Stability and Control characteristics of the Early Mark Spitfires

[TomcatViP]

Originally Posted by bongodriver

I meant to add, the reason I believe this is the effect is because the only Weight and balance diagrams I have seen of the Spitfire place the fuel tank moment just behind the datum point, as fuel reduces then the moment weight is offset by the constant moment weight of the engine which I think we can all agree is ahead of the datum.

You've probably seen a doc related to the AFT mounted tank of the spitfire, scarcely used on fighters but primal on the reco version.

[bongodriver]

Originally Posted by TomcatViP

You've probably seen a doc related to the AFT mounted tank of the spitfire, scarcely used on fighters but primal on the reco version.

No it was the diagram on this thread, and let's face it, if the fuel tank was forward of the datum then the Spitfire could not have possibly been unstable, so in this case I am argueing 'for' your cause.

[Al Schlageter]

If the early Spits were so tail heavy then why did the MkVIII have 22.5lb added (weight and mount) to the tail? moment arm 175.5"

[Al Schlageter]

Originally Posted by CaptainDoggles

Go back and read the thread; it's all there. This thread has devolved into fanboys re-interpreting the presented evidence into "merely a slight" instability because their egos can't handle it, so I'm not going to perpetuate it.

Ta ta

So a NACA engineer is a Spit fanboy?

"FIGURE 4.5. Supermarine Spitfire airplane. A high-performance fighter noted for its role in the Battle of Britain and throughout WW II, the Spitfire had desirably light elevator control forces in maneuvers and near neutral longitudinal stability. Its greatest deficiency from the combat standpoint was heavy aileron forces and sluggish roll response at high speeds. "

Some fanboys have a short memory.

[NZtyphoon]

Originally Posted by Glider

I know this is going to sound rather foolish but can someone point me in the direction of the test report that mentions 3/4 in of travel for 3 G.

Its in here somewhere but I cannot find it, any hunts welcome

Page 9 of the NACA report:



One report not yet mentioned is the Spitfire VA Stalling Characteristics by NACA: Where the Spitfire II Pilot's Notes warn about buffeting at the stall NACA sees this as "Good Stall Warning" and the Spitfire's stall characteristics "more desirable in some respects than those of any pursuit-type airplanes formerly tested in a similar manner.":





The main undesirable characteristic noted was the "uncontrollable rolling instability" with the gun ports open and in a steeply banked turn.

[bongodriver]

Interesting, thanks typhoon, the boxed extract sounds almost identical to what Mark Hanna was describing.

The main undesirable characteristic noted was the "uncontrollable rolling instability" with the gun ports open and in a steeply banked turn.

It also adds that there was 'unmistakeable' warning in the form of buffet.

[Crumpp]

You just don't have the evidence that that is actually what happened for a start

Ahh....

You can look at the slope of the Cm/CL curve.....

Ahhh, elevator oscillation graphs....


Ahhh, Abrupt pull up characteristics.....

Elevator angle / Acceleration / stick force graphs....

It is very cut and dry. No emotional involvement required.

Here is the stick travel requirement the Spitfire did not meet.....

You guys need a copy of the report?

[Crumpp]

While CG location will effect the stall velocity, stall behavior is not stability.

It is apples and oranges.

"Being flown" in the stall buffet is not the same as "turns great in the stall buffet" either.

Carry on

[IvanK]

An ode to stability and buffet with apologies to Plt Off Gillespie Magee

Oh How I thought I'd slipped the surly bonds of earth
I've danced and rolled and slipped and pulled and done a thousand things
I pulled once more .....Buffet flick ... oh no the lift has gone from my wings.

My Spit MKI yawed and clanged and bucked and pitched
The stability of this Spit MKI is such a bitch !

This I fear must be a spin
Time for me to put my best effort in.

I pulled the throttle back to Idle
I centralised the controls as I had been taught
Its times like these that things get a little fraught

I smoothly pushed on opposite rudder
But my Spit MKI she continued with the judder

I eased the stick progressively forward
smoothly smoothly son and you will get your reward.

And then it happened out she popped
All the banging and the clattering had stopped
as 90 degrees nose down my Spit MKI had flopped

But there I was at even lower Alt so very close to the heather.
Time for me to pull my best turn ever

But what should I do ?
Alas I had no clue

A fervent prayer to Crumpp Patron saint of the NACA
Surely he will guide me through this delicate matter

"Pull smoothly lad but don't let it Buffet" said Crumpp
I did as I was told ....... until I felt the fatal Thump
Impact ! .........bummer .....I was in the Hawkinge dump.

And that was that I was dead
I knew I shouldn't have listened to what got in my head

Now I really had slipped the surly bonds of earth
Up and up I went until there I was nearing heaven listening to the mirth.

When I got there what did I see ?
A raucous bunch of forum guys all from 1C

One by one they began to chant .... "Another victim of Turning room available is less than turning room required"
I hung my head in shame .... how could I have been so dumb? ..... How could this have transpired ?

At last a sign of hope, along he came Pontius ..... the world famous Pilate
Take heart young man .... my advice and gift today will make you smile a lot

The trick is to pull until you feel the "buzz" then hang on to it like glue
Only this young lad will keep you out of the Poo.
and now a gift .... a second chance at life for you.

In flash there I was 90 degrees nose down over Hawkinge
Time to do my stuff .... no time to grumble or to whinge

I smoothly pulled to the Buzz... Pilates words ringing in my ears like a bell
Boy o boy my Spit MKI she is turning well
And then there I was above the ground .... Gee that was swell.
Good on you Pontius your advice today has done me well.

So pilots all if you want to turn
pull to the buzz ..... lest you burn
Dont always listen to a Boffin
That just might lead you to a coffin.

And to the mods out there
its time to put this all to bed
please please .... close this bleeding thread !

[NZtyphoon]

Originally Posted by Crumpp

While CG location will effect the stall velocity, stall behavior is not stability.

It is apples and oranges.

"Being flown" in the stall buffet is not the same as "turns great in the stall buffet" either.

Carry on

So I guess that your comments

Originally Posted by Crumpp

Spitfire Mk I Operating Notes, July 1940.

What do you think the "violent shudder" is.....hint....PRE-STALL BUFFET.

and those that you posted on the PN's are worthless to this discussion and not worth bothering with? I take it the NACA report on the Spitfire's desirable stall behaviour was wrong because according to you the PNs say otherwise? Thanks for contradicting yourself again Crumpp...