X-PLANE
AIRPORT DATA (APT.DAT) FILE SPECIFICATIONVERSION 850
REVISION HISTORY
28 April 200912 July 200914 July 2009
6 Sept 2009
1 Feb 2011Spec converted to this new format to support new web site (http://data.x-plane.com).
Minor typos fixed
Minor errors in helipad spec fixed
Added clearer examples of taxiway signs (submitted by Donald Good – thanks!)
Clarified definitions of runway ends and thresholds

APPLICABILITY
This specification (APT.DAT 850) is supported in X-Plane 8.50 and later. However, the significant new feature set in this file version was not fully supported
until the release of X-Plane 8.61.
The prior specification for airport data was APT.DAT 810, which is recommended for X-Plane 8.10 – 8.60.

SUPPORT FOR DEPRECATED FILE FORMATS
The deprecated file specification (APT.DAT 810) is still supported. A large quantity of custom airport data exists only in this format. So airports definedaccording to this specification (APT.DAT 810) can be included in a file otherwise complying with the APT.DAT 850 specification.
The specification for APT.DAT 810 is available at http://data.x-plane.com

OVERVIEW & SCOPE
This specification defines core airport data for X-Plane. This includes the locations of runways, taxiway and apron pavement, basic airport ‘furniture’(VASI/PAPIs, windsocks, light beacons and taxiway signage) and communications frequencies. It also includes attributes for each of these features to fully
describe them (eg. it includes runway surface type, runway markings, taxiway lighting and markings, approach lighting, taxiway sign text, etc).

X-Plane Airport Data (Apt.Dat) File Specification

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This specification does not include scenery objects (such as buildings, static aeroplanes or underlying terrain textures).

BASIC CONCEPTS

Latitudes and longitudes are described in a decimal notation (eg. 20.12345678).
o A latitude of 50 degrees 30 minutes south would be defined as -50.50000000
North latitudes and east longitudes are positive. South latitudes and west longitudes are negative.
All headings are referenced to true north (not magnetic north).

FILE CHARACTERISTICS
The apt.dat files are plain text files:

Fields in the data can be separated by one or more white space characters (space, tab).
o By default, the files are generated so that columns of data are consistently aligned, but this is not required.
Blank rows are permitted and are helpful to differentiate between airports.

FILE STRUCTURE
It is recommended that all airports be created in the free WorldEditor (“WED”) tool. This will ensure that all structural requirements listed here for airport data
are met.
In common with most other X-Plane data file specification, header rows of data define the origin (“I” = PC or “A” = Mac) of a particular copy of a file, and define
the file specification version. The file specification may be followed by a reference to a sequential release data cycle and build number for the data, and a
copyright message:I
850 Version - data cycle 2009.01, build 20081054, metadata AptXP850.

Copyright © 2009, Robin A. Peel (robin@xsquawkbox.net)...

The complete copyright message must be left intact if you redistribute this data. The GNU GPL (general public License) under which this data is released isdesigned to encourage modifications, enhancements and redistribution, even in commercial derivative products. More details about this license are available
on my website (http://data.x-plane.com).

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Subsequent rows of data follow a hierarchical structure:Each row of data has a numeric ‘row code’ as its first field, to define its content.
The top level of this hierarchy defines an individual airport, defined by an airport header row (a row code of ‘1’, ‘16’ or ‘17’).
Subsequent rows define elements of an airport:o Runways (including helipads) follow the airport header row (one row per runway).
o Pavement (taxiway/apron) definitions have a header row followed by an ordered list of nodes that define its boundaries:
 Each pavement definition must each have a single boundary with no overlaps with itself.
 Nodes on this outer boundary must be defined in a counter-clockwise direction.
 Boundaries must be terminated with a node with a row code ‘113’ or ‘114’.
 Pavement definitions may overlap with another pavement chunk. But this is not recommended – instead consider precise alignmentof adjacent features by ‘snapping’ nodes to identical locations in World Editor (WED).
 A pavement definition can never overlap with itself.
 The sequencing of the pavement definitions is the layering in which they will be rendered in X-Plane, top-down. So the last piece ofpavement in the file will be rendered underneath any others with which it overlaps.
 Holes can be defined for pavement (through which the underlying terrain texture will show): Hole boundaries should follow the termination of the pavement definition in which the hole occurs (starting with a row
type ‘111’ or ‘112’).
 Hole boundaries are defined in a clockwise direction (ie, opposite direction to the boundary nodes).
 Hole boundaries must form a closed loop (ie. must terminate with a row code ‘113’ or ‘114’).
 Each pavement definition can have zero, one or multiple hole boundaries.
 Hole boundaries must be contained within the outer boundary of the pavement definition.
 Holes cannot overlap each other.
 After creating a hole boundary, it can be ‘filled’ with a new pavement chunk (probably using a different surface type).
o Linear features also have a header row followed by an ordered list of nodes that define the line:
 Linear features can be closed loops (terminating in a node of type ‘113’ or ‘114’) or just strings (terminating with ‘115’ or ‘116’).
o An airport boundary is defined with nodes in a counter-clockwise direction. A boundary can contain holes (see above) and must form aclosed loop (terminating in anode of type ‘113’ or ‘114’).
o Other airport features are defined with one row for each feature.

