# Spitfire as a diver



## tomo pauk (Mar 18, 2012)

How well it fared in dives? From what I can gather, it was slower than eg. Bf-109 to enter into dive pick up the speed (due to low wing loading?), but once in dive the thin wing was allowing for high speeds (only P-51 bettering it?). 
I'm looking forward for a well informed input, so we (Me, at least) can have a full picture on this topic


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## Aaron Brooks Wolters (Mar 18, 2012)

If I'm not mistaken the P-47 would outdo both the Mustang and Spitfire, but I could be wrong.


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## tomo pauk (Mar 18, 2012)

IIRC the P-47 needed dive flaps to overcome compressibility effects; with those is was fine?


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## Aaron Brooks Wolters (Mar 18, 2012)

Ok, I understand what your saying now. Makes sense. Your talking about maintaining control while in the dive and carrying speed also.


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## tomo pauk (Mar 18, 2012)

Yes, something along those lines. I'm also interested about the roll abilities of the main combatants when in high-speed dive; for the Spitfire I'm interested most.


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## Siegfried (Mar 18, 2012)

Spitfires supposedly could experience control reversal though I would like confirmation of that. Either way the relatively thin wing and essentially single spar design meant the early wings could twist opposit to aileron direction thus reducing roll rate. The Spitfire pilot might be able to deflect his ailerons with less effort than an Me 109 pilot but the wings countervailing twist could undo this, clipped wing versions aside.

Late war Me 109's could dive and remain in control to very high speeds. Dive problems had been traced to high mach latteral instabillity rudder horn overbalancing as early as 1942. The solution was a new taller tail which used a balance tab instead of a horn balance. These versions occaisionally outdived P-51's in the sense of regaining or retaining control at higher speeds.

Willy Messerschmitt made his name in aerodynamics via design of new wing sections that had excellent pitching characteristics.

Thw whole issue of diveing in combat seems to be a mixture of intial acceleration, mid dive acceleration, maximum speed of control.


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## wuzak (Mar 18, 2012)

The Spitfire didn't have as good acceleration in the dive as many of its contemporaries. A combination of weight, drag and power, no doubt.

The XIV was nearly equal to the P-51

Early Spitfires had difficulty with control in the dive, which was largely solved by replacing the fabric covered control surfaces with all metal ones.


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## davebender (Mar 18, 2012)

How well did a P-47 accelerate in a dive? We all know it could outdive anything if given enough time but is initital dive speed greater then the Me-109 or P-51?


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## slaterat (Mar 18, 2012)

Tempest> P47 in a the dive


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## Juha (Mar 19, 2012)

Hello Siegfried

the highest Mach number achieved in tests flights by German109 I'm aware was Mach 0.805.

It was achieved when in order to find the explanation of accidents in the front-line units the flight test unit of Messerschmitt made series of dive tests during spring 1943. The plane used was Bf109 F W.Nr. 9228. To reduce the risk of pilot over-compensation, the control movement was limited to 50% of the reference movement of the ailerons. For the first test flights the plane was in the standard condition of a 109F with G-wings, except for the movement limitation of the ailerons and the ejection seat. At this form the plane lost stability (at median centre of gravity) at speeds over Va=650 km/h ie IAS. Movements, starting at the vertical stabilizer;appeared around the yaw and longitudinal axes.
After this the stabilizer was changed to a larger one. Meaning the late production higher one. The elevator trim tab is enlarged in surface area by 100% compared to the original lower version. The horizontal stabilizer trim is limited in its upwards range of motion to +1°15 by a stop unit. With this new tail following speeds were achieved.
Maximum IAS Vamax = 737 km/h at 4.5 km, Maximum TAS Vwmax = 906 km/h at 5.8 km Maximum mach number = 0,805 at 7.0 km. This is the highest Mach number flown by a German 109 I’m aware. Bf 109K might well be capable to a bit higher max Mach number but was it ever tested flown in order to achieve that, I don’t know.

Other max Mach numbers
P-51B: 0.84 and 0.82 for the P-51D
P-38: 0.65
P-47C: 0.69
the SpitfirePR XI was able to dive to 0.89 mach and make a full recovery. In combat trim this would probably be more like 0.83-0.85 for fighter versions.

And on roll rates, there isn’t very much info on max roll rates of 109, but it seems that 109G max roll rate, 50lb stick force, was 85deg/sec at 425km/h (264mph)IAS. That means that it rolled clearly worse than metal aileron clipped wing Spit Mk V at all speeds and clearly worse than normal wing Spit Mk V up to say 410 km/h IAS. There wasn’t so big difference between 410 – 520km/h (255-323mph)IAS between 109G and normal wing Spit Mk V. One must also remember that planes were individuals and at least Frise type ailerons used in Spits before Mk 21 were sensitive to rigging errors…

On the supposed control reversal of Spitfires, I cannot recall other claims but those of one ex-member of this board who at least had very strong pro-German and anti-British views. But it is true that Spit suffered reduced aileron effectiveness at high speeds because of wing twist but the theoretical control reversal speed seems to have been beyond speeds possible to be achievable by Spitfires in dives.

Juha


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## Juha (Mar 19, 2012)

Hello Tomo
yes the initial dive acceleration of Spit was worse than that of contempory 109 but Spit had higher critical mach number but that was mostly only a theoretical advance.

Juha


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## A4K (Mar 19, 2012)

Heard a long time ago from someone that there was a strict limit set on Spitfire dive speed due to fear of wing fatigue, and that a kiwi pilot once exceeded this limit, and had a wing shear off...(?) 
I think this was a Mk.I during the battle of Britain, but can't be sure - anyone know anything about this incident (or indeed if it's true or not)?


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## stona (Mar 19, 2012)

Siegfried said:


> The Spitfire pilot might be able to deflect his ailerons with less effort than an Me 109 pilot



Actually the force required to achieve similar aileron deflection at similar speed is virtually the same. The configuration of the controls and pilot position meant that a Spitfire pilot could more easily bring greater force to bear on the controls. A Bf109 cockpit is VERY small,even compared to a Spitfire.
Cheers
Steve


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## Tante Ju (Mar 19, 2012)

stona said:


> Actually the force required to achieve similar aileron deflection at similar speed is virtually the same. The configuration of the controls and pilot position meant that a Spitfire pilot could more easily bring greater force to bear on the controls. A Bf109 cockpit is VERY small,even compared to a Spitfire.
> Cheers
> Steve



This chart shows control force was much greater on Spitfire. But report also notes subjective feel of 109 control was more solid for pilots, because of different stick and control design :

_More detailed aileron tests (measurement of stick forces and time to bank) were-made, and are described in section 5.2. These tests showed that, although the Me.109 ailerons felt much heavier than those of the Spitfire at speeds between 300 m.p.h. and 400 m.p.h., the aircraft could be made to bank at about the same rate as the Spitfire at these high airspeeds. The more " solid " feel of the Me.109 ailerons at high airspeeds is attributed to smaller stick travel (+/- 4 in. compared with +/- 8 in. on the Spitfire)., fairly rigid control circuit, and partly to the awkward seating position of the pilot. The matter is more fully discussed in section 5.2._


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## stona (Mar 19, 2012)

Yep,I haven't looked at that reprt for ages! Maybe I should have said similar up to about 300mph 

We shouldn't divert the thread into one about ailerons which is a complicated subject and only one facet of an aircraft's performance in a dive. Crucially the Spitfire ailerons,despite being much larger than those of the Bf109,did not FEEL as heavy at high speeds.

The report you quoted from was from late 1940 and refers to fabric covered ailerons on the Spitfire. The much improved metal ones were not introduced for nearly a year in July 1941.

Cheers
Steve


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## Edgar Brooks (Mar 19, 2012)

Siegfried said:


> Spitfires supposedly could experience control reversal though I would like confirmation of that..


In all of the hundreds of files, in the National Archives, I've never seen even the slightest hint of it.


> Either way the relatively thin wing and essentially single spar design meant the early wings could twist opposit to aileron direction thus reducing roll rate


.
Can we get rid of this "single spar" nonsense, once and for all, please? The front spar was bolted to the firewall (frame 5,) and the rear spar (to which the flaps and ailerons were attached, and which went all the way out to the wingtip join) was bolted to frame 10. 


> The Spitfire pilot might be able to deflect his ailerons with less effort than an Me 109 pilot but the wings countervailing twist could undo this, clipped wing versions aside.


If the wing twisted, it buckled, and anything above 1/16", aft of the mainspar, meant a full inspection, and even the slightest damage to the l/e "D" box meant a replacement wing. Clipping the wings was done, at first, to speed up the roll rate, and had nothing to do with wing twisting. Later, it was done to stop wing damage when carrying bombs under the wings (Mark XVI.)


