Stability and Control characteristics of the Early Mark Spitfires

[Fenrir]

Originally Posted by robtek

I think the fact that you have to return the stick almost to neutral after entering a high g turn (>3 g) to prevent oversteering in a Spitfire should be in game, also the very sensible elevator with large reaction for small inputs and the roll rate as documented.
This will be a problem for ham-handed pilots, but a delight for the virtuosos, as it was in RL.
I don't see that as "porking" the Spit further, but to give it the characteristics that made it famous.
Every aircraft in CoD should reflect its pro's and con's as they where documented then.

These characteristics you describe are NOT representative of all Spitfires. Therefore they should NOT be in game. Read again my post on stability. It affected *some* - and it seems I need to remind some people here that does not mean all - Mk V aircraft. A Mk V is NOT a Mk I, or Mk II.

All I can suggest is that you guys go away and read the books I've read, go further make even more research and come back and make an informed opinion then. Please for pity's sake do not take the one single example of an agenda driven poster as gospel.

The NACA test discovered what they discovered - I can't argue with their findings, FOR ONE PARTICULAR AIRCRAFT. However I cannot agree that these are representative of the breed. And as for relevance, well, I've said it already. A Mk V is not a Mk I.

[CaptainDoggles]

Originally Posted by Fenrir

The NACA test discovered what they discovered - I can't argue with their findings, FOR ONE PARTICULAR AIRCRAFT. However I cannot agree that these are representative of the breed.

What is it about the tested aircraft that makes it not a representative sample of the other aircraft?

[NZtyphoon]

Originally Posted by CaptainDoggles

What is it about the tested aircraft that makes it not a representative sample of the other aircraft?

There are some awkward little phrases in the NACA test viz:



Now, until Crumpp, or anyone else, can prove beyond reasonable doubt that NACA got their cg calculations right there is a question mark over the longitudinal stability of this Spitfire VA as tested.

[CaptainDoggles]

You know Crumpp's right about expressing CG as a percentage of MAC. The Datum point doesn't have to be in the same spot for the results to be valid. That's why it's called a datum point.

[NZtyphoon]

Originally Posted by CaptainDoggles

You know Crumpp's right about expressing CG as a percentage of MAC. The Datum point doesn't have to be in the same spot for the results to be valid. That's why it's called a datum point.

Crumpp wasted countless hours nitpicking the 100 Octane threads with minute, forensic examination of every single little detail - his contention, that the early marks of Spitfire had longitudinal stability problems which needs to be replicated by this game, needs to be proven to the same level that he demanded for 100 Octane fuel; nothing less should do.

[CaptainDoggles]

Originally Posted by NZtyphoon

Crumpp wasted countless hours nitpicking the 100 Octane threads with minute, forensic examination of every single little detail - his contention, that the early marks of Spitfire had longitudinal stability problems which needs to be replicated by this game, needs to be proven to the same level that he demanded for 100 Octane fuel; nothing less should do.

That 100-octane thread was monumentally stupid on all sides. It just does not matter, even remotely, what percentage of Spitfires were on 100 vs how many were on 87. Both should appear in the game, and both now do appear in the game (performance problems notwithstanding).

Vendettas aside, the sheet that Lane posted looks interesting.

I'm not 100% clear on what those graphs are supposed to be representing, but if we look at #4 for example, it shows the airspeed diverging wildly from equilibrium, which I would assume is due to the aircraft doing the rollercoaster "porpoise" motion.

A stable aircraft should return to equilibrium, not diverge from it.

[Crumpp]

Just some of the many references to the Longitudinal instability found in all of the early Mark Spitfires.

Spitfire Mk I Operatings Notes, July 1940:











Tommorrow I think we can discuss game behaviors to ask for in the bugtracker.

[MiG-3U]

Originally Posted by CaptainDoggles

You know Crumpp's right about expressing CG as a percentage of MAC. The Datum point doesn't have to be in the same spot for the results to be valid. That's why it's called a datum point.

There is only one accurate reference point for the CoG in the NACA report, the distance of the CoG from the leading edge at the wing root and that is given as 31.4". NACA admits that their measurements for MAC maybe in error and we can easily see that there is error because in the RM2535 the 34% CoG location at the RAE measured MAC is also given same way as distance from the leading edge at the wing root and the value is 2.638' which is 31.656". Even with these values only we can estimate that the real CoG location was about 33.7% at the MAC given by RAE instead 31.4% claimed by NACA (and NACA admited that their value might be wrong).

As we know accurate reference point at the wing root and dimensions for MAC used by RAE and A&AEE and datum line, we can also easily calculate these.

Lenght of the MAC measured by RAE and A&AEE is 78.54" (or 6,54') and position 31.4" behind leading edge at root is 26.4476" at MAC and that means that CoG was at position 33.6741% in the NACA tests using RAE and A&AEE dimensions.

However, British documentation gives CoG values usually as distance from the datum line so we need to make NACA CoG location comparable with these. And that is easy because we know that the datum line is 18.65" behind leading edge at the MAC:

26.4476" - 18.65" = 7.7976"

And this value, 7.8" aft datum line, is comparable with the other sources like A&AEE and RAE tests and loading instructions.

Over and out.

[TomcatViP]

Originally Posted by Fenrir

These characteristics you describe are NOT representative of all Spitfires. Therefore they should NOT be in game. Read again my post on stability. It affected *some* - and it seems I need to remind some people here that does not mean all - Mk V aircraft. A Mk V is NOT a Mk I, or Mk II.

All I can suggest is that you guys go away and read the books I've read, go further make even more research and come back and make an informed opinion then. Please for pity's sake do not take the one single example of an agenda driven poster as gospel.

The NACA test discovered what they discovered - I can't argue with their findings, FOR ONE PARTICULAR AIRCRAFT. However I cannot agree that these are representative of the breed. And as for relevance, well, I've said it already. A Mk V is not a Mk I.

Did RAE and NACA test the same aircraft ? Because so far we can see they draw the same conclusions.

And oh nasty they are, they even gave some recommendations in the handbook. I guess that they wanted to wage a war 70 years latter on a dark corner of the internet

[robtek]

The "agenda driven" shoe fits some feet here, i believe.