Stability and Control characteristics of the Early Mark Spitfires

[Crumpp]

Originally Posted by CaptainDoggles

I just want to point something out here: Adding instability does not necessarily make the aircraft more maneuverable.

Perfect example is the B-2 Spirit. Extremely unstable, but not particularly maneuverable.

Exactly. Instability does not do anything except make the aircraft harder to control.

It is a myth that instability has positive effects on maneuverability. In fact, it narrows the maneuvering envelope because the pilot cannot precisely control the aircraft.

[Crumpp]

NACA report makes it quite clear that there was some doubt about the correct cg position

31.4% MAC is quite clear.

[taildraggernut]

Originally Posted by Crumpp

Exactly. Instability does not do anything except make the aircraft harder to control.

It is a myth that instability has positive effects on maneuverability. In fact, it narrows the maneuvering envelope because the pilot cannot precisely control the aircraft.

So if this is true why was the Spitfire 'known' for it's ease of control?

Interesting, yet when they wanted to increase the Spitfire roll rate they had to make it less laterally stable by clipping it's wings, so not such a myth about instability, seriously think about it, stability is a resistance to change, stability will never be conducive to manouverability, neutral to slight instability would be the ideal (which is approx where the Spitfire is) and high instability starts to require computers for control.

[taildraggernut]

Heres a couple of links that clearly show the relationship between stability and maneuverability i.e. the relationship is inverse, this is what USN student pilots are being taught, I am fairly sure the USN currently are using 'adopted' standards

http://navyflightmanuals.tpub.com/P-1231/P-12310068.htm

http://navyflightmanuals.tpub.com/P-1231/P-12310031.htm

So lets get all this in perspective, longitudinal instability does 'not' mean the aircraft is difficult to control, and it 'does' mean the aircraft is more manouverable, it's all about how far on the scale you go, and the Spitfire just sits on the slightly unstable end, the 109 would sit slightly on the stable end.

I will just quote Crumpp again so you can draw your own conclusions wether he really knows what he is talking about or just has a sinister agenda.

Originally Posted by Crumpp

Exactly. Instability does not do anything except make the aircraft harder to control.

It is a myth that instability has positive effects on maneuverability. In fact, it narrows the maneuvering envelope because the pilot cannot precisely control the aircraft.

[CaptainDoggles]

Originally Posted by taildraggernut

Heres a couple of links that clearly show the relationship between stability and maneuverability i.e. the relationship is inverse, this is what USN student pilots are being taught, I am fairly sure the USN currently are using 'adopted' standards

http://navyflightmanuals.tpub.com/P-1231/P-12310068.htm

http://navyflightmanuals.tpub.com/P-1231/P-12310031.htm

So lets get all this in perspective, longitudinal instability does 'not' mean the aircraft is difficult to control, and it 'does' mean the aircraft is more manouverable, it's all about how far on the scale you go, and the Spitfire just sits on the slightly unstable end, the 109 would sit slightly on the stable end.

I will just quote Crumpp again so you can draw your own conclusions wether he really knows what he is talking about or just has a sinister agenda.

The very first line from the very first link you posted says the following:

The T-45 is a very stable aircraft yet is fully maneuverable

My eyes hurt from rolling so hard.

[fruitbat]

see you didn't get past the first line then.

[CaptainDoggles]

Originally Posted by fruitbat

see you didn't get past the first line then.

Just like Sandstone pointed out above: Everyone thinks that maneuverability requires instability. That is false, and even the US Navy says so.

Otherwise, they would not have described the T-45 as "very stable yet fully maneuverable". A child can understand this.

[fruitbat]

Originally Posted by CaptainDoggles

Just like Sandstone pointed out above: Everyone thinks that maneuverability requires instability. That is false, and even the US Navy says so.

Otherwise, they would not have described the T-45 as "very stable yet fully maneuverable". A child can understand this.

A child would be able to read to paragraph 5, unlike yourself it appears.

[Al Schlageter]

Originally Posted by CaptainDoggles

Just like Sandstone pointed out above: Everyone thinks that maneuverability requires instability. That is false, and even the US Navy says so.

Otherwise, they would not have described the T-45 as "very stable yet fully maneuverable". A child can understand this.

Sure it has to able to maneuver. It is not a V1 and flies one direction only.

[TomcatViP]

NO NO and NOOOOO

Two of the most manoeuvrable fighters today are perfectly stables: Mig29 and Su27.

It's a matter of philosophy from the manufacturer and the air forces using it.

Today, aft positioned CG is used to lower the drag in high AoA configuration : less elev surfaces deflection (especially in the case of elevons), less tail plane surface, less drag when deflected. Have a look at the range of tailplane incidences available on modern fighters (when they do not act as airbrake).

Moreover I suspect you are mixing stability (or the lack of it) and relaxed stability (what you call instability). The former is what ease the plane in flight for the pilot and, in the case of modern plane with relaxed pitch stability, is always implemented by the flight controls (the pitch crl of F16 and airbus is ctrled by the number of inputs basically - you don't have to pull and push), and relaxed stability (akka positive longitudinal instability) used in modern fighter and Airbus airliner to reduce the drag, accelerate the pitch rate or both.

I don't see why a pilot would want an unstable aircraft especially in pitch when you have to do lengthy flight in clouds, bad weather or simply T.O at dusk . There was the same prob with the Camel during WWI. they made it instable "in purpose" to give him a way to fight the superior airfoil section used by the Germans but at a very high cost : pilot SA dramatically dropped. And there we had teh same result: Experienced pilots were at ease in that situation but rookies had all their attention drown in flying the plane. Doesn't it remind you something ? ... Like section leaders landing back to base with both his wingmen shot down as depicted in a famous 1969 movie?

... And the 47 and the 51 over Europe have told us that you don't win a war with experteen but with a range of perfectly trained young pilots at ease in planes easy to master.

Regarding the Cessna, if you really push and turn the yoke My memory tell me that the 172 is quite manoeuvrable. I won't hve had a dogfight with a 29 but still you feel secure in mountainous terrains.