The file is terminated by a ‘99’:
99

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ROW CODES
Each row of data begins with an integer code that defines the type of data:
Row
Code

Meaning1
16
17Land airport header
Seaplane base header
Heliport header

100
101
102

RunwayWater runway
Helipad

110
120
130

Pavement (taxiway or ramp) header
Linear feature (painted line or light string) header
Airport boundary header

Must form a closed loop
Can form closed loop or simple string
Must form a closed loop

111
112
113
114
115
116

Node
Node with Bezier control point
Node with implicit close of loop
Node with Bezier control point, with implicit close of loop
Node terminating a string (no close loop)
Node with Bezier control point, terminating a string (no close loop)

All nodes can also include a “style” (line or lights)
Bezier control points define smooth curves
Implied join to first node in chain
Implied join to first node in chain
No “styles” used
No “styles” used

14
15
18
19
20
21

Airport viewpoint
Aeroplane startup location
Airport light beacon
WindsockTaxiway sign (inc. runway distance-remaining signs)
Lighting object (VASI, PAPI, Wig-Wag, etc.)

One or none for each airport
Zero, one or many for each airport
One or none for each airport
Zero, one or many for each airport
Zero, one or many for each airport
Zero, one or many for each airport

50 – 56

Communication frequencies

Zero, one or many for each airport

X-Plane Airport Data (Apt.Dat) File Specification

Comment

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EXAMPLE DATA
Here is some example data for KBFI. It is not real and is very incomplete, but it illustrates examples of most types of data found in an apt.dat file. This data
includes an airport header, runway, water runway, helipad, PAPI, taxiway definition, painted line, viewpoint, startup location, light beacon, windsock, taxiway
sign and an ATC communications frequency:1
21 1 0 KBFI Boeing Field King Co Intl
100 29.87
1
0 0.15 0 2 1 13L 47.53801700 -122.30746100
73.15
0.00 2101 49 1 08 35.04420900 -106.59855700 26 35.04420911 -106.59855711
102 H147.53918248 -122.30722302
2.00
10.06
10.06
1 0
0 0.25 02147.53666659 -122.30585255 2 150.28
3.30 13L PAPI-2L
110 1 0.25 150.29 A2 Exit
111 47.53770968 -122.30849802
111 47.53742819 -122.30825844
3
112 47.53752190 -122.30826710 47.53757385 -122.30824831
3 102
114 47.53768630 -122.30834929 47.53768690 -122.30838150
3 102
120 Line B1
111 47.53969864 -122.31276189 51
111 47.53977825 -122.31255145
1
115 47.54002296 -122.31189878
1447.52917900 -122.30434900 100 0 ATC Tower
15
47.52926674 -122.29919589 304.16 A8 Run Up
18
47.52920400 -122.30412800 1 BCN
1947.53900921 -122.30868700 1 WS
20
47.54099177 -122.31031317 235.71 0 2 {@L}A1{@R}31R-13L
50
12775 ATIS

0 0 1 31R

47.52919200 -122.30000000

110.950.00 2

0 0 1

DEFINITION OF DATA FIELDS
Each column in each row code is defined below, using the example data from KBFI shown above. Note that:

Some row codes store data in an identical specification, and these have been grouped together in the table below.
The specification aims to be consistent. For example, the format or latitudes and longitudes is always the same, and all headings/orientations aredefined as true (not magnetic) degrees.

