Nasal Flightplan

Note  Whenever possible, please refrain from modeling complex systems, like an FDM, autopilot or Route Manager with Nasal. This is primarily to help reduce Nasal overhead (especially GC overhead). It will also help to unify duplicated code. The FlightGear/SimGear code base already contains fairly generic and efficient systems and helpers, implemented in C++, that merely need to be better generalized and exposed to Nasal so that they can be used elsewhere. For example, this would enable Scripted AI Objects to use full FDM implementations and/or built-in route manager systems. Technically, this is also the correct approach, as it allows us to easily reuse existing code that is known to be stable and working correctly, . For details on exposing these C++ systems to Nasal, please refer to Nasal/CppBind. If in doubt, please get in touch via the mailing list or the forum first.

Because FlightGear's route manager flight plan system is exposed to Nasal, Nasal can be used to interact with flight plans. Obviously, this is very useful, especially for aircraft like airliners, which have complex route managers systems. This article shows how this can be done.

Background

The Nasal functions relating to the route manager system include:

• flightplan()
• airwaysRoute()

Flight plans are based on waypoints, which, in C++, inherit from the FGPositioned _(doxygen) class.

Waypoint hashes

The following are members of a waypoint ghost, as generated by, for example, airwaysRoute() :

wp_name

Name of the waypoint, returned as string.

wp_type

Waypoint type, returned as string. One of "basic," "navaid," "offset-navaid," "runway," "hdgToAlt," "dmeIntercept," "radialIntercept," or "vectors."

wp_role

Role of waypoint.

wp_lat or lat

Latitude of waypoint.

wp_lon or lon

Longitude of waypoint.

wp_parent_name

Name of waypoint's parent.

wp_parent

Waypoint's parent.

fly_type

How to waypoint should be flown over or reacted to. One of "Hold," "flyOver," or "flyBy."

heading_course

Heading of runway.

Examples

# get the active flight plan (the one being used by the route manager)
var fp = flightplan();

# or create one an XML file
fp = flightplan('/path/to/xml');

# save the active flight plan
fgcommand("save-flightplan", props.Node.new({"path": 'path/to/xml'}));

# duplicate a flight-plan
var secondary = fp.clone();

var dest = airportinfo('KSFO');
var rwy = dest.runway('19L');
# the the arrival runway (and airport, automatically)
fp.destination_runway(rwy)

# or if no runway is known/specified
fp.destination(dest)

Building procedures and transitions. As mentioned above there's a couple of different ways to handle this, the examples below assume the C++ code automatically deletes and re-inserts waypoints for procedures, but that's only one possible design.

var apt = airportinfo('KSFO');
# example for SIDs, STARs are the same, approaches too
var allSids = apt.sids();

# SIDs for a specific runway - note these return SID IDs as string, for compatibility with existing code
var rwySids = apt.sids('28L');

Inserting and deleting waypoints (possibly in batches)

var fp = flightplan();
# waypoint created from lat, lon, or a navaid, or anything else?
var pos = geo.aircraft_position().apply_course_distance(getprop("/orientation/heading-deg"), 100000);
var wp = createWP(pos.lat(), pos.lon(), "EPICA");

# manually insert a waypoint into the plan
fp.insertWP(fp.getPlanSize(), wp);

# route along airways, and insert a whole bunch of waypoints
# this is needed for the route-manager dialog, maybe not for a
# real FMS interface....
var segment = [<waypoint object>, <waypoint object>, <waypoint object>];
# segment is a vector of waypoints now
fp.insertWaypoints(segment, fp.getPlanSize());

Related content

Wiki articles

• Nasal library § Extension functions
• Navdata cache § Accessing via Nasal

Documentation

• flight planGhostSetMember — Members of a flight plan object that can be set.
• flight planGhostGetMember — Members of flight plan object that can be read.
• initNasalPositioned — Contains a list of functions that can be called on airport, flight plan, waypoint, procedure, or flight plan leg objects.
• FGRouteMgr::FGRouteMgr — List of fgcommands relating to the route manager.