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I don't understand your point, Kur.

Yes, the Spit may have had a sensitive elevator. Yes, in case it went into a spin it may have done so in a violent manner.

But again, there is abundant indications by pilots that flew the spit that the airframe provided pilots with sufficient warning before this dangerous behaviour occured. This is, as I explained above, due to the fact that the spit had cranked wings with the inner sections of the wing stalling before the outer sections. The resulting buffeting provided a warning to the pilot.

Stalling on the inner section is in no way dangerous as long as it is approximately symmetrical. I've seen with my own eyes during an experimental flight on a piper that also had cranked wings that basically this plane needs only 1/3 of its wing unstalled to provide sufficient lift. It will have been similar for the spit.

Now what you do is to confuse inexperienced pilots with seasoned ones. Inexperienced pilots of course will have the natural reflex to avoid any situation that puts them at discomfort as they still lack the confidence that comes with routine. They were absorbed by too many things to do at the same time that they had simply no mental resources to make the intelectual reflexion about buffeting as a safety warning even though they might have been told so in theory. They heard that being taught to them but only retained that buffeting means that stall is imminent and therefore has to be avoided. BTW on the German side inexperienced pilots also usually avoided to fly in that way that opened the slats. My guess is for the same reason as their British counterparts. Just try to put yourself in their shoes or remember you after having won your driving license. My guess is that anybody who loves his life will be prudent when trying to familiarize with a new way of motion (driving, flying) or a new type. The procedure most will adopt is to slowly increase the envelop of one's action with growing confidence. Well, that's how I feel when I have a new car with which I am not familiar with. It takes me a while to become more bold with it. I am surely not starting to race like Schumacher on the German Autobahn with a newly bought car.

Quote:

Originally Posted by 41Sqn_Stormcrow (Post 419318)

Stormcrow's comments are borne out by
NACA report Spitfire Va stalling Characteristics

I also note the following conditions in the Wright Field report quoted by Kurfurst:
NACA report Measurements of the Flying Characteristics of the Spitfire Va

Quote:

(Tests, Results and Discussion, page 5) All of the flying qualities tests were made with the
center of gravity at a distance of 31.4 inches behind the
leading edge of the wing at the root. The mean aerodynamic
chord of 85 inches was computed to be 4.80 inches
back of the leading edge of the wing at the root. The
center of gravity was therefore at 31.4 percent of the
mean aerodynamic chord. Because no accurate drawings of
the Spitfire were available, the calculated location of
the mean aerodynamic chord may be somewhat in error.

The center-of-gravity location with full military
load is not known.

According to the cg diagram of an earlier Spitfire I (attached) the cg was a maximum of 7.6" aft of the datum point, which is 19.5" aft of the wing leading edge, a total of 27.1" aft of the wing leading edge, or 4.3" forward of NACA's calculated cg.

while here the cg for a Spitfire Va tested at a loaded weight of 6,450 lbs by the A&AEE was 6.2" aft of the datum point, or 25.7" aft of the wing trailing edge, almost 6" forward of NACA's calculations, making their Va tail heavy, albeit their Spitfire weighed 6,184 lbs, which should not be enough of a difference to affect the cg that much.

How is it possible for a report to determine elevator characteristics when the cg of the test aircraft may not be set up properly? Nor do we know how the Spitfire in the RAE tests was set up.

Quote:

Originally Posted by 41Sqn_Stormcrow (Post 419318)

My point is basically the difference how the Spitfire and 109 behaved when getting near the stall. Both gave plenty of warnings, but the difference was as I see it is that once riding the stall, the Spitfire gave very little margin before you actually stalled, and once stalled it went medieval on you. The 109 otoh could be still pulled with confidence, with plenty of margin for pilot error, as the pitch control was not so sensitive at all, and stall itself was benign and recovery by easing back on the stick instant once it occured. In short I believe the stall and flying the aircraft to its limits was much easier on the 109 - which I as not such a good pilot admire the most when I fly it, and which is why I never liked to fly the 190, Spit or Yak 3. All the latter require much more finesse to fly.

That is said, the 109 due to its higher stalling speed had lower absolute limits when it came to manouvering, so it could not pull such a tight/fast turn, but this is not so important to me as I can reliably push the 109 to its limits all the time.

The 'handling' issue is complex.

Quote:

Stalling on the inner section is in no way dangerous as long as it is approximately symmetrical. I've seen with my own eyes during an experimental flight on a piper that also had cranked wings that basically this plane needs only 1/3 of its wing unstalled to provide sufficient lift. It will have been similar for the spit.

