F117 is unstable due to the interaction of the uncunventional faceted shape and aerodynamics forces. Ben Rich's team added some FBW rules (out of an F16
) to free designer to go much further in the quest for stealth.
The unstability of the B2 is more linked to the clean flying wing shape with no vertical surface.
With the F16 and the Mirage 2000 the world of high perf fighter begin a new aera were the relaxed stability was the norm. What does it means ? Simply that the balancing forces around the CG were modified to allow a more compact design with the CG moving aft with high pitch authority as a direct benefit.
If you look closely at a post 80 design with FBW added you'll see that the jet engines are put at the tip end with no long draggy inner combustion pipe such as in the early jet and mid 60's (draggy because a jet engine blowing in a pipe loose that way its flow momentum due to inner wall friction. Hence a loss in propulsive power). This as freed the designer for a more balanced design improving the overall aero efficiency, lowering the empty weight (hence the direct and OP cost) and increasing the potential modifications in the .
What the FBW do ? It simply act where the pilot can't with only minor correction to correct the induced instability of the aircraft.
This principle was re-used by Airbus to minimize the tail surface of its design (drag lowered) such as the A320 witch was a seemingly logical step forward with the introduction of airfoils with a reflex zone (that cld be discussed today).
SO instability and relaxed stability is not exactly the same thing. In fact you can possibly design an unstable aircraft with relaxed stability
... Or have a stable aircraft with some relaxed stabilty added
Or hve a stable aircraft that can be turned unstable in pitch if you move the ctrl further bckwrd
The best way to asses the Spit instability for everyone here and its uncomfortable 3/4 inch (2cm) stick travel would be to reconfigure your joystick to allow only that travel in the pitch zone.
I am sure dozen here will instantly become Spit hatter in a single day !!
By the way as ths is a Spit mkIIa thread can Devs stop the annoying characteristic of that bird in CoD that have a better P/W ratio than the 109.
Now I see most of the Spit moving in the vertical plan knowing that there is a bug with the FM.
