Professional Flight Model (PFM). This is generations beyond an AFM/AFM+ and is based upon:
• Use a wider array of wind tunnel tests CFD methods for aerodynamics parameters calculations.
• A higher level of aircraft construction details for forces calculations. For example: our landing gear model includes individual kinematics of retracting/extending is used to calculate its movement, servo-piston forces, etc. In such cases, we truly use real lengths, arms, etc. This also includes such items as a realistic simulation of airflow along the airframe due to the propeller or helicopter rotor thrust.
• Realistic simulation of Flight Control, CAS and Autopilot systems.
• Realistic simulation of Hydraulics, Fuel, Electrical, Engine and other systems influence flight characteristics.
• Unprecedented access to test data packs.
This is combined with much more detailed and accurate accounting of the physical forces on the aircraft and airfoils. DCS examples of the PFM include the A-10C, Ka-50, P-51D, UH-1H, Mi-8MTV2, F-15C and Su-27 (in development) for DCS Flaming Cliffs, and the Fw190-D9 (in development).
External Flight Model (EFM). Used by our partner developers, the EFM uses only a part of PFM - rigid body physics and contact model. What forces and moments are applied to this rigid body from aerodynamics and any other sources except the contact forces is up to EFM developer.
The difference being that a PFM would be called a Professional Flight Model if my understanding is correct.. Which would mean being of the caliber that it could be used a Commercial training tool to the fidelity of the aircraft.