X-PLANENAVIGATION DATA FOR MINIMUM SECTOR ALTITUDES (EARTH_MSA.DAT) FILE SPECIFICATIONVERSION 1150
REVISION HISTORY
21 Mar 2020

Initial Specification

APPLICABILITY
This specification (XP MSA1150) is supported in X-Plane 11.50 and later. It is identified in the data files as “1150 Version” on the second row of the file.
No prior specification for this type of file exists.

OVERVIEW & SCOPE
This specification defines all published minimum sector altitudes for navaids, fixes, airports and runway thresholds in X-Plane (PS-records in ARINC424 data).
The effect of this data is to:•Allow ATC to keep AI aircraft at or above published MSAs for vectoring

BASIC CONCEPTS•

A minimum sector altitude can only be defined at a point that is either listed in the enroute portions of earth_nav.dat or earth_fix.dat or an airport or
runway threshold in the Resources/default scenery/default apt dat/Earth nav data/apt.dat – third party sceneries are not scanned for airports.

FILE CHARACTERISTICS
The earth_msa.dat file is plain text file:••

Fields in the data can be separated by one or more white space (space, tab) characters.
By default, the files are generated so that columns of data are consistently aligned, but this is not required.

X-Plane MSA Data (earth_msa.dat) File Specification

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FILE STRUCTURE
In common with most other X-Plane data file specification, header rows of data define the origin (“I” = Intel byte order or “A” = Motorola byte order) of aparticular copy of a file and define the file specification version. The file specification must include the four-digit AIRAC cycle date (e.g. 1602 for the AIRAC cycle
effective 4-Feb-16, refer to https://www.nm.eurocontrol.int/RAD/common/airac_dates.html for cycle dates), an 8-digit build date and the reference to thisdocument. A copyright message may be added, while the total length of this line is not to exceed 1024 characters:
I1140 Version - data cycle 1602, build 20160204, metadata HoldXP1140. Copyright © 2016, Robin A. Peel (robin@xsquawkbox.net)...

Subsequent rows of data define each waypoint. Sequence is not important, but by default this file is sorted alphabetically by fix name.
The file is terminated by a ‘99’:
99

ROW CODES
Unlike other data files, no ‘row codes’ are used for hold data, since the file contains just one type of data.

EXAMPLE DATA
Here is example data for minimum sector altitudes:
3BOS K6 KBOS M 035 025 25 125 020 25 000 000
11 CRAAB K6 KBOS M 180 025 25 000 000 0
10 RW04R K6 KBOS M 180 025 25 000 000 0

X-Plane MSA Data (earth_msa.dat) File Specification

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DEFINITION OF DATA FIELDS
Each column in each row is defined below, using the example data from shown above. Note that:Row[none]

Meaning
Example value

CommentExplanation

Valid values

MSA

Published MSA around fix, intersection or navaid

No row codes are used, since all data refers to holdings

3

Type of Fix, Navaid, Airport or Runway Threshold

BOS
K6

Identifier of fix, navaid, airport or runway threshold
ICAO region code of fix or navaid

KBOS
M

Terminal region identifier - mandatory
Sector Bearing Mag/True Indicator

11 = Fix, 2 = enroute NDB, 3 = VHF navaid (VOR, TACAN, DME),
1=ARP (airport reference point), 10=runway threshold
One to five character valid identifier of known fix or navaidMust be region code according to ICAO document No. 7910
Airport code for terminal procedure use. The same point canhave different sector altitudes when used by a procedure at adifferent airport. This field cannot be empty.
See 424.18 5.165

03502525...

Sector Bearing
Sector Altitude
Radius Limit
Up to six more Bearing/Altitude/Radius tripletsSee 424.18 4.1.20.1, 5.146
See 424.18 4.1.20.1, 5.147
See 424.18 4.1.20.1, 5.145
See above

000 000 0

Terminator after a maximum of seven sectors.

Must be all zero values

FURTHER INFORMATION
Resources are available for airport and navaid designers at the X-Plane Scenery Gateway at http://gateway.x-plane.com/X-Plane MSA Data (earth_msa.dat) File Specification

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