> Late war Me 109's could dive and remain in control to very high speeds.


Not according to a Polish pilot, to whom I spoke about 30 years ago; he said that, in the 109 (which he flew post-war,) it was impossible to pull out of a dive in a straight line. You always ended up at right angles to your original line. 
Returning to the "dive" question, in 1940 tests, it was found that the Spitfire I 109E, if they started together, at full throttle settings, then dived together, they were still dead level at the bottom of the dive.
The 109E wing was limited to a pressure of 640lb:sq.ft (according to a test report,) while the Spitfire V could take 700lb:sq. ft.
The Spitfire IX was limited to 450mph, in a dive, but that was caused by engine limitations, not the airframe; the Merlin could not be taken above 3000rpm, without severely shortening its life. In an emergency 3150 rpm was permitted, but only for 20 seconds.
The fastest known (and survived) dive speed, on a Spitfire, was achieved by S/Lr Martindale, in a P.R.XI, with a TAS of 606mph (Mach .89,) before his engine exploded, and the propeller disappeared. He retained control (and, no, his ailerons did not reverse,) and glided back to an engine-off landing. A month later, he again achieved almost 600 mph, when the supercharger burst, and the engine caught fire; again he managed to land it.


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## davebender (Mar 19, 2012)

Why does this matter? 

If the pursuing aircraft can remain within effective weapons range for a few seconds the aircraft in front is likely to become swiss cheese long before anyone achieves max Mach speed in the dive.


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## stona (Mar 19, 2012)

davebender said:


> Why does this matter?



Because the original poster asked how the Spitfire was as a diver and that is a first hand account of how a Spitfire MkI compared with a contemporary Bf109E.

The stability of the aircraft in the dive might be more relevant than distance in a combat situation anyway.

Cheers
Steve


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## Edgar Brooks (Mar 19, 2012)

davebender said:


> Why does this matter?


Because, as Steve says, the original enquirer wants to know how Spitfires were in dives; perhaps you'd care to explain how your contribution helps him in his quest?


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## Siegfried (Mar 19, 2012)

Edgar Brooks said:


> In all of the hundreds of files, in the National Archives, I've never seen even the slightest hint of it.
> .
> Can we get rid of this "single spar" nonsense, once and for all, please? The front spar was bolted to the firewall (frame 5,) and the rear spar (to which the flaps and ailerons were attached, and which went all the way out to the wingtip join) was bolted to frame 10.
> 
> ...



1 The theoretical ailerons reversal speed of the pre F.22 series was lower than most ww2 fighters, whether or not it actually was pushed to an actually reversal is another matter. It did cut into roll rate.

2 The Spitfire is regarded as a single spar aircraft. The “main spar” was formed with a D shaped torsion box that was formed by the skin between the main spar and the leading edge. (It was probably vestigial from the unsuccessfully Type 224 Goshawk steam cooling program). Stringers and a smaller spar to the rear of this D box carried little of the load and served mainly to hang of control surfaces and to finish of the wing. A two spar design would have two large spars with a box formed by the upper and lower skins.

3 Me 109F had a radically redesigned wing of both new cross section and planform as well as slats so Me 109E data can not be used as a proxy for Me 109F. Me 109G wings were strenghtened.

The Spitfire no doubt was a fast diver, though it seems to have been of limited tactical use and not exploited due to its relatively underdeveloped prop pitch control and range. One of the advantges of the Kommandogaraet of German fighters was that it properly integrated prop pitch with throttle. Constant speed props still needed feathering: not with the all in one control.

Spitfire V had a major dive problem develop around 1942 caused by weight and C of G shift that was eventually solved via bob weights.


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## Gaston (Mar 20, 2012)

Do not underestimate the vertical performance of the Spitfire because of the carburator issues which robbed some slight power on negative G even on later models: Except for brief high G turns, it was used mainly as a superior boom and zoom vertical maneuvering fighter and avoided studiously low speed prolonged turning contests... After reading hundreds of combat accounts, I hardly found any accounts where the later Spitfire Mk V and especially the Mk IX was used as a prolonged low-speed turn fighter, and in every instance this happened it was completely at a loss versus the FW-190A (roughly even with the 109F or better than the Me-109G):

-Squadron Leader Alan Deere, (Osprey Spit MkV aces 1941-45, Ch. 3, p. 2: "Never had I seen the Hun stay and fight it out as these Focke-Wulf pilots were doing... In Me-109s the Hun tactic had always followed the same pattern- a quick pass and away, sound tactics against Spitfires and their SUPERIOR TURNING CIRCLE. Not so these 190 pilots: They were full of confidence... We lost 8 to their one that day..."


Vertical fighting was the bread and butter of most Spifire combats, to a more extreme extent than I have encoutered in any other fighter type, especially compared to the horizontal turn obsessed P-47D (which the Germans conceded in captured tests easily ou-turned their Me-109Gs, and this with a needle tip prop...: Source "KG 200: On Special Missions")...

Turn performance was the same by the way between the Mk V and the Mk IX, as tested by the RAE, so the edge they described for the Mk IX was entirely related to using climb, dive and zoom maneuvers, which they did in spades...

The Russains tried to use their Spitfire Mk Vs in turning combat against German aircrafts, and their usual slow turn tactics failed utterly with the Spitfire, so much so they tried to remove the outer 7.7 mm machine guns to improve its maneuverability performance, to no avail.

They then adapted their fighting technique to the Spitfire by using the dive and climb, and immediately met with success after early failures at turn-fighting: Translation: "The Spitfire is particularly adapted to vertical fighting."

"Fana de l'Aviation", no. 496, p.40:

Première citation : " Dans la journée du 29 avril, le régiment effectua 28 sorties pour escorter des bombardiers et des avions d'attaque au sol et 23 en protection de troupes, avec quatre combats aériens. Les premiers jours furent marqués par des échecs dus à une tactique de combat périmée dans le plan horizontal (l'I-16 était remarquablement agile en virage N.D.L.R), alors que *le Spitfire était particulièrement adapté au combat dans le plan vertical*. Selon A.L. Ivanov qui fit la guerre au sein du 57° Régiment, il était supérieur aux Yak-1 ou La-5."

Deuxième citation : " A basse et moyenne altitude, la version VB était surclassé par les chasseurs allemands et soviétiques de son époque. *Pour tenter d'améliorer la maniabilité et la vitesse*, les Soviétiques l’allégèrent en retirant les quatre mitrailleuses ainsi que leurs munitions, ne laissant que les canons. Cette variante fut évalué par le centre d'essais des VVS au cours de l'été de 1943. Apparemment ce ne fut pas concluant, car il n'y eu pas d'instructions pour généraliser la modification."

The idea that the Spitfire could not dive equal or better than the Me-109G is just wrong, especially at high altitudes where the Mach limit happened a lot sooner to the Me-109G, and especially so for the later Spitfire models who had very minor carburator negative G power loss issues... It would initially fall slightly behind and then catch up.

For the later Spitfire models, diving/climbing was the main way of fighting... 

As for the roll rate, it was about equal on the Mk V to the Me-109G, at 70-80°/sec, but steadily decreased to 60°/sec on one Mk XII wartime chart (probably similar here to the Mk IX), and barely 40-50° on the Mk XIV, regardless of what these Warbirds seem to do today (the aileron problem seems to have been definitely fixed post-war, but the Mk XII chart at 60°/sec seems more indicative of wartime performance, and pilot comments, to me)... Note the NACA 868 roll rate chart is dated 1947, and the Spitfire Mark there is not stated: It could be wartime Spits did a lot better rolling at high altitudes, as has been observed on other types, but NACA 868 specifies 10 000 ft., so it unlikely to be a wartime Spit...

Gaston


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## Jabberwocky (Mar 20, 2012)

Gaston said:


> As for the roll rate, it was about equal on the Mk V to the Me-109G, at 70-80°/sec, but steadily decreased to 60°/sec on one Mk XII wartime chart (probably similar here to the Mk IX), and barely 40-50° on the Mk XIV, regardless of what these Warbirds seem to do today (the aileron problem seems to have been definitely fixed post-war, but the Mk XII chart at 60°/sec seems more indicative of wartime performance, and pilot comments, to me).


 Gaston,

I'll ignore your usual copypasta rubbish as I dont have that much time, but I'll pull you up on this point. The Mk XII roll rate that you keep spouting on about, and have been doing so for years (and equally been corrected on for years), is not a steady state roll rate but TIME TO BANK...

