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Implementing VNAV support in FlightGear (view source)
Revision as of 02:11, 1 December 2013
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{{#ev:youtube|h4AUfkEcwIg}} | {{#ev:youtube|h4AUfkEcwIg}} | ||
== | |||
== Objective == | |||
Determine how to implement the building blocks required for supporting VNAV in FlightGear: | |||
In real aircraft, the purpose of the so called "performance database" is to reduce the need for the pilot to refer to a performance manual during flight and to provide the FMC (flight management computer) with data required to transmit pitch and thrust commands to the FCC (flight control computer. The performance database is | |||
also used by the FMC to provide detailed predictions along the entire aircraft trajectory. The data stored in the database includes accurate aircraft drag and | |||
engine model data, optimal speed data, maximum altitudes, and maximum and minimum speeds. The FMS onboard the aircraft also performs fuel consumption | |||
predictions based on a reference model: the FMS performance database. The PERF FACTOR entered in the M/CDU helps to the FMS predictions. | |||
Implementing aircraft performance monitoring aims to determine the monitored fuel factor. | |||
The main FMS aircraft performance predictions deal with: | |||
* fuel consumption, time, | |||
* climb and descent path, | |||
* recommended maximum altitude, and | |||
* optimization of speeds and cruise altitude taking into account economic criteria | |||
defined by the airline Cost Index. | |||
The PDB is derived from the IFP aircraft databases. Slight simplifications were taken into account because of the limited size of the FMS memory. For example, only one air conditioning setting is available (LO/ECON as appropriate). Per design, the aircraft performance databases are stored in the FMS Perf Data | |||
Base (PDB). There is only a single PDB per family of aircraft. | |||
== Background == | |||
{{cquote| I don't think any aircraft AP supports vertical route navigation yet - and the route-manage itself only has partial support for editing waypoint altitude. There's no real obstacle - waypoints store an altitude (and speed), and the AP can read it, but nobody spent time making it work yet. Vertical modes (VNAV) also tend to depend more on fuel/load and engine performance data from the FMS, which is an area that's been lacking in FlightGear, | {{cquote| I don't think any aircraft AP supports vertical route navigation yet - and the route-manage itself only has partial support for editing waypoint altitude. There's no real obstacle - waypoints store an altitude (and speed), and the AP can read it, but nobody spent time making it work yet. Vertical modes (VNAV) also tend to depend more on fuel/load and engine performance data from the FMS, which is an area that's been lacking in FlightGear, | ||
so hard to model the climb and descent profiles meaningfully. <ref>{{cite web |url=http://forum.flightgear.org/viewtopic.php?f=40&t=13777&hilit=performance+vnav#p140230 | so hard to model the climb and descent profiles meaningfully. <ref>{{cite web |url=http://forum.flightgear.org/viewtopic.php?f=40&t=13777&hilit=performance+vnav#p140230 | ||