X-Plane Airport Data (Apt.Dat) File Specification

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Row

1
16
17

Meaning
Example value

Comment
Explanation

Land airport header
Seaplane base header
Heliport header

Row codes 1, 16 and 17 share a common format (see below)
Row codes 1, 16 and 17 share a common format (see below)
Row codes 1, 16 and 17 share a common format (see below)

1
21
1
0
KBFI
Boeing Field King Co …

100

Valid values

Row code for an airport, seaplane base or heliport
Elevation of airport in feet above mean sea level (AMSL)
Flag for control tower (used only in the X-Plane ATC system)
Deprecated. Use default value (“0”)
Airport ICAO code. If no ICAO code exists, use FAA code (USA only)
Airport name. May contain spaces. Do not use special (accented) characters

0=no ATC tower, 1=has ATC tower
Use 0
Maximum four characters. Must be unique.
Text string (up to 40 characters)

Land Runway
100
Row code for a land runway (the most common)
29.87
Width of runway in metres
1
Code defining the surface type (concrete, asphalt, etc)0
Code defining a runway shoulder surface type
0.15
Runway smoothness (not used by X-Plane yet)0
Runway centre-line lights
2
Runway edge lighting (also implies threshold lights)
1
Auto-generate distance-remaining signs (turn off if created manually)
The following fields are repeated for each end of the runway
13L
Runway number (eg. “31R”, “02”). Leading zeros are required.
47.53801700
Latitude of runway end (on runway centerline) in decimal degrees-122.30746100
Longitude of runway end (on runway centerline) in decimal degrees
73.15
Length of displaced threshold in metres (this is included in implied runway length)
A displaced threshold will always be inside (between) the two runway ends
0.00
Length of overrun/blast-pad in metres (not included in implied runway length)2
Code for runway markings (Visual, non-precision, precision)
0
Code for approach lighting for this runway end
0Flag for runway touchdown zone (TDZ) lighting
1
Code for Runway End Identifier Lights (REIL)

101

1, 16 or 17

100
Two decimal places recommended. Must be >= 1.00
Integer value for a Surface Type Code0=no shoulder, 1=asphalt shoulder, 2=concrete shoulder
0.00 (smooth) to 1.00 (very rough). Default is 0.25
0=no centerline lights, 1=centre line lights
0=no edge lights, 2=medium intensity edge lights
0=no auto signs, 1=auto-generate signs
Two to three characters. Valid suffixes: “L”, “R” or “C” (or blank)
Eight decimal places supported
Eight decimal places supported
Two decimal places (metres). Default is 0.00
Two decimal places (metres). Default is 0.00
Integer value for Runway Marking CodeInteger value for Approach Lighting Code0=no TDZ lighting, 1=TDZ lighting
0=no REIL, 1=omni-directional REIL, 2=unidirectional REIL

Water runway101
Row code for a water runway
49
Width of runway in metres
1
Flag for perimeter buoys
The following fields are repeated for each end of the water runway
08
Runway number. Not rendered in X-Plane (it’s on water!)
35.04420911
Latitude of runway end (on runway centerline) in decimal degrees-106.59855711
Longitude of runway end (on runway centerline) in decimal degrees

X-Plane Airport Data (Apt.Dat) File Specification

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101
Two decimal places recommended. Must be >= 1.00
0=no buoys, 1=render buoys
Valid suffixes are “L”, “R” or “C” (or blank)
Eight decimal places supported
Eight decimal places supported

850 Version, 1-Feb-11

Row

Meaning
Example value

102

Helipad102
H1
47.53918248-122.30722302
2.00
10.06
10.06
1
0
0
0.25
0

110

Pavement (taxiways)
110
1
0.25
150.29A2 Exit120
130

Linear feature
Airport boundary
120
Line B1

Comment
Explanation

Valid values

Row code for a helipad
Designator for a helipad. Must be unique at an airport.
Latitude of helipad centre in decimal degrees
Longitude of helipad centre in decimal degrees
Orientation (true heading) of helipad in degrees
Helipad length in metres
Helipad width in metres
Helipad surface code
Helipad markings
Code defining a helipad shoulder surface type
Helipad smoothness (not used by X-Plane yet)
Helipad edge lighting

