X-Plane Airport & Navigation Data

FAQs (Frequently Asked Questions) for X-Plane users

FAQs for X-Plane users

 

Answers to common data and data usage questions for curious X-Plane users

What is the difference between an ICAO, IATA or FAA airport code?

There are at least three coding schemas for airports:

  • ICAO (International Civil Aviation Organisation) codes are used for global aviation operations, including flight planning.  These are what we use in X-Plane.  ICAO codes consist of four letters.  The first letter indicates a region in the world (see image to right)and the second indicates a country within that region (click image to right to see country codes). The last two characters identify a specific airport in that country.  For example, London Heathrow has an ICAO code of EGLL - the EG implies the United Kingdom and is common to all other UK airports (eg. EGKK for London Gatwick). The United States and Canada are 'special cases' - there are so many airports in each country that the initial letter "K" is used to identify an airport in the contiguous United States (excluding Alaska, Hawaii and anything else not on the mainland), and an initial "C" is used to identify Canadian airports.  In the USA, the remaining three letters are almost always the FAA code for that airport (see below), such as KSEA for Seattle-Tacoma International.  

  • FAA (Federal Aviation Administration) codes are also available for all airports in the USA.  These consist of three or four characters and are sometimes a combination of letters and numbers. (eg. 4AC for Albuquerque Coronado).   If a US airport has an FAA code consisting of three letters (eg. SEA), then the ICAO code can usually (but not always!) be created by prefixing the FAA code with a "K" (in the contiguous states).  If the FAA code consists of a mixture of letters and numbers (eg. 4AC or WN23), then there is no equivalent ICAO code (for example, K4AC is not a valid ICAO code).  If an airport does not have an ICAO code, then we use the FAA code in X-Plane.

  • IATA (International Air Transport Association) codes are used by airlines for reservations, ticketing and baggage checking. These are with what most passengers are familar. We do not use IATA codes in X-Plane.  IATA codes consist of exactly three letters.  They are (usually) easily interpreted.  For example, the IATA code for London Heathrow is LHR.  Others are less obvious, such as CMH for Columbus, Ohio, or ORD for Chicago O'Hare (formerly called Orchard Field).  IATA codes are not guaranteed to be unique - so where no possibility of confusion exists they are sometimes reused (though this is rare).  In the USA, the IATA code is usually (but not always) the same as the FAA code.  For example, Carlsbad, California has an FAA code of CRQ (ICAO code is KCRQ) and an IATA code of CLD.

Confused?  There's more:

  • Some airports appear to have no official code.  For example, such is the case for many small airports in the United Kingdom.
  • In X-Plane, ICAO codes are always used if they exist, otherwise the FAA code is used.  If no valid code is known, a dummy two digit number is appended to the appropriate ICAO two-letter country code for X-Plane use (such as EG01 for an airport in the United Kingdom with no known valid code).  These codes are purely arbitrary and have no real-world usage.
  • US airports in Alaska have ICAO codes that commence with PA, and those in Hawaii begin with PH.  So the designated ICAO code may (or may not) be quite different from the FAA three-character code (eg. the ICAO code for Anchorage Elmendorf is PAED but its FAA code is EDF).
  • Some airports have two ICAO codes, especially if a military base is co-located with a civilian airport.  For example, Albuquerque, New Mexico is sometimes listed as KIKR (referring to Kirtland Air Force Base) with a secondary (civilian) ICAO code of KABQ. 
  • Some European countries assign 4-number codes to small airports (eg. 1234).  A future enhancement to X-Plane will allow 6-character airport codes, so such numeric codes will be represented in the data files by the county's ICAO region code (eg. LF for France) followed by the 4 number code (giving LF1234 for a small airport in France).
  • This website also lists some history and examples of airport codes, for all you insomniacs.

What is wrong with the ILS approaches at LOWI?

Nothing!  LOWI (Innsbruck, Austria) is the new default start-up airport for X-Plane.  It is a beautiful location in a deep valley, but it has very unusual real-world approaches that can confuse the unwary.  LOWI has has LOC-DME approaches from the East and West:

  •  The LOWI LOC-DME from the East is offset 5 degrees from the runway heading and includes an "advisory" glideslope (hence it is not referred to as an "ILS").

  • The LOWI LOC-DME from the West (illustrated to the right) is even more unusual - the localizer is positioned a few miles east of LOWI, and the approach calls for overflying the field to the MDA, and then if visual, performing a course reversal to the south in the valley and landing on either runway visually (which might require yet another course reversal for a circling approach to runway 06).  Although this looks very odd on X-Plane's charts, I believe that the nav-aids properly positioned.

  • Official approach charts for LOWI can be found here.

Why can't I see any buildings at an airport?

The default airport data does not include any information about buildings and structures (such as terminals, FBOs and hangars) at an airport.  Instead, this airport 'eye candy' is developed as packages that can be installed into your Custom Scenery folder, usually as free add-ons from the various X-Plane web sites.  One of the most popular sites is X-Plane.org.

These packages might be very simple (a few hangars at a small grass strip) or might include an extreme amount of detail for a major international airport.  There is a trade off between the amount of detail included and the impact that this will have on the performance (frame rate) of X-Plane.  For a good example of custom scenery check out the package for Amsterdam Schiphol (EHAM) at X-Plane.org. 

Why are the taxiways at my airport on the wrong side of the runway?

The detailed designs of taxiways at airports are all created by other X-Plane users.  If no one has yet created taxiway designs, then my database automatically generates a simple, 'default' parallel taxiway system for each major runway.  This default taxiways will always be wrong (and there is a 50% probability that these default taxiways will be on the wrong side of the runway) but they significantly improve the appearance of an airport compared to having no taxiways.  I can easily flip these default taxiways from one side of the runway to the other - please let me know if this will provide an improvement in the appearance of any such airport.

Why do I see an aerial sitting in the middle of the runway?

Poor data quality can sometimes cause a navigation aid to be positioned in the wrong location in my data, or for the runway to be misplaced or mis-aligned.  X-Plane renders a visual representation of each navigation aid, so on rare occasions these might be seen blocking a runway!  Let me know if you see these issues (tell me the airport code and runway) and this can be fixed.

What is stored in each of the data files?

The X-Plane airport and navigation data is stored in a set of text files.  The file and/or folder names have changed with the release of X-Plane 9.0, but the scope of each file remains unchanged:

  • Airports (including heliports and seaplane bases) are stored in the apt.dat file.  This includes basic airport and boundary information, runways (including runway lighting, approach lighting and VASI/PAPIs), taxiways, taxiway markings and lighting, default start-up locations and some airport 'furniture' (windsocks, taxiway signs, etc.).  This file does not include ILS data for an airport.

  • Navigation aids are stored in the earth_nav.dat file (nav.dat prior to X-Plane 9.0).  This file includes the location, ID, name frequency and range of global NDBs, VOR/VORTACs, DMEs, ILS components (localizers, glideslopes, marker beacons and associated DMEs).

  • Fixes (intersections) are stored in the earth_fix.dat file (fix.dat prior to X-Plane 9.0).

  • Airways are stored in the earth_awy.dat file (awy.dat prior to X-Plane 9.0).

  • Astronomical data (star positions) are stored in the earth_astro.dat file (astro.dat prior to X-Plane 9.0).

Detailed definitions of the format of each file can be found on the Designers page.  Similar files are also maintained for the planet Mars, in which case any 'earth_' prefix in the file name is replaced with 'mars_'.