encountered at altitude. Optimal mixture generally 15-1 air-fuel molecules.

Benefit; more economical, runs smoother (less repairs from excessive vibrations from rich rough running), less plug fouling, less intake icing risk (from higher running temp).

Best power (max RPM or airspeed for a given throttle setting) versus best economy (peak Exhaust Gas Temperature, EGT).

Best power by leaning until RPM peaks in direct drive engine or airspeed peaks in variable pitch propeller engine.

Best economy by leaning to peak EGT or leaning till engine runs rough then enriching just to where roughness stops.

Leaning possible any time power output is <75%, typically at taxi, at climb above 3000 ft, at cruising, at descent (but full rich at final approach to anticipate a possible go-around).

If cruising at >75% power, mixture should not be leaned more than required for maximum RPM (i.e. best power ).

One way to check high lean is to enable Carb Heat (de-icing mechanism) and see if it lowers RPM. If RPM increases, mixture is very lean (hotter, less dense intake air from Carb Heat makes for richer fuel/air mixture, if RPM rises from this it indicates engine was leaned past peak RPM point).

Caution not to over-lean because less fuel means less cooling from fuel, means higher temp, means risk of engine knocking (pre-ignition or detonation, the explosion of mixture outside normal combustion cycle) or risk of damaging engine components (melted valves, cracked cylinder etc.) both of which have bad outcomes.

Hence for take off and high power settings go full rich to avoid the danger zone.


- Flaps lift vs drag

At lower flap setting lift increases strongly compared to drag, at higher setting drag increases more than lift.

- L/D Max (lift/drag)

Best glide speed, speed with lowest drag (induced and parasitic (form, interference, surface friction)) and highest lift. When engine fails this speed gives longest glide range.

- Low speeds

Less air over flight control surfaces, thus less responsive controls.

- Empennage

Tail section with horizontal and vertical stabilizers.

- Phonetic Alphabet

NATO standard radio spelling alphabet :

Alfa, Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, India, Juliett, Kilo, Lima, Mike, November, Oscar, Papa, Quebec, Romeo, Sierra, Tango, Uniform, Victor, Whiskey, X-Ray, Yankee, Zulu.

Number Nine is pronounced as Niner.

- Zulu

Designation for UTC time format used in navigation (formerly Greenwich Mean Time, GMT).

- Ground Proximity Warning System (GPWS)

Alerts pilots if aircraft is in immediate danger of flying into ground or obstacle.

- Emergency Locator Transmitter (ELT)

Device broadcasting signals on designated frequencies in case of emergency (either triggered manually or automatically).

- Annunciator panel

Cockpit warning panel with lights indicating system status.