101
Usually “H” suffixed by an integer (eg. “H1”, “H3”)
Eight decimal places supported
Eight decimal places supported
Two decimal places recommended
Two decimal places recommended (metres), must be >=1.00
Two decimal places recommended (metres), must be >= 1.00
Integer value for a Surface Type Code0 (other values not yet supported)
0=no shoulder, 1=asphalt shoulder, 2=concrete shoulder
0.00 (smooth) to 1.00 (very rough). Default is 0.25
0=no edge lights, 1=yellow edge lights

Defines an arbitrary pavement shape
Row code for a pavement chunk header (must be followed by a set of nodes)
Code defining the surface type (concrete, asphalt, etc)
Runway smoothness (not used by X-Plane yet)
Orientation (true degrees) of pavement texture ‘grain’
Description of pavement chunk (not used by X-Plane)

110Integer value for a Surface Type Code0.00 (smooth) to 1.00 (very rough). Default is 0.25
Two decimal places recommended
Text string

Painted surface markings & light strings
Boundary for future terrain ‘flattening’
Row code for a linear feature or airport boundary
Description of feature or boundary (not used by X-Plane)

X-Plane Airport Data (Apt.Dat) File Specification

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120 or 130
Text string

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Row

Meaning
Example value

Comment
Explanation

111
112
113
114
115
116

Node
Node
Node
Node
Node
Node

Node (plain)
Node with Bezier control point
Node (close loop), to close boundary
Node (close loop) with Bezier control point
Node (end) to terminate a line
Node (end) with Bezier control point

112
47.53752190-122.30826710
47.53757385-122.30824831
3
102

14

Viewpoint14
47.52917900-122.30434900
100
0
ATC Tower

15

Startup location
15
47.52926674-122.29919589
304.16112
A6 Run Up

18

Light beacon
1847.52920400-122.30412800
1
BCN

Valid values

Row code for a node. First node must follow an appropriate header row[All nodes] Latitude of node in decimal degrees[All nodes] Longitude of node in decimal degrees[112, 114, 116 only] Latitude of Bezier control point in decimal degrees[112, 114, 116 only] Latitude of Bezier control point in decimal degrees[Not for 115 or 116] Code for painted line type on line segment starting at this node
[Not for 115 or 116] Code for lighting on line segment starting at this node

111 thru 116
Eight decimal places supported
Eight decimal places supported
Eight decimal places supported. Ignore for 111, 113, 115
Eight decimal places supported. Ignore for 111, 113, 115
Integer Line Type Code. Not for 115 or 116
Integer Line Type Code. Not for 115 or 116

Maximum of one viewpoint for each airport
Row code for a viewpoint
Latitude of viewpoint in decimal degrees
Longitude of viewpoint in decimal degrees
Height (in feet) of viewpoint above ground level
Code deprecated. Use ‘0’Name of viewpoint (not used by X-Plane)

14
Eight decimal places supported
Eight decimal places supported
Integer0
Descriptive text string (optional)

Startup locations for airplanes at an airport
Row code for a startup location
Latitude of startup location in decimal degrees
Longitude of startup location in decimal degrees
Heading (true) of an aeroplane when positioned at startup location
Row code for a node. First node must follow an appropriate header row
Name of startup location (list will be displayed in X-Plane for each airport)

15
Eight decimal places supported
Eight decimal places supported
Two decimal places recommended
111 thru 116
Short descriptive text string – ten characters or lessMaximum of one beacon for each airport
Row code for an airport light beacon
Latitude of beacon in decimal degrees
Longitude of beacon in decimal degrees
Code for type of light beacon. Determines colors of beacon.
Name of viewpoint (not used by X-Plane)

X-Plane Airport Data (Apt.Dat) File Specification

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18
Eight decimal places supported
Eight decimal places supported
Integer Beacon Type CodeDescriptive text string (optional)

