What is "aircraft stability" - IN VIDEO

[JtD]

Originally Posted by Crumpp

What are you talking about???

You should know, you even highlighted it on the previous page, but in case you really can't figure it out - I am referring to phugoid and spiral modes, I've only said it about 5 times, so maybe it was lost on you. Phugoid, spiral. That's all I'm talking about. I do this because you keep bringing up an A.&A.E.E. chart supposedly illustrating how poor the Spitfire's stability was, where it shows nothing but long period oscillations, i.e. phugoid and spiral mode. This chart shows nothing out of the ordinary for a high speed fighter of that day and the characteristics shown are way better than that of the Hurricane. It appears to me that up to this minute, you don't even know what you're talking about, and yet you've made 100+ posts on the issue trying to convince innocent bystanders of something that's plainly wrong.

It is really getting on my nerves, and here it is in short form, so I can simply quote me every time you bring that chart up again out of context:

The A.&A.E.E. stability records for Spitfire K.9788 show stick free, long period dynamic stability characteristics, also known as phugoid and spiral mode. The records show typical behaviour for world war 2 fighter aircraft, and the characteristics are clearly better than those of other contemporary aircraft, in particular better than the characteristics of the Hurricane, which was also tested by the A.&A.E.E. at the same time.

[TomcatViP]

JTD the pitching moment decrease with the thickness of an airfoil. Tht's how simple it is.

The great challenge in the 50's with the thin wing design and their lack of stability came with that. The video show how the lift center is moving frwd. This move is faster when the thickness ratio decrease. This is why most of the designer during WWII did stick to the 15% ratio.

Supermarine did not have all the viscous flows knowledge as other did and ran straightforward in the thin wing solution (just like the Brits did in WWI). Hence the long dev process. of the Spitfire. That's simple.

Other planes had flaws inherent to their design and did take as long to be fully flaw free.

[JtD]

OK and thanks for the information as such.

It changes nothing about what I wrote, though, if you meant to refer to that.

[TomcatViP]

Another short video explaining the main diff. btw relaxed stability aircraft and stable aircraft:

http://www.youtube.com/watch?v=VImEvFg3smQ

I think it complete well the first one and was needed here.

[JG14_Josf]

Hi,

From the first video it seems clear enough that an unstable airplane (center of lift in front of the center of gravity) is like pushing a shopping cart and trying to keep the castor wheels facing the wrong way - impossible.

Castor wheels have center of axis ahead of the contact patch where the wheel meets the road.