Stability and Control characteristics of the Early Mark Spitfires

[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.

[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.

[Fenrir]

Originally Posted by TomcatViP

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

Can you direct me to the RAE test please? I've not read it.

Tomcat, I'm not interested in getting into a slanging match, but I'm finding your tone a little condescending. Can we both agree to keep our future posts a little less aggressive? I'm just trying to present the whole picture as I understand it, without fixating on one source.

Likewise Robtek - I have an agenda, true; I'd like to see every aircraft represented as accurately as possible with the widest possible references to minimise the possibility of error. I just happen to know a great deal about a few aeroplanes (P-38 and P-51 amongst them) with the Spitfire being high on the list. My reference library is not exactly small though by no means complete, and it has been thoroughly absorbed over 20 years. So, you'll exuse me for calling someone out if I think they are presenting data that is either unrepresentative, of poor relevance or inaccurate, on a subject i know a great deal - but not all, admittedly - about.

I'm not after a super plane in game; I simply want both sides to have the pros & cons that the prototypical aircraft had. No more, no less.

[lane]

Originally Posted by Fenrir

Can you direct me to the RAE test please? I've not read it.

Tomcat, I'm not interested in getting into a slanging match, but I'm finding your tone a little condescending. Can we both agree to keep our future posts a little less aggressive? I'm just trying to present the whole picture as I understand it, without fixating on one source.

Hi Fenrir,

Here's some of what I've found that might be of interest:

NACA A.C.R., Sept 1942: Measurments of the Flying Qualities of a Supermarine Spitfire VA Airplane
NACA A.C.R., Sept 1942: Stalling Characteristics of the Supermarine Spitfire VA Airplane





Perhaps also of interest: R & M No. 2535 High-speed Wind-tunnel Tests on Models of Four Single-engined Fighters (Spitfire, Spiteful, Attacker and Mustang)

Fwiw from A. & A.E.E. Spitfire I report 15 June 1939:

[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.

[Crumpp]

Lenght of aerodynamical mean chord (MAC): 78.54"

The rest is simple math:
Aft limit behind datum line at MAC: 26.7036" - 18.65" = 8.05"
Datum line behind leading edge at wing root: 31.656" - 8.05" = 23.6024"
NACA CoG behind datum line: 31.4" - 23.6024" = 7.7976"
NACA CoG location at MAC behind leading edge: 18.65" + 7.7976" = 26.4476"
NACA CoG % at MAC: 26.4476" / 78.54 * 100 = 33.6741%