850 Version, 1-Feb-11

Row

Meaning
Example value

Comment
Explanation

19

Windsock

Multiple windsocks permitted for each airport

19
47.53900921-122.30868700
1
WS

20

Signs
20
47.54099177-122.31031317
235.710
2{@L}A1{@R}31R-13L

21

Lighting objects
21
47.53666659-122.30585255
2
150.28
3.30
13L
PAPI-2L

50
51
52
53
54
55
56

ATC – Recorded
ATC – Unicom
ATC – CLD
ATC – GND
ATC – TWR
ATC – APP
ATC - DEP
51
12775
ATIS

Valid values

Row code for a windsock
Latitude of windsock in decimal degrees
Longitude of windsock in decimal degrees
Flag for windsock lighting
Name of viewpoint (not used by X-Plane)

19
Eight decimal places supported
Eight decimal places supported
0=unlit, 1=illuminatedDescriptive text string (optional)

Taxiway signs or runway distance-remaining signs
Row code for a sign
Latitude of sign in decimal degrees
Longitude of sign in decimal degrees
Orientation of sign in true degrees (heading of someone looking at sign’s front)
Reserved for future use. Ignore.
Code for sign size
Text to be rendered on sign front and/or back20
Eight decimal places supported
Eight decimal places supported
Two decimal places recommended
0
Integer Sign Size CodeText string formatted by Sign Text Definition (see below)

VASI, PAPI, wig-wags, etc.
Row code for a lighting object
Latitude of lighting object in decimal degrees
Longitude of lighting object in decimal degrees
Code for type of lighting object
Orientation of lighting object in true degrees (looking toward object)
Visual glideslope angle in degrees
Associated runway number (required for VASI/PAPI, etc)
Description of lighting object (not used by X-Plane

21
Eight decimal places supported
Eight decimal places supported
Integer Lighting Object CodeTwo decimal places recommended
Two decimal places. 0.00 if not required. Default is 3.00
One to three characters
Short text string (optional)

AWOS, ASOS or ATIS
Unicom (US), CTAF (US), Radio (UK)
Clearance Delivery
GroundTower
Approach
Departure
Row code for an ATC COM frequency
Frequency in MHz x 100 (eg. use “12322” for 123.225MHz)
Descriptive name (displayed on X-Plane charts)

X-Plane Airport Data (Apt.Dat) File Specification

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50 thru 56
Five digit integer, rounded DOWN where necessary
Short text string (recommend less than 10 characters)

850 Version, 1-Feb-11

CODES
Codes used to define airport data:
Codes
Code value

Comment
Code meaning

Surface Type CodeSurface type of runways or taxiways

1
2
3
4
5
12
13
14
15

Runway Marking Code
0
1
2
3
4
5

Code applicability

Asphalt
Concrete
Turf or grass
Dirt (brown)
Gravel (grey)
Dry lakebed (eg. At KEDW)
Water runways
Snow or ice
Transparent

Example: KEDW (Edwards AFB)
Nothing displayed
Poor friction. Runway markings cannot be added.
Hard surface, but no texture/markings (use in custom scenery)

Markings on runway
No runway markings
Visual markings
Non-precision approach markings
Precision approach markings
UK-style non-precision approach markings
UK-style precision approach markings

X-Plane Airport Data (Apt.Dat) File Specification

Disused runways appear like taxiways

UK uses distinctive touch-down zone markings
UK uses distinctive touch-down zone markings

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CodesCode value

Comment
Code meaning

Approach Lighting CodeApproach lighting systems

0
1
2

3
4

5

6

7
8

9
10
11

12

Code applicability

No approach lighting
ALSF-IHigh intensity Approach Light System with sequenced flashing lights
ALSF-IIHigh intensity Approach Light System with sequenced Flashing lights
Red side bar lights (barettes) the last 1000’, that align with TDZ lighting.
Calvert
British - High intensity
Calvert ILS Cat II and Cat IIBritish - High intensity with red side bar lights (barettes) the last 1000’

Barettes align with TDZ lighting
SSALR
High intensity, Simplified Short Approach Light SystemWith Runway Alignment Indicator Lights (RAIL)
SSALF
High intensity, Simplified Short Approach Light SystemWith sequenced flashing lights
SALS
High intensity, Short Approach Light System
MALSRMedium-intensity Approach Light SystemWith Runway Alignment Indicator Lights (RAIL)
MALSF

