Flight model

It is not the same at all...

F-15 do not have FBW....!

F-15 has FBW. Just because it's hydro-mechanical instead of electronic doesn't make it 'not FBW'. It does a lot, and could do even more just as it is.

But no, it isn't as capable as the modern FBW avionics.

F-15 has FBW. Just because it's hydro-mechanical instead of electronic doesn't make it 'not FBW'.

hydro-mechanical is, by definition, NOT "by wire"... "by wire" mean "electrical/electronical". BUT obviously, F-15 must have some electronic (or at least analogic electrical ) systems that regulates some maneuvers.... like the Su-27.

The fact is that M2000 is full "FBW" like the F-16...and Dasault was always in advance in this domain (even the Mirage IV was FBW)

I believe the F-15 has a stability augmentation system, which does not make it FBW by definition.

I believe the F-15 has a stability augmentation system, which does not make it FBW by definition.

Thats right...

FBW is a flight crontrol computer, that filters the pilots input, within the flight envolope, in short terms, F-15 or anyother planes pre F-16 dosent have it...

Well, and our beloved Su-27 only has fly-by-wire that controls pitch...

The lines start to get blurry as there are many levels of control assist that can be built into an aircraft flight control system. The three different tiers that I have read about are: SAS (stability augmentation system), CAS (control augmentation system), and FBW (fly-by-wire systems).

Stability Augmentation System is what is found on the F-14A/B/D prior to the DCFS (Leatherneck's upcoming module will feature an SAS). After DCFS (integrated in the very-late 1990s), the system became more of a CAS. SAS systems are purely passive and function by reducing the magnitude of control inputs, usually by using a fairly simple algorithm. Classic examples is controlling roll rate by reducing the magnitude of control inputs above certain speeds and limiting pitch inputs to reduce the risk of stall/departure. The system cannot add additional inputs, only reduce the magnitude of inputs. So it cannot do things like adjust aircraft trim, such as the PTC in the F-15.

Control Augmentation System is an intermediate step between the relatively simple SAS and true FBW. CAS can both reduce the magnitude of control inputs and add additional inputs according to algorithms. This allows the F-15 to integrate helpful features such as the pitch trim compensator, sophisticated aileron-rudder-interconnect, pitch ratio changer, and roll ratio changer. These features give a FBW-like experience with relatively constant control efforts/excursion despite dramatic changes in aircraft speeds. The F-15 in particular also gives a very FBW-like experience largely because the F-15 has both a sophisticated CAS and excellent native aerodynamics with very benign handling/departure characteristics (the F-15 engineers deserve a pat on the back :)).

The last level is true Fly-By-Wire control system. This goes beyond CAS in that all pilot control inputs are interpreted by the computer and the control surfaces moved based upon algorithms and feedback from the airframe. I believe that true FBW is a system in which there is no direct connection between the pilot's control stick and the control surfaces. The F-16 and F-117 pioneered this concept with no back-up control system. The Tornado has a system that is probably FBW, but there is "back-up" hydraulic controls. Still, according to my references, the control surfaces are effectively moved by computer outputs under normal operations. This is the same for the Su-27 which has (IIRC) back-up hydraulics, but under normal operations there is no direct link between pilot inputs and control surface movements.

The lined between an advanced CAS and FBW can get blurry, but I hope this helps to clear up the confusion (and didn't add to the confusion ;)).

-Nick

Maybe we should stick to the FBW of the Mirage :)

I think the FBW on the Mirage does a lot of work to keep the aircraft stable. If you look at the front of the wings you can see the becs/slats constantly making tiny movements to keep the plane smoothly flying.

Good info, BlackLion213!