As can clearly be seen here: http://www.spitfireperformance.com/mk12roll.gif

The graph shows the *time to transition* from 30 degree left bank to 30 degree right bank, and vica versa. At no point does it show a "60°/sec" roll rate. The HIGHEST roll rate is shows is about 50°/sec - for an anti-clockwise roll at 300 mph ASI. The SLOWEST roll rate it shows is about 14.5°/sec, for a clock-wise roll at just under 375 mph ASI.

There is a delay between roll initiation and roll acceleration. An aircraft does not instantly begin rolling at its steady state roll rate...

Secondly, as the graph does not show roll rates below 300 mph ASI, a full picture is not given of the Mk XII's rate of roll at lower speeds and thus your reading of the chart is fundamentally flawed.

NACA 868 shows a Spitfire roll rate peaking at 200 mph, at 150°/sec for a clipped wing version and 105°/sec for full wing version. It lines up exactly with the 1943 RAE test, comparing the roll rates of the Spitfire V with clipped and unclipped wings against the Typhoon, Mustang and FW 190.

You can see the graph here, at an old ubi forums thread: Roll rates | Forums - Page 3

Strange coincidence, huh... 

From the same thread, there is this information from Joseph Smith's lectures on the development of the Spitfire, with these data points:

Spitfire V / fabric covered frise ailerons:
90 deg/sec @ 170 mph (lowest speed graphed)
75 deg/sec @ 200 mph
55 deg/sec @ 250 mph
40 deg/sec @ 300 mph
27 deg/sec @ 350 mph
20 deg/sec @ 380 mph (end of graphed values)

Spitfire Mk V / metal covered frise ailerons
85 deg/sec @ 150 mph
105 deg/sec @ 200 mph <----- WOW look at that, it matches the data points too! 
90 deg/sec @ 250 mph
75 deg/sec @ 300 mph
60 deg/sec @ 350 mph
40 deg/sec @ 400 mph

Spitfire Mk V / plain ailerons with tabs
65 deg/sec @ 180 mph
75 deg/sec @ 200 mph
95 deg/sec @ 250 mph
118 deg/sec @ 300 mph
90 deg/sec @ 350 mph
70 deg/sec @ 400 mph

" Careful analysis over a long period of time on various marks of Spitfire had revealed fairly wide variations in aileron section and in the position of the ailerons relative to the wings. These differences resulted in inconsistent aileron characteristics, and it was felt that ailerons of a type which would be simple to manufacture and which would be less sensitive to manufacturing tolerances were necessary.

Quantitative data obtained from flight trials on a Spitfire Mark V with plain ailerons fitted with a balance tab had previously indicated that aileron properties comparable with those of a metal-covered Frise type could be achieved, with a reduction in drag due to the elimination of the gap. Ailerons of this type with area increased to 6 per cent of the total wing area, as against 5 per cent on earlier marks, were fitted to the stiffer Mark 21 wing and gave a high rate of roll with reasonable stick forces at high speeds. "

As for the rate of roll diminishing through the marks:

RAE testing of Mk XIV vs P-51

Rate of Roll
36. The *advantage tends to be with the Spitfire XIV.
*

Mk XII vs Mk IX

Manoeuvrability
10........... The manoeuvrability of the Spitifre XII is considered to be excellent. It was compared with the Spitfire IX (R.M. 10 SM engine), also designed as a high performance low-altitude fighter, over which it has an advantage in speed but not in climb, and *found to be much better in rate of roll*. Above 20,000 feet however, the Spitfire IX with standard wing tips has a better all-round performance and was able to out-manoeurvre the XII. It was unfortunate that in the trials the Spitfire IX was only an average aircraft on controls and was inferior to both of the Mk. XIIs flown. *It is considered that when used below 20,000 feet it will be able to out-pace, out-turn and roll as well as the FW.190*. The general manoeuvrability for dog-fighting is slightly limited by the fact that the engine cuts under negative acceleration forces. 

Mk IX vs 109G

Rate of Roll
21.........Here again the Spitfire has a *marked advantage at all speeds*. 

Mk VIII vs IX

Manoeuvrability

5......... There was nothing to choose between either aircraft as regards turning circles at any height; whether on offensive or defensive manoeuvres neither could make any impression on the other.* In rate of roll, however, the Spitfire IX was considerably better especially at low altitude. A number of full rolls through 360 degrees were timed by the same pilot flying each aircraft in turn and although quanitative tests are difficult to produce, it appeared that there was often more than 1.5 seconds superiority for the Mark IX over the Mark VIII. The Mark VIII feels fairly light on the ailerons but at high speeds it becomes very heavy, and so this new combination of extended wing and small aileron cannot be considered satisfactory. *

Strangely enough, the Mk VIII reverted to normal ailerons and normal span wings after testing....

Spitfire XIX vs Tempest V

Rate of Roll
36. The *Spitfire XIV rolls faster at speeds below 300 mph*, but definitely more slowly at speeds greater than 350.00 mph.


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## Edgar Brooks (Mar 20, 2012)

Siegfried said:


> 2 The Spitfire is regarded as a single spar aircraft. .


By whom? Certainly not by Supermarine and the RAF (via the newish Haynes Manual,) who both show a "rear spar" in various drawings. 


> Stringers and a smaller spar to the rear of this D box carried little of the load and served mainly to hang of control surfaces and to finish of the wing. A two spar design would have two large spars with a box formed by the upper and lower skins.


There were no "stringers." The wing had ribs, throughout its entire span, which were attached to both spars, then covered by the top and bottom skins. You have a main spar, with a rigid "D" box attached to its front, ribs attached to its rear, to which is attached a rear spar, all covered with aluminium skins, which were made still thicker, as the war progressed; now, please, find some other hobbyhorse.
An excerpt from a report on a wing twisting test of 1940:-





And this is one of your "stringers," or , as Supermarine titled it RIB 14:-




If you look carefully you'll also find references to "spars" and "rear spar."


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## tomo pauk (Mar 20, 2012)

Thanks for the input, the entries by Edgar Jabberwocky are most helpful.


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## stona (Mar 20, 2012)

Edgar will be familiar with this.

"Each wing comprises a leading edge D spar,a REAR AUXILIARY SPAR and 21 ribs attached to both the D spar and the auxiliary spar.
The front spar,comprising the upper and lower booms and the spar web,together with the thick skin of the wing leading edge,combine to form a D shaped box......

Each wing is attached to the fuselage by seven large bolts.These go through the upper and lower spar booms,joining it to the carry-through stub spars on Frame 5 of the fuselage.
An additional large bolt secures THE REAR SPAR." 

Cheers
Steve


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## fastmongrel (Mar 20, 2012)

It says single spar on wikipedia so it must be true I mean when has wikipedia ever got anything completely wrong


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## Tante Ju (Mar 20, 2012)

Edgar Brooks said:


> By whom? Certainly not by Supermarine and the RAF (via the newish Haynes Manual,) who both show a "rear spar" in various drawings.



By this definition every aircraft is a two spar design - you have to hang aileron, flap etc. to somewhere...


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## tomo pauk (Mar 20, 2012)

Not really, IIRC P-40 was having 5 spars, P-47 from 3 to 5 (depending what wing section we talk about).


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## Siegfried (Mar 20, 2012)

fastmongrel said:


> It says single spar on wikipedia so it must be true I mean when has wikipedia ever got anything completely wrong



wing | main spar | construction note | 1940 | 0363 | Flight Archive twin spar

This article clearly explains the difference between a single spar and a two spar design. It classifies the Spitifre as a single spar design. The main spar of the Spitfire carries the lifting forces while the D-box of the leading edge carries torsional loads. Anything aft of this is structurally not significant and that includes the so calle rear spar. From a structural point of view the rear spar does not carry any load in normal flight.


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## Edgar Brooks (Mar 20, 2012)

A friend of mine was called a "bastard," by our Production Manager, but I happen to know that his parents were married, when he was born. What something/someone is called isn't necessarily the whole story (or even true.)
If Supermarine (who built the thing, not "Flight" magazine) say that the wing contains two spars, then what gives others the right, 70 years on, to argue?


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## stona (Mar 20, 2012)

I'll stick with Supermarine too. It was the Supermarine Spitfire,not the Flight Magazine Spitfire after all.
Steve


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## Juha (Mar 20, 2012)

I'm with Siegfried in this, the Spit and Bf 109 wings are generally known as single spar wings in spite of the auxiliary spar, the latter was called aux. just because of it wasn't a proper spar and wasn't the rear of a strenght box.

Juha


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## cimmex (Mar 20, 2012)

The Spanish Me109 Buchon had two wing spars to carry the heavy Hispano cannon.
Regards 
Cimmex
pics here but you must be registered to see.
http://www.warbirdforum.de/forum/thread.php?threadid=27176&sid=47e659aed64c9597e5fb55f0185c0cb6


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## riacrato (Mar 20, 2012)

Juha said:


> I'm with Siegfried in this, the Spit and Bf 109 wings are generally known as single spar wings in spite of the auxiliary spar, the latter was called aux. just because of it wasn't a proper spar and wasn't the rear of a strenght box.
> 
> Juha


 
Exactly. The context is important here.