Medium-intensity Approach Light System with sequenced flashing lights
MALS
Medium-intensity Approach Light System
ODALS
Omni-directional approach light systemFlashing lights, not strobes, not sequenced
RAIL
Runway Alignment Indicator Lights
Sequenced strobes and green threshold lights, with no other approach lights

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CodesCode value

Comment
Code meaningLine Type Code

Painted lines and light strings
Note that for all linear features that involve runway entrance hold lines and associated lights (4, 5, 6, 103 & 104 below), the runway is
assumed to be to the LEFT of the string and the taxiway to the RIGHT (looking along string from its first node)

Code applicability

0
1
2
3
4
5
6
7
8
9
51-59

Nothing.
Solid yellow line
Broken yellow line
Double solid yellow lines
Two broken yellow lines and two solid yellow lines. Broken line on left of string.
Broken yellow line with parallel solid yellow line. Broken line on left of string.
Yellow cross-hatched line
Solid yellow line with broken yellow line on each side
Widely separated, broken yellow line
Widely separated, broken double yellow line
Line types 1-9 above with a black border

Taxiway centre lines
Miscellaneous boundaries
Taxiway edge lines
Runway hold positions
Other (non-runway) hold locations
ILS hold
Taxiway centerlines in runway safety zones
Mark ‘lanes’ for queuing aeroplanesMark ‘lanes’ for queuing aeroplanes
Use on concrete surfaces for higher contrast

20
21
22

Solid white line
White chequerboard pattern
Broken white line

Roadway markings
Roadway markings
Roadway centreline

101
102
103
104
105
106

Note that lights added to the edge boundary of a piece of pavement (or hole) will be placed off the edge of the pavement (about one meter).
Green embedded lights, bidirectional along string axis
Taxiway centrelines
Blue lights, omnidirectional
Taxiway edge
Closely spaced, embedded amber lights. Unidirectional to right of string
Hold lines
Closely spaced, pulsating embedded amber lights. Unidirectional to right of string
Runway hold lines
Alternating green and amber embedded lights, bidirectional along string axis
Centrelines in runway safety zones
Red lights, omnidirectional
Edge lights in dangerous/critical zones (eg. on bridges)

Beacon Type Code
0
1
2
3
4

Sign Size Code
1
2
3
4
5

Airport light beacons
No beacon. Suppresses automatic creation of beacon by X-Plane.
White-green flashing
White-yellow flashing
Green-yellow-white flashing
White-white-green flashing

Use a dummy airport lat/lon for the location.
Civilian land airport
Seaplane base
Heliport
Military airport

Taxiway sign sizes & types
Small taxiway signMedium taxiway sign
Large taxiway sign
Large distance-remaining sign on runway edge
Small distance-remaining sign on runway edge

X-Plane Airport Data (Apt.Dat) File Specification

Alternatively, can be auto generated for a runway
Alternatively, can be auto generated for a runway

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CodesCode value

Comment
Code meaning

Lighting Object CodeLighting objects

1
2
3
4
5
6

Code applicability

VASI
PAPI-4L, on left of runway
PAPI-4R, on right of runway
Space Shuttle PAPI, 20 degree glidepath
Tri-colour VASI
Runway guard (“wig-wag”) lights

Location is centre point between the two VASI units
Left-handed: red indication appears first on right 2 lights
Right-handed: red indication appears first on left 2 lights
Deprecated. Use normal PAPI.
Pulsating double amber lights alongside runway entrances

TAXIWAY SIGN TEXT DEFINITION
The text on taxiway signs follows a specification shared with the FlightGear flight simulator.
In summary, the text and images on a taxiways sign are represented in X-Plane by:

Instructions define the style of the text and images on the sign. These are always prefixed with the "@" symbol:
o Black lettering on a yellow background (direction signs) ("@Y").
o Yellow lettering on a black background (location signs) ("@L").
o White lettering on a black background (runway distance-remaining signs) ("@B").
o White lettering on a red background (runway holding point signs) ("@R").
o Instructions must be included inside curly braces (eg. “{@Y}”)
Single-character glyphs define a series of numbers or characters on the sign. These translate one-to-one to the text on the sign. The only allowable
single characters are:o The numbers "0" through "9", for all sign styles.
o The uppercase letters "A" through "Z". Only UPPERCASE characters are allowed! No letters are allowed on distance remaining signs.
o The following single-character symbols are allowed for runway ("@R") and location ("@Y") signs only: Space (represented by an underscore "_")
 Large dot (represented by an asterisk ("*")
 Vertical separator (represented by the vertical bar "|") (also referred to as a "frame separator") Period, comma, slash and hyphen (".", ",", "/" and "-")
Multi-character glyphs define symbols:o Directional arrows (eg. "^lu" for a left-up arrow, "^rd" for a right-down arrow) are allowed for red ("@R") and yellow ("@Y") signs only.
o The only allowable arrows are: "^l", "^r", "^u", "^d", "^lu", "^ld", "^ru", "^rd" Note that for diagonal arrows, the left/right must precede the up/down. For example, "^dr" is invalid.

