What is a "natural flight loop"? I'm roughly (edit: very well) familiar with flight simulation, but recently I came across a new term. In this brochure (scroll to the second page) by Airbus about flight simulators, they talk about 


  Natural Flight Loop models:
  
  GRM, Aerodynamics...


I've never heard that term before. What does "Natural Flight Loop" mean? Is it Airbus-specific?

(GRM is probably ground-reaction model, aerodynamics is obvious - but that doesn't really explain Natural flight loop, does it?)



EDIT: Ok, "roughly familiar" is a bit understated... I should have made clearer that I'm an aerospace engineer. Actually I have been working on flight dynamics models for simulators myself, so I understand very well, what it needs to develop an accurate flight simulator from a technical point of view (yup - natural flight loop seems to be what is required for FAA FTD Level 6 devices and FFS). 

The issue that remains is that I'm curious what this natural flight loop contains in detail.

Is there someone out there who can tell me if this is...


executable code (like a .dll or whatsoever),
mathematical equations (with probably huge lookup-tables for the parameters),
something like Simulink models (or Modelica or ... )?
does it contain separate models for actuators, gear, aerodynamics, weight &amp; balance,...?
does it contain just the open loop model or also the flight control system?
At Airbus, the Natural Flight Loop is the set of the models that simulate the Natural
Aircraft behaviour: kinematics, mass, fuel, center of gravity, inertia, thrust, ground handling, ground reaction, slat/flap, aerodynamics.

Let me know if you need more info.