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## Edgar Brooks (Mar 20, 2012)

Juha said:


> I'm with Siegfried in this, the Spit and Bf 109 wings are generally known as single spar wings in spite of the auxiliary spar, the latter was called aux. just because of it wasn't a proper spar and wasn't the rear of a strenght box.


R.J. Mitchell (the designer) called it a rear spar, not an auxiliary; not once, on any of his drawings, will you find the words "auxiliary spar," but, always "rear spar."
According to all of you, we have ribs bolted to a main spar, then bolted to a non-spar (which is rigidly bolted, by three, not a single, bolts to a fuselage former,) all covered by sheets of metal rivetted in place, and it imparts no extra strength to the overall structure. Truly we have myopia taken to a new level.


> Exactly. The context is important here.


I'm delighted that you agree.


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## Gaston (Mar 21, 2012)

Jabberwocky said:


> Gaston,
> 
> I'll ignore your usual copypasta rubbish as I dont have that much time, but I'll pull you up on this point. The Mk XII roll rate that you keep spouting on about, and have been doing so for years (and equally been corrected on for years), is not a steady state roll rate but TIME TO BANK...
> 
> ...



Which shows you know little about how they roll: The distinction you are making is actually pretty small on most single engine types unless it was a roll reversal, which it is not...



Jabberwocky said:


> Secondly, as the graph does not show roll rates below 300 mph ASI, a full picture is not given of the Mk XII's rate of roll at lower speeds and thus your reading of the chart is fundamentally flawed.....



True, but we still can easily extrapolate the rest which points to a non-spectacular result of around 60°/sec, which is exactly what I suggested... And it was still basically a Mk V with a Gryphon engine, for which Mk V we DO have lower speed data, however desperately you want to avoid it...:

NACA on Mk V`s roll rate :

"Measurements of the flying qualities of a Supermarine Sptitife VA airplane." NACA Advanced Confidental Report, by William H. Phillips and Joseph R. Vensel. 

The tests were conducted at Langley field, Va., during the period from December 30, 1941 to January 29, 1942. Sixteen flights and apprx. 18 hours flying time were required to complete the tests. 

[...] 

Desription of the the Supermarine Spitfire airplane 

Name and Type : Supermarine Spitfire VA (Air Mininstry No. W3119). 
Engine : R-R Merlin XLV 
Weight, empty : 4960 lbs 
Normal gross weight : 6237 lbs 
Weight as flown for tests : 6184 lbs 

Ailerons (metal-covered) 
Lenght (each) : 6 feet, 10 1/2 inches 
Area (total area, each) : 9.45 sq. feet 
Balance area (each) : 2.45 square feet 



Lateral Stability and Control 

Aileron-control characteristics : The effectiveness of the ailerons of the Supermarine Spitfire airplane was determined by recording the rolling velocity produced by abrubtly deflecting the ailerons at various speeds. The aileron angles and stick forces were measured. It should be noted that the airplane tested was equipeed with metal covered ailerons. 

[...] 

The ailerons were sufficiently effective at low speeds, and were relatively light at small deflections in high speed flight. *The forces required to obtain high rolling velocities in high-speed flight were considered excessive.* 
With a stick force of 30 lbs, full deflection of the ailerons could be obtained at speeds lower than 110 miles per hour. A value of pb/2V of 0.09 radian in left rolls and 0.08 radian in right rolls were obtained with full deflection. 

Rolling velocity (at 6000 ft altitude) of about 59 degrees per second could be obtained with 30 lbs stick force at 230 miles per hour indicated speed. 

*The ailerons were relatively light for small deflections, but the slope of the curve of stick force against deflection increased progressively with deflection, so that about five times as much force was required to fully deflect the ailerons as was needed to reach one-half of the maximum travel.* The effectiveness of the ailerons increased almost linearly with deflection all the way up to maximum position. The value of pb/2V obtained for a given ailerons deflection was nearly the same in speeds and conditions tested. It may be concluded, therefore, that there was very little reduction in aileron effectiveness either by separation of flow near minimum speeds or by wing twist at high speed. 

Fig 27 shows the aileron deflection, stick force, and helix angle obtained in a series of roll at various speeds intended to represent the maximum rolling velocity that could be readily obtained. 

*The pilot was able to exert a maximum of about 40 lbs on the stick.* *With this force, full deflection could be attained only up to about 130 miles per hour.* Beyond this speed, the rapid increase in stick force near maximum deflection prevented full motion of the control stick. Only one-half of the available deflection was reached with a 40 lbs stick force at 300 miles per hour, with the result that the pb/2V obtainable at this speed was reduced to 0.04 radian, or one-half that reached at low speeds. 

Another method of presenting the results of the aileron-roll measurements is that given in figure 28, where the force for different rolling velocities is plotted as a function of speed. The relatively light forces required to reach small rolling velocities are readily seen from this figure. *The excessive forces required to reach high rolling velocities and the impossibility of obtaining maximum aileron deflection much above 140 miles per hour are also illustrated.* 


From : 

STABILITY AND CONTROL SUB-COMMITEE. AERONAUTICAL RESEARCH COMMITEE 
Comparision of aileron control charactheristics as determined in Flight Tests of P-36, P-40, 'Spitfire' and 'Hurricane' Pursuit airplanes. 

By William H. Philps. N.A.C.A. Confidental Bulletin. 16th November, 1942 

[..] 

The aileron effectiveness of the various airplanes is compared in the following table on the basis of the response obtained with stick forces of 30 and 5 pounds. A force of 30 lbs is somewhat less than the greatest stick force exerted by the pilot. Repeated flight measurements have shown, however, that this forcer is a reasonable upper limit for manouvering at high speeds. A comparision at a stick force of 5 lbs are also included to bring out a rather interesting fact regarding the order of merit of aileron effectiveness for the various airplanes when very light forces are used : 

Rolling velocities obtained with 30 lbs stick force at 230 mph indicated airspeed at 10 000 ft. (deg/sec) 

P-36 : 43 
P-40 : 90 
Hurricane : 64 
*Spitfire : 63 *

Rolling velocities obtained with 5 lbs stick force at 230 mph indicated airspeed at 10 000 ft (deg/sec) 

P-36 : 9 
P-40 : 8 
Hurricane : 19 
Spitfire : 15 



This from Jeff Ethell: 

"The elevator is very light, while the rudder is stiff and the ailerons even more so. Every Spitfire I have flown take more muscle to roll than most other fighters. As speed increases, both rudder and ailerons get heavier, creating a curious mismatch at high speeds... on has to handle the almost oversensitive elevators with a light fingertip touch while arm-wrestling the stiff ailerons." 

* And this if from Alex Heshaw, the Chief pilot of the Castle Bromwhich Spitfire plant. He basically flew hundreds of Spitfires after they left the factory and were tested for airworthyness. 

"I loved the Spit, every Marks of it. But I must admit, that altough later Marks were much faster, they were also progressively inferior to previous Marks in manouveribility. When we checked how a Spit behaves during roll, we counted how many complete rolls we could do under a given time. With the Mark II and V, we did 2 1/2 rolls, but the Mark IX was heavier, and only capable of 1 1/2 rolls. The later, more heavier versions could do even less. Designing an aircraft is about finding balance. It`s hardly possible to improve performance without degrading other properties of the aircraft.* " 

This last quote is particularly noteworthy, because it points to scale of comparison between the Mk V and the various later, heavier marks.

What I think is a true representative value of the Spitfire's roll rate is the RAAF's roll rate chart which pegs the Mk V at a peak of 78°/sec against a fair selection of other aircrafts: The peak was similarly at a very low, below 200 mph, speed, just like many other charts... 

If you take the Australian 78° value and substract over one third, as advised by Alex Heshaw, you get the roughly the same 50-55° degree value as in the Spit XII chart... What a coincidence!


Most Me-109 pilots peg the Spitfire as close in roll rate to the Me-109, but the Me-109 got better with speed while the Spitfire got decidedly worse, as the M XII chart show... And *no* Spitfire pilot ever said it matched closely or even remotely the FW-190A... So that gives an indication of the real roll value range...

It is true today's warbirds show faster roll rates than 80° sec, but maybe the Spitfire ailerons were more affected by actual ammunition load and the weight of the real guns?

Also, as I pointed out earlier, at high altitudes it could be the Spitfire's roll rates got much better in thinner air: This pattern has been shown on other roll rate charts such as that of the P-59 Airacomet...