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o
o
o
o
o
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o

ILS-critical boundary ("critical"). These do not require a sign style.
Runway safety zone boundary ("safety"). These do not require a sign style.
No-entry symbols ("no-entry"). These do not require a sign style.
Hazard (end of taxiway) ("hazard"). These do not require a sign style.
Switch sides - flip to the back of the sign and start a new text string for the back ("@@")
Roman numerals (for ILS categories, such as "CAT III") ("r1", "r2" and "r3") are allowed for red ("@R") and yellow ("@Y") signs only.
Multi-character glyphs must be included inside curly braces (eg. “{r1}”)

There are rules about how these three types of data must be structured on a taxiway sign:
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Instructions and single-character glyphs must be UPPERCASE.
Multi-character glyphs must be lowercase
Instructions and multi-character glyphs must be enclosed in curly braces ("{}"), to distinguish them from a set of single-character glyphs.
o If there are multiple consecutive instructions and/or multi-character glyphs, they can be separated within the same set of curly braces by acomma (eg. “{@Y,^l}”)Spaces are not allowed. Spaces are represented by the underscore ("_") character.

Examples of sign text:
Sign

Sign type

Text to generate this sign

Direction sign{@Y}A{^r}Location sign{@L}T

Location and direction sign{@L}A{@Y,^l}E{^r}Complex sign{@Y,^l}E|{^lu}F{@L}A{@Y}T{^ru}|E{^r}

Direction sign{@Y}MIL{^r}

Direction to runway{@Y}27*33{^r}

Direction to multiple
runways
Runway hold{@Y}{^l}5|13{^u}Runway crossing{@R,^ld}5-23{^ru}|{^lu}9-27{^rd}X-Plane Airport Data (Apt.Dat) File Specification{@R}15-33

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Sign

Sign type

Text to generate this sign

Runway approach area{@R}15-APCH

Location & runway hold{@L}T{@R}18-36

Runway safety areaboundary
ILS critical zone boundary{safety}
If on back of a runway hold sign (above) would be: {@L}T{@R}18-36{@@}{safety}{critical}

Hazard (end of taxiway){hazard}Distance remaining

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{@B}3
Distance from opposite end of runway might be on back of sign: {@B}3{@@}7

Common errors in sign text:
These are the most common errors found in airport submissions:
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Using a space instead of an underscore symbol for direction (@Y) and runway (@R) signs (eg. "{@Y}RWY 04{^ru}")
Using spaces or underscores in location (@L) signs (eg. “{@L}STAND_24”). These are not allowed.
Forgetting the "@" symbol that prefixes an instruction (eg. "{Y}RWY_04{^ru}")
Using lower case text for single-character glyphs (eg. "{@Y}Rwy_04{^ru}")
Invalid diagonal arrows - the left/right must precede the up/down (eg. "{@Y}RWY_04{^ur}")Forgetting the "^" symbol that prefixes an arrow (eg. "{@Y,ru}B{@L}B")
Mismatched curly braces (do not use regular parentheses) (eg. "{@Y}RWY_04(^ru}")

If there are errors in the text on a taxiways sign, then X-Plane will not render the sign. Such errors are identified and logged in the log.txt file in your X-Plane
system folder. Look for log entries such as:
Syntax error - unknown glyph at B{@L}B
Syntax error - missing closing brace.
(in sign '{@L}B5{@R}NO_ENTRY{@Y}{@@}{@Y,ru}B{@L}B')

FURTHER INFORMATION
Resources are available for airport designers on my web site at http://data.x-plane.com

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