Spit IIa

[winny]

Originally Posted by Crumpp

Not at all. In fact that is big myth.

Remember, a stable airplane can do any maneuver an unstable aircraft can. The stable airplane can do it just as fast and more precisely requiring a less skilled pilot to do the same thing. It can also do things the unstable one cannot. Such as not destroy itself by overloading the airframe, shoot down other airplanes much faster, land with more control and precision, maneuver better in rough air, and hold a precise altitude/heading in instrument conditions.

Unstable just means the airplane is skittish and hard to control.



Sure it was....

The RAE even recognized it attempted to fix it. Eventually it was eliminated in the very late marques with an empennage redesign.

So, when someone refers to a Modern Aircraft being unstable (I'm thinking of the ones that need a computer to fly them) are they talking about the same 'unstability'? Is it even true? (I'm not arguing here, I'd just like to know)

About the 'problem', how come the vast majority of Spitfire pilots say it was so easy to fly? How did this problem manifest it's self?

[Crumpp]

Is it even true?

YES!! They are much more maneuverable than if the designer had built a stable aircraft.

They are so twitchy a human being cannot react fast enough to keep them from destroying themselves.

Hence you answered your own question:

I'm thinking of the ones that need a computer to fly them

IIRC, IL2 players complained quite a bit about the P51 Mustang FM's being twitchy.

That is sort of how an airplane with a small enough stability margin to be considered neutral in longitudinal flying qualities will behave.

[CaptainDoggles]

In some cases the negative or "relaxed" stability of the aircraft is a consequence of the design, rather than an explicit design goal. I'm thinking here of the F-117 and the B-2, whose fuselages are very unorthodox due to stealth requirements. Aircraft such as these require FBW systems to stay aloft.

In fact I once heard the B-2 described as being "held in the air by sheer computing power"

Other aircraft such as the F-16 are designed to be intentionally unstable.

People often get mixed up due to the terms stable/unstable having very specific, prescribed meanings.

[Crumpp]

The problem is people confuse "unstable" with "agile" and "stable" with "sluggish" because the terms stable/unstable have very specific, prescribed meanings that aren't necessarily in line with the common vernacular.

Yes, terminology is very important. Take the "maximum lift coefficient" term. That is often used to define the highest Coefficient of Lift over a given range.

http://www.google.com/search?q=Cruis...w=1920&bih=941

http://enpub.fulton.asu.edu/aero/mae...ingchapter.pdf

"Maximum coefficient of lift" is the term for the CLmax a section can produce and defines the Angle of Attack the airfoil stalls.

http://www.google.com/search?q=Cruis...0&bih=941&bs=1

[TomcatViP]

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.

[JtD]

You don't have the real life forces on your joystick. So stick travel doesn't give you the feedback you get in the plane.

[robtek]

Originally Posted by JtD

You don't have the real life forces on your joystick. So stick travel doesn't give you the feedback you get in the plane.

As the required forces in the spit are very low, being the "problem", i dont think that matters so much.

There is a spring in your stick, isnt it?

Also there is always ffb a possibility.

[JtD]

I don't pull 5 lb on my stick, let alone 50, which even with the low stick forces in the Spit were necessary on occasion to bring the plane to the limit.

Stick forces in the Spit were low but OK, not "the problem".

[TomcatViP]

Originally Posted by JtD

You don't have the real life forces on your joystick. So stick travel doesn't give you the feedback you get in the plane.

No but variable neutral zone can makes you feel as if you had to pull harder

[CaptainDoggles]

Originally Posted by TomcatViP

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.

I'm not certain if you're agreeing or disagreeing with me, or just expounding on the design of the F-117 and B-2