One Spitfire pilot quote I read long ago did say: "It took more effort to roll it than other aircraft types, and this had to be kept in mind when going up agaisnt the FW-190..."

They did go through considerable testing with the wing tips clipped: Did it bridge the gap with the FW-190A?: One pilot's curt answer: "Hardly." 

Ah, the British understatement... 

But if you want to indulge in the fantasy of Spitfires closely matching the FW-190A in roll rate, hey, nobody's holding you back! Me, I'm quite taken by Eric Brown-inspired fantasies of vertical fighting against the Spitfire in my FW-190A!   

Don't do it while awake though...

Gaston


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## riacrato (Mar 21, 2012)

Edgar Brooks said:


> R.J. Mitchell (the designer) called it a rear spar, not an auxiliary; not once, on any of his drawings, will you find the words "auxiliary spar," but, always "rear spar."
> According to all of you, we have ribs bolted to a main spar, then bolted to a non-spar (which is rigidly bolted, by three, not a single, bolts to a fuselage former,) all covered by sheets of metal rivetted in place, and it imparts no extra strength to the overall structure. Truly we have myopia taken to a new level.
> 
> I'm delighted that you agree.


 
You will agree that it is not as simple as what is bolted to what. The question is wheter it is designed structurally to form a torsion box. And afaik it is true that the forward spar and the leading edge form the stress carrying portion of the wing in the case of the Spitfire. Even the excerpt you posted mentions that. Hence it is considered a single spar design from a structural point of view.

But if you find a source saying the Spitfire has a strength box between the first and second spar, I'd be "delighted" to see that.


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## Jabberwocky (Mar 21, 2012)

Gaston, I have all those test documents, you're telling me nothing I didn't already know.

RAE tests of Spitfire rolling velocity were done with 50 lbs of stick force or maximum aileron deflection. 

NACA Mk V tests give 59 degrees a second, but on an war weary example that they could only get * 40 lbs *of stick force out of the aircraft. The roll tests were done at just *30 lbs* stick force.

RAAF Mk VB tests during the A6M evaulation were also at *30 lbs* of stick force, yet they show 78 deg/second at a speed of just over 150 mph ASI at 10,000 ft. The later Boomerang rolling trials test have exactly the same measurements (see this thread: http://www.ww2aircraft.net/forum/aviation/fighter-best-roll-rate-23223.html for the 'Boomerang' graph)

NACA P-36, P-40, Hurricane, Spitfire tests were done with just* 30 lbs *of stick force on a Spitfire Mk I with fabric covered ailerons - and still they got 64 degrees a second, a better rate of roll than the Mk VA with metal ailerons...

Nothing you've linked to shows Spitfire roll rates at the same conditions as the RAE tested them. Nothing you've added disproves the RAE's tests that show the Spitfire's lateral control improving thoroughout the war. Nothing you've added disproves the AFDU Tactical trials, which have the Spitfire IX and XIV at roughly approximate roll rates and both better than the P-51 and the 109G.

*
PS: Its intellectually dishonest to take old (2003 old) posts from ubi.com Il-2 discussion boards and just copy/paste them trying to pass them off as your own. At least have the courtesy and honesty to add a link to the older discussions:
*

http://forums.ubi.com/showthread.php/14137-Spitfire-roll-rate

Its like deja-vu all over again, only Gaston, you're not half the expert that Barbi/Kurfurst/Isegrim was. At least he actually went out and researched these things.


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## Siegfried (Mar 21, 2012)

riacrato said:


> You will agree that it is not as simple as what is bolted to what. The question is wheter it is designed structurally to form a torsion box. And afaik it is true that the forward spar and the leading edge form the stress carrying portion of the wing in the case of the Spitfire. Even the excerpt you posted mentions that. Hence it is considered a single spar design from a structural point of view.
> 
> But if you find a source saying the Spitfire has a strength box between the first and second spar, I'd be "delighted" to see that.



Immagine a situation in which a Spitifre suffers an impact on the wing leading edge by a 30mm canon shell destroying everything up to but not including the spar.

We can say that the Spitfire wing has lost most of its torsional strength and the pilot would need to be very carefull to avoid high G manouvers.

If the same shell hit the leading edge of a two spar design the overall strenght and torsional rigididy would hardly be effected at all as the leading edge skinning is an insignificant component in terms of structure. I could be covered in cardboard reinforced plastic as it acts as a wind shield only.


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## Edgar Brooks (Mar 21, 2012)

riacrato said:


> You will agree that it is not as simple as what is bolted to what. .


No, I won't; we're dealing with pure semantics, here. To recap, somebody said that he thinks that he read, somewhere, that the Spitfire might have suffered aileron reversal, but didn't provide any evidence. Another contributor said that this was possible, because the Spitfire had a single spar, thereby implying that the wing, aft of that, was free to twist, which would have reversed the action of the aileron. We know that the Spitfire had a second spar (whether you call it auxiliary [which it wasn't] or rear [which it was] is academic, since it was there.) The rear spar was fixed to the fuselage, which means that it was not free to flap up and down as the wing (allegedly) flexed. If the skin (which was rigidly rivetted or screwed to the underlying ribs [not stringers] ) and spars (both of them) wrinkled by as much as 1/16" (1.5mm) the wing had to be checked, and the attachment bolts checked for bending, which must make the idea (that the wing could flex enough to reverse the aileron direction) questionable, if not completely ludicrous.


> The question is wheter it is designed structurally to form a torsion box.


No, it isn't; the question is whether the wing was free to flap up and down enough to negate the action of the ailerons


> And afaik it is true that the forward spar and the leading edge form the stress carrying portion of the wing in the case of the Spitfire. Even the excerpt you posted mentions that. Hence it is considered a single spar design from a structural point of view.


How it is considered is immaterial; it's how it was actually built which matters.


> But if you find a source saying the Spitfire has a strength box between the first and second spar, I'd be "delighted" to see that


Since Mitchell had a loathing of technical expressions ("It's all balls" was his response,) you'll find only simple words, like "front spar" and "rear spar," which brings us, not-so-neatly, back to square one.


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## Edgar Brooks (Mar 21, 2012)

Siegfried said:


> Immagine a situation in which a Spitifre suffers an impact on the wing leading edge by a 30mm canon shell destroying everything up to but not including the spar.
> 
> We can say that the Spitfire wing has lost most of its torsional strength and the pilot would need to be very carefull to avoid high G manouvers.
> 
> If the same shell hit the leading edge of a two spar design the overall strenght and torsional rigididy would hardly be effected at all as the leading edge skinning is an insignificant component in terms of structure. I could be covered in cardboard reinforced plastic as it acts as a wind shield only.


Or, lets say that the 30mm shell missed, leaving the Spitfire pilot free to turn his aircraft, using his non-reversing ailerons, and shoot his attacker down.


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## riacrato (Mar 21, 2012)

Yes Edgar, it is purely academic. If you choose to ignore the fact that the torsion box of the Spitfire wing was formed by the leading edge and the main spar because to you a torsion box is just semantics instead of being basics in wing design and layout, fine. Ignoring proven technical / scientific concepts seems to be the thing these days.

BTW: I never claimed the Spitfire suffered from aileron reversal excessively.


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## Tante Ju (Mar 21, 2012)

Edgar Brooks said:


> Another contributor said that this was possible, because the Spitfire had a single spar, thereby implying that the wing, aft of that, was free to twist, which would have reversed the action of the aileron. We know that the Spitfire had a second spar (whether you call it auxiliary [which it wasn't] or rear [which it was] is academic, since it was there.) The rear spar was fixed to the fuselage, which means that it was not free to flap up and down as the wing (allegedly) flexed. If the skin (which was rigidly rivetted or screwed to the underlying ribs [not stringers] ) and spars (both of them) wrinkled by as much as 1/16" (1.5mm) the wing had to be checked, and the attachment bolts checked for bending, which must make the idea (that the wing could flex enough to reverse the aileron direction) questionable, if not completely ludicrous.



I don't think Spitfire had capacity for actual aileron reversal. However report shown show the aircraft had a very low aileron reversal speed compared to other two spar and even single spar aircraft, in order of 5-600 mph, depending on report. This suggest clear that the wing was more prone to flexing under aileron load, making the question of if it was single spar or two spar design a bit academic. Because of known twisting tendency, it was either a single spar design with load bearing more towards leading edge and so not well situated position to carry twist load (force generated far, at trail edge) - which is I believe is true - or it was an extreme poor executed two spar design which had a rear spar designed into it, but was just not working at all (since it could do little to carry twist loads). Every above suggest the 'rear spar' had no real load bearing capacity, it was what is called an auxilary spar, good to hang things on it, but cannot carry real load.