Absolutely true, but IMHO there is some misunderstanding about the stalling of the wing roots. All fighters and aircraft are designed as such, its hardly unique to the Spitfire at all. They make planes to stall in the root first because the pilot needs to retain aileron control. On the Spit, Fw 190 etc., pretty much every plane w/o slats its achieved by using washing, or cranking the wings so that the outer section has lower AoA than the inner and would thus reach stalling incidence later. On slatted aircraft like the 109, Lavochkins etc. the same is achieved by leading edge slats - its no coincidence that these cover the wing area ahead of the ailerons!

Quote:

Now what you do is to confuse inexperienced pilots with seasoned ones. Inexperienced pilots of course will have the natural reflex to avoid any situation that puts them at discomfort as they still lack the confidence that comes with routine. They were absorbed by too many things to do at the same time that they had simply no mental resources to make the intelectual reflexion about buffeting as a safety warning even though they might have been told so in theory. They heard that being taught to them but only retained that buffeting means that stall is imminent and therefore has to be avoided. BTW on the German side inexperienced pilots also usually avoided to fly in that way that opened the slats. My guess is for the same reason as their British counterparts. Just try to put yourself in their shoes or remember you after having won your driving license. My guess is that anybody who loves his life will be prudent when trying to familiarize with a new way of motion (driving, flying) or a new type. The procedure most will adopt is to slowly increase the envelop of one's action with growing confidence. Well, that's how I feel when I have a new car with which I am not familiar with. It takes me a while to become more bold with it. I am surely not starting to race like Schumacher on the German Autobahn with a newly bought car.

Absolutely agree, when I was doing my licence I had three cars to learn on (one of them being an absolutely horrid old Ford Escort, which I absolutely hated) and I always needed about 5 hours in the new ones to get familiar and instinctly 'feel' their behaviour. OTOH I am very familiar with my own car, which has superb and delightful response (which is why I am so reluctant to give it up) and can really get the maximum out of it now, and with growing experience, I need a lot less time to adjust to a new car.

Back to the planes, as a rookie I would be more confident to experiment and push things a bit more in a plane that tolerates my mistakes more. Straightforward handling and not having to bother with a million others things like engine controls helps a confused rookie a lot. The car example is pretty good actually, because while learning to drive the most difficult thing was to absorb all the things and information that were happening around me, giving me very little capacity to actually drive the car. With time and experience, much of that absorbing becomes a second nature, and automatic, instinctual.

ps. as for the Autobahn, its a dreadful experience at first if you are not got used to cars flashing by constantly at 200 + km/h..

Quote:

Originally Posted by Kurfürst (Post 419336)

NACA report Spitfire Va stalling Characteristics with reference to the concluding remarks on page 9...

Quote:

The airplane possessed some unusual characteristics in stalls that are not required in reference 1. The motion beyond the stall was not violent and an unusual
amount of lateral control was available in many flight conditions, even when full up elevator was applied. The good stalling characteristics allowed the airplane to be
pulled rapidly to maximum lift coefficient in accelerated maneuvers in spite of its neutral static longitudinal stability.

From Spitfire Va Flight Characteristics

Quote:

Characteristics of the elevator control in accelerated Flight: (pages 8 & 9)

The elevator control was found to be powerful enough to develop either the maximum lift coefficient or the allowable load factor at any speed....(page 8 )

The Spitfire airplane had the unusual quality that allowed it to be flown in a partly stalled condition in accelerated flight without becoming laterally unstable. Violent buffeting occurred, but the control stick could be pulled relatively far back after the initial stall flow breakdown without causing loss of control. With the gun ports open, lateral instability in the form of a right rolll occurred, but not until an up-elevator deflection of 10° had been reached and unmistakeable warning in the form of buffeting had occurred. This subject is discussed more fully in reference 2.

The excellent stall warning made it easy for the pilots to rapidly approach maximum lift coefficient in a turn so long as the speed was low enough to avoid undesirably large accelerations at maximum lift coefficient.
The excellent stall warning possessed by the Spitfire was obtained at the expense of a high maximum lift coefficient. The maximum lift coefficient in accelerated flight was 1.21, while the average lift coefficient throughout a stalled turn was usually about 1.01 (9)

The report goes on to state:

Quote:

In turns at speeds high enough to prevent reaching maximum lift coefficient because of the excessive accelerations involved, the small static longitudinal stability of the Spitfire caused undue sensitivity of the normal acceleration to small movements of the stick. As shown by the time histories of high-speed turns (figs. 15 to 18 ), it was necessary for the pilot to pull back the stick and then ease it forward almost to its original position in order to enter a turn rapidly without overshooting the desired normal acceleration. Although this procedure appears to come naturally to a skillful pilot, flight records from other airplanes show that a turn may be entered rapidly and the desired normal acceleration may be held constant by a single rearward motion of the stick provided the static stability of an airplane is sufficiently large. By careful flying, the pilot was able to make smooth turns at high speed, as shown by figures 17 and 18. Ordinarily, however, small movements of the stick caused appreciable variations in the normal acceleration, as shown in figures 15 and 20.

