FPAL is a descriptive language with a syntax similar to C.

Comments

Three types of comments are supported:

Single line comments starting with # (pound)
Single line comments starting with // (double slash)
Multi line comments starting with /* and ending with */

Here is an example showing all three types of comments:

# this is a comment
/*
 * this comment spans multiple lines
 */
// another single line comment

Comments are ignored by the parser.

Strings

Strings are enclosed in double quotes (“). Note that identifiers such as airport names or navaid names are not strings. Strings can contain the wildcard characters asterisk (*) to match any set of characters and question mark (?) to match a single character.

Language keywords

rule

Marks an FPAL rule. Rules are found at the top level of the file. The syntax is

rule <uuid v4> {
}

Addressing statements

A rule generates output in case it matches. The following types of output are recognized:

info

The string following the statement is written as an informational message.

warning

The string following the statement is written as a warning.

error

The string following the statement is written as an error.

aftn

The list of AFTN addresses separated by spaces is added to the flight plan addresses.

sita

The list of SITA addresses separated by spaces is added to the flight plan addresses.

email

The list of email addresses separated by spaces is added to the flight plan addresses.

fax

The list of fax numbers separated by spaces is added to the flight plan addresses.

Conditions

Conditions determine whether a rule matches. They can appear within a rule but also independently with an identifier which can then be referenced in a rule. This allows convenient sharing of conditions.

cond "MY_CONDITION" {
}

The following conditions are supported.

and

The list of expressions contained inside the block have to evaluate to true for the condition to match.

or

One expression contained inside the black has to evaluate to true for the condition to match.

gand

Global and. Iterates over all waypoints in the global context.

gor

Global or. Iterates over all waypoints in the global context. To illustrate the concept, let’s look at a rule that would trigger on a flight plan that has a flight rule change:

cond {
   and {
      gor {
         vfr;
         airspace EFIN/fir F000-F999;
      }
      gor {
         ifr;
         airspace EFIN/fir F000-F999;
      }
   }
}

This rule triggers when both elements inside the and match. As the outer condition would iterate over all waypoints and thus the inner conditions only “see” one waypoint, we have to use gor to go over all waypoints. If at least one waypoint is VFR and in the Helsinki FIR, the gor condition will match. The same for the second gor and as they both match, the surrounding and will match and thus the rule.

seq

Matches when the conditions inside the element are met for subsequent waypoints.

seq {
   airport EDDS;
   navaid DKB;
}

Would match if the next waypoint after the airport EDDS is the navaid DKB.

not

None of the conditions in the expression may evaluate to true for the condition to match. not can be combined with other operators such as not and, not or or not dep.

dep / departure

Matches if the current waypoint is the first waypoint (departure aerodrome).

dest / destination

Matches if the current waypoint is the last waypoint (destination aerodrome).

gdep

Returns the first waypoint (departure aerodrome).

gdest

Returns the last waypoint (destination aerodrome).

false

Never matches.

true

Always matches. Can be used in statements like the following to test whether the waypoint is not the departure aerodrome:

not dep true;

airspace

Matches if the waypoint is inside the airspace specified by the statement. Airspaces are identified by the name in ADR. Optionally an altitude band can be specified. Without altitude information, the vertical extension of the airspace is used.

airspace EDGG/fir F050-F100;

Would match between flight level 50 and flight level 100 in the Langen FIR in Germany.

ident

Matches if the waypoint is in the given list of identifiers. This means the type of waypoint does not have to be specified.

airport

Matches if the waypoint is one of the specified airports.

airport EDDS;
airport "ED*";
airport EDDS EDDM;

The first example matches the airport EDDS, the second all airports in Germany (starting with “ED”), the latter the airports EDDS and EDDM.

intersection

Matches the waypoint if it is one of the specified IFR waypoints.

intersection ABTAL;
intersection ABTAL VATER UNSER;

navaid

Matches the waypoint if it is one of the given navaids.

vor

Matches the waypoint if it is one of the given VORs.

dme

Matches the waypoint if it is one of the given DMEs.

tacan

Matches the waypoint if it is one of the given TACANs.

ndb

Matches the waypoint if it is one of the given NDBs.

regex

Matches the waypoint if the given regular expression matches.

ifr

Matches the waypoint if the flight rules at the waypoint are IFR.

ifrgat

Matches the waypoint if the flight rules are IFR GAT (as opposed to IFR OAT for military IFR and other flight rules).

vfr

Matches the waypoint if the flight rules at the waypoint are VFR.

vfrday

Matches the waypoint if the flight rules at the waypoint are VFR at daytime.

vfrnight

Matches the waypoint if the flight rules at the waypoint are VFR night time.

mtom

Matches if the aircraft’s MTOM. Value is in kilograms and can be a range.

mtom 0 ... 1999

timetable

A timetable expresses a date/time span and evaluates to true when the current time is within the span.

timetable {
   applicability 2014-05-01T00:00:00Z;
   {
      sat sun;
   }
};

A timetable has an applicability group and then a group with day and time of day statements.

otherinfo

Returns true when the other information part of the flight plan (item 18) matches the following criteria.

not otherinfo RMK/"ASL\\d{10}";

This condition matches when the flight plan does not contain a RMK/ASL with a 10 digit number.

flighttype

Matches the flight type against the expression. The following example tests for military and state flights:

flighttype MX;

radius

Matches a given radius in nautical miles (NM) around a given point within a given altitude range. Example:

radius 25 airport LGIO MSL-F050;

polygon

alternate

Matches if either the first or second alternate is in the list of alternates given.

alternate1

Matches if the first alternate is in the list of alternates given.

alternate2

Matches if the second alternate is in the list of alternates given.

aircraftid

Matches if the aircraft ID is in the list given.

daylightsaving

Matches when daylight time saving in the specified timezone is active.

daylingsaving CET

would evaluate to true from the last Sunday in March until the last Sunday in October.

GND

Ground level for the altitude range instruction.

MSL

Sea level for the altitude range instruction.

UNL

Unlimited ceiling for the altitude range instructions.

Altitude range

Operators

The language knows the following operators.

At sign (@)

Colon (:)

Comma (,)

Dot (.)

Assignment (=)

Minus (-)

Left square bracket ([)

Right square bracket (])

Left curly bracket ({)

Opens a new block. Must be closed by the right curly bracket (}).

Right curly bracket (})

Closes a block which must have been opened before with the left curly bracket ({).