I believe Mk 21 was considerable imporved for reversal speeds, suggest new wing was better designed.


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## stona (Mar 21, 2012)

Here's a picture.







That bit labelled 61. We can argue semantics and call it what we like. I'll call it what Supermarine called it...Rear Spar.

Cheers
Steve


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## Shortround6 (Mar 21, 2012)

There are aircraft with two spar wings that do not form a torsion box and there are aircraft with two spar wings that do use a torsion box construction and loading.

It is in the designers intention and construction. The Buffalo used a torsion box. it also used heavier than normal metal skinning between the spars to help form the torsion box. The Potez 230 used a torsion box which interested the Germans in 1940 enough to have them ship the plane back to Germany for further study. 

The Hurricane had a two spar wing, I doubt it was a torsion box when fabric covered. Did it become a torsion box in the metal covered version ( there were other changes besides just replacing fabric with metal) ?

If you build a two spar wing and make it a torsion box things like landing gear bays and gun bays have to _outside the "box"_ or have considerable reinforcement around them to carry the loads. 

Just like the Spitfire had to be careful about what could be done with the leading edge. 

Semantics does count but we also have to _KNOW_ the designers intent and not _GUESS_ from first impressions.


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## Edgar Brooks (Mar 21, 2012)

riacrato said:


> If you choose to ignore the fact that the torsion box of the Spitfire wing was formed by the leading edge and the main spar because to you a torsion box is just semantics instead of being basics in wing design and layout, fine. .


And if you choose to twist my words, when I used the word "semantics" to describe the pointless debate about whether it was called a rear, or auxiliary, spar, that's fine, too. I do not call (and never have called) the leading edge a "torsion box," since it has been universally known, since WWII, as the "D" box; it would be much appreciated if you do not accuse me of saying something, which I manifestly have not.


> Ignoring proven technical / scientific concepts seems to be the thing these days.


If I had a clue what you're on about, I might be able to respond.


> BTW: I never claimed the Spitfire suffered from aileron reversal excessively


BTW: I never said that you did.
And this is the "torsion box," which Supermarine simply called "leading edge," and, if you look carefully, there's no true leading edge, at the nose, simply a "leading edge strap," which went from rib to rib, and to which the skins were rivetted. 
lt might be some sort of "scientific concept" that the non-existent leading edge formed a "torsion box," but, according to my old eyes, there's no way that it could.




Oh, and this is the auxiliary spar, or, as you'll see how Supermarine viewed it, the rear spar:-


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## cimmex (Mar 21, 2012)

This is really a funny discussion. So a one spar wing would have no rear spar, same as very early wings with no movable ailerons did and where the whole wing was twisted instead.
Regards 
Cimmex


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## stona (Mar 21, 2012)

cimmex said:


> So a one spar wing would have no rear spar
> Regards
> Cimmex



Well yes,according to the illustration drawn by that well known aircraft manufacturer "Flight Magazine" cited previously in this thread. 
Incidentally their drawing of a two spar design much more closely resembles the construction of a Spitfire wing.
Cheers
Steve


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## riacrato (Mar 21, 2012)

Edgar Brooks said:


> And if you choose to twist my words, when I used the word "semantics" to describe the pointless debate about whether it was called a rear, or auxiliary, spar, that's fine, too. I do not call (and never have called) the leading edge a "torsion box," since it has been universally known, since WWII, as the "D" box; it would be much appreciated if you do not accuse me of saying something, which I manifestly have not.


And what do you think the purpose of the 'D' box is?


> If I had a clue what you're on about, I might be able to respond.


You obviously don't.



> BTW: I never said that you did.


Then why do you even mention it in a reply to me.


> lt might be some sort of "scientific concept" that the non-existent leading edge formed a "torsion box," but, according to my old eyes, there's no way that it could.


The leading edge taking the majority of torsional loads seems impossible to you? Then I surely can't help you.


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## riacrato (Mar 21, 2012)

stona said:


> Well yes,according to the illustration drawn by that well known aircraft manufacturer "Flight Magazine" cited previously in this thread.
> Incidentally their drawing of a two spar design much more closely resembles the construction of a Spitfire wing.
> Cheers
> Steve


From first appearance, yes. But the idea behind was to show where torsional loads are carried. And in this context the drawing for the one spar wing is more fitting.


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## Juha (Mar 21, 2012)

Edgar Brooks said:


> R.J. Mitchell (the designer) called it a rear spar, not an auxiliary; not once, on any of his drawings, will you find the words "auxiliary spar," but, always "rear spar."
> According to all of you, we have ribs bolted to a main spar, then bolted to a non-spar (which is rigidly bolted, by three, not a single, bolts to a fuselage former,) all covered by sheets of metal rivetted in place, and it imparts no extra strength to the overall structure. Truly we have myopia taken to a new level...



Now through the time manufactures had called parts of their products in non-standard names. So what is important is the princible behind the structure. The Flight article explain the different ways to construct wings in late 30s and a certain principle called single spar wing was utilised by Mitchell, Messerschmitt and Günther brothers in their mid 30s fighter designs. BTW the leading edge skins of Spitfire were .080". Behind the front/main spar .036". Wonder why? Would that had something to do with strenght demanded.

Juha


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## Shortround6 (Mar 21, 2012)

We seem to be getting into hair splitting here.

You can design a 2 spar wing in which each spar takes 50% of the load, or design wings where the load is 60/40 or 70/30 or even lower, i.e. the rear spar is just a convent place to hang the hinges for the ailerons and flaps. 

How low a percentage does the rear spar have to carry before the classification changes from a two spar wing to a single spar wing?

Do any of us KNOW what percentage was carried by the rear spar of the Spitfire ( if any)?

Without access to the original calculations or intentions of the designer we are left guessing from appearances and making assumptions.

My guess/assumption is that since the spar was continuous from end to end ( unlike many false or hinge spars) and was attached to the fuselage it contributed something to the bending strength and torsional strength of the wing. I have no answer to " how much is something" or what basic category of wing construction ( and four classes means a lot of wing designs are being squashed into one category or another).


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## Juha (Mar 21, 2012)

stona said:


> Here's a picture.
> 
> 
> 
> ...



And what about No 71, would that by some strange reason be named as the MAIN spar?

Juha


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## Juha (Mar 21, 2012)

Hello Shortround
now for ex in Morgan's and Shacklady's Spitfire bible they say that the wing was built up around the torsion box leading edge formed by the built-up spar. And all books which talked about Spitfire's wing I can recall reading since late 60s describred it as single spar wing. Clearly the rear spar carried some load but the main strenght item was the leading edge D-box.

Juha


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## Juha (Mar 21, 2012)

Shortround6 said:


> ...The Hurricane had a two spar wing, I doubt it was a torsion box when fabric covered. Did it become a torsion box in the metal covered version ( there were other changes besides just replacing fabric with metal) ?...



In the fabric covered wing there were WW like structure made by beams between the spars. The metal skinned wings were like normal 2-spar wings with ribs and stringers.

Juha


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## Elmas (Mar 21, 2012)

Not bad if someone will have a look to this, in particular Part. 5:

http://www.ilb.rwth-aachen.de/KLAUSUREN/formulary.pdf


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## stona (Mar 21, 2012)

Juha said:


> And what about No 71, would that by some strange reason be named as the MAIN spar?
> Juha



Yes,what's your point?
Cheers
Steve


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## riacrato (Mar 21, 2012)

Juha said:


> BTW the leading edge skins of Spitfire were .080". Behind the front/main spar .036". Wonder why? Would that had something to do with strenght demanded.
> 
> Juha


 
Thank you, I was just searching for those numbers. And on top of that iirc the leading edge up to the main spar was forged from single pieces.


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## Juha (Mar 21, 2012)

stona said:


> Yes,what's your point?
> Cheers
> Steve



Why main spar why not front spar?

Juha


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## Edgar Brooks (Mar 21, 2012)

riacrato said:


> And what do you think the purpose of the 'D' box is?.


To act as the "leading edge" of the aerofoil section, to separate the airflow, and thereby impart lift to the whole (non-twisting) wing, and, with it the rest of the aircraft.


> You obviously don't.


Very helpful.


> Then why do you even mention it in a reply to me.


Well, strangely enough, I consider this site to be open to all, and read by many; I do not consider it to be your sole province, so my answer was for all readers to see.


> The leading edge taking the majority of torsional loads seems impossible to you? Then I surely can't help you


It's just as well that I'm not asking for your help, just clarification, then. As far as I'm concerned, the mainspar (to which the leading edge components are attached) takes the majority of the torsional loads, with the front half-ribs going along for the ride.


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## Edgar Brooks (Mar 21, 2012)

Juha said:


> Why main spar why not front spar?