This hardly speaks about a deadly stall and it certainly doesn't mean the Spitfire was inherently dangerously unstable as claimed by Crumpp. It would be interesting to know whether this Spitfire, as tested, might have been marginally unstable, because, as noted, the cg position was not accurately known. It would also be interesting to know how the elevator control was affected by the extended mass balances described by Jeffrey Quill.

Getting back to flight qualities in CloD, how would it be possible to replicate these qualities?

Quote:

As this phrase, as it stands here, is to my knowledge right, it does not apply to the spitfire.

Yes and that is why I specifically did not address the Spitfire. In the Spitfire, the benefit of having an elliptical wing efficiency was all but eliminated in compensating for the stall characteristics of an elliptical wing.

Quote:

Stormcrow's comments are borne out by
NACA report Spitfire Va stalling Characteristics

It would help if you understood everything that report says instead of select phrases out of context. If you can't do that , it is practically impossible to hold a discussion.

If you read the report, it states the conditions the aircraft exhibited a very harsh stall. One of those conditions would be in a steep bank with gun ports open. Under those conditions, the aircraft would develop a roll instability and resulting spin.

The conditions matter in aerodynamics.

Yes the Spitfire gave very good stall warning. That large buffet zone comes at a price in diminishing turn performance.

Longitudinal Stability has nothing to do with stall characteristics except to determine how fast the pilot can move the wing through its useable angle of attack range.

The NACA rated the Spitfire as having unacceptable longitudinal stability and control in all conditions of flight. It is either neutral or unstable and this was corrected with bob weights in later marks.

That is not a bias, it is just a fact. None of these aircraft were perfect regarding stability and control. Some were worse than others and it is a fact the early mark Spitfires exhibited a dangerous longitudinal instability. It was an infant science when they were developed.

Quote:

The motion beyond the stall was not violent and an unusual
amount of lateral control was available in many flight conditions

Quote:

The Spitfire airplane had the unusual quality that allowed it to be flown in a partly stalled condition in accelerated flight without becoming laterally unstable

You know that this matter can't be resolved right, do you?

not violent: there is no meter for the stall to be "violent/not violent".
unusual amount: is it possible to quantify the usual one? And usual compared to?
many flight conditions: which ones?
party stlled: again... no numbers.

If we want the real numbers we have to rent a spitfire, install on it all the modern testing stuff and run it.

I've never loved much the 109 while I've always hated the Oleg's Spitfire (but I love the real one since I was a kid): anyway I've never trusted the myth of the elliptical wings because of these planes fly against the physic laws compared to all the other ww2 planes.

Quote:

Originally Posted by Crumpp (Post 419623)

It would help if you understood everything that report says instead of select phrases out of context. If you can't do that , it is practically impossible to hold a discussion.

Some were worse than others and it is a fact the early mark Spitfires exhibited a dangerous longitudinal instability. It was an infant science when they were developed.

Nonsense Crumpp - you are the one who is taking things out of context - note what the report said about the cg calculations cf the A&AEE report on the same aircraft type - the possibility was that the Spitfire flown by NACA was slightly tail heavy.

Not forgetting also what Quill had to say about the early Spitfires - "In general configuration the Mk I and Mk II production aeroplanes were almost identical to the prototype and so there was no problem with their stability. (231-232)" I'll take his word over yours any day.

As for having a "discussion" with you Crumpp - not interested because I know you'll turn it into a loooong, tedious thread, arguing over minute detail, while sticking to your opinion that the Spitfire was "dangerously unstable" no matter what. I don't care what you think because I know you're not interested in any one else's opinion, except when they agree with you.

Quote:

Originally Posted by 6S.Manu (Post 419637)

The numbers and graphs start on page 25 of the NACA report on the Spitfire Va flight characteristics - which can be downloaded and viewed in its entirety, as can the NACA report on the Spitfire Va stall. Testing a real one would be interesting - Duxford anyone?

Quote:

the possibility was that the Spitfire flown by NACA was slightly tail heavy.

Operating Notes Spitfire Mk IIa:

http://img571.imageshack.us/img571/5556/spinning1n.jpg

Operating Notes warning on the Longitudinal Instability:

http://img35.imageshack.us/img35/3848/elevatorload.jpg

NACA on the stall:

http://img521.imageshack.us/img521/5...sopenstall.jpg

NACA on the Longitudinal Instability:

http://img208.imageshack.us/img208/5...estability.jpg

While CG certainly does effect stall onset and characteristics, I am certain the NACA was capable of doing a weight and balance. A new weight and balance would have been a requirement once the aircraft was rigged for testing.

They were very aware of the effect of CG position on stall characteristics too.

Both the stall characteristics and the longitudinal instability are included in the General Operating Notes for the Marks that did not recieve bob weights.