Stability and Control characteristics of the Early Mark Spitfires

[taildraggernut]

Originally Posted by CaptainDoggles

Thanks for posting, Lane.



So at normal CG, the A&AEE concludes that the aircraft is longitudinally unstable. I'm sure certain characters will try to wriggle out of this one, but it seems open-and-shut to me. I'm sure we will be deluded with marginally-relevant allusions to British aerodynamics pioneers, and pilot quotes saying that the Spitfire was a dream to fly. Nobody's saying it wasn't a good aircraft.

Seeing people describe this thread as a "character assassination" has been amusing.

Appart from ACE there, can you quote 'anybody' that said the Spit was not unstable?

No I didn't think so, in fact nobody is denying it, the instability is 'not' the apparent problem that Crumpp is trying to emphasise, the Mustang was longitudinaly unstable, heres an example where you needed to take your own advice and pay attention to what people write.

[CaptainDoggles]

Originally Posted by taildraggernut

Appart from ACE there, can you quote 'anybody' that said the Spit was not unstable?

In fact, yes I can.

Here:

Originally Posted by NZtyphoon

Crumpp is putting a worst-case scenario on the "buffeting"

...

in other threads he has gone as far as to claim that early Spitfires were longitudinally unstable and dangerous to fly

Originally Posted by NZtyphoon

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.

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.

--

No I didn't think so

Foot in mouth, etc.

Now let's stop this silly derailment of this thread and stay on topic

[taildraggernut]

Originally Posted by CaptainDoggles

In fact, yes I can.

Here:
Foot in mouth, etc.

Sorry no cigar, only NZTyphoons quotes actually mentions stability and even then it is more emphasis on the dangerous to fly part, which clearly the Spitfire was not dangerous to fly...at all.

[ATAG_Dutch]

So with a full tank, trimmed for level flight, pulling back on the stick then releasing to neutral would return the aircraft to level flight.

With a half full tank in the same conditions, pulling back on the stick would need a push on the stick to return to normal flight, and a bigger push when the tank is near empty.

That's my simplistic understanding of longitudinal stability or not as the case may be.

All modern military aircraft are designed with inherent instability which requires a computer to control. Instability is necessary for manoeuvrability.

I totally fail to see the point in this thread, other than to ask the devs to model a changing CofG and longitudinal stability according to fuel load. Is that the point?

[CaptainDoggles]

Originally Posted by ATAG_Dutch

I totally fail to see the point in this thread, other than to ask the devs to model a changing CofG and longitudinal stability according to fuel load. Is that the point?

Here's a simple example from the game: Right now, to hold a turn in the spit you have to hold the stick back a significant amount.

In reality, after initiating the turn I believe it was necessary to relax your pressure on the stick (move it closer to center). Otherwise, the aircraft could tighten its turn, and if you are above corner speed that means it would be easy to inadvertently exceed the G limits and damage the airframe.

There's a quote I remember reading from a pilot who said he actually had to push the stick almost all the way forward to hold a turn, because the aircraft kept wanting to tighten up.

--

I also think that the very light stick forces and (lack of) control harmonization should be modeled.

[ATAG_Dutch]

Originally Posted by CaptainDoggles

There's a quote I remember reading from a pilot who said he actually had to push the stick almost all the way forward to hold a turn, because the aircraft kept wanting to tighten up.

I too have read such anecdotes, however the aircraft had to be returned to the factory for a new monocoque, as for some reason a batch of Spits had been produced out of shape.

Dangerous to trust pilot's anecdotes, as we keep being told.

Edit: Plus you'd be unconscious well before you endangered the airframe.

[winny]

I have another question, the RAE refer to the bf-109 as being " too stable for a fighter".

So is instability a good or bad thing?

[Al Schlageter]

Originally Posted by winny

I have another question, the RAE refer to the bf-109 as being " too stable for a fighter".

So is instability a good or bad thing?

It depends if one is BLUE or RED.

[CaptainDoggles]

Originally Posted by winny

I have another question, the RAE refer to the bf-109 as being " too stable for a fighter".

So is instability a good or bad thing?

I've read that quote, but Mike Williams seems to have sort of picked it out without including a lot of context from the original source, so it's hard to know exactly what they were referring to.

Here's the quote for people unfamiliar:

Longitudinally the aeroplane is too stable for a fighter. There is a large change of directional trim with speed. No rudder trimmer is fitted; lack of this is severely felt at high speeds, and limits a pilot's ability to turn left when diving.

Now, the way I interpret it is that they're referring to the trim problem. I could be wrong. There could be a truncated sentence or two preceding the quote that makes it more clear, but that's how I interpret it.

Edit: I think in this case that they're correct. You don't want the pilot's attention on trimming the aircraft every five seconds; you want the pilot's attention devoted to situational awareness.

[winny]

Originally Posted by CaptainDoggles

I've read that quote, but Mike Williams seems to have sort of picked it out without including a lot of context from the original source, so it's hard to know exactly what they were referring to.

For your reference, the quote, in context.



Apologies for the quality, it's an iPad screen grab.