Because it was more important than the rear spar, perhaps?
Sorry to rain on the parade, but, as you'll see, it was also known as the front spar:-





I realise the quality isn't the best, but the original is, at least, 70 years old.


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## Elmas (Mar 22, 2012)

Edgar Brooks said:


> It's just as well that I'm not asking for your help, just clarification, then. As far as I'm concerned, _*the mainspar*_ (to which the leading edge components are attached) _*takes the majority of the torsional loads*_, with the front half-ribs going along for the ride.



Good Lord........
Have you ever heard of the Bredt formula?


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## riacrato (Mar 22, 2012)

Edgar Brooks said:


> It's just as well that I'm not asking for your help, just clarification, then. As far as I'm concerned, the mainspar (to which the leading edge components are attached) takes the majority of the torsional loads, with the front half-ribs going along for the ride.


The skinning on the leading edge is much thicker than that of the rest of the wing. The "C" portion was forged from a single piece for additional strength. Together with the spar they formed a stiff D-box taking the majority of torsional loads.

Your own quoted article: _"The leading edge of the wing is covered with 14 gauge, forming with the main spar, a torsion box."_


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## Elmas (Mar 22, 2012)




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## Edgar Brooks (Mar 22, 2012)

Elmas said:


> Good Lord........
> Have you ever heard of the Bredt formula?


No, and R.J.Mitchell probably hadn't, either.


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## Elmas (Mar 22, 2012)

Edgar Brooks said:


> No, and R.J.Mitchell probably hadn't, either.


That you don't know the Bredt formula is quite evident from your posts.
Not so sure about the same ignorance about the Bredt formula by R.J. Mitchell and his team even if, in the early '30s, the stressed skin wing and fuselage construction was in its infancy.


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## Edgar Brooks (Mar 22, 2012)

Put quite simply, you can twist and turn, throw in as many red herrings as you like, even do handstands, but the fact remains that the Spitfire had a mainspar, which was also known as the "front spar," by Supermarine, and a rear spar, as noted on Supermarine's drawings.


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## Elmas (Mar 22, 2012)

It is not my intention to be rude but to establish a study of the Spitfire wing on a scientific basis and not on completely wrong "feelings".
Fortunately the Boeings, Airbuses, etc. etc. on which from time to time I don't know you, but myself for sure and many other people travel every day are designed by some Gentlemen that perfectly know the Bredt formula.....


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## Juha (Mar 22, 2012)

Edgar Brooks said:


> Because it was more important than the rear spar, perhaps?
> Sorry to rain on the parade, but, as you'll see, it was also known as the front spar:-
> I realise the quality isn't the best, but the original is, at least, 70 years old.



Hello Edgar
Firstly thanks for the photos on original drawings, I probably have seen some before but not all, very interesting indeed.
And you didn't spoil my day. As I wrote I have read several books/articles on Spit and in all they describe the wing as single spar construction with the heavy gauge leading edge and the main spar forming a torsion box. In fact that and the structure of the main spar, built up of square section booms and joined by a channel section web and stiffeners together with the thinness of the wing were IMHO the most interesting elements of the design. And of course that thinness of the wing was the main reason for the very high critical Mach number for Spit and same time the thinness and the single spar structure were reasons why wing twist and the following diminishing of aileron effectiveness was bigger problem to Spit than to many other WWII fighters, most of which were later designs. 

So as a diver Spit had very high critical Mach number and because it had light elevators it could also be pulled out from dive fairly easily. On the other hand some Spit Vs were lost because too much Gs were pulled during the pull-outs (the main reason for that was wrong loading of planes in front-line sqns which produced too aft CG) which was at first corrected with bob weights in control circus and later with small modifications in elevators so they could drop the bob weights and Spit also suffered poorer initial acceleration in dive than more "tightly packed" 109 and 190 and had some lateral control issues at high speeds, 109 had more but 190 less.

Juha


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## tomo pauk (Mar 22, 2012)

All in all the discussion is bound to produce a nice overview of both construction and capability of Spitfire's wing. Please keep it clean


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## stona (Mar 22, 2012)

Edgar,Mitchell's quote was given by Jeffrey Quill.

"At that time I was only 23 and had not trained as an engineer,so I had something of an inferiority complex when it came to dealing with the aerodynamics and structures experts at Woolston with slide rules sticking out of their pockets. But Mitchell put me right about this one day,in his usual very direct way.
He said. 

'Look,I'll give you a bit of advice Jeffrey. If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it,take it from me it's all balls.
I have never forgotten what he said,and in fact it's absolutely true'

I'll take that from the man who designed one of the best and most important fighter aircraft in history.

Cheers
Steve


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## Edgar Brooks (Mar 22, 2012)

Juha said:


> Firstly thanks for the photos on original drawings, I probably have seen some before but not all, very interesting indeed.
> And you didn't spoil my day. As I wrote I have read several books/articles on Spit and in all they describe the wing as single spar construction with the heavy gauge leading edge and the main spar forming a torsion box. In fact that and the structure of the main spar, built up of square section booms and joined by a channel section web and stiffeners together with the thinness of the wing were IMHO the most interesting elements of the design. And of course that thinness of the wing was the main reason for the very high critical Mach number for Spit and same time the thinness and the single spar structure were reasons why wing twist and the following diminishing of aileron effectiveness was bigger problem to Spit than to many other WWII fighters, most of which were later designs.


Thanks for calming things down; I tend to get a touch irritated when I see red herrings dragged across what should be a fairly simple discussion. People seem to forget that Mitchell's original design was supposed to meet a criterion of a speed of "not less than 310mph at 15,000ft." I do wonder if that Bredt formula (which only seems to show shapes with a completely wrap-round leading edge) takes account of an item in which two sheets of duralumin come together at the apex, and are rivetted to an underlying strap of metal. I would expect the strength of the (usually aluminium or magnesium) rivets to have some sort of effect, but I'm a researcher, not an engineer.


> So as a diver Spit had very high critical Mach number and because it had light elevators it could also be pulled out from dive fairly easily. On the other hand some Spit Vs were lost because too much Gs were pulled during the pull-outs (the main reason for that was wrong loading of planes in front-line sqns which produced too aft CG) which was at first corrected with bob weights in control circus and later with small modifications in elevators so they could drop the bob weights and Spit also suffered poorer initial acceleration in dive than more "tightly packed" 109 and 190 and had some lateral control issues at high speeds, 109 had more but 190 less.


Well, I don't think that the Mach No. was that high, since the IX was limited to 450mph, by the constraints of the engine (I don't know about the XIV, etc., with the Griffon.) Talking to a friend, yesterday, he reminded me of an incident, reported by Pierre Clostermann, when diving a Spitfire VI, in which he said that the controls locked solid, and he was only able to pull out by use of the elevator trim. I don't know, for sure, if he tried the ailerons (though saying that the controls locked solid implies that he did,) but, if he did, they didn't work, neither did the wing flex (which is what this thread is, or was, all about.)
As well as the bobweights (which were decidedly unpopular with many pilots, when they were asked to test them,) other items were tried, to do away with the tail-heaviness, like removal of the IFF, and one of the oxygen cylinders once an efficient regulator had been fitted. The weights got as heavy as 6.5lbs, but the Air Ministry tried to get them back to 3.5lbs; they were installed on the bellcarank, in the elevator system, behind the pilot's seat. Later, heavier, weights were installed in Seafires, and were attached directly to the joystick; in his book "Up In Harm's Way" Mike Crosley says that it wasn't realised that this was probably a death warrant to many pilots. As he says, none got back to tell the tale; to abandon the Spitfire/Seafire it was recommended that the pilot should turn it on its back, and drop out, but this caused the bobweight to reverse its action, and throw the elevators to full "up," dropping the airframe straight into the sea.


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## Edgar Brooks (Mar 22, 2012)

Elmas said:


> It is not my intention to be rude but to establish a study of the Spitfire wing on a scientific basis and not on completely wrong "feelings".


I do not go by "feelings," but by research. As far as possible I try to correlate facts, to gain a consensus, before coming up with a conclusion.


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## Edgar Brooks (Mar 22, 2012)

riacrato said:


> The skinning on the leading edge is much thicker than that of the rest of the wing. ]


True


> The "C" portion was forged from a single piece for additional strength.


No, it wasn't; it was formed by two pieces of 14swg duralumin, laid over, and rivetted to, short ribs, then brought together at the apex, and rivetted to an underlying (not very wide) piece of aluminium. The underside piece also had many removable inspection plates. As well as the gun tubes, the l/e box was also used for items like heating tubes, carrying warm air out to the nos 3 4 guns.


