Hooray wrote in Fri Nov 09, 2018 6:17 pm:Note that supporting VNAV properly is a completely separate issue: http://wiki.flightgear.org/Implementing ... FlightGear.
it0uchpods wrote in Sat Nov 10, 2018 5:24 am:Let me warn you that this is extremely out of date, and is no longer accurate in many cases. [...]
In fact, I have a partially working VNAV simulation for the Airbus already implemented
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.
At the center of the FMS functionality is the flight plan construction and subsequent construction of the four-dimensional aircraft trajectory defined by the specified flight plan legs and constraints and the aircraft performance. Flight plan and trajectory prediction work together to produce the four-dimensional trajectory and consolidate all the relevant trajectory information into a flight plan/profile buffer.
http://www.davi.ws/avionics/TheAvionics ... Cap_15.pdf
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