This is a timely topic for us in HEMS, as the new training rules called for in the HEMS rule (public law) will involve the increased use of flight simulators and flight training devices. Indeed, one of the questions put to the action team I serve on for NEMSPA was "how can the FAA incentivize the use of flight simulators?"
Click here to read the AOPA letter to the FAA.
US Federal Aviation Administration (FAA)
Flight Training Devices (FTD)
FAA FTD Level 4 - Similar to a Cockpit Procedures Trainer (CPT), but for helicopters only. This level does not require an aerodynamic model, but accurate systems modeling is required.
FAA FTD Level 5 - Aerodynamic programming and systems modeling is required, but it may represent a family of aircraft rather than only one specific model.
FAA FTD Level 6 - Aircraft-model-specific aerodynamic programming, control feel, and physical cockpit are required.
FAA FTD Level 7 - Model specific, helicopter only. All applicable aerodynamics, flight controls, and systems must be modeled. A vibration system must be supplied. This is the first level to require a visual system. (added, no motion...)
Full Flight Simulators (FFS)
FAA FFS Level A - A motion system is required with at least three degrees of freedom. Airplanes only
FAA FFS Level B - Requires three axis motion and a higher-fidelity aerodynamic model than does Level A. The lowest level of helicopter flight simulator.
FAA FFS Level C - Requires a motion platform with all six degrees of freedom. Also lower transport delay (latency) over levels A & B. The visual system must have an outside-world horizontal field of view of at least 75 degrees for each pilot.
FAA FFS Level D - The highest level of FFS qualification currently available. Requirements are for Level C with additions. The motion platform must have all six degrees of freedom, and the visual system must have an outside-world horizontal field of view of at least 150 degrees, with a Collimated (distant focus) display. Realistic sounds in the cockpit are required, as well as a number of special motion and visual effects.
( Courtesy Wikipedia)