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## Elmas (Mar 22, 2012)

"_Sapiens nihil affirmat quod non probet_", ( A wise man do not affirm things without demonstrating them) Ancient Romans used to say.
And if you are not able do demonstate your ideas in a scientific, and thus a mathematical way, they can be only considered feelings.
Some time ago, by request of a Friend of mine who owns an aeromodeling magazine, I did write some articles about the design of the wings were the Bredt formula ( and others) are explained for persons with not much, if any, mathematical background.
But unfortunately the articles are in Italian.....
"_Et de hoc satis_" (and for me thats enough") the Romans used to say: if you are of the idea that in that masterpiece of structural engineering that is the Spitfire wing "_the mainspar takes the majority of the torsional loads_", well, you can have it.
Ciao

btw, I'm perfectly aware of those Mitchell's phrases


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## riacrato (Mar 22, 2012)

Edgar Brooks said:


> True
> 
> No, it wasn't; it was formed by two pieces of 14swg duralumin, laid over, and rivetted to, short ribs, then brought together at the apex, and rivetted to an underlying (not very wide) piece of aluminium. The underside piece also had many removable inspection plates. As well as the gun tubes, the l/e box was also used for items like heating tubes, carrying warm air out to the nos 3 4 guns.


 
Like I mentioned above, it was just what i read, i wasn't sure about it. It would've give the D-box = torsion box argument more weight, but I think even if it's not true, the evidence is enough.

I found the source in the meantime, but it's just an internet site, so not reliable. I'm posting it just for the interested, not as proof:http://spitfiresite.com/2011/07/guided-tour-of-the-spitfire-pr-mk-xix-the-bowser-wing.html/dsc06603


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## Juha (Mar 22, 2012)

Siegfried said:


> Spitfires supposedly could experience control reversal though I would like confirmation of that. Either way the relatively thin wing and essentially single spar design meant the early wings could twist opposit to aileron direction thus reducing roll rate...



Hello Siegfried
accidentally I came across a test report from April 1941 according to which Spit aileron reverse speed was 477mph IAS that means 477mph TAS at SL, 555mph at 10000ft TAS and 654mph TAS at 20000ft. That was calculated from test data, earlier based on conventional theory was appr. 550mph IAS, so not much a danger to Mk I-V and from Mk Vc onwards the stronger C-wing became the standard wing before late in the war it was replaced with E-wing. But according to the same report at 400mph IAS aileron lose 65% of its effectiveness due to wing twist.

And The RAE 1231 (DSIR 23/12865) gives reversal speed 580 mph EAS for the Spitfire V with standard wings and that value is calculated from flight test results.

Juha


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## Juha (Mar 22, 2012)

Edgar Brooks said:


> ...Well, I don't think that the Mach No. was that high, since the IX was limited to 450mph, by the constraints of the engine (I don't know about the XIV, etc., with the Griffon.) Talking to a friend, yesterday, he reminded me of an incident, reported by Pierre Clostermann, when diving a Spitfire VI, in which he said that the controls locked solid, and he was only able to pull out by use of the elevator trim. I don't know, for sure, if he tried the ailerons (though saying that the controls locked solid implies that he did,) but, if he did, they didn't work, neither did the wing flex (which is what this thread is, or was, all about.)
> As well as the bobweights (which were decidedly unpopular with many pilots, when they were asked to test them,) other items were tried, to do away with the tail-heaviness, like removal of the IFF, and one of the oxygen cylinders once an efficient regulator had been fitted. The weights got as heavy as 6.5lbs, but the Air Ministry tried to get them back to 3.5lbs; they were installed on the bellcarank, in the elevator system, behind the pilot's seat. Later, heavier, weights were installed in Seafires, and were attached directly to the joystick; in his book "Up In Harm's Way" Mike Crosley says that it wasn't realised that this was probably a death warrant to many pilots. As he says, none got back to tell the tale; to abandon the Spitfire/Seafire it was recommended that the pilot should turn it on its back, and drop out, but this caused the bobweight to reverse its action, and throw the elevators to full "up," dropping the airframe straight into the sea.



The limit was according to Mk IX, XI and XVI Pilot's Notes Mach .85 and the 450mph was IAS speed and in force up to 20'000 ft, between 20'000 and 25´000 it was 430 mph IAS etc. Already at 10'000 ft 450 mph IAS means 524 mph TAS. I'd be a little careful with Closterman's statements, his books are great reads but IMHO he puts a bit too much "colour" in some of his stories. But it is true that the controls of Mk VIs and VIIs were heavier than those of other marks because of their pressure cabins, control runs when running out from cabins had to went through glands, it that is a right technical term, which added friction and so made controls heavier.

Juha


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## Shortround6 (Mar 22, 2012)

riacrato said:


> Like I mentioned above, it was just what i read, i wasn't sure about it. It would've give the D-box = torsion box argument more weight, but I think even if it's not true, the evidence is enough.
> 
> I found the source in the meantime, but it's just an internet site, so not reliable. I'm posting it just for the interested, not as proof:http://spitfiresite.com/2011/07/guided-tour-of-the-spitfire-pr-mk-xix-the-bowser-wing.html/dsc06603



There may be some translation difficulties. Forged and formed are not the same thing and even extrusions are not forged. Even stamped is not the same as forged. Sheet aluminium is rolled, not forged and even if stamped or other wise bent, folded, or twisted into a particular shape it is still not forged. 
Forged in one piece would also show no seams, welded, riveted or otherwise.


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## stona (Mar 22, 2012)

riacrato said:


> Like I mentioned above, it was just what i read, i wasn't sure about it. It would've give the D-box = torsion box argument more weight, but I think even if it's not true, the evidence is enough.
> 
> I found the source in the meantime, but it's just an internet site, so not reliable. I'm posting it just for the interested, not as proof:http://spitfiresite.com/2011/07/guided-tour-of-the-spitfire-pr-mk-xix-the-bowser-wing.html/dsc06603



Don't believe everything on the internet. You could refer to drawings already posted or even take a look at this original document,one of the many that Edgar has made available over the years.






Paragraph 5 confirms the joint running along the wing's leading edge.

I have a photograph which I can't seem to find of a Spitfire in American service in North Africa. It is in shabby condition and the paint of the leading edge has worn,clearly revealing the filler in this butt joint.

Cheers
Steve


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## cimmex (Mar 22, 2012)

“Paragraph 5 confirms the joint running along the wing's leading edge.”
Sorry can’t follow you. For what you want to make a proof?
Regards 
Cimmex


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## Edgar Brooks (Mar 22, 2012)

riacrato said:


> Like I mentioned above, it was just what i read, i wasn't sure about it. It would've give the D-box = torsion box argument more weight, but I think even if it's not true, the evidence is enough.
> I found the source in the meantime, but it's just an internet site, so not reliable. I'm posting it just for the interested, not as proof:


For someone, who's unaware (as I was up to about 5 years ago) how the treatment of the Spitfire changed, over the years, it's easy to be fooled into thinking that the l/e is a single piece. 
Up to August, 1942, the paint manufacturers had been unable to come up with a genuinely smooth, while remaining matt, cellulose paint; Joe Smith did his own research, and found a synthetic paint which filled the requirements, and the Air ministry were sufficiently impressed to change the paint specification (later, Beaufighters Typhoons changed, as well, and there's a possibility it also applied to Lancasters, but that remains to be seen,) and, at the same time, called for improved finish in the area of the leading edges of the wings. 
This involved filling the gap/crack on the extreme nose, plus all rivet "divots," with a stopper, rubbing it down, then priming, rubbing that down, then the final paint finish, all designed to give a completely smooth surface over the front 20% of the wing. This added 50 manhours to the job, but was felt to be worth it. According to an I.C.I. man this was extended to include the front portions of the tailplane and fin, at some later stage.
During the 1970s, I was involved in some voluntary work on a XVI (now somewhere in Southern California,) and, though I have no photos (never thought of it, and the paint stripper burnt like Hell,) I can attest to the seam, running the whole length of the wing.


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## Edgar Brooks (Mar 22, 2012)

cimmex said:


> “Paragraph 5 confirms the joint running along the wing's leading edge.”
> Sorry can’t follow you. For what you want to make a proof?


That the leading edge was not a one-piece casting.


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## cimmex (Mar 22, 2012)

thank you, now I got it.
cimmex


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## stona (Mar 22, 2012)

A detail from a picture of P9374 (a Mk I) under restoration.







Between the new and unpainted fillet and the unhelpfully positioned protective mat you can just make out the double line of rivets fastening the two halves of the leading edge box to the internal aluminium strip.

It's more visible on this image of a Mk IX undergoing restoration.






Cheers
Steve

Edit. Eureka,the "US" Spitfire I mentioned earlier.


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