Implementing VNAV support in FlightGear: Difference between revisions

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Implementing VNAV support in FlightGear (view source)

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* {{cite web |url=http://human-factors.arc.nasa.gov/publications/20051025130903_VNAVCogEngJournal1TM.pdf |title=Why VNAV in Descent is Difficult to Use }}
* {{cite web |url=http://human-factors.arc.nasa.gov/publications/20051025130903_VNAVCogEngJournal1TM.pdf |title=Why VNAV in Descent is Difficult to Use }}
}}
}}
== The Performance Database ==
There are typically two loadable databases that support the core flight management functions. These are the navigation database which must be updated on a monthly cycle and the performance database that only gets updated if there’s been a change in the aircraft performance characteristics (i.e., engine variants or structural variants affecting the drag of the aircraft).
The performance database contains aircraft/engine model data consisting of drag, thrust, fuel flow, speed/altitude envelope, thrust limits, and a variety of optimized and tactical speed schedules that are unique
to the aircraft.
Typically, the performance database contains data sets for
* take-off and configuration speeds
* approach and landing speeds
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.


== Problem ==
== Problem ==
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Determine how to implement the building blocks required for supporting VNAV (vertical navigation) in FlightGear:
Determine how to implement the building blocks required for supporting VNAV (vertical navigation) 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 ==
== Background ==
Retrieved from "https://wiki.flightgear.org/Special:MobileDiff/65093"

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